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This part 75 sets forth safety standards compliance with which is mandatory in each underground coal mine subject to the Federal Mine Safety and Health Act of 1977. Some standards also are applicable to surface operations. Regulations and criteria supplementary to these standards also are set forth in this part.
The following definitions apply in this part.
Act. The Federal Mine Safety and Health Act of 1977.
Active workings. Any place in a coal mine where miners are normally required to work or travel.
Adequate interrupting capacity. The ability of an electrical protective device, based upon its required and intended application, to safely interrupt values of current in excess of its trip setting or melting point.
Anthracite. Coals with a volatile ratio equal to 0.12 or less. The volatile ratio is the volatile matter content divided by the volatile matter plus the fixed carbon.
Approval documentation. Formal papers issued by the Mine Safety and Health Administration which describe and illustrate the complete assembly of electrical machinery or accessories which have met the applicable requirements of 30 CFR part 18.
Certified or registered. As applied to any person, a person certified or registered by the State in which the coal mine is located to perform duties prescribed by this part 75, except that in a State where no program of certification or registration is provided or where the program does not meet at least minimum Federal standards established by the Secretary, such certification or registration shall be by the Secretary.
Circuit-interrupting device. A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically at a predetermined overcurrent value without damage to the device when operated within its rating.
Coal mine. Includes areas of adjoining mines connected underground.
Filter Self-Rescuer (FSR). A type of gas mask approved by MSHA and NIOSH under 42 CFR part 84 for escape only from underground mines and which provides at least 1 hour of protection against carbon monoxide.
Ground fault or grounded phase. An unintentional connection between an electric circuit and the grounding system.
Low voltage. Up to and including 660 volts, medium voltage means voltages from 661 to 1,000 volts; and high voltage means more than 1,000 volts.
Motor-starter enclosure. An enclosure containing motor starting circuits and equipment.
Nominal voltage. The phase-to-phase or line-to-line root-mean-square value assigned to a circuit or system for designation of its voltage class, such as 480 or 4,160 volts. Actual voltage at which the circuit or system operates may vary from the nominal voltage within a range that permits satisfactory operation of equipment.
Permissible. (1) As applied to electric face equipment, all electrically operated equipment taken into or used inby the last open crosscut of an entry or a room of any coal mine the electrical parts of which, including, but not limited to, associated electrical equipment, components, and accessories, are designed, constructed, and installed, in accordance with the specifications of the Secretary, to assure that such equipment will not cause a mine explosion or mine fire, and the other features of which are designed and constructed, in accordance with the specifications of the Secretary, to prevent, to the greatest extent possible, other accidents in the use of such equipment. The regulations of the Secretary or the Director of the Bureau of Mines in effect on March 30, 1970, relating to the requirements for investigation, testing, approval, certification, and acceptance of such equipment as permissible shall continue in effect until modified or superseded by the Secretary, except that the Secretary shall provide procedures, including, where feasible, testing, approval, certification, and acceptance in the field by an authorized representative of the Secretary, to facilitate compliance by an operator with the requirements of § 75.500 within the periods prescribed in § 75.500.
(2) As applied to equipment other than permissible electric face equipment: (i) Equipment used in the operation of a coal mine to which an approval plate, label, or other device is attached as authorized by the Secretary and which meets specifications which are prescribed by the Secretary for the construction and maintenance of such equipment and are designed to assure that such equipment will not cause a mine explosion or a mine fire. (ii) The manner of use of equipment means the manner of use prescribed by the Secretary.
Qualified person. As the context requires:
(1) An individual deemed qualified by the Secretary and designated by the operator to make tests and examinations required by this part 75; and
(2) An individual deemed, in accordance with minimum requirements to be established by the Secretary, qualified by training, education, and experience, to perform electrical work, to maintain electrical equipment, and to conduct examinations and tests of all electrical equipment.
Respirable dust. Dust collected with a sampling device approved by the Secretary and the Secretary of Health and Human Services in accordance with part 74—Coal Mine Dust Personal Sampler Units of this title. Sampling device approvals issued by the Secretary of the Interior and Secretary of Health, Education, and Welfare are continued in effect.
Rock dust. Pulverized limestone, dolomite, gypsum, anhydrite, shale, adobe, or other inert material, preferably light colored, 100 percent of which will pass through a sieve having 20 meshes per linear inch and 70 percent or more of which will pass through a sieve having 200 meshes per linear inch; the particles of which when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air; and which does not contain more than 5 percent combustible matter or more than a total of 4 percent free and combined silica (SiO 2 ), or, where the Secretary finds that such silica concentrations are not available, which does not contain more than 5 percent of free and combined silica.
Secretary. The Secretary of Labor or the Secretary's delegate.
Self-Contained Self-Rescuer (SCSR). A type of closed-circuit, self-contained breathing apparatus approved by MSHA and NIOSH under 42 CFR part 84 for escape only from underground mines.
Short circuit. An abnormal connection of relatively low impedance, whether made accidentally or intentionally, between two points of different potential.
Working face. Any place in a coal mine in which work of extracting coal from its natural deposit in the earth is performed during the mining cycle.
Working place. The area of a coal mine inby the last open crosscut.
Working section. All areas of the coal mine from the loading point of the section to and including the working faces.
(a) The provisions of Subpart D—Ventilation of this part 75 require that certain examinations and tests be made by a certified person. A certified person within the meaning of those provisions is a person who has been certified as a mine foreman (mine manager), an assistant mine foreman (section foreman), or a preshift examiner (mine examiner). A person who has been so certified is also a qualified person within the meaning of those provisions of subpart D of this part which require that certain tests be made by a qualified person and within the meaning of § 75.1106.
(b) A person who is certified as a mine foreman, an assistant mine foreman, or a preshift examiner by the State in which the coal mine is located is, to the extent of the State's certification, a certified person within the meaning of the provisions of subpart D of this part and § 75.1106 referred to in paragraph (a) of this section.
(c)(1) The Secretary may certify persons in the categories of mine foreman, assistant mine foreman, and preshift examiner whenever the State in which persons are presently employed in these categories does not provide for such certification. A person's initial certification by MSHA is valid for as long as the person continues to satisfy the requirements necessary to obtain the certification and is employed at the same coal mine or by the same independent contractor. The mine operator or independent contractor shall make an application which satisfactorily shows that each such person has had at least 2 years underground experience in a coal mine, and has held the position of mine foreman, assistant mine foreman, or preshift examiner for a period of 6 months immediately preceding the filing of the application, and is qualified to test for methane and for oxygen deficiency. Applications for Secretarial certification should be submitted in writing to the Health and Safety Activity, Mine Safety and Health Administration, Certification and Qualification Center, P.O. Box 25367, Denver Federal Center, Denver, Colorado 80225.
(2) A person certified by the Secretary under this paragraph will be a certified person, within the meaning of the provisions for subpart D of this part and § 75.1106 referred to in paragraph (a) of this section, as long as that person continues to satisfy the requirements for qualification or certification and is employed at the same coal mine or by the same independent contractor.
Motor-Driven Mine Equipment
(Approved Under Schedules 2, 2A, 2B, and 2C)
Approval No.
Date
Air Compressors
128
March 21, 1927.
128A
July 16, 1926.
Coal Drills and Drilling Machines
Hand Drills
109
September 19, 1922.
154
August 1, 1928.
184
February 7, 1930.
227
July 29, 1931.
254
July 15, 1933.
Post Drills
119
April 15, 1925.
119A
Do.
225
July 10, 1931.
225A
Do.
228
August 12, 1931.
228A
February 17, 1932.
230
August 20, 1931.
230A
Do.
237
December 1, 1931.
237A
Do.
Drilling Machines
147
February 8, 1928.
147A
Do.
176
September 9, 1929.
176A
Do.
Loading and Conveying Equipment
loading machines
Unmounted Type
122
January 8, 1926.
122A
Do.
Caterpillar-Mounted Type
150
May 11, 1928.
186
March 15, 1930.
222
May 8, 1931.
222A
July 28, 1931.
229
August 17, 1931.
229A
Do.
235
November 27, 1931.
235A
October 29, 1931.
278
January 17, 1935.
278A
Do.
283A
March 12, 1935.
284A
Do.
285A
Do.
294
September 18, 1935.
300A
May 6, 1936.
127
July 16, 1926.
127A
September 23, 1927.
Track-Mounted Type
194
June 6, 1930.
194A
Do.
217
February 27, 1931.
217A
Do.
276
January 11, 1935.
277
January 17, 1935.
282A
March 12, 1935.
291A
July 3, 1935.
Pit-Car Loaders
167
March 27, 1929.
167A
Do.
175
July 26, 1929.
175A
June 24, 1929.
250
December 10, 1932.
250A
Do.
252A
February 20, 1933.
Conveyors
Belt Type
236
November 19, 1931.
287A
March 12, 1935.
296A
January 6, 1936.
Chain Type
151
May 19, 1928.
209
December 2, 1930.
240
March 12, 1932.
240A
Do.
298A
March 3, 1936.
Power Units for Conveyors
265
February 12, 1934.
265A
March 19, 1934.
390A
March 23, 1934.
Shaker Type
247
October 21, 1932.
257A
August 11, 1933.
262A
December 8, 1933.
271
May 20, 1935.
271A
October 17, 1934.
274A
December 13, 1934.
286A
March 12, 1935.
295
September 20, 1935.
299A
April 9, 1936.
Scraper-type Loaders
138
August 5, 1927.
138A
Do.
196
September 29, 1930.
196A
July 26, 1930.
226
July 27, 1931.
255
July 31, 1933.
256
Do.
