Approval, Exhaust Gas Monitoring, and Safety Requirements for the Use of Diesel-Powered Equipment in Underground Coal Mines; Final Rule

[Federal Register: October 25, 1996 (Volume 61, Number 208)]
[Rules and Regulations]               
[Page 55411-55461]


[[Page 55411]]


_______________________________________________________________________

Part III





Department of Labor





_______________________________________________________________________



Mine Safety and Health Administration



_______________________________________________________________________



30 CFR Parts 7, et al.



Approval, Exhaust Gas Monitoring, and Safety Requirements for the Use 
of Diesel-Powered Equipment in Underground Coal Mines; Final Rule


[[Page 55412]]



DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Parts 7, 31, 32, 36, 70, and 75

RIN 1219-AA27

 
Approval, Exhaust Gas Monitoring, and Safety Requirements for the 
Use of Diesel-Powered Equipment in Underground Coal Mines

AGENCY: Mine Safety and Health Administration, Labor.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This final rule establishes new requirements for the approval 
of diesel engines and other components used in underground coal mines; 
requirements for monitoring of gaseous diesel exhaust emissions by coal 
mine operators; and safety standards for the use of diesel-powered 
equipment in underground coal mines. The final rule is derived in part 
from existing MSHA regulations, and provides protection against 
explosion, fire, and other safety and health hazards related to the use 
of diesel-powered equipment in underground coal mines. The final rule 
also amends certain equipment safety standards in part 75 previously 
applicable only to electric-powered equipment to apply to diesel-
powered equipment. The new standards are consistent with advances in 
mining technology, address hazards not covered by existing standards, 
and impose minimal additional paperwork requirements.

EFFECTIVE DATES: This regulation is effective April 25, 1997, except 
for subparts E and F of part 7, the removal of part 31, the
amendments 
to part 36, and Sec. 75.1907 which are effective November 25, 1996. 
Incorporations by reference were approved by the Director of the 
Federal Register as of April 25, 1997.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office 
of Standards, Regulations, and Variances, Mine Safety and Health 
Administration, 4015 Wilson Boulevard, Arlington, VA 22203-1984. Ms. 
Silvey can be reached at psilvey (Internet E-mail), 703-235-
1910 (voice), or 703-235-5551 (facsimile).

SUPPLEMENTARY INFORMATION:

I. Background

    Coal mine operators began to introduce diesel-powered equipment 
into underground mines in the early 1970's. The number of diesel units 
operating in underground coal mines has increased from approximately 
150 in 1974 to over 2,900 units operating in 173 mines in 1995. MSHA 
projects that the number of diesel units operating in underground coal 
mines could increase to approximately 4,000 in 250 underground coal 
mines by the year 2000.
    Although diesel-powered equipment does not have the inherent 
electrocution hazard of electric-powered equipment, it nonetheless 
presents a number of safety and health risks. By introducing an 
internal combustion engine into an environment where explosive levels 
of methane can be present, diesel-powered equipment brings with it 
risks of fire or explosion. Diesel engines also have high temperature 
exhaust components which, in the presence of coal and other 
combustibles in the underground mine environment, present a fire 
hazard. The handling and storage of diesel fuel underground also 
present potentially serious fire hazards. Finally, diesel engines 
produce exhaust gases containing carbon monoxide, oxides of nitrogen, 
and particulate matter, presenting potentially serious health risks to 
miners.
    Before publication of this final rule, MSHA's regulations contained 
limited safety and health and machine approval requirements that 
specifically addressed the use of diesel-powered equipment in 
underground coal mines. In the 1980's, the increase of the numbers of 
this equipment in underground coal mines, coupled with the health and 
safety risks associated with its use, highlighted the need for a 
regulatory approach specifically tailored to diesel-powered equipment 
operated in underground coal mines.
    In response to this need, the Secretary of Labor convened a Federal 
advisory committee in 1987 to evaluate and make recommendations for the 
safe and healthful use of diesel-powered equipment in underground coal 
mines. The Diesel Advisory Committee addressed approval issues--
covering equipment design and performance; use issues--addressing the 
safe use of diesel equipment in the mine environment; and health 
issues--concerning the evaluation and control of health hazards 
associated with diesel equipment. In July 1988, the Committee issued a 
report of its recommendations entitled ``Report of the Mine Safety and 
Health Advisory Committee on Standards and Regulations for Diesel-
Powered Equipment in Underground Coal Mines''. In its report the 
Committee concluded that MSHA should develop regulations to govern the 
approval and use of diesel-powered equipment in underground coal mines, 
and identified a number of specific areas to be addressed.
    On October 4, 1989, the Mine Safety and Health Administration 
published a Notice of Proposed Rulemaking in the Federal Register [54 
FR 40950] that included criteria for the approval of diesel engines and 
other related equipment; addressed exposure limits, monitoring, and 
recordkeeping requirements for certain diesel emissions; and provided 
corresponding safety standards for the use of diesel-powered equipment 
in underground coal mines, including the safe storage and transport of 
diesel fuel, and the training of persons performing work on diesel 
equipment. On the same day, MSHA also published an Advance Notice of 
Proposed Rulemaking [54 FR 40996] soliciting comment on the approach 
and scope of an MSHA approval program for diesel machines. MSHA held 
four public hearings on the proposed rule: in Salt Lake City, Utah; 
Pittsburgh, Pennsylvania; Chicago, Illinois; and Birmingham, Alabama.
    This final rule, which includes specifications for the approval of 
diesel engines as well as provisions for the safe and healthful use of 
such equipment in underground coal mines, is derived from the data, 
information, and public comments compiled during the rulemaking 
process. The final rule, like the proposal, takes an integrated 
approach to the control of diesel safety and health hazards, requiring 
clean-burning engines on diesel-powered machines, maintained by persons 
who have been adequately trained for the task. Sufficient ventilating 
air is required where diesel-powered equipment is operated to control 
the potential health hazards of diesel exhaust. Sampling every shift 
confirms the effectiveness of the mine ventilation system in addressing 
these hazards.

Part 7 Equipment Approval

    MSHA regulations require the Agency's approval of the design of 
electrical equipment to be used in the production areas of underground 
coal mines. This equipment must be designed to eliminate fire and 
explosion hazards. MSHA's approval program has been very successful in 
reducing the number of fires, explosions and other hazards associated 
with electric-powered equipment. The final rule establishes a similar 
approach for diesel-powered equipment used in areas of underground coal 
mines where permissible (explosion-proof) electric equipment is 
required, ensuring the same level of safety in mines where diesel-
powered equipment is used.

[[Page 55413]]

    The permissibility requirements for diesel-powered equipment used 
in gassy non-coal mines in MSHA's part 36 regulations
have been in 
place for a number of years. Although specific regulations did not 
exist for diesel-powered equipment operated in underground coal mines, 
MSHA has used the ventilation plan approval process to require the use 
of permissible diesel-powered equipment, approved under part 36, in 
those areas of underground coal mines where permissible electric 
equipment is required. However, mine ventilation plans have generally 
only addressed fire and explosion protection for equipment operating 
near the point of coal extraction (inby), and other locations where 
methane may be present, and have not addressed other possible safety 
hazards associated with the use of diesel-powered equipment in other 
(outby) areas. Additionally, mine ventilation plans have not dealt with 
such important concerns as the storage and handling of diesel fuel and 
regular maintenance of diesel equipment.
    The final rule requires that only approved engines be used in 
diesel-powered equipment in underground coal mines, and establishes 
approval requirements for diesel engines to be used in both permissible 
areas (inby) and nonpermissible areas (outby) under part 7, subpart E. 
The subpart E approval requirements are modeled after existing approval 
requirements in part 36 for engines used in gassy non-coal mines. 
Certain other safety features, such as flame arresters, spark 
arresters, and water scrubbers, must be added to the engines used in 
permissible areas to ensure that they can be operated safely in the 
coal mine environment. An engine in combination with these safety 
features is termed a diesel power package. A separate approval was 
established in the final rule for the power package because the power 
package manufacturer is normally a company other than the engine 
manufacturer and controls the assembly of the power package. In 
addition, approval requirements for power packages under part 7, 
subpart F, are incorporated into machines approved under existing part 
36. This is similar to the approach taken for electrical equipment 
where explosion-proof components are incorporated into machines 
approved under part 18.
    In order to protect miners from harmful contaminants emitted from 
diesel engines, the approval requirements in the final rule contain 
test procedures and limits on the concentrations of carbon monoxide and 
oxides of nitrogen. Based on commenters' recommendations, the final 
rule requires that the same test cycle be used for testing both the 
gaseous and particulate emissions. In response to commenters' 
recommendations, the final rule is based on ISO 8178, an international 
consensus standard, which establishes a common test cycle for the 
measurement of gaseous and particulate emissions. All equipment testing 
under part 7 is intended to be conducted at test sites other than MSHA 
facilities, such as manufacturers' laboratories, independent testing 
laboratories, or other government or university laboratories.

Part 70 Exhaust Gas Monitoring.

    The final rule addresses the monitoring and control of gaseous 
diesel exhaust emissions. The final rule requires area sampling as part 
of the onshift examination during every work shift. These monitoring 
provisions will ensure, in a reliable and systematic manner, that 
miners will be protected from exposure to harmful levels of gaseous 
contaminants.
    The final rule requires that mine operators take representative 
samples of carbon monoxide and nitrogen dioxide in strategic locations 
to determine concentrations of these contaminants in miners' 
workplaces. The sampling locations are based on knowledge of the 
specific operation of diesel equipment underground and the behavior of 
gaseous emissions generated by these machines. Samples exceeding an 
action level of 50 percent of the threshold limit values 
(TLV<Register>) for carbon monoxide and nitrogen dioxide trigger 
corrective action by the mine operator.

Part 75 Safety Requirements

    The final rule specifies minimum ventilating air quantities in 
areas where diesel equipment is operated, and requires that the 
quantities be incorporated into the mine operator's approved mine 
ventilation plan. As part of the equipment approval process in
part 7 
of the final rule, diesel engines used underground are tested for 
gaseous and particulate emissions. The required minimum ventilating air 
quantity is determined based on the results of these emission tests and 
is included on the approval plate for each unit of diesel-powered 
equipment. The approval plate quantity of ventilating air is the air 
quantity needed to dilute the exhaust gases to their permissible 
exposure limits. This air quantity should be used in ventilation system 
design by the mine operator and in the evaluation and approval of 
minimum air quantities in ventilation plans by MSHA.
    Under the final rule individual units of diesel equipment must be 
ventilated, as a general rule, with the air quantity specified on the 
equipment's approval name plate. The quantity of air required in areas 
where multiple units of equipment are operated is based on a simple 
addition of approval plate air quantities. The final rule also allows 
for adjustments in air quantities for multiple units of equipment, if 
sampling of contaminants indicates that lesser air quantities will 
result in dilution to the necessary levels. In addition, the final rule 
establishes specific locations where air quantities must be measured.
    Under the final rule, low sulfur fuel must be used to operate 
diesel-powered equipment underground. Low sulfur fuel, which is readily 
available and widely used throughout the United States, will lower 
gaseous and particulate emissions, helping to protect miners from 
exposure to harmful diesel exhaust contaminants. In addition, the final 
rule prohibits the use of flammable liquids as additives in diesel fuel 
used underground and requires that only additives registered with the 
Environmental Protection Agency in accordance with 40 CFR
Part 79 be 
used in diesel-powered equipment.
    The use of diesel fuel underground can present risks to miners' 
safety, because the spilling of fuel on hot surfaces or electric 
components, or the inadvertent ignition of stored diesel fuel, can 
result in fire. Additionally, a fire started with a combustible 
material other than diesel fuel that then spreads to diesel fuel stored 
underground could be catastrophic. Diesel fuel handling and storage are 
addressed in the final rule by specific requirements for diesel fuel 
storage and the transportation of fuel from one location to another.
    New design, installation, and maintenance requirements are 
established under the final rule for fire suppression systems installed 
on diesel-powered equipment and fuel transportation units. The 
requirements in the final rule address the risk of fire on diesel-
powered equipment caused by, for example, hot exhaust components, 
dragging brakes, and shorted electrical components igniting diesel 
fuel, hydraulic fluid, brake fluid, lube oil, and other combustible 
materials. The final rule also requires that automatic fire-suppression 
systems be listed or approved by a nationally recognized independent 
testing laboratory.
    The final rule recognizes that regular maintenance of diesel-
powered equipment is essential. Inadequate equipment maintenance can 
result in the creation of a fire or explosion

[[Page 55414]]

hazard, and the levels of harmful gaseous and particulate components in 
diesel exhaust can rise when equipment is not adequately maintained. In 
response, the final rule requires diesel-powered equipment to be 
examined on the same weekly basis as electric equipment. The rule 
specifically requires that air filters be changed and scrubbers be 
flushed regularly, and that weekly gaseous emission tests be conducted 
on certain diesel equipment while the engine is operating. The final 
rule also requires that persons performing certain work on diesel-
powered equipment be qualified. Commenters agreed that requiring 
diesel-powered equipment to be maintained in approved condition is 
necessary to ensure that features installed to reduce the risk of fire, 
explosion, and harmful emissions are operating properly. The final rule 
does not adopt the proposal that MSHA approve the training plans used 
for qualification. Under the final rule, training to establish 
qualification for persons performing maintenance may be obtained 
through the equipment manufacturer, community colleges, training 
schools, or other training providers.
Amendments to Existing Part 75 Requirements
    The final rule amends certain existing MSHA regulations in
part 75 
by extending their applicability to diesel-powered equipment. The final 
rule requires that certain types of diesel-powered equipment be 
equipped with methane monitors to detect dangerous levels of methane, 
and also with cabs or canopies to protect miners from roof falls. 
Additionally, the final rule clarifies that accumulation of coal dust 
and other combustible materials is prohibited on diesel-powered 
equipment. These safety features have been proven to save miners' 
lives.

