VOLUME V - COAL MINES
75.1101-5 Installation of Foam Generator Systems
Automatically-operated high-expansion foam devices may be used for fire suppression at belt drives. The capacity of the unit shall be sufficient to cover 50 feet of fire-resistant belt conveyor (150 feet of nonfire-resistant belt) as well as the takeup and gear reducing units and electrical controls with foam in 5 minutes. In calculating the capacity, the volume of foam generated need not fill the entry to the roof but must be capable of filling the entry to the top belt.
Generally, the foam generator should be located on the intake air side of the belt drive and other components to be protected so as to take advantage of the ventilating air in moving the foam and preventing air, contaminated by smoke and hot gases, from entering into the foaming unit. Smoke and hot gases in the intake air to the unit decrease the efficiency of foam generation. The warning device actuated by the sensor or foam generator should be located where a miner is in constant attendance.
The foaming agent used in most foam generators tend to corrode metal parts. Therefore, care should be taken to flush out and clear the unit after operation.
The development of a foam plug in a passageway will affect the
ventilation pattern. If the belt is in a neutral airway, smoke
will be trapped in the entry decreasing visibility and travel.
75.1101-8 Water Sprinkler Systems; Arrangement of Sprinklers
The installation of a water sprinkler system for fire suppression at belt drives generally requires two branch lines so that an effective water discharge pattern can be produced. A single branch line located at the top belt ordinarily does not offer an equivalent flow pattern. However, the following single branch line system can be considered equivalent when the following conditions are met:
- The entry width does not exceed 16 feet, and the entry height is not less than 6 feet.
- The static water pressure is not less than 250 psig, and the quantity of water delivered with all nozzles operating is not less than 1.0 gallon per minute per square foot of top belt surface area.
- The nozzles are mounted above the top conveyor belt near the roof, and reasonable water coverage of the belt surfaces is achieved by splashing action.
The maximum distance between sprinklers shall not be more than 8 feet to achieve a reasonable water spray pattern. In general,the sprinklers need not be closer than 6 feet apart. If sprinklers are too close together, the cooling action of the water from one sprinkler may affect the operation of another.
It is important that sprinklers be located so as to be actuated by the heat from a potential fire. The sprinklers shall operate in the temperature range 150oF to 300oF. Under some circumstances, sprinklers operating below 212oF may be actuated by steam.
If a large number of sprinklers are actuated by steam, the quantity of water flowing through these may decrease the quantity of water through those sprinklers in the fire area.
Sprinklers cannot be tested directly for the yearly functional examination without destroying their usefulness. In order to test a sprinkler system, the end sprinkler should be removed to ensure adequate water flow. The sprinklers should be free of dirt, and all damaged sprinklers should be replaced.
Sprinkler system lines are normally filled with water. Where freezing temperatures exist, the pipes may freeze and burst, or ice may form and plug the lines. Alternative systems developed for this situation are:
- Regular dry pipe system.
- Preaction system.
- Deluge system.
- Combined dry-pipe and preaction system.
These alternative methods are acceptable provided they offer equivalent protection and are installed in accordance with the provisions of the Fire Protection Handbook published by the National Fire Protection Association.
75.1101-13 Dry Powder Chemical Systems; General
Suppression at belt drives by all-purpose dry powder was included to serve primarily where freezing temperatures exist.The dry powder system operates for a short period of time(1 minute) whereas the deluge or sprinkler systems operate for 10 minutes or longer. Therefore, the dry powder system must be carefully designed to be effective. The discharge pattern from the nozzles is critical, and, normally, the locations of the nozzles shall be designed by an expert. Damaged or misaligned nozzles should be replaced promptly. The dry powder system consists of an open pipeline system. In order to prevent moisture and dust from entering pipes, the nozzles should be loosely covered. This can be achieved by tape covering, by water-proof grease or equivalent means. Caps that are tightly fastened should be checked to ensure they will blow off readily;screw caps are unacceptable. If grease or similar materials are used, the orifices should be checked to insure the material has not hardened.
When the dry powder system operates, the mine passageway becomes filled with a dense cloud (ammonium phosphate). This material is nontoxic, but may impair breathing and vision. For this reason,guard rails or equivalent devices must be provided for the safety of miners in the immediate vicinity.