Mining Machines, Machinery-Moving Equipment, Miscellaneous Trucks, and Water Spray Supply Units
mining machines
Shortwall Machines
103
November 2, 1917.
103A
Do.
105
February 9, 1922.
105A
Do.
106
Do.
106A
Do.
107
Do.
107A
Do.
108
Do.
108A
Do.
111
October 16, 1922.
111A
Do.
113
November 4, 1924.
113A
Do.
114
February 7, 1925.
114A
Do.
115
Do.
115A
Do.
153
July 31, 1928.
153A
Do.
193
June 3, 1930.
193A
Do.
197
July 31, 1930.
197A
Do.
198
August 1, 1930.
198A
Do.
201
September 8, 1930.
201A
Do.
204
October 13, 1930.
204A
December 13, 1930.
223
May 13, 1931.
223A
Do.
241
March 18, 1932.
241A
Do.
258
August 15, 1933.
259A
August 16, 1933.
260A
August 17, 1933.
273
November 30, 1934.
288
March 27, 1935.
288A
Do.
292
September 11, 1935.
292A
Do.
293A
Do.
Longwall Machines
185
February 24, 1930.
185A
Do.
218
March 10, 1931.
218A
Do.
246
August 19, 1932.
246A
Do.
261
September 12, 1933.
Track or caterpillar mounted
112
March 13, 1924.
112A
Do.
118
March 12, 1925.
118A
Do.
125
April 26, 1926.
125A
Do.
172
April 30, 1929.
172A
Do.
188
April 15, 1930.
188A
Do.
207
November 14, 1930.
207A
Do.
216
February 12, 1931.
216A
Do.
231
August 31, 1931.
231A
Do.
242
April 7, 1932.
244
June 18, 1932.
244A
September 20, 1932.
253A
February 25, 1933.
267
June 27, 1934.
268A
July 25, 1934.
269A
September 24, 1934.
280A
March 4, 1935.
297
January 27, 1936.
297A
Do.
Mine Pumps
140
November 1, 1927.
140A
Do.
143
Do.
143A
Do.
144
Do.
144A
Do.
199
August 18, 1930.
199A
Do.
208
November 29, 1930.
210
December 15, 1930.
210A
Do.
211
December 17, 1930.
211A
Do.
213
December 29, 1930.
213A
Do.
214
January 2, 1931.
214A
Do.
215
Do.
215A
Do.
248
October 31, 1932.
248A
November 23, 1932.
264
January 31, 1934.
264A
Do.
272
October 23, 1934.
272A
Do.
Rock-Dusting Machines
130
November 5, 1926.
137
July 2, 1927.
146
January 20, 1928.
146A
April 3, 1928.
180
October 30, 1929.
180A
January 17, 1930.
206
November 12, 1930.
279
February 14, 1935.
Room and Car-Spotting Hoists
116
February 13, 1925.
116A
Do.
164
January 21, 1931.
164A
Do.
165
Do.
165A
Do.
169
April 5, 1929.
169A
February 26, 1934.
190
April 20, 1930.
251A
January 16, 1933.
263
January 11, 1934.
266A
February 27, 1934.
Storage-Battery Locomotives and Power Trucks
(Approved under Schedules 15, 2C, 2D, and 2E)
Gathering Locomotives
1501
October 11, 1921.
1502
November 13, 1922.
1503
March 24, 1923.
1505
April 5, 1924.
1507
August 20, 1925.
1508
March 21, 1925.
1509
September 25, 1925.
1511
November 10, 1925.
1512
November 11, 1925.
1513
February 25, 1926.
1516
December 28, 1926.
1517
February 10, 1927.
1520
May 27, 1929.
1521
June 13, 1930.
1522
September 12, 1930.
1523
December 19, 1930.
1525
July 25, 1934.
1526
December 20, 1935.
Tandem Locomotive
1518
November 21, 1927.
Power Trucks
1506
May 5, 1924.
1505A
June 21, 1926.
1510C
December 31, 1926.
1514
December 18, 1926.
1515
December 28, 1926.
1512C
September 13, 1928.
1519C
April 6, 1929.
1524C
June 25, 1934.
Junction, Distribution, and Splice Boxes
(Approved under Schedules 2D and 2E)
Junction Boxes
400
June 16, 1928.
400A
August 5, 1925.
401
May 11, 1927.
401A
Do.
402
Do.
402A
Do.
403
April 14, 1931.
403A
Do.
405A
December 4, 1933.
(a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a qualified person for this purpose if he is a certified person under § 75.100.
(b) Pending issuance of Federal standards, a person will be considered a qualified person for testing for methane and for oxygen deficiency:
(1) If he has been qualified for this purpose by the State in which the coal mine is located; or
(2) The Secretary may qualify persons for this purpose in a coal mine in which persons are not qualified for this purpose by the State upon an application and a satisfactory showing by the operator of the coal mine that each such person has been trained and designated by the operator to test for methane and oxygen deficiency and has made such tests for a period of 6 months immediately preceding the application. Applications for Secretarial qualification should be submitted to the Health and Safety Activity, Mine Safety and Health Administration, Certification and Qualification Center, P.O. Box 25367, Denver Federal Center, Denver, Colo. 80225.
Notwithstanding the provisions of § 75.150, on and after January 1, 1971, no person shall be a qualified person for testing for methane unless he demonstrates to the satisfaction of an authorized representative of the Secretary that he is qualified to test for methane with a portable methane detector approved by the Bureau of Mines or the Mine Safety and Health Administration under part 22 of this chapter (Bureau of Mines Schedule 8C).
A person is a qualified person within the meaning of the provisions of Subpart D—Ventilation of this part requiring that tests of air flow be made by a qualified person only if he is a certified person under § 75.100 or a person trained and designated by a certified person to perform such tests.
(a) Except as provided in paragraph (f) of this section, an individual is a qualified person within the meaning of §§ 75.511 and 75.512 to perform electrical work (other than work on energized surface high-voltage lines) if:
(1) He has been qualified as a coal mine electrician by a State that has a coal mine electrical qualification program approved by the Secretary; or,
(2) He has at least 1 year of experience in performing electrical work underground in a coal mine, in the surface work areas of an underground coal mine, in a surface coal mine, in a noncoal mine, in the mine equipment manufacturing industry, or in any other industry using or manufacturing similar equipment, and has satisfactorily completed a coal mine electrical training program approved by the Secretary; or,
(3) He has at least 1 year of experience, prior to the date of the application required by paragraph (c) of this section, in performing electrical work underground in a coal mine, in the surface work areas of an underground coal mine, in a surface coal mine, in a noncoal mine, in the mine equipment manufacturing industry, or in any other industry using or manufacturing similar equipment, and he attains a satisfactory grade on each of the series of five written tests approved by the Secretary and prescribed in paragraph (b) of this section.
(b) The series of five written tests approved by the Secretary shall include the following categories:
(1) Direct current theory and application;
(2) Alternating current theory and application;
(3) Electric equipment and circuits;
(4) Permissibility of electric equipment; and,
(5) Requirements of subparts F through K of this part 75.
(c) In order to take the series of five written tests approved by the Secretary, an individual shall apply to the District Manager and shall certify that he meets the requirements of paragraph (a)(3) of this section. The tests will be administered in the Coal Mine Safety and Health Districts at regular intervals, or as demand requires.
(d) A score of at least 80 percent of each of the five written tests will be deemed to be a satisfactory grade. Recognition shall be given to practical experience in that 1 percentage point shall be added to an individual's score in each test for each additional year of experience beyond the 1 year minimum requirement specified in paragraph (a)(3) of this section; however, in no case shall an individual be given more than 5 percentage points for such practical experience.
(e) An individual may, within 30 days from the date on which he received notification from the Administration of his test scores, repeat those on which he received an unsatisfactory score. If further retesting is necessary after this initial repetition, a minimum of 30 days from the date of receipt of notification of the initial retest scores shall elapse prior to such further retesting.
(f) An individual who has, prior to November 1, 1972, been qualified to perform electrical work specified in §§ 75.511 and 75.512 (other than work on energized surface high-voltage lines) shall continue to be qualified until June 30, 1973. To remain qualified after June 30, 1973, such individual shall meet the requirements of either paragraph (a) (1), (2), or (3) of this section.
(g) An individual qualified in accordance with this section shall, in order to retain qualification, certify annually to the District Manager, that he has satisfactorily completed a coal mine electrical retraining program approved by the Secretary.
An individual is a qualified person within the meaning of § 75.705 for the purpose of repairing energized surface high voltage lines only if he has had at least 2 years experience in electrical maintenance, and at least 2 years experience in the repair of energized high voltage surface lines located on poles or structures.
(a)(1) A person is a qualified hoisting engineer within the provisions of subpart O of this part, for the purpose of operating a steam-driven hoist in a coal mine, if he has at least 1 year experience as an engineer in a steam-driven hoisting plant and is qualified by the State in which the mine is located as a steam-hoisting engineer; or
(2) If a State has no program for qualifying persons as steam-hoisting engineers, the Secretary may qualify persons for this purpose if the operator of the coal mine in which such persons are employed, or the independent contractor, makes an application and a satisfactory showing that each such person has had 1 year experience in operating steam-driven hoists and has held the position of hoisting engineer for a period of 6 months immediately preceding the application. A person's qualification is valid for as long as this person continues to satisfy the requirements necessary for qualification and is employed at the same coal mine or by the same independent contractor.
