engine operating at its maximum power output and with the cooling spray initially in operation. The water to the cooling spray will be shut off, the water in all compartments designed to hold cooling water will be drained, and the final exhaust-gas temperature at which the fuel to the engine is automatically shut off will be noted. The temperature must be between 180° and 190° F.

(vi) Following this test the temperature at the control point will be permitted to drop to 160° F. At this temperature it must be possible to start the engine. If a manual reset is provided in the automatic fuel shut-off control it shall be possible to reset the control and start the engine when the temperature at the control point is 160° F.

(vii) At the option of the Bureau's engineers any other tests may be made to determine the adequacy of a part for the service intended.

(6) Determination of surface temperature of engine and accessories. (1) The surface temperatures of the engine, the exhaust cooling system, and any accessories will be determined with the engine operating at its maximum power output for a period sufficient for all parts of the engine and its accessories to reach their respective equilibrium temperatures. The exhaust-gas cooling system will be in operation, but no air will be circulated over the engine or accessories. Under the foregoing conditions the following surface temperatures will be measured: (a) Exhaust-gas manifold at inlet; (b) exhaust-gas manifold at outlet; (c) engine-surface temperatures at various locations; (d) crankcase; (e) exhaust flame arrester; (f) intake flame arrester; and (g) at any other location considered necessary.

(ii) The temperature of any surface measured under the foregoing conditions shall not exceed 400° F.

(iii) At the option of the Bureau's engineers the engine may be operated under the foregoing test conditions while completely surrounded by an inflammable natural gas-air mixture. Combustible materials likely to be encountered in service may be placed on any surface. Operation under such conditions shall not cause an ignition of the surrounding inflammable atmosphere.

(iv) In addition to the foregoing tests any other tests may be made at the op

tion of the Bureau's engineers to determine the adequacy of the cooling of surfaces of the engine and its accessories.

(7) Tests of exhaust-gas dilution system. The adequacy of the exhaust-gas dilution system will be determined by tests of the assembled locomotive. The engine will be operated in normal air, at minimum speed and at maximum rated speed, and will be at temperature equilibrium during the tests. Samples of the final (diluted) exhaust of the locomotive and of the undiluted engine exhaust will be collected simultaneously at both speeds. Analyses of these samples will serve as a basis for calculating the extent of dilution effected by the system. The dilution ratios thus obtained will be applied to the data obtained in tests described in subparagraph (2) of this paragraph to determine whether the concentrations of carbon monoxide, oxides of nitrogen, and aldehydes in the diluted exhaust of the locomotive are within the required limits.

(8) Tests of fuel tank. The fuel tank will be tested to determine that it is fueltight, that the vent will maintain atmospheric pressure within the tank, and that the vent and closure do not permit the egress of liquid fuel.

(b) Tests of electrical equipment—(1) Detailed inspection of class 1 electrical parts. In the investigation of any machine or equipment for approval and also in the investigation of separate electrical units (individual motors, controllers, etc.) as to suitability for use on permissible machines, explosion-proof casings shall be given careful inspection by the Bureau's engineers. This inspection will include the following items:

(i) A detailed check of parts against drawings as to materials, dimensions, and position, making notations for necessary correction of discrepancies between the drawings and the parts checked.

(ii) Measurement of joints, bearings, and other possible flame paths.

(iii) Examination for unnecessary through holes.

(iv) Examination for adequacy of lead entrance design and construction.

(v) Examination for adequacy of electrical clearance of insulation between live parts of opposite polarity and between live parts and ground.

(vi) Examination for adequacy and security of fastenings.

66-067 0-67-12

NOTE: For further information regarding the details of this inspection reference should be made to Bureau of Mines Information Circular 7185. Inspection and Testing of MineType Electrical Equipment for Permissibility.

(2) Explosion tests of class 1 electrical parts. (1) To test enclosures for their ability to retain flame, they will be filled and surrounded with explosive 'mixtures containing varying percentages of Pittsburgh natural gas' and air. The mix

ture within the enclosure will be ignited by a spark plug or other suitable means, and a record of explosion pressures developed will be taken. The point of ignition will be varied to determine the condition that gives the greatest pressure. For some of the tests, bituminous-coal dust will be introduced into enclosures, and the effects will be noted. Motor armatures and rotors will be stationary in some tests and revolving in others.