II. Discussion of the Final Rule

A. General Discussion

Recordkeeping Requirements in the Final Rule
    Recordkeeping requirements in the final rule are found in 
Secs. 7.83 and 7.97, Application requirements; Secs. 7.90 and 7.105, 
Approval marking; Secs. 7.108, Power package checklist; Sec. 75.363, 
Hazardous condition; posting, correcting and recording; Sec. 75.371 
(r), (kk), (ll), (mm), (nn), (oo), and (pp), Mine ventilation plan, 
contents; Sec. 75.1901(a), Diesel fuel requirements; 
Sec. 75.1904(b)(4)(i), Underground diesel fuel tanks and safety cans; 
Sec. 75.1911(i) and (j), Fire suppression systems for diesel-powered 
equipment and fuel transportation units; Sec. 75.1912(h) and (i), Fire 
suppression systems for permanent underground diesel fuel storage 
facilities; Sec. 75.1914 (f)(1), (f)(2), (g)(5), (h)(1) and (h)(2), 
Maintenance of diesel-powered equipment; Sec. 75.1915(a), (b)(5), 
(c)(1), and (c)(2), Training and qualification of persons working on 
diesel-powered equipment.
    The paperwork burden imposed on manufacturers by the final rule 
totals 558, which is an increase of 790 burden hours for the transfer 
of hours from part 36 approval requirements, and a decrease of 232 
hours for the removal of parts 31 and 32. In the first year the final 
rule is in effect, the burden hours on mine operators will be 56,258, 
of which large and small mine operators will incur 54,774 and 1,484 
hours, respectively. After the first year, the burden hours to mine 
operators will be 52,228, of which large and small mine operators will 
incur 50,949 and 1,279 hours, respectively.
    In the first year that the final rule is in effect, the total new 
paperwork burden hours to mine operators and manufacturers will be 
56,816 [56,258 + (790-232)]. After the first year, the total new 
paperwork burden hours to mine operators and manufacturers will be 
52,786 [52,228 + (790-232)].
    MSHA solicited comments regarding the burden estimates or any other 
aspect of the collection of information in the proposed rule. Proposed 
paperwork requirements were submitted to the Office of Management and 
Budget (OMB) for review in accordance with section 3504(h) of the 
Paperwork Reduction Act of 1980 (PRA 80). Comments by OMB were filed 
under comment numbers 1219-0111, 1219-0112, and 1219-0114. Control 
number 1219-0100 was approved for proposed paperwork burden hours 
required by part 7.
    When proposed in 1989, the information collection requirements in 
the diesel equipment regulations were calculated under PRA 80. The 
final rule calculations are done in compliance with the Paperwork 
Reduction Act of 1995 (PRA 95). Generally, changes in the final rule 
burden hour and cost estimates from the proposed requirements result 
from the revision necessitated by PRA 95. When the change represents a 
regulatory change, it is so noted in the discussion of the appropriate 
section within the preamble. For details on the calculation of 
paperwork hours and costs see ``VII, Paperwork Reduction Act of 1995'' 
in the Regulatory Impact Analysis, which may be accessed electronically 
or may be requested from MSHA's Office of Standards, Regulations, and 
Variances.
    Information is to be recorded, maintained for the period specified, 
and made accessible, upon request, to authorized representatives of the 
Secretary and to miners' representatives. Records are to be stored in a 
manner that is secure and not susceptible to alteration, to preserve 
the integrity of records for review by interested parties. This may be 
done traditionally, by recording in a book, or electronically by 
computer.
    Examples of books that MSHA considers to be secure and not 
susceptible to alteration include, but are not limited to, record books 
that are currently approved by state mine safety agencies, and 
permanently bound books. Examples of books that would not be considered 
secure include loose-leaf binders and spiral notebooks.
    Recognizing the trend of electronic storage and retrieval of 
information through computers to be an increasingly common business 
practice, MSHA permits the use of electronically stored records, 
provided that they are secure and not susceptible to alteration, that 
they are able to capture the information and signatures required, and 
that information is accessible to authorized representatives of the 
Secretary and miners' representatives. ``Secure'' is intended to mean 
unalterable or unable to be modified. An example of acceptable storage 
would be a ``write once, read many'' drive. Electronic records meeting 
these criteria are practical and as reliable as traditional records. 
Although the final rule does not require backing up the data, some 
means is necessary to ensure that the condition and existence of 
electronically stored information is not compromised or lost.
    The 1995 Paperwork Reduction Act mandates agencies to encourage the 
use of electronic submission of responses to minimize the burden of the 
collection of information on respondents. Likewise, one of the major 
objectives of Executive Order No. 12866 is to make the regulatory 
process more accessible and open to the public as a means to reduce the 
duplication of information between agencies. Elsewhere in this 
preamble, MSHA announces the electronic availability of its rulemaking 
documents with access instructions. The mining community and other 
interested parties are encouraged to access on-line material as needed.

B. Section-by-Section Discussion

    The following section-by-section portion of the preamble discusses 
each provision affected. The text of the final

[[Page 55415]]

rule is included at the end of the document.
General Discussion of Diesel Equipment Approvals and Safety 
Requirements
    One of the three major areas addressed by the Diesel Advisory 
Committee was the approval of diesel-powered equipment. Historically, 
MSHA and its predecessor agencies have approved equipment intended for 
use in areas of mines where methane and other substances pose the 
danger of a fire or explosion. Through the approval process, equipment 
is evaluated against technical requirements which, when met, will 
render the equipment safe for its intended use in the mine environment. 
In part as a result of this process, the approved equipment used in 
mines in the United States is recognized as among the safest in the 
world.
    The Advisory Committee recommended that diesel-powered equipment 
for use in underground mines be subject to MSHA approval in much the 
same way that electrical equipment has been regulated. Under existing 
standards, electrical equipment operated in the area of extraction and 
in return airways of underground coal mines and gassy metal and 
nonmetal mines, where methane may accumulate, must be approved as 
permissible (explosion-proof). Electrical equipment operated elsewhere 
in these mines is not required to be permissible, but is subject to 
certain safety requirements to protect against fire, shock, and other 
hazards of operation. The Advisory Committee further recommended:
    <bullet> Only diesel-powered equipment currently considered 
permissible should be permitted to continue to operate in areas of coal 
mines where permissible electrical equipment is required.
    <bullet> Separate specifications should be developed for diesel-
powered equipment used in areas where permissible equipment is required 
and elsewhere.
    <bullet> An approval program for diesel-powered equipment and 
portable, attended equipment should be established. This program should 
identify those equipment design features most readily addressed by the 
equipment manufacturers.
    <bullet> A time schedule should be developed to allow for 
conversion of outby equipment presently in use through retrofits, 
replacement, or additional interim safety features to meet the 
applicable new requirements.
    <bullet> Equipment newly introduced underground after a fixed date 
should meet the new standards.
    <bullet> Current safety requirements including those that are 
applicable to electric equipment should apply to diesel equipment as 
appropriate.
    <bullet> Only approved diesel engines should be used in underground 
equipment and the approval requirements should include measurements of 
exhaust gas pollutants and determination of a nameplate airflow 
quantity. Measurement of particulate generation should also be included 
in the engine approval process.
    In the proposed rule, MSHA outlined three new subparts for existing 
part 7, which set approval requirements for diesel engines and power 
packages to be used in underground coal mines. The Agency also gave 
notice of its intention to develop approval requirements for fully 
assembled diesel-powered machines under a proposed subpart H for 
permissible equipment and subpart I for large outby equipment. 
Requirements for a limited class of light-duty equipment and stationary 
unattended equipment were proposed in part 75. A special class of 
equipment consisting of ambulances and fire fighting equipment was 
proposed that could be used in emergency situations as part of the 
mine's evacuation plan. The proposal also included provisions to permit 
fire prevention features in lieu of surface temperature controls for 
diesel locomotives.
    Currently, MSHA approves diesel equipment under 30
CFR Part 36 for 
use in ``gassy noncoal mines''. In underground coal mines, ventilation 
plans specify the use of diesel-powered equipment approved as 
permissible under part 36 in areas where permissible electric equipment 
is required. In addition to the equipment approval under part 36, MSHA 
regulations address the approval of diesel mine locomotives in
30 CFR 
Part 31, and of mobile diesel-powered equipment for noncoal mines in
30 
CFR Part 32. The proposal suggested that parts 31, 32, and
36 could be 
revised or revoked, and solicited comment. Some commenters favored 
retaining all of the existing diesel approval regulations since they 
still could have some application for equipment used in metal and 
nonmetal mines. Commenters generally agreed that the proposed rules for 
part 7 should supersede any applicability these existing approval 
regulations have for diesel engines used in underground coal mines.
    The final rule for part 7 governs the approval of diesel engines 
intended for use in underground coal mines. As recommended by the 
Advisory Committee and as set forth in the proposed rule, the final 
rule requires that all diesel engines used in underground coal mines be 
approved.
    Part 7 was originally promulgated in 1988 to establish application 
procedures and requirements for MSHA approval of certain products for 
use in underground mines, with testing conducted by the applicant or a 
third party. Traditionally, MSHA's role in approving products for 
safety emphasized testing by the Agency. Under part 7, testing is 
performed by the applicant or by a third party selected by the 
applicant, with MSHA maintaining the right to observe product testing. 
This approach has permitted MSHA to focus on its product audit function 
and keep pace with technological improvements in mining products.
    As originally promulgated, part 7 applied to only two types of 
products: brattice cloth and ventilation tubing under subpart B, and 
battery assemblies under subpart C. Subsequently, three additional 
subparts were developed covering multiple-shot blasting units; electric 
motor assemblies; and electric cables, signaling cables, and cable 
splice kits. As designed, part 7 expedites the approval process, while 
providing greater assurance that the products are manufactured in 
accordance with safety specifications.
    The final rule for part 7 is organized into two subparts--E and F. 
Subpart E sets diesel engine performance and exhaust emission 
requirements. As more fully discussed elsewhere in the preamble, 
subpart E creates two classes of engine approvals--one for Category A 
engines and one for Category B engines. Engines intended for use where 
permissible electric equipment is required in underground coal mines 
must have a Category A approval; engines for use elsewhere in 
underground coal mines must meet the requirements for Category B 
engines.
    Subpart F of the final rule sets standards for safe design of 
diesel engines with respect to both fire and explosion hazards. The 
final rule establishes requirements for approval of diesel ``power 
packages'' on engines intended to be used where electric equipment is 
required to be permissible under existing standards. The term ``power 
packages'' refers to an approved engine and those components added to 
the engine, such as flame arresters, which prevent the ignition of 
methane, and surface temperature controls, which prevent the ignition 
of accumulations of combustible materials and combustible liquids. 
Permissible equipment is designed to be explosion-proof.
    Subpart G of the proposed rule would have established requirements 
for diesel