(b)(1) A person is a qualified hoisting engineer within the provisions of subpart O of this part, for the purpose of operating an electrically driven hoist in a coal mine, if he has at least 1 year experience operating a hoist plant in a mine or maintaining electric-hoist equipment in a mine and is qualified by the State in which the mine is located as an electric-hoisting engineer; or
(2) If a State has no program for qualifying persons as electric-hoisting engineers, the Secretary may qualify persons for this purpose if the operator of the coal mine in which such persons are employed, or the independent contractor, makes an application and a satisfactory showing that each such person has had 1 year experience in operating electric-driven hoists and has held the position of hoisting engineer for a period of 6 months immediately preceding the application. A person's qualification is valid for as long as this person continues to satisfy the requirements for qualification and is employed at the same coal mine or by the same independent contractor.
(c) Applications for Secretarial qualification should be submitted to the Health and Safety Activity, Mine Safety and Health Administration, Certification and Qualification Center, P.O. Box 25367, Denver Federal Center, Denver, Colo. 80225.
(a) To be qualified as an AMS operator, a person shall be provided with task training on duties and responsibilities at each mine where an AMS operator is employed in accordance with the mine operator's approved Part 48 training plan.
(b) An AMS operator must be able to demonstrate to an authorized representative of the Secretary that he/she is qualified to perform in the assigned position.
The operator of each coal mine shall maintain a list of all certified and qualified persons designated to perform duties under this part 75.
Each operator must submit to the district manager, of the Coal Mine Safety and Health District in which the mine is located, a program or plan setting forth what, when, how, and where the operator will train and retrain persons whose work assignments require that they be certified or qualified. The program must provide—
(a) For certified persons, annual training courses in first aid, principles of mine rescue, and the provisions of this part 75; and
(b) For qualified persons, annual courses in performance of the task which they perform as qualified persons.
This subpart C sets forth requirements for controlling roof, face and ribs, including coal or rock bursts, in underground coal mines. Roof control systems installed prior to the effective date of this subpart are not affected so long as the support system continues to effectively control the roof, face and ribs.
Automated temporary roof support (ATRS) system. A device to provide temporary roof support from a location where the equipment operator is protected from roof falls.
Pillar recovery. Any reduction in pillar size during retreat mining.
(a) The roof, face and ribs of areas where persons work or travel shall be supported or otherwise controlled to protect persons from hazards related to falls of the roof, face or ribs and coal or rock bursts.
(b) No person shall work or travel under unsupported roof unless in accordance with this subpart.
(a) The method of mining shall not expose any person to hazards caused by excessive widths of rooms, crosscuts and entries, or faulty pillar recovery methods. Pillar dimensions shall be compatible with effective control of the roof, face and ribs and coal or rock bursts.
(b) A sightline or other method of directional control shall be used to maintain the projected direction of mining in entries, rooms, crosscuts and pillar splits.
(c) A sidecut shall be started only from an area that is supported in accordance with the roof control plan.
(d) A working face shall not be mined through into an unsupported area of active workings, except when the unsupported area is inaccessible.
(e) Additional roof support shall be installed where—
(1) The width of the opening specified in the roof control plan is exceeded by more than 12 inches; and
(2) The distance over which the excessive width exists is more than 5 feet.
(a) For roof bolts and accessories addressed in ASTM F432-95, “Standard Specification for Roof and Rock Bolts and Accessories,” the mine operator shall—
(1) Obtain a manufacturer's certification that the material was manufactured and tested in accordance with the specifications of ASTM F432-95; and
(2) Make this certification available to an authorized representative of the Secretary and to the representative of miners.
(b) Roof bolts and accessories not addressed in ASTM F432-95 may be used, provided that the use of such materials is approved by the District Manager based on—
(1) Demonstrations which show that the materials have successfully supported the roof in an area of a coal mine with similar strata, opening dimensions and roof stresses; or
(2) Tests which show the materials to be effective for supporting the roof in an area of the affected mine which has similar strata, opening dimensions and roof stresses as the area where the roof bolts are to be used. During the test process, access to the test area shall be limited to persons necessary to conduct the test.
(c)(1) A bearing plate shall be firmly installed with each roof bolt.
(2) Bearing plates used directly against the mine roof shall be at least 6 inches square or the equivalent, except that where the mine roof is firm and not susceptible to sloughing, bearing plates 5 inches square or the equivalent may be used.
(3) Bearing plates used with wood or metal materials shall be at least 4 inches square or the equivalent.
(4) Wooden materials that are used between a bearing plate and the mine roof in areas which will exist for three years or more shall be treated to minimize deterioration.
(d) When washers are used with roof bolts, the washers shall conform to the shape of the roof bolt head and bearing plate.
(e)(1) The diameter of finishing bits shall be within a tolerance of plus or minus 0.030 inch of the manufacturer's recommended hole diameter for the anchor used.
(2) When separate finishing bits are used, they shall be distinguishable from other bits.
(f) Tensioned roof bolts. (1) Roof bolts that provide support by creating a beam of laminated strata shall be at least 30 inches long. Roof bolts that provide support by suspending the roof from overlying stronger strata shall be long enough to anchor at least 12 inches into the stronger strata.
(2) Test holes, spaced at intervals specified in the roof control plan, shall be drilled to a depth of at least 12 inches above the anchorage horizon of mechanically anchored tensioned bolts being used. When a test hole indicates that bolts would not anchor in competent strata, corrective action shall be taken.
(3) The installed torque or tension ranges for roof bolts as specified in the roof control plan shall maintain the integrity of the support system and shall not exceed the yield point of the roof bolt nor anchorage capacity of the strata.
(4) In each roof bolting cycle, the actual torque or tension of the first tensioned roof bolt installed with each drill head shall be measured immediately after it is installed. Thereafter, for each drill head used, at least one roof bolt out of every four installed shall be measured for actual torque or tension. If the torque or tension of any of the roof bolts measured is not within the range specified in the roof control plan, corrective action shall be taken.
(5) In working places from which coal is produced during any portion of a 24-hour period, the actual torque or tension on at least one out of every ten previously installed mechanically anchored tensioned roof bolts shall be measured from the outby corner of the last open crosscut to the face in each advancing section. Corrective action shall be taken if the majority of the bolts measured—
(i) Do not maintain at least 70 percent of the minimum torque or tension specified in the roof control plan, 50 percent if the roof bolt plates bear against wood; or
(ii) Have exceeded the maximum specified torque or tension by 50 percent.
(6) The mine operator or a person designated by the operator shall certify by signature and date that measurements required by paragraph (f)(5) of this section have been made. This certification shall be maintained for at least one year and shall be made available to an authorized representative of the Secretary and representatives of the miners.
(7) Tensioned roof bolts installed in the roof support pattern shall not be used to anchor trailing cables or used for any other purpose that could affect the tension of the bolt. Hanging trailing cables, line brattice, telephone lines, or other similar devices which do not place sudden loads on the bolts are permitted.
(8) Angle compensating devices shall be used to compensate for the angle when tensioned roof bolts are installed at angles greater than 5 degrees from the perpendicular to the bearing plate.
(g) Non-tensioned grouted roof bolts. The first non-tensioned grouted roof bolt installed during each roof bolting cycle shall be tested during or immediately after the first row of bolts has been installed. If the bolt tested does not withstand at least 150 foot-pounds of torque without rotating in the hole, corrective action shall be taken.
When roof bolts are installed by a continuous mining machine with integral roof bolting equipment:
(a) The distance between roof bolts shall not exceed 10 feet crosswise.
(b) Roof bolts to be installed 9 feet or more apart shall be installed with a wooden crossbar at least 3 inches thick and 8 inches wide, or material which provides equivalent support.
(c) Roof bolts to be installed more than 8 feet but less than 9 feet apart shall be installed with a wooden plank at least 2 inches thick and 8 inches wide, or material which provides equivalent support.
(a) Except in anthracite mines using non-mechanized mining systems, when conventional roof support materials are used as the only means of support—
(1) The width of any opening shall not exceed 20 feet;
(2) The spacing of roadway roof support shall not exceed 5 feet;
(3)(i) Supports shall be installed to within 5 feet of the uncut face;
(ii) When supports nearest the face must be removed to facilitate the operation of face equipment, equivalent temporary support shall be installed prior to removing the supports;
(4) Straight roadways shall not exceed 16 feet wide where full overhead support is used and 14 feet wide where only posts are used;
(5) Curved roadways shall not exceed 16 feet wide; and
(6) The roof at the entrance of all openings along travelways which are no longer needed for storing supplies or for travel of equipment shall be supported by extending the line of support across the opening.
(b) Conventional roof support materials shall meet the following specifications:
(1) The minimum diameter of cross-sectional area of wooden posts shall be as follows:
Post length (in inches)
Diameter of round posts (in inches)
Cross-sectional area of split posts (in square inches)
60 or less
4
13
Over 60 to 84
5
20
Over 84 to 108
6
28
Over 108 to 132
7
39
Over 132 to 156
8
50
Over 156 to 180
9
64
Over 180 to 204
10
79
Over 204 to 228
11
95
Over 228
12
113
(2) Wooden materials used for support shall have the following dimensions:
(i) Cap blocks and footings shall have flat sides and be at least 2 inches thick, 4 inches wide and 12 inches long.
(ii) Crossbars shall have a minimum cross-sectional area of 24 square inches and be at least 3 inches thick.
(iii) Planks shall be at least 6 inches wide and 1 inch thick.
(3) Cribbing materials shall have at least two parallel flat sides.
(c) A cluster of two or more posts that provide equivalent strength may be used to meet the requirements of paragraph (b)(1) of this section, except that no post shall have a diameter less than 4 inches or have a cross-sectional area less than 13 square inches.
(d) Materials other than wood used for support shall have support strength at least equivalent to wooden material meeting the applicable provisions of this section.
