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U.S. Department of Labor Mine Safety and Health Administration Protecting Miners' Safety and Health Since 1978 |
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*********************************************************************** Editorial Note: Based on FedReg. Doc. 08-11528, this section has been changed. The new version is in BOLD. The old section will remain, pending the next publication of the 30 CFR. The effective date for this is April 18,2008. *********************************************************************** 30 CFR § 75.335 Seal requirements. Seals shall be designed, constructed, and maintained to protect miners from hazards related to sealed areas. Seal designs and the installation of each seal shall be approved in accordance with § 75.336 . (a) Seal strength requirements. Seals constructed on or after May 22, 2007 shall be designed, constructed, and maintained to withstand-- (1) 50 psi overpressure when the atmosphere in the sealed area is monitored and maintained inert in accordance with paragraph (b) of this section; (2) 120 psi overpressure if the atmosphere is not monitored, and is not maintained inert, and the conditions in paragraphs (a)(3)(i) through (iii) of this section are not present; or (3) An overpressure greater than 120 psi if the atmosphere is not monitored and is not maintained inert and; (i) The atmosphere in the area to be sealed is likely to contain homogeneous mixtures of methane between 4.5 percent and 17.0 percent and oxygen exceeding 17.0 percent throughout the entire area; (ii) Pressure piling is likely due to opening restrictions near the proposed seal area; or (iii) Other conditions are encountered, such as the likelihood of a detonation in the proposed seal area. (iv) Where the conditions in paragraphs (a)(3)(i), (ii), or (iii) of this section are encountered, the operator must revise the ventilation plan to be submitted to the District Manager to address the potential hazards. The plan shall include seal strength sufficient to address the conditions. (b) Sampling and monitoring requirements. Effective May 22, 2007, a certified person as defined in § 75.100 shall monitor atmospheres of sealed areas. For seals constructed prior to May 22, 2007 and for seals designed for 50 psi overpressure, mine operators shall develop and follow a protocol to monitor methane and oxygen concentrations, and to maintain an inert atmosphere in the sealed area. The protocol shall be approved in the ventilation plan. (1) A certified person shall sample atmospheres of sealed areas weekly when the barometric pressure is decreasing or the seal is outgassing. At least one sample shall be taken at each set of seals. If a seal is ingassing during the weekly examination, a sample shall be collected during the next weekly examination. If the seal is ingassing during the second consecutive weekly examination, the operator shall examine that seal daily until the seal is outgassing, unless the seal does not outgas. In this case, an alternative plan needs to be developed and submitted to the District Manager. The District Manager may approve different sampling frequencies and locations in the ventilation plan, or approve the use of atmospheric monitoring systems in lieu of weekly sampling. The mine operator shall revise the protocol, if repeated sampling indicates that a seal is not likely to outgas. (2) Certified persons conducting sampling shall be trained in the sampling procedures included in the protocol, as provided by paragraph (b)(5) of this section, before they conduct sampling, and annually thereafter. The mine operator must certify the date and content of training provided certified persons and retain each certification for one year. (3) The atmosphere shall be considered inert when-- (i) The oxygen concentration is less than 10.0 percent; (ii) The methane concentration is less than 3.0 percent; or (iii) The methane concentration is greater than 20.0 percent. (4) When oxygen concentrations are 10.0 percent or greater and methane concentrations are from 3.0 percent to 20.0 percent in a sealed area, the mine operator shall take two additional gas samples at one- hour intervals. If the two additional gas samples are from 3.0 percent to 20.0 percent and oxygen is 10.0 percent or greater-- (i) The mine operator shall implement the action plan in the protocol; or (ii) Persons shall be withdrawn from the affected area, except those persons referred to in section 104(c) of the Act. (5) The protocol shall address-- (i) Sampling procedures, including equipment and methods to be used; (ii) Location of sampling points; (iii) Procedures to establish a baseline analysis of oxygen and methane concentrations at each sampling point over a 14-day sampling period. The baseline shall be established after the atmosphere in the sealed area becomes inert or the trend reaches equilibrium; (iv) Frequency of sampling; (v) Size and conditions of the sealed area; and (vi) Use of atmospheric monitoring systems, where applicable; (vii) The protocol shall include an action plan that addresses the hazards presented and actions taken when gas samples indicate oxygen concentrations of 10.0 percent or greater for each of the following ranges of methane concentrations-- (A) 3.0 percent or greater but less than 4.5 percent; and (B) 4.5 percent or greater but less than 17.0 percent; and (C) 17.0 percent to 20 percent. (6) The certified person shall promptly record each sampling result, including the location of the sampling points, and oxygen and methane concentrations. The results of oxygen and methane samples shall be recorded as the percentage of oxygen and methane measured by the certified person and any hazardous condition found, in accordance with § 75.363. (7) The mine operator shall retain sampling records at the mine for at least one year from the date of sampling. (c) Welding, cutting, and soldering with an arc or flame are prohibited within 150 feet of a seal. (d) For seals constructed after May 22, 2007, at least two sampling pipes shall be installed in each seal. One pipe shall extend approximately 15 feet into the sealed area and another shall extend into the center of the first connecting crosscut inby the seal. Each sampling pipe shall be equipped with a shut-off valve and appropriate fittings for taking gas samples. (e) For each set of seals constructed after May 22, 2007, the seal at the lowest elevation shall have a corrosion-resistant water drainage system. Seals shall not impound water. 