[[Page 55416]]

power packages intended for use in areas of underground coal mines 
where permissible electrical equipment is not required. As this 
equipment is not designed to be operated in a potentially explosive 
methane environment, the proposed rule would not have required these 
power packages to have explosion-proof features. However, these diesel 
engines do present fire hazards which must be controlled. Under the 
proposal, subpart G would have set standards for surface temperatures, 
exhaust cooling, and safety system controls. As discussed more fully 
below, the final rule does not retain subpart G, but addresses these 
hazards through new requirements in part 75.
    The proposed rule, responding to a recommendation of the Advisory 
Committee, also established a category of ``limited class of light-duty 
diesel-powered equipment.'' This category included machines with light-
duty cycles, such as pickup trucks and personnel carriers. This 
equipment, while light-duty as compared to production equipment, can, 
nevertheless, present a fire hazard. For this ``limited class'' of 
diesel-powered equipment, instead of requiring surface temperature 
controls, the proposal set standards for fire prevention features that 
would prevent fuel, hydraulic fluid, and lubricants from coming into 
contact with hot engine surfaces. Features such as special fuel system 
protection, fire suppression systems, safe electrical systems, and 
engine compartment sensors that shut down the engine in the event of 
overheating were specified in the proposal for additional fire 
protection. Other necessary safety features, such as braking systems, 
were also addressed by the proposal. As recommended by the Advisory 
Committee, these requirements were not made part of the approval 
process described above, but were set forth in the proposal as safety 
standards for underground coal mines, appearing in 30 CFR
Part 75.
    The final rule retains many of the provisions of the ``limited 
class'' concept in the proposal, but broadens the scope of the 
equipment subject to these requirements to include all equipment not 
required to be permissible (outby equipment). This change eliminates 
the need for formal approval of outby equipment, and simplifies the 
final rule. This aspect of the final rule, and the diesel-powered 
equipment approval requirements, are discussed in detail under the 
section-by-section analysis which follows.
    In the proposed rule MSHA notified the public of its intentions to 
develop two new approval regulations. Subpart H would have established 
requirements for the approval of fully assembled permissible diesel-
powered equipment, and subpart I would have established approval 
requirements for fully assembled nonpermissible diesel-powered 
equipment. These sections would have included machine features 
currently required by part 36 for permissible equipment and similar 
features, described above, for ``limited class'' equipment. These 
subparts would have required the incorporation of appropriate power 
packages as described in proposed subparts F and G.
    In the advance notice of proposed rulemaking, which accompanied the 
proposed rule, MSHA requested comments on this regulatory approach. 
Commenters objected to a formal approval program for nonpermissible 
equipment, but supported the incorporation of machine safety features 
in the use requirements specified in part 75. Commenters also supported 
the need for continuing the approval program for permissible equipment.
    In response to these comments, the final rule retains part 36 as 
the basis for the approval program for permissible diesel-powered 
equipment and adopts the machine safety features specified for the 
limited class of light-duty equipment in the proposal for all 
nonpermissible equipment. Subparts H and I are not further developed. 
Instead, the final rule adopts the fire prevention features specified 
for limited class equipment for all nonpermissible equipment. 
Additionally, the final rule enhances the fire prevention features that 
now apply to all nonpermissible equipment. This approach eliminates the 
need for subpart G of the proposal dealing with power packages for 
outby equipment.
    The final rule makes certain revisions to part 36 to update and 
make these existing requirements more flexible. The final rule revises 
part 36 to remove references to ``gassy noncoal mines and tunnels'', 
thus making these existing regulations applicable to equipment intended 
for use in coal as well as in metal and nonmetal mines. In addition, 
part 36 is amended to afford equipment manufacturers the option of 
incorporating in equipment submitted for approval either a part 7, 
subpart F power package, or engine and safety component systems that 
meet the existing requirements of part 36. Under the final rule,
part 
36-approved equipment with a part 7, subpart F power package will be 
suitable for use in underground coal mines where permissible electrical 
equipment is required. Part 36 equipment with engine and safety 
component systems certified under part 36 will continue to be 
recognized for use in metal and nonmetal mines where permissible 
equipment is required.
    These changes are responsive to commenters who recommended that 
part 36 continue to be utilized for approving diesel-powered equipment. 
The final rule revisions to part 36 also retain, as recommended by 
commenters, a distinction between approval requirements for equipment 
used in coal mines and approval requirements for metal and nonmetal 
mining equipment.
    The final rule revokes parts 31 and 32. MSHA previously identified 
these regulations for elimination in its response to the President's 
March 4, 1995, Regulatory Reform Initiative. Parts 31 and 32 are 
outdated and, with the final rule changes to parts 7 and 36, are 
obsolete. Only nine approvals have been issued under part 31 since its 
inception, and none have been issued since 1977. No other MSHA 
standards require part 31-approved equipment, and diesel mine 
locomotive manufacturers have submitted approval applications under 
part 36 for locomotives intended to be used where permissible equipment 
is required. With the revocation of part 31, diesel mine locomotive 
manufacturers may continue to acquire equipment approvals under part 
36.
    The part 32 approval requirements for mobile diesel-powered 
equipment used in noncoal mines are likewise unnecessary. No MSHA 
regulation requires the use of part 32 equipment, and no
part 32 
machine approval has been issued since 1981. Part 32 engine 
certifications have continued to be issued by MSHA, however, and some 
state and federal agencies' regulations make reference to
part 32. 
State and federal agencies that reference part 32 are directed to look 
to part 7, subpart E, which contains engine requirements, and to 
Secs. 75.1909 and 75.1910, which contain the requirements for other 
machine features. Together, these final standards cover the 
requirements previously found under part 32. These new sections of the 
final rule will continue to accommodate those government agencies that 
reference MSHA approval or certification regulations.
    Likewise, manufacturers seeking part 32 engine approvals will be 
able to acquire the requisite engine approval through the new part 7, 
subpart E. Existing part 32 engine approvals continue to be valid.
    A significant issue for the Advisory Committee and in the proposal 
was the schedule set for compliance with the new standards for diesel-
powered equipment. The Advisory Committee

[[Page 55417]]

recommended that MSHA require diesel equipment newly introduced 
underground to meet the new standards after a certain date. The 
Committee further recommended that MSHA set a schedule for existing 
diesel equipment to meet any new requirements.
    The proposal called for the part 7 approval requirements to be 
effective 60 days after publication of the final rule. The schedule for 
requiring in-mine use of diesel equipment meeting the new requirements 
was set by proposed Sec. 75.1907. Under these provisions, the new 
requirements would have been met over a schedule ranging from six 
months to five years after the effective date of the final rule.
    The final rule follows the approach of the proposal, setting 
effective dates for the new approval requirements, as well as the 
schedule for requiring in-mine use of diesel-powered equipment which 
meets the new requirements. In response to the comments and as a result 
of not adopting proposed subparts G, H, and I, the final rule sets a 
compliance schedule ranging from 60 days to three years after 
publication of the final rule. In order to facilitate implementation of 
the final rule, MSHA will begin accepting approval applications under 
revised parts 7 and 36 immediately. In addition, MSHA will continue 
power package testing until the Agency determines that a competitive 
capacity exists in the private sector. At that time, MSHA will 
discontinue power package testing and rely solely on the part 7 testing 
provisions.
Subpart E Overview
    Subpart E of the final rule is new and amends existing part 7. As 
an amendment to these existing regulations, the general administrative 
provisions of subpart A of part 7 apply to the new subpart E 
application requirements.
    Subpart E establishes engine performance and exhaust emission 
requirements for MSHA approval of diesel engines for use in underground 
coal mines. As discussed elsewhere in this preamble, diesel engines for 
use in metal and nonmetal mines are approved under part 36.
    The final rule, like the proposal, creates two classes of engine 
approvals--Category A and B--for diesel engines to be used in 
underground coal mines. Several commenters objected to the proposed 
approval of diesel engines for use in outby areas, noting that outby 
electrical equipment is not subject to approval under existing 
standards. However, other commenters stated, and the Diesel Advisory 
Committee acknowledged, that all diesel engines in underground coal 
mines should meet certain safety and performance specifications. In its 
report the Advisory Committee suggested that, depending on equipment 
location and use, different requirements would be appropriate for 
diesel engines. One commenter to the proposal recommended that all 
diesel engines be approved as permissible.
    For underground coal mines, MSHA believes that clean-burning 
engines are critically important. Unlike electrical equipment, diesel 
engines emit exhaust which contains toxic gases that can be harmful to 
miners. Inappropriately designed engines can pollute the mine 
atmosphere excessively, elevating toxic gases to levels that cannot be 
controlled with normal ventilation practices.
    To achieve the objective of clean-burning, appropriately designed 
engines in mines, the final rule sets performance standards for all 
diesel engines, whether they are operated in the face area or outby.
    The emission test requirements for Category A and B engines are the 
same, except that Category A engines are tested with methane injected 
into the intake system. Equipment operating at or near the point of 
coal extraction and in return air courses may encounter concentrations 
of methane gas, which is liberated during mining. Testing an engine 
with methane injected in its intake simulates operation of the engine 
in these areas of coal mines. Operation in methane atmospheres causes 
an increase in exhaust emissions, which requires higher ventilation 
rates.
    Under the final rule, diesel equipment used in areas where 
permissible electrical equipment is required by existing standards 
incorporate fire and explosion prevention features provided by a power 
package. Such a power package must include a Category A engine and 
components added to the engine to prevent the ignition of methane and 
accumulations of combustibles. Power packages intended for use with 
Category A diesel engines must be approved under part 7, subpart F of 
the final rule.
    Current safety standards require that intake air courses in areas 
away from or outby the mining face be maintained free of explosive 
concentrations of methane. Engines used on equipment operated in these 
outby areas must have a Category B approval under the final rule. 
Engines approved under Category B are emission tested without the 
injection of methane into the engine's intake system.
    The proposed technical requirements for diesel engines addressed 
the control of gaseous exhaust emissions and quantification of the 
engines' particulate matter generation. The proposed rule also set 
specifications for the equipment used and the standard laboratory test 
conditions for determining gaseous and particulate output for diesel 
engines. The proposed requirements for measuring gaseous emissions were 
derived from now-removed part 32 and existing part 36,
and the proposed 
requirements for measuring diesel particulate were based on the 
Environmental Protection Agency's requirements published in 40 CFR
Part 
86. In addition, the proposal specified the engine operating parameters 
as well as a method to calculate the ventilation rate and particulate 
index for the engine.
    Engine manufacturers do not manufacture engines specifically for 
mining. Typically, ``off-road'', heavy-duty diesel engines are utilized 
in mining equipment. Over-the-road utility vehicles and smaller general 
industry equipment are also used in mines. At the time of the proposed 
rule, the only certification test specifications designed for engines 
used in mining were the MSHA engine certification standards in now-
removed part 32 and in existing part 36.
    In the proposal, MSHA used its rules in now-removed part 32 and 
existing part 36 for the steady-state test for gaseous diesel exhaust 
emission. The test equipment specified in the proposal for diesel 
exhaust particulate measurement was modeled after the transient test 
equipment required in 40 CFR Part 86, subpart N.
    Commenters to the proposal stated that a correlation should not be 
made between MSHA's proposed rule and then-current EPA testing, because 
the proposal used a test with specific points in a ``steady state'', 
while EPA used a ``transient test.'' Commenters also recommended using 
the same test cycle for both gaseous and particulate matter. In 
addition, commenters generally recommended comparability of testing for 
similar types of tests and indicated a desire to use international 
standards whenever possible.
    The International Organization for Standardization (ISO) has 
prepared ``ISO 8178 Reciprocating Internal Combustion Engines--Exhaust 
Emission Measurement'', which includes test specifications for off-road 
diesel engines. The ISO is a recognized international standard-setting 
body. Equipment manufacturers, as well as other standard-setting 
bodies, make reference to and adopt the standards developed by the ISO.