(e) Posts and jacks shall be tightly installed on solid footing.
(f) When posts are installed under roof susceptible to sloughing a cap block, plank, crossbar or materials that are equally effective shall be placed between the post and the roof.
(g) Blocks used for lagging between the roof and crossbars shall be spaced to distribute the load.
(h) Jacks used for roof support shall be used with at least 36 square inches of roof bearing surface.
Pillar recovery shall be conducted in the following manner, unless otherwise specified in the roof control plan:
(a) Full and partial pillar recovery shall not be conducted on the same pillar line, except where physical conditions such as unstable floor or roof, falls of roof, oil and gas well barriers or surface subsidence require that pillars be left in place.
(b) Before mining is started in a pillar split or lift—
(1) At least two rows of breaker posts or equivalent support shall be installed—
(i) As close to the initial intended breakline as practicable; and
(ii) Across each opening leading into an area where full or partial pillar extraction has been completed.
(2) A row of roadside-radius (turn) posts or equivalent support shall be installed leading into the split or lift.
(c) Before mining is started on a final stump—
(1) At least 2 rows of posts or equivalent support shall be installed on not more than 4-foot centers on each side of the roadway; and
(2) Only one open roadway, which shall not exceed 16 feet wide, shall lead from solid pillars to the final stump of a pillar. Where posts are used as the sole means of roof support, the width of the roadway shall not exceed 14 feet.
(d) During open-end pillar extraction, at least 2 rows of breaker posts or equivalent support shall be installed on not more than 4-foot centers. These supports shall be installed between the lift to be started and the area where pillars have been extracted. These supports shall be maintained to within 7 feet of the face and the width of the roadway shall not exceed 16 feet. Where posts are used as the sole means of roof support, the width of the roadway shall not exceed 14 feet.
Except during the installation of roof supports, the end of permanent roof support shall be posted with a readily visible warning, or a physical barrier shall be installed to impede travel beyond permanent support.
(a) Except in anthracite mines and as specified in paragraphs (b) and (c) of this section, an ATRS system shall be used with roof bolting machines and continuous-mining machines with integral roof bolters operated in a working section. The requirements of this paragraph shall be met according to the following schedule:
(1) All new machines ordered after March 28, 1988.
(2) All existing machines operated in mining heights of 36 inches or more after March 28, 1989; and
(3) All existing machines operated in mining heights of 30 inches or more but less than 36 inches after March 28, 1990.
(b) After March 28, 1990 the use of ATRS systems with existing roof bolting machines and continuous-mining machines with integral roof bolters operated in a working section where the mining height is less than 30 inches shall be addressed in the roof control plan.
(c) Alternative means of temporary support shall be used, as specified in the roof control plan, when—
(1) Mining conditions or circumstances prevent the use of an ATRS system; or
(2) Temporary supports are installed in conjunction with an ATRS system.
(d) Persons shall work or travel between the support device of the ATRS system and another support, and the distance between the support device of the ATRS system and support to the left, right or beyond the ATRS system, shall not exceed 5 feet.
(e) Each ATRS system shall meet each of the following:
(1) The ATRS system shall elastically support a deadweight load measured in pounds of at least 450 times each square foot of roof intended to be supported, but in no case less than 11,250 pounds.
(2) The controls that position and set the ATRS system shall be—
(i) Operable from under permanently supported roof; or
(ii) Located in a compartment, which includes a deck, that provides the equipment operator with overhead and lateral protection, and has the structural capacity to elastically support a deadweight load of at least 18,000 pounds.
(3) All jacks affecting the capacity of the ATRS system and compartment shall have check valves or equivalent devices that will prevent rapid collapse in the event of a system failure.
(4) Except for the main tram controls, tram controls for positioning the equipment to set the ATRS system shall limit the speed of the equipment to a maximum of 80 feet-per-minute.
(f) The support capacity of each ATRS system and the structural capacity of each compartment shall be certified by a registered engineer as meeting the applicable requirements of paragraphs (e)(1) and (e)(2) of this section. The certifications shall be made available to an authorized representative of the Secretary and representative of the miners.
(a) When manually installing temporary support, only persons engaged in installing the support shall proceed beyond permanent support.
(b) When manually installing temporary supports, the first temporary support shall be set no more than 5 feet from a permanent roof support and the rib. All temporary supports shall be set so that the person installing the supports remains between the temporary support being set and two other supports which shall be no more than 5 feet from the support being installed. Each temporary support shall be completely installed prior to installing the next temporary support.
(c) All temporary supports shall be placed on no more than 5-foot centers.
(d) Once temporary supports have been installed, work or travel beyond permanent roof support shall be done between temporary supports and the nearest permanent support or between other temporary supports.
(a) A visual examination of the roof, face and ribs shall be made immediately before any work is started in an area and thereafter as conditions warrant.
(b) Where the mining height permits and the visual examination does not disclose a hazardous condition, sound and vibration roof tests, or other equivalent tests, shall be made where supports are to be installed. When sound and vibration tests are made, they shall be conducted—
(1) After the ATRS system is set against the roof and before other support is installed; or
(2) Prior to manually installing a roof support. This test shall begin under supported roof and progress no further than the location where the next support is to be installed.
(c) When a hazardous roof, face, or rib condition is detected, the condition shall be corrected before there is any other work or travel in the affected area. If the affected area is left unattended, each entrance to the area shall be posted with a readily visible warning, or a physical barrier shall be installed to impede travel into the area.
(d) A bar for taking down loose material shall be available in the working place or on all face equipment except haulage equipment. Bars provided for taking down loose material shall be of a length and design that will allow the removal of loose material from a position that will not expose the person performing this work to injury from falling material.
(a) Before rehabilitating each area where a roof fall has occurred or the roof has been removed by mining machines or by blasting—
(1) The mine operator shall establish the clean up and support procedures that will be followed;
(2) All persons assigned to perform rehabilitation work shall be instructed in the clean-up and support procedures; and
(3) Ineffective, damaged or missing roof support at the edge of the area to be rehabilitated shall be replaced or other equivalent support installed.
(b) All persons who perform rehabilitation work shall be experienced in this work or they shall be supervised by a person experienced in rehabilitation work who is designated by the mine operator.
(c) Where work is not being performed to rehabilitate an area in active workings where a roof fall has occurred or the roof has been removed by mining machines or by blasting, each entrance to the area shall be supported by at least one row of posts on not more than 5-foot centers, or equally effective support.
(a)(1) All persons who perform the work of removing permanent roof supports shall be supervised by a management person experienced in removing roof supports.
(2) Only persons with at least one year of underground mining experience shall perform permanent roof support removal work.
(b) Prior to the removal of permanent roof supports, the person supervising roof support removal in accordance with paragraph (a)(1) of this section shall examine the roof conditions in the area where the supports are to be removed and designate each support to be removed.
(c)(1) Except as provided in paragraph (g) of this section, prior to the removal of permanent supports, a row of temporary supports on no more than 5-foot centers or equivalent support shall be installed across the opening within 4 feet of the supports being removed. Additional supports shall be installed where necessary to assure safe removal.
(2) Prior to the removal of roof bolts, temporary support shall be installed as close as practicable to each roof bolt being removed.
(d) Temporary supports installed in accordance with this section shall not be removed unless—
(1) Removal is done by persons who are in a remote location under supported roof; and
(2) At least two rows of temporary supports, set across the opening on no more than 5-foot centers, are maintained between the miners and the unsupported area.
(e) Each entrance to an area where supports have been removed shall be posted with a readily visible warning or a physical barrier shall be installed to impede travel into the area.
(f) Except as provided in paragraph (g) of this section, permanent support shall not be removed where—
(1) Roof bolt torque or tension measurements or the condition of conventional support indicate excessive loading;
(2) Roof fractures are present;
(3) There is any other indication that the roof is structurally weak; or
(4) Pillar recovery has been conducted.
(g) Permanent supports may be removed provided that:
(1) Removal is done by persons who are in a remote location under supported roof; and
(2) At least two rows of temporary supports, set across the opening on no more than 5-foot centers, are maintained between the miners and the unsupported area.
(h) The provisions of this section do not apply to removal of conventional supports for starting crosscuts and pillar splits or lifts except that prior to the removal of these supports an examination of the roof conditions shall be made.
(a) A supply of supplementary roof support materials and the tools and equipment necessary to install the materials shall be available at a readily accessible location on each working section or within four crosscuts of each working section.
(b) The quantity of support materials and tools and equipment maintained available in accordance with this section shall be sufficient to support the roof if adverse roof conditions are encountered, or in the event of an accident involving a fall.
For each longwall mining section, the roof control plan shall specify—
(a) The methods that will be used to maintain a safe travelway out of the section through the tailgate side of the longwall; and
(b) The procedures that will be followed if a ground failure prevents travel out of the section through the tailgate side of the longwall.
(a)(1) Each mine operator shall develop and follow a roof control plan, approved by the District Manager, that is suitable to the prevailing geological conditions, and the mining system to be used at the mine. Additional measures shall be taken to protect persons if unusual hazards are encountered.
(2) The proposed roof control plan and any revisions to the plan shall be submitted, in writing, to the District Manager. When revisions to a roof control plan are proposed, only the revised pages need to be submitted unless otherwise specified by the District Manager.
(b)(1) The mine operator will be notified in writing of the approval or denial of approval of a proposed roof control plan or proposed revision.
(2) When approval of a proposed plan or revision is denied, the deficiencies of the plan or revision and recommended changes will be specified and the mine operator will be afforded an opportunity to discuss the deficiencies and changes with the District Manager.