(ii) Not less than 10 tests will be made of each design of explosion-proof enclosure. If, on account of the size of enclosure or questionable construction features, it is the judgment of the Bureau's engineers that the explosion-proof qualities cannot be completely demonstrated in 10 tests, more than that number will be made.

4

(iii) The explosion tests of an enclosure shall not result in: (a) Discharge of flame from any joint, bearing, or opening; (b) ignition of surrounding explosive mixtures; (c) development of dangerous afterburning; or (d) excessive pressures. (Indicated pressures of 150 pounds per square inch gage or over are considered as being excessive.) An enclosure will be rejected if failing to meet any one of the four above conditions.

(3) Adequacy tests of electrical parts. In addition to explosion tests, certain other tests may be made at the option of the Bureau's engineers to determine the adequacy of an accessory for the service intended:

'Investigation has shown that, for practical purposes, Pittsburgh natural gas (containing a high percentage of methane) is a satisfactory substitute for pure methane in these tests.

The term "afterburning" as used in this part is applied to combustion, immediately after an internal explosion, of a gaseous mixture that was not in the enclosure at the time of that explosion, but was drawn in as the result of the cooling of the products of the original explosion.

are

(i) Where the durability of battery cells, headlights, or other parts is in doubt, such mechanical tests as deemed necessary may be made to determine points requiring strengthening.

(ii) If there is any question on the efficacy of ventilation of battery boxes, tests may be made to check the ventilation.

(iii) Switches or circuit breakers and contactors intended to function as switches shall be capable of interrupting any overload currents that will flow without causing the protective devices to open the circuit. They also shall be capable of opening these overloads five times at 2-minute intervals without grounding or short-circuiting.

(iv) Fuses or other automatic circuitinterrupting devices may be tested to determine whether they provide the necessary protection without damaging the explosion-proof qualities of their enclosures.

(4) Factory inspection and tests. If necessary to expedite the investigation the Bureau of Mines will conduct inspections or tests of the locomotive assembly, or any part thereof, at the plant of the manufacturer.

(5) Additional tests. The Bureau of Mines reserves the right to make any additional tests, not covered by the provisions of this part, that may be considered necessary to determine the adequacy of the locomotive, or any part thereof.

[Sched. 22, 9 F. R. 13748, Nov. 17, 1944]

§ 31.6 Granting of approval.

(a) Notification of approval or disapproval. (1) After the Bureau of Mines has considered the results of the investigation, and suitable drawings and specifications have been placed on file, a formal written notification of approval or disapproval of the locomotive will be supplied to the applicant by letter from the Bureau of Mines. If the locomotive meets all requirements, the notification of approval will not be accompanied by test date or detailed results of tests. the locomotive fails to meet any of the requirements, notification of such failure will be accompanied by details of the failure with a view to possible remedy of defects. The Bureau of Mines will not otherwise release, or make public, results of tests of locomotives that fail to meet the requirements.

If

(2) No verbal reports of the Bureau's decisions concerning the investigation will be given, and no verbal or informal approvals will be granted.

(3) The manufacturer shall not be free to advertise his equipment as permissible or approved until he has received the formal notification of approval in which an approval number is assigned.

(4) All drawings and specifications that must be submitted to the Bureau in connection with the investigation will be retained by the Bureau. A drawing list numbered to correspond to the approval number will accompany the notification of approval. This list will include the drawings and specifications covering the details of construction upon which the approval is based. The applicant receiving an approval shall keep exact duplicates of the drawings and specifications retained by the Bureau. These are to be adhered to in commercial production of the approved locomotive.

(b) Approval plate. (1) With the notification of approval the applicant will receive a photograph of a design of approval plate. The plate will bear the seal of the Bureau of Mines, the approval number, designation of the type of equipment for which the approval is granted, and the name of the manufacturer. The plate will bear also a statement regarding maintenance of the equipment in approved condition.