[[Page 55418]]

    ISO 8178 is an international test standard for measuring off-road 
diesel engine emissions. It contains a detailed description of the test 
equipment requirements and standard procedures for conducting a steady-
state test to determine both gaseous and particulate emissions. The ISO 
8178 procedures also specify an 8-point test cycle for measuring both 
gaseous and particulate emissions. ISO 8178 does not set emission 
limits.
    The final rule is based on the ISO 8178 ``Reciprocating Combustion 
Engines--Exhaust Emission Measurement'', part 1 test procedures that 
apply to gaseous and particulate emission testing for diesel engines. 
This change from the proposal is responsive to commenters' concerns 
about correlating the proposed rule and EPA diesel engine tests, and 
simplifies the test procedures. For example, under the final rule the 
gaseous emission tests are reduced to 8 test points from 39 test points 
under the proposal. The particulate emission tests are also reduced 
from 10 to 8 test points. In addition, the final rule permits the tests 
for exhaust gaseous and particulate emission tests to be performed 
concurrently following the same test cycle, rather than independently 
following different cycles. A number of minor changes are made in 
Secs. 7.86, 7.87, 7.88, and 7.89 of the final rule, so that the tests 
performed under these sections conform to the ISO 8178 requirements. 
Substantive changes to these sections are discussed in this overview 
and in the section-by-section discussion that follows.
    The final rule adds one requirement to the ISO 8178 test 
procedures. Section 7.89(a)(5)(iii) requires that 1.0 percent of 
methane be added to the intake air for testing Category A engines. This 
addition to the ISO 8178 procedure should present no technical 
difficulties for manufacturers or third-party laboratories. MSHA, 
however, will provide technical assistance for setting up this aspect 
of the test procedure upon request. The final rule also requires a test 
to determine the maximum fuel-to-air ratio, and specifies requirements 
for determining the gaseous ventilation rate and particulate index for 
diesel engines.
    Basing the final rule on an international consensus standard 
enables diesel engine manufacturers to test with a single set of 
procedures common to both the United States and foreign markets. Also, 
existing test facilities established to perform tests to these 
international standards can be used to perform the tests prescribed by 
this final rule. In addition, use of the ISO 8178 test procedures leads 
to better comparability with international testing practices, and 
provides a more competitive posture for American products in foreign 
markets. Many off-road engine manufacturers are already complying with 
EPA and California Air Resources Board (CARB) requirements, which 
include testing in accordance with ISO 8178 procedures.
    One commenter to the proposal objected to permitting engine 
manufacturers or third-party laboratories to test diesel engines for 
conformance to approval standards, questioning the objectivity of such 
an approach. MSHA experience over eight years with manufacturers and 
third- party laboratory testing under existing part 7 and the Agency's 
program for off-site testing (POST) of diesel engines confirms that 
non-MSHA testing is performed competently and produces reliable 
results. In addition, MSHA will initially witness all tests conducted 
by manufacturers and third parties to ensure continued reliability of 
test results. In all cases, MSHA will accept only results of tests 
performed by manufacturers or third-party laboratories which have the 
capability to competently perform the required tests with properly 
calibrated instrumentation.
    Section 7.81  Purpose and effective date. The part 7, subpart E 
approval requirements are effective November 25, 1996. MSHA will begin 
accepting applications under subpart E immediately, but will complete 
any in-house part 32 applications, or evaluate such applications under 
the new part 7, subpart E, at the applicant's choice. As discussed 
elsewhere in this preamble, the requirements for the use of approved 
diesel engines in underground coal mines are effective in 3 years.
    Commenters to the proposal generally supported the approval 
requirements of subpart E for diesel-powered equipment to be used in 
underground coal mines. Several commenters suggested, however, that a 
phase-in period, up to three years, be established. According to these 
commenters, manufacturers would use the phase-in period to gain 
experience with the new test procedures, become familiar with new 
engine approval application procedures, and re-evaluate their existing 
approvals.
    The final rule does not incorporate a phase-in period for diesel 
engine approvals. Diesel engine manufacturers and third-party testing 
facilities are familiar with the ISO 8178 test procedures on which the 
final rule is based, and have the capability to perform these tests in 
their laboratories with minor changes. In fact, two engine 
manufacturers and a testing laboratory have tested diesel engines for 
MSHA approval using the ISO 8178 procedure.
    With this diesel engine testing experience and capability already 
present in the marketplace, MSHA finds no reason to provide an extended 
phase-in period for the approval standards for diesel-powered 
equipment, and anticipates that manufacturers and third-party testing 
laboratories can immediately begin testing engines under subpart E.
    Section 7.82  Definitions. In addition to the existing definitions 
in Sec. 7.2, Sec. 7.82 of the final rule sets out and clarifies the key 
terms which apply in subpart E. Commenters generally agreed with the 
proposed definitions, which were derived from definitions developed for 
ISO 8178 and the Society of Automotive Engineers (SAE) Recommended 
Practice J177.
    No comments were received on the proposed definitions for 
``Category A engines'', ``Category B engines'', ``corrosion-resistant 
material'', ``diesel engine'', ``exhaust emission'', ``percent load'', 
and ``steady-state condition''. These terms and their proposed 
definitions are adopted in the final rule.
    The definitions of the terms ``rated speed'' and ``intermediate 
speed'' in the proposed rule have been modified in the final rule in 
response to a commenter who recommended that MSHA's definitions of 
these terms conform to definitions contained in internationally 
accepted standards. The definitions of these terms in the final rule 
are conformed to the definitions in ISO 8178.
    The term ``peak torque speed'' in the proposed rule has been 
changed to ``maximum torque speed'' in the final rule to conform with 
ISO 8178. Both terms convey the same meaning.
    One commenter objected to the definition of ``diesel particulate 
matter'' as ``any material, with the exception of water, which is 
collected on a filter passed by an air diluted exhaust stream.'' 
According to this commenter the proposed definition was vague and too 
dependent on the filter used and method of sampling. The final rule 
does not include the proposed definition, adopting instead the 
definition for diesel particulates contained in ISO 8178. The ISO 
definition is more specific, providing that diesel particulates are 
``any material collected on a specified filter media after diluting 
diesel exhaust gases with clean filtered air at a temperature less than 
or equal to 325 K (52 deg. C) as measured at a point immediately 
upstream of the primary filter. This is primarily carbon, condensed 
hydrocarbons, and sulphates

[[Page 55419]]

and associated water.'' In addition, the filter and sampling methods, 
which are well detailed in ISO 8178, are included in the final rule. 
The objective of this definition is to facilitate accurate, repeatable 
tests for the diesel particulate matter in an engine's exhaust. Other 
definitions may be more appropriate for addressing health effects.
    The same commenter also objected to the proposed definition of 
``total oxides of nitrogen'' as focusing only on nitric oxide and 
nitrogen dioxide. The commenter suggested revisions to these 
definitions and offered definitions for several other terms used in the 
proposed rule, including ``gaseous ventilation'', ``particulate 
index'', ``threshold limit value'', ``permissible exposure limit'' and 
``recommended exposure limit.'' According to the commenter, these terms 
were not used consistently in the proposal. The final rule does not 
adopt these suggested changes. Many of these terms have accepted 
meanings that are well known. However, changes throughout the final 
rule have been made to be sure the terms are used consistently and 
appropriately.
    The proposed definition of rated horsepower is revised in the final 
rule to conform with current procedures for evaluating engines under 
existing part 36. This change will help define an engine's power output 
as it is related to performance testing. A definition for the term 
``operational range'' is added to also conform with current procedures 
for evaluating engines under existing part 36.
    Section 7.83  Application requirements. The proposed application 
requirements were derived from now-removed part 32 and existing
part 36 
and are largely unchanged in the final rule. The application procedures 
are designed to provide sufficient information to demonstrate 
compliance with the technical requirements of subpart E, and form the 
basis for approval of diesel engines.
    The final rule adopts the proposal to permit applicants to submit 
composite drawings in lieu of individual drawings. This approach 
reduces paperwork and affords applicants flexibility in the preparation 
of their drawings.
    The final rule also provides for certain information to be 
submitted after approval testing. This information includes the 
ventilation rate and particulate index for the engine, and the fuel 
deration chart, which provides guidance for how to adjust approved 
engines to compensate for altitude.
    Like existing part 7 and other MSHA approval standards, the 
documentation formulated in the application process forms the basis for 
MSHA's approval. Approved diesel engines must be manufactured in 
accordance with the specifications contained in the approval and, once 
put into service, approved engines must be maintained and operated 
within the parameters set in the MSHA approval.
    In general, commenters concurred with the proposed application 
requirements. One commenter suggested that a description of the design 
features which promote efficiency and control over production of toxic 
emissions specifically include fuel injection timing. MSHA agrees that 
specifications for the fuel injection system of diesel engines and the 
fuel injection timing are key in controlling exhaust emissions. The 
proposal included a requirement that the fuel injection system be 
detailed in approval applications. However, a requirement specifying 
the fuel injection timing was not included in the proposed rule.
    The final rule adopts the proposed requirement for a description of 
the fuel injection system, and adopts in paragraph (b)(6) the 
suggestion that fuel injection timing also be specified. This 
information had been required in now-removed part 32 and is required 
for part 36 engine approvals and to help ensure accurate measurement of 
the engine's emissions during the tests and proper maintenance of the 
engine's fuel injection timing.
    Although the Agency allows electronic record storage in other areas 
of this regulation, electronic computer submission of part 7 approval 
applications is not yet available. MSHA's Approval and Certification 
Center is developing a means for computer submission, and at present 
has pilot programs to facilitate the use of electronic reporting. 
However, the system is in the formative stage and is not yet available 
for public use.
    The paperwork hours in the approval application, including test 
requirements, are assigned OMB control number 1219-0100.
    Section 7.84 Technical requirements. This section of the final rule 
sets the specific technical requirements for Category A and Category B 
diesel engines. The objective of this aspect of the final rule is to 
set standards which, when met, will produce clean-burning diesel 
engines that are safe and appropriate for use in the confined 
environment of underground coal mines.
    Like the proposal, the final rule's requirements for the gaseous 
emissions of diesel engines are based on appropriate sections of 
existing part 36 approval regulations for diesel engines.
Experience 
confirms that compliance with these regulations, which address fuel 
injection adjustments and fuel-to-air ratios, produces engines that 
operate without excessive gaseous emissions that can be harmful to 
miners.
    One commenter to the proposal suggested that the fuel injection 
system on approved diesel engines be required to be fixed and sealed so 
that it could not be changed. According to the commenter, sealing the 
system would prevent unauthorized changes.
    The final rule does not adopt this suggested change, as adjustments 
to diesel engine fuel injection systems are necessary for maintenance 
and to compensate for altitude. Adjustments such as these permit the 
fuel-to-air ratio for diesel engines to be maintained at a level which 
minimizes exhaust emissions.
    The final rule does, however, adopt the proposed security 
requirements to prevent unauthorized fuel injection system adjustments. 
Fuel injection system adjustments are required to be changeable only 
after breaking a seal, or by altering the injection system's design. 
For example, a shim may be added or removed to change the fuel pump's 
performance. These parts are supplied by engine manufacturers and must 
be used in accordance with the engine's approval. For engines with 
electronic fuel injectors, specialized computer interface equipment is 
used to adjust the computer programming sequence. The programming 
sequence must be installed by the engine manufacturer and is listed 
with the engine approval documentation. After adjustments are made in a 
fuel injection system, any seal removed must be replaced. Failure to 
follow these procedures for adjusting a fuel injection system would 
result in the engine no longer being in approved condition. Under 
Sec. 75.1914(a) of the final rule, diesel engines used in underground 
coal mines are required to be maintained in approved condition.
    Consistent with a recommendation of the Diesel Advisory Committee, 
the technical requirements for diesel engines also include undiluted 
exhaust limits for carbon monoxide and oxides of nitrogen, both of 
which have toxic properties which can be harmful to miners. The limits 
set for these gases, which are determined when the engine is operated 
at its maximum fuel-to-air ratio, are derived from existing 
Sec. 36.26(b) and now-removed Sec. 32.4(f). As noted in the proposal, 
applying these exhaust gas limits to diesel engines for use in outby 
areas is new.
    One commenter questioned why the proposal set the same undiluted 
exhaust gas limits for Category A and B engines, except that the carbon 
monoxide limit