(3) Before new support materials, devices or systems other than roof bolts and accessories, are used as the only means of roof support, the District Manager may require that their effectiveness be demonstrated by experimental installations.
(c) No proposed roof control plan or revision to a roof control plan shall be implemented before it is approved.
(d) Before implementing an approved revision to a roof control plan, all persons who are affected by the revision shall be instructed in its provisions.
(e) The approved roof control plan and any revisions shall be available to the miners and representative of miners at the mine.
(a) The following information shall be included in each roof control plan:
(1) The name and address of the company.
(2) The name, address, mine identification number and location of the mine.
(3) The name and title of the company official responsible for the plan.
(4) A typical columnar section of the mine strata which shall—
(i) Show the name and the thickness of the coalbed to be mined and any persistent partings;
(ii) Identify the type and show the thickness of each stratum up to and including the main roof above the coalbed and for distance of at least 10 feet below the coalbed; and
(iii) Indicate the maximum cover over the area to be mined.
(5) A description and drawings of the sequence of installation and spacing of supports for each method of mining used.
(6) When an ATRS system is used, the maximum distance that an ATRS system is to be set beyond the last row of permanent support.
(7) When tunnel liners or arches are to be used for roof support, specifications and installation procedures for the liners or arches.
(8) Drawings indicating the planned width of openings, size of pillars, method of pillar recovery, and the sequence of mining pillars.
(9) A list of all support materials required to be used in the roof, face and rib control system, including, if roof bolts are to be installed—
(i) The length, diameter, grade and type of anchorage unit to be used;
(ii) The drill hole size to be used; and
(iii) The installed torque or tension range for tensioned roof bolts.
(10) When mechanically anchored tensioned roof bolts are used, the intervals at which test holes will be drilled.
(11) A description of the method of protecting persons—
(i) From falling material at drift openings; and
(ii) When mining approaches within 150 feet of an outcrop.
(12) A description of the roof and rib support necessary for the refuge alternatives.
(b) Each drawing submitted with a roof control plan shall contain a legend explaining all symbols used and shall specify the scale of the drawing which shall not be less than 5 feet to the inch or more than 20 feet to the inch.
(c) All roof control plan information, including drawings, shall be submitted on 8
1/2 by 11 inch paper, or paper folded to this size.
(a) This section sets forth the criteria that shall be considered on a mine-by-mine basis in the formulation and approval of roof control plans and revisions. Additional measures may be required in plans by the District Manager. Roof control plans that do not conform to the applicable criteria in this section may be approved by the District Manager, provided that effective control of the roof, face and ribs can be maintained.
(b) Roof Bolting. (1) Roof bolts should be installed on centers not exceeding 5 feet lengthwise and crosswise, except as specified in § 75.205.
(2) When tensioned roof bolts are used as a means of roof support, the torque or tension range should be capable of supporting roof bolt loads of at least 50 percent of either the yield point of the bolt or anchorage capacity of the strata, whichever is less.
(3) Any opening that is more than 20 feet wide should be supported by a combination of roof bolts and conventional supports.
(4) In any opening more than 20 feet wide—
(i) Posts should be installed to limit each roadway to 16 feet wide where straight and 18 feet wide where curved; and
(ii) A row of posts should be set for each 5 feet of space between the roadway posts and the ribs.
(5) Openings should not be more than 30 feet wide.
(c) Installation of roof support using mining machines with integral roof bolters. (1) Before an intersection or pillar split is started, roof bolts should be installed on at least 5-foot centers where the work is performed.
(2) Where the roof is supported by only two roof bolts crosswise, openings should not be more than 16 feet wide.
(d) Pillar recovery. (1) During development, any dimension of a pillar should be at least 20 feet.
(2) Pillar splits and lifts should not be more than 20 feet wide.
(3) Breaker posts should be installed on not more than 4-foot centers.
(4) Roadside-radius (turn) posts, or equivalent support, should be installed on not more than 4-foot centers leading into each pillar split or lift.
(5) Before full pillar recovery is started in areas where roof bolts are used as the only means of roof support and openings are more than 16 feet wide, at least one row of posts should be installed to limit the roadway width to 16 feet. These posts should be—
(i) Extended from the entrance to the split through the intersection outby the pillar in which the split or lift is being made; and
(ii) Spaced on not more than 5-foot centers.
(e) Unsupported openings at intersections. Openings that create an intersection should be permanently supported or at least one row of temporary supports should be installed on not more than 5-foot centers across the opening before any other work or travel in the intersection.
(f) ATRS systems in working sections where the mining height is below 30 inches. In working sections where the mining height is below 30 inches, an ATRS system should be used to the extent practicable during the installation of roof bolts with roof bolting machines and continuous-mining machines with integral roof bolters.
(g) Longwall mining systems. (1) Systematic supplemental support should be installed throughout—
(i) The tailgate entry of the first longwall panel prior to any mining; and
(ii) In the proposed tailgate entry of each subsequent panel in advance of the frontal abutment stresses of the panel being mined.
(2) When a ground failure prevents travel out of the section through the tailgate side of the longwall section, the roof control plan should address—
(i) Notification of miners that the travelway is blocked;
(ii) Re-instruction of miners regarding escapeways and escape procedures in the event of an emergency;
(iii) Re-instruction of miners on the availability and use of self-contained self-rescue devices;
(iv) Monitoring and evaluation of the air entering the longwall section;
(v) Location and effectiveness of the two-way communication systems; and
(vi) A means of transportation from the section to the main line.
(3) The plan provisions addressed by paragraph (g)(2) of this section should remain in effect until a travelway is reestablished on the tailgate side of a longwall section.
(a) Revisions of the roof control plan shall be proposed by the operator—
(1) When conditions indicate that the plan is not suitable for controlling the roof, face, ribs, or coal or rock bursts; or
(2) When accident and injury experience at the mine indicates the plan is inadequate. The accident and injury experience at each mine shall be reviewed at least every six months.
(b) Each unplanned roof fall and rib fall and coal or rock burst that occurs in the active workings shall be plotted on a mine map if it—
(1) Is above the anchorage zone where roof bolts are used;
(2) Impairs ventilation;
(3) Impedes passage of persons;
(4) Causes miners to be withdrawn from the area affected; or
(5) Disrupts regular mining activities for more than one hour.
(c) The mine map on which roof falls are plotted shall be available at the mine site for inspection by authorized representatives of the Secretary and representatives of miners at the mine.
(d) The roof control plan for each mine shall be reviewed every six months by an authorized representative of the Secretary. This review shall take into consideration any falls of the roof, face and ribs and the adequacy of the support systems used at the time.
This subpart sets requirements for underground coal mine ventilation.
In addition to the applicable definitions in § 75.2, the following definitions apply in this subpart.
Air course. An entry or a set of entries separated from other entries by stoppings, overcasts, other ventilation control devices, or by solid blocks of coal or rock so that any mixing of air currents between each is limited to leakage.
AMS operator. The person(s), designated by the mine operator, who is located on the surface of the mine and monitors the malfunction, alert, and alarm signals of the AMS and notifies appropriate personnel of these signals.
Appropriate personnel. The person or persons designated by the operator to perform specific tasks in response to AMS signals. Appropriate personnel include the responsible person(s) required by § 75.1501 when an emergency evacuation is necessary.
Atmospheric Monitoring System (AMS). A network consisting of hardware and software meeting the requirements of §§ 75.351 and 75.1103-2 and capable of: measuring atmospheric parameters; transmitting the measurements to a designated surface location; providing alert and alarm signals; processing and cataloging atmospheric data; and, providing reports. Early-warning fire detection systems using newer technology that provides equal or greater protection, as determined by the Secretary, will be considered atmospheric monitoring systems for the purposes of this subpart.
Belt air course. The entry in which a belt is located and any adjacent entry(ies) not separated from the belt entry by permanent ventilation controls, including any entries in series with the belt entry, terminating at a return regulator, a section loading point, or the surface.
Carbon monoxide ambient level. The average concentration in parts per million (ppm) of carbon monoxide detected in an air course containing carbon monoxide sensors. This average concentration is representative of the composition of the mine atmosphere over a period of mining activity during non-fire conditions. Separate ambient levels may be established for different areas of the mine.
Incombustible. Incapable of being burned.
Intake air. Air that has not yet ventilated the last working place on any split of any working section, or any worked-out area, whether pillared or nonpillared.
Intrinsically safe. Incapable of releasing enough electrical or thermal energy under normal or abnormal conditions to cause ignition of a flammable mixture of methane or natural gas and air of the most easily ignitable composition.
Noncombustible structure or area. Describes a structure or area that will continue to provide protection against flame spread for at least 1 hour when subjected to a fire test incorporating an ASTM E119-88 time/temperature heat input, or equivalent. The publication ASTM E119-88 “Standard Test Methods for Fire Tests of Building Construction and Materials” is incorporated by reference and may be inspected at any MSHA Coal Mine Safety and Health District Office, or at MSHA's Office of Standards, Regulations, and Variances, 200 Constitution Avenue NW, Washington, DC 20210; 202-693-9440; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. In addition, copies of the document can be purchased from the American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; 610-832-9500; http://www.astm.org. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
Noncombustible material. Describes a material that, when used to construct a ventilation control, results in a control that will continue to serve its intended function for 1 hour when subjected to a fire test incorporating an ASTM E119-88 time/temperature heat input, or equivalent. The publication ASTM E119-88 “Standard Test Methods for Fire Tests of Building Construction and Materials” is incorporated by reference and may be inspected at any Coal Mine Safety and Health District Office, or at MSHA's Office of Standards, Regulations, and Variances, 200 Constitution Avenue NW, Washington, DC 20210; 202-693-9440; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. In addition, copies of the document can be purchased from the American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; 610-832-9500; http://www.astm.org. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
Point feeding. The process of providing additional intake air to the belt air course from another intake air course through a regulator.