After operation of the system, the pipelines must be cleaned of dust and dried. If dust remains in the pipe, it may absorb moisture and cake. The all-purpose powder is slightly corrosive to metal parts especially when wetted. Thus, metal equipment and components of the fire suppression system should be cleaned.
The yearly test of the suppression system can be made by checking the powder storage compartment, the gas expelling unit, and by blowing the dry air (preferably bottled nitrogen) through the piping. It is important to ensure that the dry powder is not exposed to the humid atmosphere. If so, it will absorb moisture and cake. It is recommended that all dry powder be discharged through the system every 2 years.
75.1103-2 Automatic Fire Sensors; Approved Components;Installation Requirements
Fire sensors used in belt passageways shall be listed or approved by Underwriters' Laboratories (UL) or Factory Mutual (FM). New or unique devices to be used as fire sensors that are not yet listed by UL or FM and which may meet the requirements of these regulations shall be submitted to the Technical Support Group,MSHA, through the Chief, Division of Safety, Coal Mine Safety and Health, 4015 Wilson Boulevard, Arlington, Virginia 22203, for a determination of acceptability and recommendation.
75.1103-3 Automatic Fire Sensor and Warning Device Systems; Minimum Requirements; General
The district manager can approve a sensor and alarm system even though the components are not listed or approved by a recognized testing laboratory. Some components, such as electronic items and new or unique devices, are not listed or approved by these agencies. However, such approval should be done judiciously,requiring detailed description and possible future compliance,if applicable, with Factory Mutual Research Corporation (FM) or Underwriters' Laboratories, Inc. (UL), standards. It is not mandatory that all components of the fire-warning device systems be listed or approved by UL or FM. However, MSHA will require that all components be adequate with regard to "type and quality." For some components, this may mean the listing of approval by UL or FM.
All automatic fire warning systems must meet the requirements of 30 CFR 75.1103-4 through 75.1103-7, including when more than one type of system is installed in a belt entry. For example, if a CO monitoring system is installed in conjunction with a point-type heat sensor system, both systems must meet the installation and maintenance requirements of 30 CFR 75.1103-4 through 77.1103-7 and be fully operative at all times. This policy will not require the secondary system to be a complete system.
Application of this policy must take into consideration the installation and debugging phase that sometimes occurs when new types of fire warning systems are installed. Operators should be afforded a reasonable time for a redundant or replacement system to be installed and tested. Proper application of this policy is facilitated by the operator informing MSHA of plans to install anew system.
75.1103-4 Automatic Fire Sensor and Warning Device Systems; Installation;
Recognizing that a rise in temperature may activate either fire detection system installed on separate flights at the flight connection point, systems which activate either fire detection system upon a rise in temperature within 125 feet of the connection point can be considered equivalent to a system which provides identification of fire within each belt flight if the district manager determines that the miners are provided equivalent protection. If it has been determined that the system has failed to provide identification of a fire within a belt flight, any citations issued should be cited as a violation of this Section.
Where practicable, point-type sensors responding to temperature rise should be installed at or near the center of the belt and not more than 12 or less than 6 inches from the roof, except where installation of sensors in extremely high areas would pose a hazard through the use of ladders or scaffolding, or local irregularities prevent such installation.
Heat detecting Twisto Wire and Protecto Wire are acceptable as sensors, provided they are properly installed with two twists per linear foot. Proper tension is required on the Twisto Wire, and if Protecto Wire is used, it must be in minimum lengths of 12 inches and properly secured by soldering or other substantial means. However, acceptability does not apply to a system unless the entire system is in compliance with these regulations.
Any fire sensor and warning device system installed in a return airway must be approved as permissible by the Approval and Certification Center under Part 23. An approval under Part 23requires that only components specified in the approval may be used with the system unless authorization for the use of different components has been obtained from the Approval and Certification Center by the mine operator. The unauthorized substitution of components different from those which were specified in the approval of a permissible fire sensor and warning device system used on a belt conveyor in a return airway shall be cited as a violation of Section 75.1103-7(b).
Some coal mines have intermixed heat sensors and heat sensor cables with reverse conductor color codes in the same polarized fire sensor and warning device system. Therefore, heat sensors which are polarized so that the white conductor must be positive have been installed in heat sensor cables which are polarized so the black conductor must be positive. Likewise, heat sensor cables which are polarized so that the white conductor must be positive have been connected to heat sensor cables which are polarized so that the black conductor must be positive.