[[Page 55420]]

was 0.30 percent for Category A engines, while the carbon monoxide 
limit for Category B engines was set at 0.25 percent. This aspect of 
the proposal, which is adopted without change in the final rule, 
recognizes a difference in the test procedure between Category A and B 
engines. As noted above, Category A engines must be designed to operate 
safely in face areas and return air courses where methane may be 
present. Thus, Category A engine testing is performed with 1.0 percent 
methane injected into the intake air. The methane acts as additional 
fuel in the engine, which affects the fuel-to-air ratio. This change in 
fuel-to-air ratio increases emission levels, especially carbon monoxide 
and oxides of nitrogen. Thus, the final rule technical requirements 
permit a slightly elevated carbon monoxide level for Category A engines 
during testing so as to avoid imposing an unnecessarily strict test 
requirement for this class of diesel engines. The ventilating air 
requirement, however, is based on the actual emissions measured during 
testing.
    The final rule also defines procedures to establish the ventilating 
air quantities necessary to maintain the gaseous emissions of diesel 
engines within existing required ambient limits. Emissions from both 
Category A and Category B engines are diluted to the same ambient 
levels when their ventilating air requirements are calculated. Like the 
proposal and consistent with the recommendations of the Diesel Advisory 
Committee, the final rule addresses this issue by requiring that a 
ventilation rate be set for each engine model. Under the final rule, 
this ventilation rate must appear on the engine's approval plate. The 
ventilation rate, calculated under Sec. 7.88 of the final rule, 
indicates the amount of air necessary to dilute carbon dioxide, carbon 
monoxide, nitric oxide, and nitrogen dioxide to within allowable 
levels. For consistency, the levels specified in the final rule are 
those set by existing Sec. 75.322. These exposure standards are based 
on the 1972 threshold limit values set by the American Conference of 
Governmental Industrial Hygienists (ACGIH) and have applied to 
underground coal mines for nearly 25 years. This aspect of the final 
rule comports with the recommendation of the Diesel Advisory Committee 
that gaseous diesel exhaust components not be treated differently from 
contaminants generated by other mining sources. The final rule does not 
adopt updated exposure standards at this time because this issue 
remains in the rulemaking process for Air Quality standards.
    The exposure levels adopted by the final rule for purposes of 
calculating the ventilation rate for an engine will lead to lower 
required air quantities for ventilating subpart E-approved engines, as 
compared to engines approved under now-superseded part 36. This is 
because engines previously approved under part 36 were required to 
dilute oxides of nitrogen and carbon dioxide to levels lower than 
currently specified by the threshold limit values (TLV<Register>'s) in 
Sec. 75.322. The ventilation rates set for engines under the final rule 
will be more precisely related to current exposure standards. In 
addition, Sec. 75.325(g) of the final rule revises the percentage of 
the approval plate air quantity that is required when multiple units of 
diesel equipment operate in the same air current. Finally, as discussed 
elsewhere, the final rule is designed to produce an integrated system 
of controls to protect miners from overexposure to harmful diesel 
emissions.
    Commenters generally accepted the value and purpose of setting a 
ventilation rate for each diesel engine model. Knowledge of the 
ventilation rate needed to control gaseous emissions to safe levels 
will allow comparison of the efficiency and ventilation demands of 
different engine models, and facilitate evaluation of their general 
ventilation needs during use. One commenter, however, urged that the 
gaseous ventilation rate for control of diesel engine exhaust gases not 
be part of the approval process. According to this commenter, existing 
ventilation and air quality standards are adequate.
    The final rule adopts the requirements for determining the 
ventilation rate necessary to dilute diesel engine exhaust 
contaminants. Ventilation systems provide different quantities of air 
at different locations in the mine. Knowing the ventilating air 
quantities needed for diesel-powered equipment will allow the mine 
operator to make informed decisions about equipment selection and 
utilization and mine ventilation.
    Other commenters, who acknowledged the purpose of establishing 
ventilation rates for approved diesel engines, recommended for the sake 
of clarity that the levels set for the gases be specified in the final 
rule. In the proposal, MSHA had set these levels by reference to the 
time weighted average (TWA) concentrations for the gases. The final 
rule adopts this suggestion and the levels for carbon dioxide, carbon 
monoxide, nitric oxide and nitrogen dioxide are specified in the final 
rule. The levels in the final rule are identical to the levels in 
existing Sec. 75.322, and MSHA intends that the levels in the final 
rule conform with any levels that may ultimately be updated. 
Specifically, if any of the levels for any of these contaminants are 
revised as part of MSHA's Air Quality rulemaking, MSHA intends to 
conform the levels in this section to any revised levels.
    The proposed requirement for fuel deration received no comments. 
The purpose of this requirement, which is adopted without change from 
the proposal, is to ensure that the fuel-to-air ratio does not increase 
due to the lower density of air at higher altitudes. Not correcting the 
maximum fuel delivery on the engine for higher altitude operation 
results in increased emission levels. The fuel injection rate 
established during the approval may be required to be reduced when the 
engine is used at a higher altitude.
    Implementing a recommendation of the Diesel Advisory Committee, the 
proposed rule also called for a particulate index to be set for 
approved diesel engines. The particulate index specifies the quantity 
of air needed to dilute the particulate generated by the engine to 1 
milligram of diesel particulate matter per cubic meter of air. The 
control of particulate matter in diesel engine exhaust was a 
significant issue for the Advisory Committee. The Committee concluded 
that whole diesel exhaust represents a probable risk for causing human 
lung cancer, and recommended that MSHA develop a regulatory scheme to 
monitor and control diesel particulate underground. The Committee did 
not recommend an exposure level, but did urge that consideration be 
given to what level of exposure to diesel particulate presents a health 
risk to miners. MSHA is currently developing regulations, separate from 
this rule, to address this issue.
    The Diesel Advisory Committee also recommended that a particulate 
index be set for engines so that the mining industry and MSHA could 
compare the particulate levels generated by different engines in terms 
of a ventilating air quantity. For example, if the particulate indices 
for diesel engines of the same horsepower were established as 7,500 
cubic feet of air per minute (cfm) and 12,000 cfm respectively, an 
equipment manufacturer, mine operator, and MSHA personnel could use 
this information, along with consideration of the type of machine the 
engines would power and the area of the mine in which it would be used, 
to make certain decisions. For example, a mine operator could use this 
information when choosing an engine to roughly estimate an engine's 
contribution of diesel particulate to the mine's total respirable

[[Page 55421]]

dust. MSHA would use this information when evaluating mine dust control 
plans. Equipment manufacturers can use the particulate index to design 
and install exhaust after-treatments.
    The final rule retains the proposed requirement for a particulate 
index to be set for approved diesel engines. Unlike the ventilation 
rate set for each engine, the particulate index value will not appear 
on the engine's approval plate. The particulate index, calculated under 
Sec. 7.89 of the final rule, indicates what air quantity is necessary 
to dilute the diesel particulate in the engine exhaust to 1 milligram 
of diesel particulate matter per cubic meter of air. This information 
will be available to the mining industry from the engine manufacturer 
and MSHA.
    Some commenters to the proposal objected to the use of a 
particulate index to establish required ventilation air quantities for 
diesel engines. These commenters noted that a diesel particulate 
permissible exposure level has not yet been set and maintained that 
suitable monitoring technology is not available for widespread field 
use. These commenters also urged that control of diesel particulate in 
underground mines be accomplished through a combination of measures, 
including fuel requirements, equipment design, and controls such as 
ventilation and equipment maintenance. The commenters recommended that 
the particulate index not be part of the engine ventilation rate, and 
concluded that such an index should be viewed as a guideline providing 
useful information about diesel engines. The commenters further 
suggested that additional evaluation be undertaken to determine 
appropriate procedures for setting a particulate index.
    The overall approach of the final rule is to control diesel 
emissions in the underground mine environment through various 
established methods, including those suggested by commenters. The 
information provided by the particulate index is part of the multi-
level approach recommended by the Diesel Advisory Committee.
    As explained above, the particulate index value determined for a 
diesel engine is intended to provide useful information about diesel 
engines, as the commenters suggested. In addition, the particulate 
index value does not appear on the equipment's approval plate and 
therefore is not considered in setting the engine's required 
ventilation rate.
    Section 7.85  Critical characteristics. Critical characteristics, 
which are specified for all part 7-approved products, are those 
features or specifications which, because of their importance to proper 
operation of the equipment, must be inspected or tested on each unit 
manufactured. The proposal called for inspecting or testing each diesel 
engine to verify that the fuel rate is set to altitude, and the fuel 
injection pump adjustment is sealed, if applicable. No comments were 
received on this aspect of the proposal, and the final rule adopts the 
proposal without substantive change. Instead of requiring the fuel rate 
to be set to altitude, the final rule specifies that the fuel rate be 
properly set.
    As discussed elsewhere in this preamble, the rate of fuel delivery 
to a diesel engine significantly affects its gaseous and particulate 
emission. As noted earlier, correct adjustment of the fuel injection 
pump is essential to the efficient operation of diesel engines.
    Inspecting or testing the proposed critical characteristics for 
diesel engines approved under part 7, subpart E reasonably ensures that 
the performance and emission characteristics of production engines will 
be equivalent to those of the engine tested for approval. As a result, 
miners are protected against harmful exposure to diesel emissions.
    No comments were received on this aspect of the proposal, which is 
adopted by the final rule, with the change noted above.
    Section 7.86  Test equipment and specifications. This section 
adopts the measurement and evaluation methods for emissions from diesel 
engines as described in ISO 8178-1. The final rule describes the 
apparatus, or test cell, required for testing diesel engine 
performance, and sets the specifications for operating this testing 
equipment to perform steady-state tests for both gaseous and 
particulate emissions.
    The major components of a test cell are a dynamometer with engine 
operating controls, and gaseous and particulate emission measurement 
systems. This test cell is used to perform the test required by 
Secs. 7.87, 7.88, and 7.89 of the final rule. Most engine testing 
laboratories today have the equipment and meet the specifications 
called for by ISO 8178-1 and the final rule.
    The final rule's test cell requirements are substantially the same 
as the proposed requirements, except that the specifications for the 
testing apparatus and test conditions are revised to conform with ISO 
8178-1. Commenters to the proposal did not direct attention to these 
requirements, but did express concern about correlating the proposed 
rule test requirements and Environmental Protection Agency diesel 
engine tests, and recommended that the MSHA procedures conform to 
internationally accepted test procedures. The adoption of the ISO 8178-
1 provisions eliminates this issue and is responsive to commenters' 
concerns.
    Like the proposal, the final rule also sets specifications for the 
fuel to be used during testing of diesel engines. The proposed rule 
would have required No. 2D diesel fuel with certain properties. A 
uniform test fuel is important to obtaining repeatable test results and 
test data that can be compared. Commenters did not direct their 
attention to this aspect of the proposal, except that they generally 
encouraged adoption of international standards to the extent possible.
    The final rule revises the proposed requirements for diesel engine 
test fuel to conform with the fuel requirements in Sec. 75.1901. 
Section 75.1901 of the final rule specifies the use of diesel fuel 
containing no more than 0.05 percent sulfur. Under this section, diesel 
fuel used for engine testing must also be low in sulfur content. In 
addition, the properties specified for test fuel conform with the test 
fuel EPA requires for testing diesel engines that use low sulfur fuel. 
Thus, the final rule will not require testing laboratories to acquire 
special fuel to comply with the final rule.
    The final rule also adopts the proposal that Category A engines, 
which are intended for operation in areas of mines where concentrations 
of methane gas could be encountered, be tested with 1.0 percent of 
methane added to the engine's intake air. As noted above, this addition 
to the ISO 8178 test procedure adopted by the final rule should present 
no technical difficulties for manufacturers or third-party 
laboratories. MSHA, however, will provide technical assistance for 
setting up this aspect of the test procedure upon request.
    Metering in 1.0 percent of methane to the intake air of Category A 
engines replicates a foreseeable operating condition in underground 
mines. In addition, methane gas acts as a fuel when it is aspirated 
into a diesel engine, increasing its output of carbon monoxide and 
oxides of nitrogen. These emission effects need to be accounted for in 
determining the gaseous ventilation rate for Category A engines.
    Section 7.87  Test to determine the maximum fuel-to-air ratio. As 
noted earlier, the tests prescribed by this section are performed using 
the test cell meeting the requirements of Sec. 7.86. Determining the 
maximum fuel-to-air ratio for diesel engines is essential to 
controlling harmful diesel engine emissions. Too rich a fuel and air