Return air. Air that has ventilated the last working place on any split of any working section or any worked-out area whether pillared or nonpillared. If air mixes with air that has ventilated the last working place on any split of any working section or any worked-out area, whether pillared or nonpillared, it is considered return air. For the purposes of § 75.507-1, air that has been used to ventilate any working place in a coal producing section or pillared area, or air that has been used to ventilate any working face if such air is directed away from the immediate return is return air. Notwithstanding the definition of intake air, for the purpose of ventilation of structures, areas or installations that are required by this subpart D to be ventilated to return air courses, and for ventilation of seals, other air courses may be designated as return air courses by the operator only when the air in these air courses will not be used to ventilate working places or other locations, structures, installations or areas required to be ventilated with intake air.
Worked-out area. An area where mining has been completed, whether pillared or nonpillared, excluding developing entries, return air courses, and intake air courses.
Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main mine fans except in anthracite mines. In anthracite mines, booster fans installed in the main air current or a split of the main air current may be used provided their use is approved in the ventilation plan.
(a) Each main mine fan shall be—
(1) Installed on the surface in an incombustible housing;
(2) Connected to the mine opening with incombustible air ducts;
(3) Equipped with an automatic device that gives a signal at the mine when the fan either slows or stops. A responsible person designated by the operator shall always be at a surface location at the mine where the signal can be seen or heard while anyone is underground. This person shall be provided with two-way communication with the working sections and work stations where persons are routinely assigned to work for the majority of a shift;
(4) Equipped with a pressure recording device or system. Mines permitted to shut down main mine fans under § 75.311 and which do not have a pressure recording device installed on main mine fans shall have until June 10, 1997 to install a pressure recording device or system on all main mine fans. If a device or system other than a circular pressure recorder is used to monitor main mine fan pressure, the monitoring device or system shall provide a continuous graph or continuous chart of the pressure as a function of time. At not more than 7-day intervals, a hard copy of the continuous graph or chart shall be generated or the record of the fan pressure shall be stored electronically. When records of fan pressure are stored electronically, the system used to store these records shall be secure and not susceptible to alteration and shall be capable of storing the required data. Records of the fan pressure shall be retained at a surface location at the mine for at least 1 year and be made available for inspection by authorized representatives of the Secretary and the representative of miners;
(5) Protected by one or more weak walls or explosion doors, or a combination of weak walls and explosion doors, located in direct line with possible explosive forces;
(6) Except as provided under paragraph (e) of this section, offset by at least 15 feet from the nearest side of the mine opening unless an alternative method of protecting the fan and its associated components is approved in the ventilation plan.
(b)(1) If an electric motor is used to drive a main mine fan, the motor shall operate from a power circuit independent of all mine power circuits.
(2) If an internal combustion engine is used to drive a main mine fan—
(i) The fuel supply shall be protected against fires and explosions;
(ii) The engine shall be installed in an incombustible housing and be equipped with a remote shut-down device;
(iii) The engine and the engine exhaust system shall be located out of direct line of the air current exhausting from the mine; and
(iv) The engine exhaust shall be vented to the atmosphere so that the exhaust gases do not contaminate the mine intake air current or any enclosure.
(c) If a main mine fan monitoring system is used under § 75.312, the system shall—
(1) Record, as described in paragraph (a)(4) the mine ventilating pressure;
(2) Monitor bearing temperature, revolutions per minute, vibration, electric voltage, and amperage;
(3) Provide a printout of the monitored parameters, including the mine ventilating pressure within a reasonable period, not to exceed the end of the next scheduled shift during which miners are underground; and
(4) Be equipped with an automatic device that signals when—
(i) An electrical or mechanical deficiency exists in the monitoring system; or
(ii) A sudden increase or loss in mine ventilating pressure occurs.
(5) Provide monitoring, records, printouts, and signals required by paragraphs (c)(1) through (c)(4) at a surface location at the mine where a responsible person designated by the operator is always on duty and where signals from the monitoring system can be seen or heard while anyone is underground. This person shall be provided with two-way communication with the working sections and work stations where persons are routinely assigned to work for the majority of a shift.
(d) Weak walls and explosion doors shall have cross-sectional areas at least equal to that of the entry through which the pressure from an explosion underground would be relieved. A weak wall and explosion door combination shall have a total cross-sectional area at least equal to that of the entry through which the pressure from an explosion underground would be relieved.
(e) If a mine fan is installed in line with an entry, a slope, or a shaft—
(1) The cross-sectional area of the pressure relief entry shall be at least equal to that of the fan entry;
(2) The fan entry shall be developed out of direct line with possible explosive forces;
(3) The coal or other solid material between the pressure relief entry and the fan entry shall be at least 2,500 square feet; and
(4) The surface opening of the pressure relief entry shall be not less than 15 feet nor more than 100 feet from the surface opening of the fan entry and from the underground intersection of the fan entry and pressure relief entry.
(f) In mines ventilated by multiple main mine fans, incombustible doors shall be installed so that if any main mine fan stops and air reversals through the fan are possible, the doors on the affected fan automatically close.
(a) Main mine fans shall be continuously operated, except as otherwise approved in the ventilation plan, or when intentionally stopped for testing of automatic closing doors and automatic fan signal devices, maintenance or adjustment of the fan, or to perform maintenance or repair work underground that cannot otherwise be made while the fan is operating.
(b) Except as provided in paragraph (c) of this section, when a main mine fan is intentionally stopped and the ventilating quantity provided by the fan is not maintained by a back-up fan system—
(1) Only persons necessary to evaluate the effect of the fan stoppage or restart, or to perform maintenance or repair work that cannot otherwise be made while the fan is operating, shall be permitted underground;
(2) Mechanized equipment shall be shut off before stopping the fan; and
(3) Electric power circuits entering underground areas of the mine shall be deenergized.
(c) When a back-up fan system is used that does not provide the ventilating quantity provided by the main mine fan, persons may be permitted in the mine and electric power circuits may be energized as specified in the approved ventilation plan.
(d) If an unusual variance in the mine ventilation pressure is observed, or if an electrical or mechanical deficiency of a main mine fan is detected, the mine foreman or equivalent mine official, or in the absence of the mine foreman or equivalent mine official, a designated certified person acting for the mine foreman or equivalent mine official shall be notified immediately, and appropriate action or repairs shall be instituted promptly.
(e) While persons are underground, a responsible person designated by the operator shall always be at a surface location where each main mine fan signal can be seen or heard.
(f) The area within 100 feet of main mine fans and intake air openings shall be kept free of combustible material, unless alternative precautions necessary to provide protection from fire or other products of combustion are approved in the ventilation plan.
(g) If multiple mine fans are used, the mine ventilation system shall be designed and maintained to eliminate areas without air movement.
(h) Any atmospheric monitoring system operated during fan stoppages shall be intrinsically safe.
(a) To assure electrical and mechanical reliability of main mine fans, each main mine fan and its associated components, including devices for measuring or recording mine ventilation pressure, shall be examined for proper operation by a trained person designated by the operator. Examinations of main mine fans shall be made at least once each day that the fan operates, unless a fan monitoring system is used. No examination is required on any day when no one, including certified persons, goes underground, except that an examination shall be completed prior to anyone entering the mine.
(b)(1) If a main mine fan monitoring system is used, a trained person designated by the operator shall—
(i) At least once each day review the data provided by the fan monitoring system to assure that the fan and the fan monitoring system are operating properly. No review is required on any day when no one, including certified persons, goes underground, except that a review of the data shall be performed prior to anyone entering the underground portion of the mine. Data reviewed should include the fan pressure, bearing temperature, revolutions per minute, vibration, electric voltage, and amperage; and
(ii) At least every 7 days—
(A) Test the monitoring system for proper operation; and
(B) Examine each main mine fan and its associated components to assure electrical and mechanical reliability of main mine fans.
(2) If the monitoring system malfunctions, the malfunction shall be corrected, or paragraph (a) of this section shall apply.
(c) At least every 31 days, the automatic fan signal device for each main mine fan shall be tested by stopping the fan. Only persons necessary to evaluate the effect of the fan stoppage or restart, or to perform maintenance or repair work that cannot otherwise be made while the fan is operating, shall be permitted underground. Notwithstanding the requirement of § 75.311(b)(3), underground power may remain energized during this test provided no one, including persons identified in § 75.311(b)(1), is underground. If the fan is not restarted within 15 minutes, underground power shall be deenergized and no one shall enter any underground area of the mine until the fan is restarted and an examination of the mine is conducted as described in § 75.360 (b) through (e) and the mine has been determined to be safe.
(d) At least every 31 days, the automatic closing doors in multiple main mine fan systems shall be tested by stopping the fan. Only persons necessary to evaluate the effect of the fan stoppage or restart, or to perform maintenance or repair work that cannot otherwise be made while the fan is operating, shall be permitted underground. Notwithstanding the provisions of § 75.311, underground power may remain energized during this test provided no one, including persons identified in § 75.311(b)(1), is underground. If the fan is not restarted within 15 minutes, underground power shall be deenergized and no one shall enter any underground area of the mine, until the fan is restarted and an examination of the mine is conducted as described in § 75.360 (b) through (e) and the mine has been determined to be safe.
(e) Circular main mine fan pressure recording charts shall be changed before the beginning of a second revolution.