If the colors are matched when splicing heat sensors and heat sensor cables with one conductor color code into heat sensor cables of the opposite conductor color code in accordance with customary electrical practice (black to black, white to white),the system will malfunction and no audible or visual signal will appear at the control station when an improperly polarized heat sensor(s) is activated. Although it is possible to correctly intermix heat sensors and heat sensor cables of opposite conductor color codes in polarized fire sensor and warning device systems, the potential confusion created by the differences in conductor color codes could create a safety hazard. Even if assurances are given that initial installation will be done in accordance with instructions to splice black to white conductors,there can be no satisfactory assurance that later maintenance will always be performed correctly because the method is contrary to common practice. Therefore, the use of heat sensors and heat sensor cables with opposite conductor color codes within the same polarized fire sensor and warning device system is not acceptable under Section 75.1103-2. Enforcement personnel should recognize that it is not important which conductor color code is used in a polarized fire sensor and warning device system as long as the conductor color code and polarity of all heat sensors and heat sensor cables within the system are the same and the polarity of the heat sensors cable is compatible with the control unit and other components of the system.
The assistance of a coal mine inspector (electrical) or electrical engineer should be requested, when necessary, to determine if a mine operator has installed heat sensors or heat sensor cables with opposite conductor color codes within a polarized fire sensor and warning device system.
Other sensors addressed in paragraph (a)(2) that respond to effects of fire other than heat may be acceptable subject to individual determination. The Technical Support Group, in Bruceton, Pennsylvania, will provide assistance where needed in making this determination.
"Unplanned removal of power" and "preplanned removal of power"referred to in paragraphs (a)(3) and (e) do not include those times when it is necessary to remove the power to make minor repairs or adjustments. An examination is not required for that period of time normally required for shift change, provided the time required for shift change does not exceed 2 hours.
Where the operator chooses to make the examinations referred to in lieu of an automatic fire sensor and warning device system that will provide the 4-hour protection, the examination referred to would be required if the power supply to the sensor and alarm is removed, or the power is removed from the belt for more than 30 minutes during a production shift, or the belt is stopped prior to the beginning of an idle shift or an idle period such as weekends or holidays.
A battery must be disconnected automatically from the sensor system in the event the power is cut off as required by Section 75.321, unless the sensor system is intrinsically safe.
75.1103-5 Automatic Fire Warning Devices; Manual Resetting
"Effective warning signal" as used in paragraph (a) of this Section means "a signal indicating an emergency and requiring immediate action." Both audible and visual signals shall be provided as required by Section 75.1103-1.
The audible signal shall be capable of being heard from any point within the full range of the assigned duty locations of the person referred to in paragraphs (a)(1) and (a)(2), and the signal shall be audible above the normal sounds of the mining operation. This Section should be used to cite a failure of the system, when activated, when it does not provide an effective warning signal at either the work locations where miners may be endangered from a fire at the belt flight or at a manned location where personnel have communication with all miners who may be endangered.
The visual signal shall be capable of attracting the attention of persons referred to in paragraphs (a)(1) and (a)(2) under normal mine lighting conditions.
Both signals need not be located in the same place. In some instances, the signals may be acceptable located a considerable distance apart, provided such signals can be seen or heard by responsible persons.
An alarm signal at the section telephone equivalent to that of aloud speaking telephone or "Page" system will be accepted for compliance with paragraph (a).
Sensors responding to effects of fire other than heat may be acceptable subject to individual determination. The Technical Support Group, Bruceton, Pennsylvania, will provide assistance where needed in making this determination.
Means for "Rapid Evaluation" as addressed in paragraph (b) is any method that will effectively demonstrate that the sensor and warning device systems are operative and capable of performing in the event of a fire. This will be determined on a system-by-system basis by the district manager.
MSHA will accept a system in which the trouble signal is or is not distinctive from the alarm signal. However, in this later instance, both the trouble and alarm signal will indicate a"fire" situation. The mine operator will then be required to respond to the signal prepared to control a fire. That is to say, that the communication lines need not be electrically monitored for short circuits, ground faults, and open circuits.
If communication lines are incorporated into a fire-warning system, MSHA will accept the use of communication systems without electrical supervision.