[[Page 55422]]

mixture produces engine exhaust with elevated levels of carbon monoxide 
and oxides of nitrogen.
    Under this section, engines are required to be operated at several 
speed/torque conditions to determine the concentrations of carbon 
monoxide and the oxides of nitrogen. Acceptable performance is achieved 
when the levels of these exhaust gases do not exceed the limits set by 
Sec. 7.84(b) of the final rule throughout the operational range of the 
engine.
    Commenters did not address the proposed test to determine the 
maximum fuel-to-air ratio for diesel engines. The final rule adopts the 
proposal without change.
    Section 7.88  Test to determine the gaseous ventilation rate. The 
test to determine the gaseous ventilation rate for a diesel engine is 
required by the final rule to be performed using the test cell required 
by Sec. 7.86. This test may be performed together with the test to 
determine the particulate index required by Sec. 7.89.
    The test required by this section measures the undiluted exhaust 
gas concentrations of carbon monoxide, carbon dioxide, nitric oxide, 
and nitrogen dioxide in the exhaust. These constituent gases of diesel 
engine exhaust are potentially harmful to miners in the confined 
environment of underground mines.
    In accordance with Sec. 7.86, exhaust gas measurements must be made 
at 8 specified points while the engine is operated at each rated speed 
and horsepower requested by the approval applicant. For Category A 
engines, 1.0 percent methane is added to the engine's intake, as 
discussed above.
    Like the proposal, the final rule specifies the calculations to be 
performed using the results obtained from the test procedure. These 
calculations produce a gaseous ventilation rate for the diesel engine. 
As discussed above, the ventilation rate indicates the amount of 
ventilating air necessary to dilute carbon monoxide, carbon dioxide, 
nitric oxide and nitrogen dioxide to within permitted levels. The 
ventilation rate for each approved Category A or B diesel engine will 
appear on the engine's approval plate. Knowledge of the ventilation 
rate needed to control gaseous emissions to safe levels will allow 
comparison of the efficiency and ventilation demands of different 
engine models, and their general ventilation needs during use can be 
evaluated.
    As discussed above, commenters generally accepted the value and 
purpose of setting a ventilation rate for each diesel engine model. One 
commenter urged that the ventilation rate not be part of the approval 
process, while others supported the approach taken in the proposed and 
final rules. These commenters, however, suggested that the levels for 
the exhaust gases be stated in the final rule. The final rule adopts 
this suggestion in Sec. 7.84(c).
    Section 7.89  Test to determine the particulate index. Like the 
other engine tests prescribed by the final rule, the test to determine 
the particulate index for an engine is required by the final rule to be 
performed using the test cell required by Sec. 7.86. As noted above, 
this test may be performed concurrently with the test to determine an 
engine's gaseous ventilation rate required by Sec. 7.88.
    The test required by this section measures the amount of 
particulate in the engine's exhaust when it is operated at eight 
specified operating conditions. For Category A engines, 1.0 percent 
methane is added to the engine's intake, as discussed above.
    The proposed rule would have required that the particulate index be 
determined using a different set of test points than those used to 
determine the gaseous ventilation rate. The particulate index tests 
were based on a cycle of 10 test points. In response to commenters' 
suggestions that the particulate and gaseous emissions tests be 
conducted using the same test cycle and internationally accepted test 
procedures, the final rule adopts the same ISO 8178-4, 8-point test 
cycle for both the particulate and gaseous emissions tests.
    The Diesel Advisory Committee observed that whole diesel exhaust 
represents a probable risk for causing human lung cancer. While 
proposing no specific exposure level, the Diesel Advisory Committee 
recommended control of diesel particulate in engines used underground 
through a combination of measures, including equipment design.
    Like the proposal, the final rule does not set a particulate limit 
for engines. Instead, the final rule specifies the calculations to be 
performed using the results obtained from the test procedures in this 
section. From the calculations, a particulate index is derived. As 
discussed above, the particulate index for an engine does not appear on 
its MSHA approval plate. This information will be available, however, 
from MSHA and the engine manufacturer.
    Section 7.90  Approval markings. This section requires that each 
approved diesel engine be identified with a permanent approval plate 
containing certain information. Approval markings to identify equipment 
appropriate for use in mining have been used for more than 85 years, 
and are routinely relied upon by users of mining equipment as well as 
state and federal inspection authorities.
    The information required to be displayed on diesel engine approval 
plates includes the MSHA-assigned approval number, together with the 
engine's model number, ventilation rate, rated power, high idle 
setting, and the altitude above which the engine must be derated. 
Including these specifications on diesel engine approval plates gives 
engine users convenient, immediate access to information important to 
proper maintenance and operation of diesel engines.
    Commenters directed little attention to this aspect of the 
proposal, which is adopted without change in the final rule. Commenters 
who objected to setting a ventilation rate for diesel engines as part 
of the approval process repeated this concern with respect to the 
requirement for the ventilation rate to appear on engine approval 
plates. As discussed above, setting a gaseous ventilation rate for 
diesel engines comports with the recommendations of the Diesel Advisory 
Committee and provides diesel equipment users with information 
important to protecting miners. Knowledge of the rate of ventilation 
needed to control the gaseous exhaust emissions of a diesel engine 
facilitates comparison of the efficiency and ventilation demands of 
different engine models.
    The other information required by the final rule to appear on an 
engine's approval plate likewise provides engine users needed data. The 
high idle setting informs maintenance personnel of the engine speed 
appropriate for conducting several of the tests to be performed as part 
of the engine's permissibility checklist. Together, an engine's 
approval number, model number, and its rated power and speed facilitate 
use of the manufacturer's maintenance procedures. The maintenance 
procedures, along with the altitude above which the engine must be 
derated, specify the adjustments which must be made to ensure that an 
engine continues to operate in approved condition.
    Burden hours required to make and mount MSHA approval plates are 
assigned OMB control number 1219-0100.
    Section 7.91  Post-approval product audit. This section 
incorporates the standard audit requirement for part 7-approved 
equipment, specifying that approval holders must make a diesel engine 
available for audit by MSHA, at no cost to the Agency. The obligation 
to

[[Page 55423]]

supply an engine for audit under this section arises only upon request 
by MSHA, and is limited to no more frequently than once a year, except 
for cause. Under existing Sec. 7.8(b), the approval holder may observe 
any tests conducted under the audit.
    Post-approval audits are a critical part of MSHA's quality control 
program for approved equipment. By inspecting and testing an engine for 
continuing compliance with its approval specifications, potential 
problems can be detected and confidence in the approval process is 
maintained. Since the inception of post-approval product audits under 
part 7, MSHA has detected numerous discrepancies, which have been 
effectively corrected.
    Commenters directed no attention to this aspect of the proposal, 
which is adopted without change from the proposal.
    Section 7.92  New technology. This section is designed to 
facilitate the introduction of new technology or new applications of 
existing technology. It allows MSHA to approve a diesel engine that 
incorporates technology for which the requirements of subpart E are not 
applicable, provided that MSHA determines the engine is as safe as one 
which meets the requirements of subpart E. To make this determination, 
MSHA develops appropriate technical requirements and test procedures 
when novel designs are submitted for approval. Experience with this 
provision under existing regulations has shown that new innovations can 
be effectively evaluated and made available for use in a prompt 
fashion, thus serving the best interests of miners' safety and health.
    Commenters supported this aspect of the proposal, stressing that 
research and technological improvements in diesel engines can be 
expected. The final rule adopts the proposal without change.
Subpart F Overview
    Subpart F of the final rule amends existing part 7, which specifies 
testing by the approval applicant or a third party. As an amendment to 
the existing regulations, the general administrative provisions of 
subpart A of part 7 apply to these new subpart F application 
requirements.
    Subpart F establishes design and performance requirements for MSHA 
approval of ``diesel power packages'' for use in areas of underground 
coal mines where permissible electrical equipment is required by 
existing safety standards. A ``diesel power package'' is a diesel 
engine, together with the attached safety components, such as flame 
arresters, spark arresters, surface temperature controls, shut down 
systems, and the exhaust cooling system that make a diesel engine 
explosion-proof and reduce the engine's surface temperature to a safe 
level. Like the proposal, the final rule requirements for diesel power 
packages are largely derived from existing MSHA approval regulations in 
part 36, which apply to diesel engines for use in gassy underground 
mines. The final rule is also consistent with current MSHA practices 
for coal mines using diesel-powered equipment and with the 
recommendations of the Diesel Advisory Committee. The Advisory 
Committee specifically recommended an approval program for diesel power 
packages.
    Commenters generally accepted the proposal for MSHA approval of 
diesel power packages, recognizing the need for diesel-powered 
equipment used in underground coal mines to meet critical 
specifications and to be properly tested for safe operation in a 
potentially explosive atmosphere. Some commenters directed their 
attention to the effective date of subpart F, expressing concern about 
the availability of commercial testing facilities. For the reasons 
discussed below, the final rule does not adopt an extended phase-in 
period. However, accommodations are made in the final rule to simplify 
the implementation of testing in the private sector, and MSHA will 
continue to perform diesel power package testing to subpart F 
specifications for up to 3 years, pending the development of private 
sector resources.
    Other commenters recommended that diesel engine exhaust after-
treatment devices, such as particulate filters or catalytic converters, 
be required as part of diesel power packages. These commenters also 
suggested that the ventilation rate and particulate index set under 
Secs. 7.88 and 7.89 of the final rule credit the use of such devices.
    The final rule responds to these comments in part. Under the MSHA 
approval program in subpart E, MSHA will evaluate exhaust gas and 
particulate controls, provided these devices are integral to the engine 
design and are part of normal production engines. The effectiveness of 
such controls will also be considered in setting the engine's 
ventilation rate and particulate index. This approach will ensure that 
the controls are compatible with the engine and are effective. MSHA has 
already approved, under existing regulations, engines which incorporate 
techniques such as electronic fuel injection systems. Exhaust after-
treatment devices that are not part of an engine's design and 
production have been developed which can reduce the particulate matter 
in diesel engine exhaust. Also, catalytic converters are available 
which can be added to engines to reduce the levels of some harmful 
gaseous emissions. MSHA encourages the use of these devices, and under 
existing regulations has approved, as safe, several power packages that 
utilize catalytic converters and particulate filters. However, under 
the final rule MSHA will not evaluate the effectiveness of these 
exhaust after-treatment devices. Exhaust after-treatment devices 
encompass a wide range of concepts that have demonstrated varying 
degrees of effectiveness and reliability. The evaluation of these types 
of after-treatment devices is beyond the scope of a part 7 approval 
program.
    For the same reasons, the final rule does not adopt a commenter's 
suggestion that the particulate index for an engine be adjusted to 
reflect the use of a diesel particulate filter. Also, the particulate 
index for an engine is intended to be used by manufacturers and mine 
operators as an aid for, among other things, selecting appropriate 
after-treatment devices such as particulate filters. Therefore, under 
the final rule the particulate index for an engine will indicate the 
particulate contained in the raw engine exhaust.
    Other aspects of the final rule will, however, recognize exhaust 
after-treatment controls. The positive effects of catalytic converters 
in lowering levels of harmful exhaust gases may be considered under 
Sec. 75.325(i) for reducing the quantity of ventilating air required 
where multiple pieces of diesel-powered equipment are in use. Also, 
particulate filters can be effective in maintaining compliance with the 
respirable dust standard set by existing Sec. 70.100.
    During the course of this rulemaking, the question has been raised 
as to whether the final rule should require that some or all diesel 
engines be equipped with particulate filters. As noted above, MSHA 
encourages the use of such filters and other emission controls. 
However, the proposed rule did not raise this issue and MSHA received 
only limited comment regarding the appropriate role of diesel 
particulate filters. The final rule, therefore, does not require the 
use of these filters. However, MSHA is currently developing a proposed 
rule to address control of miners' exposure to diesel particulate. This 
rulemaking will afford an opportunity to fully develop this issue.
    Other commenters suggested that diesel engine cooling system