(f)(1) Certification. Persons making main mine fan examinations shall certify by initials and date at the fan or another location specified by the operator that the examinations were made. Each certification shall identify the main mine fan examined.
(2) Persons reviewing data produced by a main mine fan monitoring system shall certify by initials and date on a printed copy of the data from the system that the review was completed. In lieu of certification on a copy of the data, the person reviewing the data may certify electronically that the review was completed. Electronic certification shall be by handwritten initials and date in a computer system so as to be secure and not susceptible to alteration.
(g)(1) Recordkeeping. By the end of the shift on which the examination is made, persons making main mine fan examinations shall record all uncorrected defects that may affect the operation of the fan that are not corrected by the end of that shift. Records shall be maintained in a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration.
(2) When a fan monitoring system is used in lieu of the daily fan examination—
(i) The certified copies of data produced by fan monitoring systems shall be maintained separate from other computer-generated reports or data; and
(ii) A record shall be made of any fan monitoring system malfunctions, electrical or mechanical deficiencies in the monitoring system and any sudden increase or loss in mine ventilating pressure. The record shall be made by the end of the shift on which the review of the data is completed and shall be maintained in a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration.
(3) By the end of the shift on which the monthly test of the automatic fan signal device or the automatic closing doors is completed, persons making these tests shall record the results of the tests. Records shall be maintained in a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration.
(h) Retention period. Records, including records of mine fan pressure and the certified copies of data produced by fan monitoring systems, shall be retained at a surface location at the mine for at least 1 year and shall be made available for inspection by authorized representatives of the Secretary and the representative of miners.
(a) If a main mine fan stops while anyone is underground and the ventilating quantity provided by the fan is not maintained by a back-up fan system—
(1) Electrically powered equipment in each working section shall be deenergized;
(2) Other mechanized equipment in each working section shall be shut off; and
(3) Everyone shall be withdrawn from the working sections and areas where mechanized mining equipment is being installed or removed.
(b) If ventilation is restored within 15 minutes after a main mine fan stops, certified persons shall examine for methane in the working places and in other areas where methane is likely to accumulate before work is resumed and before equipment is energized or restarted in these areas.
(c) If ventilation is not restored within 15 minutes after a main mine fan stops—
(1) Everyone shall be withdrawn from the mine;
(2) Underground electric power circuits shall be deenergized. However, circuits necessary to withdraw persons from the mine need not be deenergized if located in areas or haulageways where methane is not likely to migrate to or accumulate. These circuits shall be deenergized as persons are withdrawn; and
(3) Mechanized equipment not located on working sections shall be shut off. However, mechanized equipment necessary to withdraw persons from the mine need not be shut off if located in areas where methane is not likely to migrate to or accumulate.
(d)(1) When ventilation is restored—
(i) No one other than designated certified examiners shall enter any underground area of the mine until an examination is conducted as described in § 75.360(b) through (e) and the area has been determined to be safe. Designated certified examiners shall enter the underground area of the mine from which miners have been withdrawn only after the fan has operated for at least 15 minutes unless a longer period of time is specified in the approved ventilation plan.
(ii) Underground power circuits shall not be energized and nonpermissible mechanized equipment shall not be started or operated in an area until an examination is conducted as described in § 75.360(b) through (e) and the area has been determined to be safe, except that designated certified examiners may use nonpermissible transportation equipment in intake airways to facilitate the making of the required examination.
(2) If ventilation is restored to the mine before miners reach the surface, the miners may return to underground working areas only after an examination of the areas is made by a certified person and the areas are determined to be safe.
(e) Any atmospheric monitoring system operated during fan stoppages shall be intrinsically safe.
(f) Any electrical refuge alternative components exposed to the mine atmosphere shall be approved as intrinsically safe for use during fan stoppages. Any electrical refuge alternative components located inside the refuge alternative shall be either approved as intrinsically safe or approved as permissible for use during fan stoppages.
(a) Tests for methane shall be made by a qualified person with MSHA approved detectors that are maintained in permissible and proper operating condition and calibrated with a known methane-air mixture at least once every 31 days.
(b) Tests for oxygen deficiency shall be made by a qualified person with MSHA approved oxygen detectors that are maintained in permissible and proper operating condition and that can detect 19.5 percent oxygen with an accuracy of ±0.5 percent. The oxygen detectors shall be calibrated at the start of each shift that the detectors will be used.
(c) Handheld devices that contain electrical components and that are used for measuring air velocity, carbon monoxide, oxides of nitrogen, and other gases shall be approved and maintained in permissible and proper operating condition.
(d) An oxygen detector approved by MSHA shall be used to make tests for oxygen deficiency required by the regulations in this part. Permissible flame safety lamps may only be used as a supplementary testing device.
(e) Maintenance of instruments required by paragraphs (a) through (d) of this section shall be done by persons trained in such maintenance.
(a)(1) The air in areas where persons work or travel, except as specified in paragraph (a)(2) of this section, shall contain at least 19.5 percent oxygen and not more than 0.5 percent carbon dioxide, and the volume and velocity of the air current in these areas shall be sufficient to dilute, render harmless, and carry away flammable, explosive, noxious, and harmful gases, dusts, smoke, and fumes.
(2) The air in areas of bleeder entries and worked-out areas where persons work or travel shall contain at least 19.5 percent oxygen, and carbon dioxide levels shall not exceed 0.5 percent time weighted average and 3.0 percent short term exposure limit.
(b) Notwithstanding the provisions of § 75.322, for the purpose of preventing explosions from gases other than methane, the following gases shall not be permitted to accumulate in excess of the concentrations listed below:
(1) Carbon monoxide (CO)—2.5 percent
(2) Hydrogen (H 2 )—.80 percent
(3) Hydrogen sulfide (H 2 S)—.80 percent
(4) Acetylene (C 2 H 2 )—.40 percent
(5) Propane (C 3 H 8 )—.40 percent
(6) MAPP (methyl-acetylene-propylene-propodiene)—.30 percent
Concentrations of noxious or poisonous gases, other than carbon dioxide, shall not exceed the threshold limit values (TLV) as specified and applied by the American Conference of Governmental Industrial Hygienists in “Threshold Limit Values for Substance in Workroom Air” (1972). Detectors or laboratory analysis of mine air samples shall be used to determine the concentrations of harmful, noxious, or poisonous gases. This incorporation by reference has been approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies are available from MSHA's Office of Standards, Regulations, and Variances, 200 Constitution Avenue NW, Washington, DC 20210; 202-693-9440; and at every MSHA Coal Mine Safety and Health District Office. The material is available for examination at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
(a) Location of tests. Tests for methane concentrations under this section shall be made at least 12 inches from the roof, face, ribs, and floor.
(b) Working places and intake air courses. (1) When 1.0 percent or more methane is present in a working place or an intake air course, including an air course in which a belt conveyor is located, or in an area where mechanized mining equipment is being installed or removed—
(i) Except intrinsically safe atmospheric monitoring systems (AMS), electrically powered equipment in the affected area shall be deenergized, and other mechanized equipment shall be shut off;
(ii) Changes or adjustments shall be made at once to the ventilation system to reduce the concentration of methane to less than 1.0 percent; and
(iii) No other work shall be permitted in the affected area until the methane concentration is less than 1.0 percent.
(2) When 1.5 percent or more methane is present in a working place or an intake air course, including an air course in which a belt conveyor is located, or in an area where mechanized mining equipment is being installed or removed—
(i) Everyone except those persons referred to in § 104(c) of the Act shall be withdrawn from the affected area; and
(ii) Except for intrinsically safe AMS, electrically powered equipment in the affected area shall be disconnected at the power source.
(c) Return air split. (1) When 1.0 percent or more methane is present in a return air split between the last working place on a working section and where that split of air meets another split of air, or the location at which the split is used to ventilate seals or worked-out areas changes or adjustments shall be made at once to the ventilation system to reduce the concentration of methane in the return air to less than 1.0 percent.
(2) When 1.5 percent or more methane is present in a return air split between the last working place on a working section and where that split of air meets another split of air, or the location where the split is used to ventilate seals or worked-out areas—
(i) Everyone except those persons referred to in § 104(c) of the Act shall be withdrawn from the affected area;
(ii) Other than intrinsically safe AMS, equipment in the affected area shall be deenergized, electric power shall be disconnected at the power source, and other mechanized equipment shall be shut off; and
(iii) No other work shall be permitted in the affected area until the methane concentration in the return air is less than 1.0 percent.
(d) Return air split alternative. (1) The provisions of this paragraph apply if—
(i) The quantity of air in the split ventilating the active workings is at least 27,000 cubic feet per minute in the last open crosscut or the quantity specified in the approved ventilation plan, whichever is greater;
(ii) The methane content of the air in the split is continuously monitored during mining operations by an AMS that gives a visual and audible signal on the working section when the methane in the return air reaches 1.5 percent, and the methane content is monitored as specified in § 75.351; and
(iii) Rock dust is continuously applied with a mechanical duster to the return air course during coal production at a location in the air course immediately outby the most inby monitoring point.
(2) When 1.5 percent or more methane is present in a return air split between a point in the return opposite the section loading point and where that split of air meets another split of air or where the split of air is used to ventilate seals or worked-out areas—
(i) Changes or adjustments shall be made at once to the ventilation system to reduce the concentration of methane in the return air below 1.5 percent;
(ii) Everyone except those persons referred to in § 104(c) of the Act shall be withdrawn from the affected area;
(iii) Except for intrinsically safe AMS, equipment in the affected area shall be deenergized, electric power shall be disconnected at the power source, and other mechanized equipment shall be shut off; and
(iv) No other work shall be permitted in the affected area until the methane concentration in the return air is less than 1.5 percent.