(2) The manufacturer shall have this design reproduced as a plate for attachment to each permissible locomotive. A sample plate and a sketch or description of its proposed mounting on the locomotive shall be sent to the Central Experiment Station, Bureau of Mines, Pittsburgh, Pa., 15213, for approval before final adoption.

(c) Purpose and significance of approval plate. (1) The approval plate identifies the equipment as having complied with the requirements of the Bureau of Mines for use in gassy and dusty mines.

(2) The use of the approval plate on his equipment obliges the manufacturer to maintain the quality of his product and to see that each locomotive is constructed according to drawings and specifications accepted by, and on file with, the Bureau of Mines. Equipment exhibiting changes in design that do not have official authorization from the Bureau are not per

missible and therefore must not bear the approval plate.

[Sched. 22, 9 F. R. 13750, Nov. 17, 1944, as amended by Supp. 1, 20 F. R. 2720, Apr. 23, 1955]

§ 31.7 Withdrawal of approval.

The Bureau of Mines reserves the right to rescind for cause, at any time, an approval granted under this part. [Supp. 22, 9 F. R. 13750, Nov. 17, 1944] § 31.8 Changes in design subsequent to approval.

All approvals are granted with the understanding that the manufacturer will make his equipment according to final drawings and specifications submitted to the Bureau of Mines. Therefore, before making any change in an approved locomotive the manufacturer shall first obtain the Bureau's approval of the change. This procedure is as follows:

(a) The manufacturer shall write to the Central Experiment Station, requesting an extension of his original approval and stating the change or changes desired. With this letter he should submit a set of revised drawings- and specifications showing the change or changes in detail.

(b) The Bureau will consider the application and inspect the drawings and specifications to determine whether it will be necessary to make tests.

(c) If tests are unnecessary, the applicant will be advised by letter from the Bureau of Mines of the approval or disapproval of the change.

(d) If tests are necessary, the applicant will be advised of the fee and the material required for the tests.

[Sched. 22, 9 F. R. 13750, Nov. 17, 1944, as amended by Supp. 1, 20 F. R. 2720, Apr. 23, 1955]

missible condition and is used in a permissible manner. The use of diesel locomotives underground involves, in addition to proper maintenance of the locomotive itself, certain other factors, such as ventilation, which are of equal importance in establishing safe operating conditions. The following recommendations on the use of diesel locomotives underground are included in this part as an expression by the Bureau of Mines of the conditions that should be enforced in the use of such equipment. Any locomotive used under conditions that do not comply with these recommendations shall not be considered by the Bureau as being permissible. The recommendations are as follows:

(a) Ventilation—(1) Definition of ventilation requirements. The use of diesel mine locomotives underground should be restricted to haulageways where positive ventilation is maintained by mechanical means. If possible haulage by diesel locomotives should be on the intake of a separate split of the ventilating air current or arrangements should be made in some manner so that air carrying exhaust gases from the engine is returned to the surface without traversing working places. The quantity of ventilating air supplied must be adequate to dilute all toxic or objectionable constituents of the engine exhaust to such extent that the composition of the air of the haulageways, or any working place connected thereto, meets recognized hygienic standards for working environments. The air supplied for ventilation in haulageways where diesel locomotives are used should not contain combustible gas or other contaminants in such concentration that combustion processes in the engine may be altered, with resultant increase in production of toxic or objectionable constituents in the engine exhaust.

(2) Quantity of ventilating air. (1) The minimum quantity of ventilating air that must be supplied per unit time will be determined in the approval tests of each permissible locomotive, and this quantity will be shown upon all approval plates issued for diesel mine locomotives. This quantity shall apply to the use of one locomotive only; if more than one locomotive is used in any continuous course of air, then the air quantity required for one locomotive must be multiplied by the number of locomotives in use. Approved locomotives may be used only in places

where at least this minimum quantity of ventilation is in effect. As this minimum required quantity of ventilation will be determined during the approval tests, with engines that are new and presumably in the best mechanical condition, it will be desirable always to supply ventilation in excess of the minimum quantity indicated on the approval plate, thus furnishing a factor of safety in operation.