[[Page 55424]]

components, such as radiators, not be included as part of the approval 
of diesel power packages so as to permit changes in cooling system 
components to be made in the field without affecting the engine's 
approval. The final rule does not adopt this suggestion. The inter-
relationship of the components in the cooling system of a diesel engine 
is critically important to controlling power package surface 
temperatures, which, when elevated, can lead to a fire. Consequently, 
the engine cooling system components must be considered an integral 
part of a diesel power package. This aspect of the final rule does not 
prohibit field radiator changes, provided that the inter-relationship 
of the engine's cooling system components is maintained in approved 
condition.
    A number of minor changes are made in Secs. 7.97, 7.98, 7.100, 
7.101, 7.102, and 7.103 of the final rule to clarify the requirements 
of these sections. Substantive changes to these sections are discussed 
in the section-by-section discussion which follows.
    Section 7.95  Purpose and effective date. The final rule's part 7, 
subpart F approval requirements apply to diesel power packages intended 
for equipment used in areas of underground coal mines where this 
equipment is required to be permissible. The design, performance and 
testing requirements of this section are effective November 25, 1996. 
MSHA will begin accepting applications under new subpart F immediately. 
To accommodate all interests, the Agency also will complete any in-
house part 36 safety component certification applications, or evaluate 
such applications under new subpart F, at the applicant's choice. As 
noted elsewhere in this preamble, the requirements for approved diesel 
power packages in equipment used in underground coal mines become 
effective in 3 years.
    As noted above, several commenters urged that an extended phase-in 
period of several years be included in the final rule. According to the 
commenters, a phase-in period is needed to allow for the development of 
competent third- party testing facilities, particularly with respect to 
explosion-proof testing. Other commenters suggested that subpart F be 
made effective immediately, so as to accelerate conformance to the new 
requirements for the benefit of miners' safety.
    A number of the final rule's test requirements can be performed 
effectively with inexpensive, simple test equipment or facilities, or 
with the power package installed in the mining equipment. For example, 
the static pressure test required by Sec. 7.104 to evaluate the 
structural integrity of power package components can be performed using 
currently available hand pump devices. Likewise, explosion-proof 
testing can be performed in inexpensive test chambers of relatively 
simple design.
    Nonetheless, MSHA recognizes that some testing capabilities are not 
immediately available in the private sector, such as surface 
temperature testing and exhaust gas cooling efficiency testing with 
methane gas injection in the intake air. To facilitate the approval of 
power packages and accommodate the needs of applicants, MSHA may be 
consulted for simple alternative procedures which can be used to 
provide the same results. In addition, MSHA will perform the tests 
required by subpart F for diesel power package approval at its Approval 
and Certification Center upon request by applicants. MSHA anticipates 
providing these test services, for the fees set in accordance with 30 
CFR Part 5, for up to 3 years, or until private sector testing 
capability is available. MSHA reserves the right to determine when 
competent private sector testing capability is available and to 
discontinue MSHA testing.
    Section 7.96  Definitions. In addition to the existing definitions 
in Secs. 7.2 and 7.82, this section of the final rule sets out and 
clarifies the key terms used in subpart F.
    Commenters did not direct specific attention to this aspect of the 
proposal. The final rule adopts the proposed definitions, with five 
exceptions, adds two terms and definitions, and deletes three 
definitions from the proposal which now appear in subpart E. These 
changes are intended to add flexibility to the final rule and respond 
to confusion among some commenters with respect to the substantive 
requirements of subpart F.
    The definition for ``exhaust conditioner'' has been revised to 
remove the words ``corrosion-resistant.'' The requirement for the 
exhaust conditioner to be made of corrosion-resistant material is 
adopted from the proposal in Sec. 7.98(s)(4)(i). The definitions for 
``exhaust system'' and ``intake system'' are revised to include the 
phrase ``but is not limited to'', to recognize the use of components 
not otherwise mentioned in the definitions for these terms. The term 
``explosive mixture'' has been changed to ``flammable mixture'' to 
conform with part 36, and the definition for this term has been 
modified with the non-substantive change of removing the word 
``violently.'' The definition for ``fastening'' has been modified for 
the sake of clarity to remove the words ``device such as'' when 
referring to bolts, screws, or studs. The term ``high idle speed/no 
load'' has been revised to ``high idle speed.'' This is another non-
substantive change, since ``no load'' is specified in the definition of 
the term. New definitions for ``dry exhaust conditioner'' and ``wet 
exhaust conditioner'' are added to the final rule to more clearly 
differentiate between the requirements for these systems. Under the 
final rule, a dry exhaust conditioner is defined as a device which 
cools exhaust gases without direct contact with water, such as a heat 
exchanger. A wet exhaust conditioner is defined as a system which cools 
exhaust gases through direct contact with water. Minor changes to the 
definitions for ``step (rabbet) joint'' and ``threaded joint'' have 
been made for the sake of clarity. The terms ``corrosion-resistant 
material,'' ``idle speed/no load,'' and ``rated speed'' and their 
definitions are deleted from subpart F. These terms are common to both 
subparts E and F, and have already been defined in subpart E. Section 
7.96 has been modified to incorporate the definitions of subpart E, 
Sec. 7.82.
    Section 7.97  Application requirements. This section is derived 
from existing part 36 and requires that an application for approval of 
a diesel power package contain sufficient information to document 
compliance with the technical requirements of the final rule. The list 
of information specified for inclusion in the approval application, 
which is revised from the proposal in response to commenters and to 
fully identify the engine and the fan blade material, is intended to 
help applicants supply the data necessary for a prompt evaluation. The 
final rule permits applicants to submit composite drawings. This 
approach reduces paperwork, affords applicants flexibility in the 
preparations of their drawings, and has proven to be effective in other 
MSHA approval programs.
    Like existing part 7 and other MSHA approval standards, the 
documentation formulated in the application process under Sec. 7.97 
forms the basis for MSHA's approval of a diesel power package. Approved 
diesel power packages must be manufactured in accordance with the 
specifications contained in the approval and, once put into service, 
approved power packages must be maintained and operated within the 
parameters set in the MSHA approval.
    The paperwork hours in the approval application, including test 
requirements, are assigned OMB control number 1219-0100.
    Section 7.98  Technical requirements. This section of the final 
rule sets specific technical requirements

[[Page 55425]]

for diesel power packages. Diesel power packages are intended for use 
with Category A engines so that they can be operated safely and not 
create a fire or explosion hazard. Consistent with the Advisory 
Committee's recommendation that permissible diesel equipment be 
required in areas of underground coal mines where permissible electric 
equipment is required, the final rule's technical specifications 
introduce many of the safety features currently required for 
permissible electric-powered equipment.
    Like the proposal, the final rule is derived largely from existing 
technical requirements in part 36 for diesel-powered equipment intended 
for use in gassy non-coal mines. The final rule also addresses the 
hazard of combustible coal dust by specifying a maximum surface 
temperature of 302  deg.F (150  deg.C). This is the same technical 
requirement applied to permissible electric-powered equipment. Other 
aspects of the final rule set specifications necessary to control 
engine surface temperatures, sparking, and the passage of flame from 
the exhaust system or components to the external atmosphere. Any of 
these conditions could ignite an explosion or fire in the underground 
coal mine environment.
    Commenters generally accepted the proposed technical requirements, 
which, as noted above, are based on long-standing regulations which 
have been proven effective and workable. Commenters did, however, raise 
several issues.
    Some commenters sought wider tolerances for explosion-proof 
enclosures in diesel power packages, citing experience in the United 
States and Europe. These commenters directed their attention to the 
proposed specifications for joints in engine exhaust systems, and 
suggested that MSHA review the proposed specification of 0.004 inches 
for maximum clearance for joints all in one plane.
    The final rule retains this specification, which has proven to be 
effective for decades. Commenters offered no basis for the 
recommendation for a wider tolerance.
    Other commenters suggested that electric starting devices for 
diesel engines be prohibited. The proposed rule recognized the 
conventional use of hydraulic, pneumatic or other mechanically actuated 
starting mechanisms, but also retained the flexibility to evaluate 
other means of starting under Sec. 7.107 of the rule concerning new 
technology. This aspect of the proposal differs from the existing part 
36 regulations from which this proposal was derived.
    The final rule is intended to serve as a flexible set of 
regulations that will continue to be workable over a period of years. 
Throughout the final rule MSHA has adopted the more current practices 
and, where appropriate, provides that alternatives may be developed 
which are safe and effective. With this in mind, the final rule does 
not expressly prohibit the use of electric starting devices for diesel 
engines, adopting the proposal to permit MSHA to evaluate other 
starting mechanisms. Such alternatives are subject to evaluation under 
Sec. 7.107 and must be found by MSHA to be as safe as the pneumatic and 
hydraulic starting mechanisms presently in use.
    Some commenters asked for clarification of proposed paragraph (i) 
with respect to the safety shutdown system required for diesel power 
packages. The safety shutdown system is required to automatically shut 
off the fuel supply and stop the engine in response to certain 
dangerous engine conditions. MSHA intended in the proposal, and the 
final rule clarifies, that the shutdown system must respond to both 
high exhaust temperature and low water level in the engine's exhaust 
conditioner. Either of these conditions can rapidly lead to a fire or 
explosion hazard.
    In addition, the final rule has been revised from the proposal to 
cover other safety system shutdowns that may be installed by the 
applicant. Section 75.342 requires methane monitors on some permissible 
equipment, and the final rule requires permissible equipment to be 
provided with a fire suppression system meeting the requirements of 
Sec. 75.1911. Both of these standards specify that the diesel engine 
must shut down when either an elevated level of methane is encountered 
or when the fire suppression system is actuated. This requirement will 
most likely be satisfied by a connection to the safety shutdown system. 
The technical requirements of this rule now cover these additional 
sensors.
    Another commenter suggested that the safety shutdown system include 
automatic brake lock-up to prevent diesel-powered equipment from 
rolling. This aspect of a machine's safety is evaluated under the 
existing requirements of part 36 and is not part of a diesel
power-
package approval. Thus, the final rule does not adopt this suggestion.
    The final rule adopts clarifying revisions in addition to changes 
made in response to commenters. In several instances more precise 
language is adopted to differentiate between requirements for wet and 
dry exhaust conditioner systems. Proposed Sec. 7.98(d) has been revised 
in the final rule to refer to ``nonmetallic rotating parts'' instead of 
``fans'', to conform with other MSHA regulations. Paragraph (p)(2)(ix) 
has been revised to require that the minimum thread engagement of 
fastenings must meet the requirements of the explosion tests in 
Sec. 7.104. This is a correction. This change conforms to paragraph 
(p)(2)(viii), which requires both tests for acceptance of a minimum 
thread engagement of fastenings less than \3/8\ inch. In addition, 
paragraph (q)(7) of the final rule does not retain the proposed 
requirement that a ``minimum of four fastenings'' be used for 
explosion-proof joints. MSHA's experience shows that flange designs 
with fewer than four fastenings have proven to be effective. Paragraph 
(r)(5) has been revised to note that the opening for connection of a 
gage to measure the intake vacuum must be closed by a plug or other 
suitable device that is sealed or locked in place except when in use. 
This language conforms to the language of part 36, and closing of this 
opening is necessary to perform certain tests in this subpart. 
Paragraph (s)(1) has been revised to require that the flame arrester 
prevent the discharge of glowing particles, conforming it to the 
requirement in part 36. Finally, paragraph (s)(5) has been revised to 
note that the opening for connection of a gage to measure the 
backpressure must be closed by a plug or other suitable device that is 
sealed or locked in place except when in use. This language also 
conforms to part 36, and is needed to perform some of the tests under 
this subpart.
    Section 7.99  Critical characteristics. Critical characteristics, 
which are specified for all part 7-approved products, are those 
features or specifications which, because of their importance to proper 
operation of the equipment, must be inspected or tested on each unit 
manufactured. The proposal focused on power package features essential 
to preventing fires and explosions in the underground coal mine 
environment, such as flame-arresting path clearances and the explosion-
proof integrity of the power package. Commenters did not direct their 
attention to this aspect of the proposal, which is adopted without 
change in the final rule.
    Section 7.100  Explosion tests. This section describes the tests to 
be performed on diesel power packages to ascertain whether they are 
explosion-proof, as specified by the technical