(e) Bleeders and other return air courses. The concentration of methane in a bleeder split of air immediately before the air in the split joins another split of air, or in a return air course other than as described in paragraphs (c) and (d) of this section, shall not exceed 2.0 percent.
(a) A person designated by the operator shall supervise any intentional change in ventilation that—
(1) Alters the main air current or any split of the main air current in a manner that could materially affect the safety or health of persons in the mine; or
(2) Affects section ventilation by 9,000 cubic feet per minute of air or more in bituminous or lignite mines, or 5,000 cubic feet per minute of air or more in anthracite mines.
(b) Intentional changes shall be made only under the following conditions:
(1) Electric power shall be removed from areas affected by the ventilation change and mechanized equipment in those areas shall be shut off before the ventilation change begins.
(2) Only persons making the change in ventilation shall be in the mine.
(3) Electric power shall not be restored to the areas affected by the ventilation change and mechanized equipment shall not be restarted until a certified person has examined these areas for methane accumulation and for oxygen deficiency and has determined that the areas are safe.
(a)(1) In bituminous and lignite mines the quantity of air shall be at least 3,000 cubic feet per minute reaching each working face where coal is being cut, mined, drilled for blasting, or loaded. When a greater quantity is necessary to dilute, render harmless, and carry away flammable, explosive, noxious, and harmful gases, dusts, smoke, and fumes, this quantity shall be specified in the approved ventilation plan. A minimum air quantity may be required to be specified in the approved ventilation plan for other working places or working faces.
(2) The quantity of air reaching the working face shall be determined at or near the face end of the line curtain, ventilation tubing, or other ventilation control device. If the curtain, tubing, or device extends beyond the last row of permanent roof supports, the quantity of air reaching the working face shall be determined behind the line curtain or in the ventilation tubing at or near the last row of permanent supports. When machine-mounted dust collectors are used in conjunction with blowing face ventilation systems, the quantity of air reaching the working face shall be determined with the dust collector turned off.
(3) If machine mounted dust collectors or diffuser fans are used, the approved ventilation plan shall specify the operating volume of the dust collector or diffuser fan.
(b) In bituminous and lignite mines, the quantity of air reaching the last open crosscut of each set of entries or rooms on each working section and the quantity of air reaching the intake end of a pillar line shall be at least 9,000 cubic feet per minute unless a greater quantity is required to be specified in the approved ventilation plan. This minimum also applies to sections which are not operating but are capable of producing coal by simply energizing the equipment on the section.
(c) In longwall and shortwall mining systems—
(1) The quantity of air shall be at least 30,000 cubic feet per minute reaching the working face of each longwall, unless the operator demonstrates that a lesser air quantity will maintain continual compliance with applicable methane and respirable dust standards. This lesser quantity shall be specified in the approved ventilation plan. A quantity greater than 30,000 cubic feet per minute may be required to be specified in the approved ventilation plan.
(2) The velocity of air that will be provided to control methane and respirable dust in accordance with applicable standards on each longwall or shortwall and the locations where these velocities will be provided shall be specified in the approved ventilation plan. The locations specified shall be at least 50 feet but no more than 100 feet from the headgate and tailgate, respectively.
(d) Ventilation shall be maintained during installation and removal of mechanized mining equipment. The approved ventilation plan shall specify the minimum quantity of air, the locations where this quantity will be provided and the ventilation controls required.
(e) In anthracite mines, the quantity of air shall be as follows:
(1) At least 1,500 cubic feet per minute reaching each working face where coal is being mined, unless a greater quantity is required to be specified in the approved ventilation plan.
(2) At least 5,000 cubic feet per minute passing through the last open crosscut in each set of entries or rooms and at the intake end of any pillar line, unless a greater quantity is required to be specified in the approved ventilation plan.
(3) When robbing areas where air currents cannot be controlled and air measurements cannot be obtained, the air shall have perceptible movement.
(f) The minimum ventilating air quantity for an individual unit of diesel-powered equipment being operated shall be at least that specified on the approval plate for that equipment. Such air quantity shall be maintained—
(1) In any working place where the equipment is being operated;
(2) At the section loading point during any shift the equipment is being operated on the working section;
(3) In any entry where the equipment is being operated outby the section loading point in areas of the mine developed on or after April 25, 1997;
(4) In any air course with single or multiple entries where the equipment is being operated outby the section loading point in areas of the mine developed prior to April 25, 1997; and
(5) At any other location required by the district manager and specified in the approved ventilation plan.
(g) The minimum ventilating air quantity where multiple units of diesel-powered equipment are operated on working sections and in areas where mechanized mining equipment is being installed or removed must be at least the sum of that specified on the approval plates of all the diesel-powered equipment on the working section or in the area where mechanized mining equipment is being installed or removed. The minimum ventilating air quantity shall be specified in the approved ventilation plan. For working sections such air quantity must be maintained—
(1) In the last open crosscut of each set of entries or rooms in each working section;
(2) In the intake, reaching the working face of each longwall; and
(3) At the intake end of any pillar line.
(h) The following equipment may be excluded from the calculations of ventilating air quantity under paragraph (g) if such equipment exclusion is approved by the district manager and specified in the ventilation plan:
(1) Self-propelled equipment meeting the requirements of § 75.1908(b);
(2) Equipment that discharges its exhaust into intake air that is coursed directly to a return air course;
(3) Equipment that discharges its exhaust directly into a return air course; and
(4) Other equipment having duty cycles such that the emissions would not significantly affect the exposure of miners.
(i) A ventilating air quantity that is less than what is required by paragraph (g) of this section may be approved by the district manager in the ventilation plan based upon the results of sampling that demonstrate that the lesser air quantity will maintain continuous compliance with applicable TLV ®'s.
(j) If during sampling required by § 70.1900(c) of this subchapter the ventilating air is found to contain concentrations of CO or NO 2 in excess of the action level specified by § 70.1900(c), higher action levels may be approved by the district manager based on the results of sampling that demonstrate that a higher action level will maintain continuous compliance with applicable TLV ®'s. Action levels other than those specified in § 70.1900(c) shall be specified in the approved ventilation plan.
(k) As of November 25, 1997 the ventilating air quantity required where diesel-powered equipment is operated shall meet the requirements of paragraphs (f) through (j) of this section. Mine operators utilizing diesel-powered equipment in underground coal mines shall submit to the appropriate MSHA district manager a revised ventilation plan or appropriate amendments to the existing plan, in accordance with § 75.371, which implement the requirements of paragraphs (f) through (j) of this section.
In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per minute reaching each working face where coal is being cut, mined, drilled for blasting, or loaded, and to any other working places as required in the approved ventilation plan. A lower mean entry air velocity may be approved in the ventilation plan if the lower velocity will maintain methane and respirable dust concentrations in accordance with the applicable levels. Mean entry air velocity shall be determined at or near the inby end of the line curtain, ventilation tubing, or other face ventilation control devices.
(a) In any mine opened on or after March 30, 1970, or in any new working section of a mine opened before that date, where trolley haulage systems are maintained and where trolley wires or trolley feeder wires are installed, an authorized representative of the Secretary shall require enough entries or rooms as intake air courses to limit the velocity of air currents in the haulageways to minimize the hazards of fires and dust explosions in the haulageways.
(b) Unless the district manager approves a higher velocity, the velocity of the air current in the trolley haulage entries shall be limited to not more than 250 feet per minute. A higher air velocity may be required to limit the methane content in these haulage entries or elsewhere in the mine to less than 1.0 percent and provide an adequate supply of oxygen.
(a) Brattice cloth, ventilation tubing and other face ventilation control devices shall be made of flame-resistant material approved by MSHA.
(b)(1) Ventilation control devices shall be used to provide ventilation to dilute, render harmless, and to carry away flammable, explosive, noxious, and harmful gases, dusts, smoke, and fumes—
(i) To each working face from which coal is being cut, mined, drilled for blasting, or loaded; and
(ii) To any other working places as required by the approved ventilation plan.
(2) These devices shall be installed at a distance no greater than 10 feet from the area of deepest penetration to which any portion of the face has been advanced unless an alternative distance is specified and approved in the ventilation plan. Alternative distances specified shall be capable of maintaining concentrations of respirable dust, methane, and other harmful gases, in accordance with the levels specified in the applicable sections of this chapter.
(c) When the line brattice or any other face ventilation control device is damaged to an extent that ventilation of the working face is inadequate, production activities in the working place shall cease until necessary repairs are made and adequate ventilation is restored.
(a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—
(1) Permissible, if the fan is electrically operated;
(2) Maintained in proper operating condition;
(3) Deenergized or shut off when no one is present on the working section; and
(4) Located and operated to avoid recirculation of air.
(b) If a deficiency exists in any auxiliary fan system, the deficiency shall be corrected or the auxiliary fan shall be deenergized immediately.
(c) If the air passing through an auxiliary fan or tubing contains 1.0 percent or more methane, power to electrical equipment in the working place and to the auxiliary fan shall be deenergized, and other mechanized equipment in the working place shall be shut off until the methane concentration is reduced to less than 1.0 percent.
(d) When an auxiliary fan is stopped—
(1) Line brattice or other face ventilation control devices shall be used to maintain ventilation to affected faces; and
(2) Electrical equipment in the affected working places shall be disconnected at the power source, and other mechanized equipment shall be shut off until ventilation to the working place is restored.
MANDATORY SAFETY STANDARDS—UNDERGROUND COAL MINES (U.S.C.). Retrieved via LawPlayer, https://lawplayer.com/us/act/cfr-title-30-part-75
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