30 CFR § 75.335 Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or after October 20, 2008 shall be designed, constructed, and maintained to withstand-- (1)(i) At least 50-psi overpressure when the atmosphere in the sealed area is monitored and maintained inert and designed using a pressure-time curve with an instantaneous overpressure of at least 50 psi. A minimum overpressure of at least 50 psi shall be maintained for at least four seconds then released instantaneously. (ii) Seals constructed to separate the active longwall panel from the longwall panel previously mined shall be designed using a pressure- time curve with a rate of pressure rise of at least 50 psi in 0.1 second. A minimum overpressure of at least 50 psi shall be maintained; or (2)(i) Overpressures of at least 120 psi if the atmosphere in the sealed area is not monitored, is not maintained inert, the conditions in paragraphs (a)(3)(i) through (iii) of this section are not present, and the seal is designed using a pressure-time curve with an instantaneous overpressure of at least 120 psi. A minimum overpressure of 120 psi shall be maintained for at least four seconds then released instantaneously. (ii) Seals constructed to separate the active longwall panel from the longwall panel previously mined shall be designed using a pressure- time curve with a rate of pressure rise of 120 psi in 0.25 second. A minimum overpressure of 120 psi shall be maintained; or (3) Overpressures greater than 120 psi if the atmosphere in the sealed area is not monitored and is not maintained inert, and (i) The atmosphere in the sealed area is likely to contain homogeneous mixtures of methane between 4.5 percent and 17.0 percent and oxygen exceeding 17.0 percent throughout the entire area; (ii) Pressure piling could result in overpressures greater than 120 psi in the area to be sealed; or (iii) Other conditions are encountered, such as the likelihood of a detonation in the area to be sealed. (iv) Where the conditions in paragraphs (a)(3)(i), (ii), or (iii) of this section are encountered, the mine operator shall revise the ventilation plan to address the potential hazards. The plan shall include seal strengths sufficient to address such conditions. (b) Seal design applications. Seal design applications from seal manufacturers or mine operators shall be in accordance with paragraphs (b)(1) or (b)(2) of this section and submitted for approval to MSHA's Office of Technical Support, Pittsburgh Safety and Health Technology Center, P.O. Box 18233, Cochrans Mill Road, Pittsburgh, PA 15236. (1) An engineering design application shall-- (i) Address gas sampling pipes, water drainage systems, methods to reduce air leakage, pressure-time curve, fire resistance characteristics, flame spread index, entry size, engineering design and analysis, elasticity of design, material properties, construction specifications, quality control, design references, and other information related to seal construction; (ii) Be certified by a professional engineer that the design of the seal is in accordance with current, prudent engineering practices and is applicable to conditions in an underground coal mine; and (iii) Include a summary of the installation procedures related to seal construction; or (2) Each application based on full-scale explosion tests or equivalent means of physical testing shall address the following requirements to ensure that a seal can reliably meet the seal strength requirements: (i) Certification by a professional engineer that the testing was done in accordance with current, prudent engineering practices for construction in a coal mine; (ii) Technical information related to the methods and materials; (iii) Supporting documentation; (iv) An engineering analysis to address differences between the seal support during test conditions and the range of conditions in a coal mine; and (v) A summary of the installation procedures related to seal construction. (3) MSHA will notify the applicant if additional information or testing is required. The applicant shall provide this information, arrange any additional or repeat tests, and provide prior notification to MSHA of the location, date, and time of such test(s). (4) MSHA will notify the applicant, in writing, whether the design is approved or denied. If the design is denied, MSHA will specify, in writing, the deficiencies of the application, or necessary revisions. (5) Once the seal design is approved, the approval holder shall promptly notify MSHA, in writing, of all deficiencies of which they become aware. (c) Seal installation approval. The installation of the approved seal design shall be subject to approval in the ventilation plan. The mine operator shall-- (1) Retain the seal design approval and installation information for as long as the seal is needed to serve the purpose for which it was built. (2) Designate a professional engineer to conduct or have oversight of seal installation and certify that the provisions in the approved seal design specified in this section have been addressed and are applicable to conditions at the mine. A copy of the certification shall be submitted to the District Manager with the information provided in paragraph (c)(3) of this section and a copy of the certification shall be retained for as long as the seal is needed to serve the purpose for which it was built. (3) Provide the following information for approval in the ventilation plan-- (i) The MSHA Technical Support Approval Number; (ii) A summary of the installation procedures; (iii) The mine map of the area to be sealed and proposed seal locations that include the deepest points of penetration prior to sealing. The mine map shall be certified by a professional engineer or a professional land surveyor. (iv) Specific mine site information, including-- (A) Type of seal; (B) Safety precautions taken prior to seal achieving design strength; (C) Methods to address site-specific conditions that may affect the strength and applicability of the seal including set-back distances; (D) Site preparation; (E) Sequence of seal installations; (F) Projected date of completion of each set of seals; (G) Supplemental roof support inby and outby each seal; (H) Water flow estimation and dimensions of the water drainage system through the seals; (I) Methods to ventilate the outby face of seals once completed; (J) Methods and materials used to maintain each type of seal; (K) Methods to address shafts and boreholes in the sealed area; (L) Assessment of potential for overpressures greater than 120 psi in sealed area; (M) Additional sampling locations; and (N) Additional information required by the District Manager. |
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