[[Page 55426]]

requirements in Sec. 7.98. Like the proposal, the final rule is derived 
from existing Sec. 36.46. Using an explosive mixture of natural gas and 
air, or methane and air, the tests prescribed by the final rule 
determine the power package's integrity in the event of an explosion 
inside the intake or exhaust system. This could be caused by an engine 
backfire during starting or ingestion of methane into the engine while 
it is running. The prescribed tests determine whether flame arresters 
and joints are capable of preventing propagation of the internal 
explosion to the surrounding atmosphere. These tests also determine the 
lowest water level in the exhaust conditioner that will act effectively 
as a flame arrester, and the peak explosion pressures generated in each 
segment of the intake and exhaust system. Excessive pressures may be an 
indication of a design flaw.
    Commenters did not raise issues regarding the proposed explosion 
tests. However, the final rule includes one change from the proposal to 
better ensure the ability of a diesel power package to withstand an 
internal explosion, and another change to revise the speeds at which 
dynamic tests are to be conducted. The final rule also includes non-
substantive changes for clarification and to conform the final rule 
with existing MSHA regulations.
    Paragraphs (a)(2) (v) and (vi) of the final rule specify an 
internal peak pressure of 110 psig instead of the proposed 125 psig, 
during power package explosion-proof testing. Excessive internal 
pressures during explosion-proof testing indicate the potential for 
failure of the diesel power package in use, with potentially 
catastrophic results in the underground coal mine environment. Lowering 
the peak pressure expected during explosion-proof testing recognizes 
that diesel power package designs differ and that it is difficult to 
select the optimum location for pressure measurements. When pressures 
greater than 110 psig are measured during testing, the final rule 
specifies redesign of the system to reduce the pressure or more 
rigorous testing to verify the integrity of the system. Due to the 
critical nature of this test, MSHA has adopted the same approach in its 
explosion-proof test requirements for electric motors. The final rule 
conforms these like requirements.
    Paragraph (a)(2)(vii) of the final rule requires that dynamic tests 
be conducted at two speeds--1800<plus-minus>200 RPM and 
1000<plus-minus>200 RPM--instead of at rated speed and 50 percent of 
rated speed specified in the proposal. The speeds set by the final rule 
correspond to the speeds at which dynamic tests are performed 
successfully at MSHA facilities. Also some test facilities may not be 
capable of performing tests at the rated speed called for by the 
proposal. This change is also reflected in paragraphs (a)(3)(iii) (A) 
and (B).
    For clarification, the final rule also adopts more precise language 
to identify requirements which apply to wet exhaust conditioners, 
distinguishing them from dry systems. The final rule also defines 
natural gas that may be used in explosion-proof testing in a manner 
that better recognizes the variables in the make-up of the hydrocarbons 
found in natural gas. As a result, the final rule affords greater 
flexibility for manufacturers and testing laboratories.
    Section 7.101  Surface temperature tests. This section describes 
the tests necessary to ascertain that diesel power packages will not 
create a fire hazard in underground coal mines due to coal dust or 
other combustible materials contacting hot surfaces. Like the proposal, 
the final rule is derived from Sec. 36.48, and sets a maximum external 
surface temperature of 302  deg.F (150  deg.C). The test protocol 
simulates the operation of a diesel power package under heavy use 
conditions. A note has been added to this section to alert the 
applicant that this test may be done simultaneously with the exhaust 
gas cooling efficiency test described in Sec. 7.102 of the final rule.
    Commenters did not direct their attention to this aspect of the 
proposal. The final rule is unchanged from the proposal, except for a 
non-substantive clarifying change regarding wet exhaust conditioners 
and the elimination of the reference to the use of natural gas. A 
reference to natural gas, which consists primarily of methane, is 
redundant. Instead, the final rule specifies the percentage of methane 
to be added to the intake. Elimination of the reference to natural gas 
also conforms this section to similar tests, which also determine 
engine performance and which only specify methane, in subpart E of part 
7.
    Section 7.102  Exhaust gas cooling efficiency test. This section 
describes the test procedures for measuring the temperature of the 
exhaust gas at the discharge point from the exhaust conditioner. 
Acceptable performance under this test is exhaust gases that do not 
exceed 170  deg.F (76  deg.C) for power packages with a wet exhaust 
conditioner, and 302  deg.F (150  deg.C) for a dry system. The proposed 
and final rules are derived from existing Sec. 36.47 and address the 
hazard of hot exhaust gases creating a fire or explosion hazard.
    Commenters raised only one issue concerning this aspect of the 
proposal, suggesting clarification of the different performance 
requirements for wet and dry exhaust conditioners. The final rule 
adopts this suggestion.
    Section 7.103  Safety system controls test. This section is derived 
from Sec. 36.47 and describes tests to evaluate the performance of the 
safety shutdown systems required for diesel power packages. As 
discussed above, these systems automatically shut down a diesel engine 
in response to potentially dangerous conditions, such as overheating. 
The tests prescribed introduce failure modes, such as loss of engine 
coolant, and initiate the safety system. Acceptable performance is 
achieved when the safety system automatically shuts down the engine 
before the technical requirements for approval are exceeded.
    Commenters recommended that the final rule more clearly delineate 
the different requirements for wet and dry exhaust conditioners. The 
final rule adopts this suggestion in paragraphs (a)(3), (a)(4), (b)(2), 
and (b)(3).
    Commenters also suggested that paragraph (a)(7)(ii) be amended to 
include a caveat about the surface temperature of a turbocharger not 
exceeding 302 deg. F (150 deg. C). This comment is not adopted because 
the final rule addresses surface temperature control under Sec. 7.101 
and requires that all external surfaces of power packages, including 
turbochargers, not exceed 302  deg.F (150 deg. C). Paragraph (b)(7) has 
been revised to accept starting mechanisms constructed of nonsparking 
materials in addition to starting mechanisms that prevent the 
engagement of the starter while the engine is running. This revision 
conforms to Sec. 7.98(j)(1), which permits both options under the final 
rule, as it would have under the proposal.
    Section 7.104  Internal static pressure test. This section 
describes tests to determine if the design of the intake and exhaust 
system components of diesel power packages is structurally sound. The 
prescribed tests specify internally pressurizing each segment of the 
intake and exhaust system. The pressure required to be applied is four 
times the maximum pressure observed in the tests performed under 
Sec. 7.100, or 150 psig (<plus-minus>5 psig), whichever is less. 
Acceptable performance is based on an assessment of key points in the 
intake and exhaust system, such as joints and welds, for evidence of 
leakage or damage.
    Commenters raised no issues with respect to the proposal. Paragraph 
(b)(2)(vi) has been added to limit

[[Page 55427]]

permanent distortion of any planar surface of the diesel power package 
to 0.04-inches/linear foot or less. This change conforms this 
requirement to the same requirement applied to the explosion tests in 
Sec. 7.100(b)(7).
    Section 7.105  Approval markings. This section requires that each 
approved diesel power package be identified with a permanent approval 
plate inscribed with the MSHA approval number. If the power package 
includes a wet exhaust conditioner that functions as an exhaust flame 
arrester, the final rule requires that the approval plate also indicate 
the grade limitation for the power package. This information is 
important so that users are aware of the maximum grade on which the 
exhaust conditioner will be effective as a flame arrester.
    As noted elsewhere in this preamble, approval markings have been 
used for more than 85 years, and are routinely relied upon by users of 
mining equipment as well as state and federal authorities to identify 
equipment appropriate for use in mining.
    Another commenter suggested clarification of the proposal with 
respect to the grade limitation for certain diesel power packages. The 
final rule has been revised in response to this commenter to clarify 
that the grade limitation applies to systems which use a wet exhaust 
conditioner as a flame arrester. No grade limitation is appropriate for 
power packages with a dry exhaust conditioner.
    Burden hours required to make and mount MSHA approval plates are 
assigned OMB control number 1219-0100.
    Section 7.106  Post-approval product audit. This section 
incorporates the standard audit requirement for part 7-approved 
equipment, specifying that approval holders must make a diesel power 
package available for audit by MSHA, at no cost to the Agency. The 
obligation to supply a power package under this section arises only 
upon request by MSHA, and is limited to no more frequently than one a 
year, except for cause. Under existing Sec. 7.8(b), the approval holder 
may observe any tests conducted under the audit.
    Post-approval audits are a critical part of MSHA's quality control 
program for approved equipment. By inspecting and testing a diesel 
power package for continuing compliance with the specifications for its 
approval potential problems can be detected and confidence in the 
approval process is maintained. Since the inception of post-approval 
product audits under part 7, MSHA has detected numerous discrepancies 
which have been effectively corrected.
    Commenters directed no attention to this aspect of the proposal, 
which is adopted without change from the proposal.
    Section 7.107  New technology. This section is designed to 
facilitate the introduction of new technology or new applications of 
existing technology. It allows MSHA to approve a diesel power package 
that incorporates technology for which the requirements of subpart F 
are not applicable, provided that MSHA determines the power package is 
as safe as one which meets the requirements of subpart F. To make this 
determination, MSHA develops appropriate technical requirements and 
test procedures when applications for the approval of novel designs are 
submitted. To provide confidence in the adequacy of the design, such 
tests may be required to be performed by MSHA. Experience with this 
provision under existing regulations has shown that technological 
innovations can be effectively evaluated and made available for use in 
a prompt fashion, thus serving the best interests of miners' safety and 
health. Commenters generally supported this aspect of the proposal, and 
the final rule adopts the proposal without change.
    Section 7.108  Power package checklist. This section requires that 
approved diesel power packages be accompanied by a description of the 
features which must be checked and tests that must be performed to 
ascertain that the power package is in approved condition. These 
instructions, which are developed as part of the approval process, are 
intended to aid power package users in keeping this equipment in safe 
operating condition.
    Commenters did not direct specific attention to this aspect of the 
proposal, which is adopted without change in the final rule.
Part 7, Subparts G, H and I
    The final rule does not adopt proposed subpart G to part 7, nor 
further develops the advance notice of rulemaking published 
concurrently with the proposal concerning subparts H and I to part 7. 
Subpart G-approved power packages would have been required for 
nonpermissible, heavy-duty diesel-powered equipment used in underground 
coal mines. Subpart H would have established regulations for the 
approval of fully assembled permissible diesel-powered machines, and 
subpart I would have set requirements for the approval of fully 
assembled nonpermissible, heavy-duty diesel-powered equipment. In lieu 
of this approach, the final rule responds to the commenters who urged 
that safety and fire protection features for nonpermissible diesel-
powered equipment be addressed in the Agency's part 75 safety standards 
for underground coal mines. Existing part 36 is retained by the final 
rule and revised to specifically apply to permissible diesel-powered 
equipment for use in underground coal mines. Subpart H is not further 
developed by the final rule.
    In the proposal, subparts G and I were developed as an approach to 
several of the Advisory Committee's concerns. In its deliberations, the 
Advisory Committee considered the risk of fire on nonpermissible 
diesel-powered equipment caused by hot surfaces igniting combustibles 
such as hydraulic and lubricating oils, diesel fuel, and coal dust. To 
address this hazard, the Committee recommended limiting engine surface 
temperatures. Under the proposal, surface temperature controls and 
other machine safety features for heavy-duty nonpermissible diesel 
equipment would have been addressed in subparts G and I.
    The Committee, however, also recognized the difficulty of applying 
such controls to all nonpermissible diesel-powered equipment, 
especially light-duty, utility equipment. The Advisory Committee, 
therefore, recommended that a ``limited class'' of light-duty equipment 
be identified for which less complex fire prevention measures would be 
required, such as fire suppression systems which shut down the engine, 
guarded drive shafts to prevent damage of fuel and hydraulic lines in 
the event of a shaft failure, protection of the fuel tank and lines, 
and proper design of the electrical system to prevent electrical arcs. 
The proposal included these requirements for a ``limited class'' of 
light-duty equipment in the part 75 safety standards for underground 
coal mines.
    The Advisory Committee also examined what additional features 
should be included in the approval requirements for completely 
assembled units of diesel-powered equipment. The Committee recommended 
that MSHA develop an approval program that would emphasize other 
equipment safety features which could be readily addressed by equipment 
manufacturers. These features included safeguarding of the fuel system, 
an exhaust gas