(ii) Ventilation on haulageways should be measured at intervals sufficiently frequent to insure that the required air quantities are being maintained. Records should be kept of such measurements.

(3) Quality of ventilating air. The air supplied for ventilation in connection with the use of diesel locomotives underground should contain not less than 20 percent by volume of oxygen (dry basis) and should not contain more than 0.25 percent inflammable gas. This statement applies to the air current before the exhaust gases from the locomotive are added to it.

(4) Examination of air of working places. (i) The air of haulageways in which diesel locomotives are used should be examined at intervals sufficiently frequent to determine that the composition of the intake air conforms with the requirements given in subparagraph (3) of this paragraph and that the concentration of contaminants, such as carbon dioxide, carbon monoxide, and oxides of nitrogen, added to this air by the locomotive are within acceptable limits. Methods used in determining the concentrations of these contaminants and the composition of the intake air of the haulageways should be sufficiently sensitive and accurate to produce reliable results, as the interpretation of these results may in some instances depend on variations in concentration of as little as 0.01 percent or less. Concentrations of gases considered permissible in working environments are as follows:

Carbon dioxide (CO)-not more than 0.5 percent by volume.

Carbon monoxide (CO)-not more than 0.01 percent by volume.

Oxides of nitrogen (NO,)-not more than 0.0025 percent by volume.

Oxygen (0)-not less than 20 percent by volume.

(ii) Ventilation and locomotive operating condition should be such that the composition of the air of haulageways, and working places connected thereto,

always remains within these tolerable limits.

(iii) Aldehydes are self-evident if present in objectionable concentrations and need not be determined by analysis. Production of sulfur gases by the locomotive may be controlled by using a fuel oil of low sulfur content.

(iv) A smoky exhaust is a good practical indication of faulty operation and is usually accompanied by the production of excessive quantities of carbon monoxide. Therefore abnormal smoke production should be sufficient reason for removing a locomotive from service until this condition has been corrected.

(v) In the event that any of the foregoing conditions of air quality are not maintained, as determined by analysis of the air, or by observation, operation of locomotives should be stopped until proper conditions of air quality are established, either by increasing ventilation or by correcting mechanical imperfections in the locomotives, whichever is found to be the cause of the undesirable conditions.

(vi) Records should be kept of all air analyses and of any changes in ventilation or adjustments of locomotives made as a result of these analyses.

(1)

(b) Maintenance-(1) General. The maintenance of diesel locomotives in permissible condition is absolutely essential if hazards in the use of such equipment are to be avoided. To insure adequate maintenance a qualified and authorized person should be made responsible for all maintenance work. This person should be thoroughly familiar with the proper procedures for maintaining diesel locomotives in permissible condition and he should be assisted when necessary by competent mechanics.

(ii) Inspection and maintenance procedures shall be in accordance with the instructions furnished by the manufacturer. When diesel locomotives are operated for the first time in any situation, daily inspections should be made of the intake and exhaust systems of the engine as outlined below and of other accessories of the locomotive to accumulate information on the frequency of inspections required. Records of all inspections should be kept and a routine inspection schedule should be drafted from experience and information obtained in daily inspections during the first several months of operation.

(iii) All maintenance work should be done in accordance with detailed instructions furnished by the manufacturer of the locomotive. These instructions should form the basis of a routine inspection and maintenance schedule. Some of the more important inspection and maintenance procedures are summarized below.

(2) Engine fuel-injection system—(i) Injection valves. Improperly functioning injection valves may cause incomplete combustion of some of the fuel and lead to increased production of smoke, carbon monoxide, and aldehydes. It is important therefore to maintain injection valves in proper operating condition. Particular attention should be paid to preventing leaking injection valves and to preventing imperfect atomization or distribution of the fuel.

The manufacturer's recommendations regarding inspection and maintenance of injection valves should be followed and periodic checks on injection pressure and spray pattern should be made as outlined in these recommendations.

(ii) Fuel pump. The fuel pump on the engine is set by the manufacturer in accordance with permissibility requirements of the Bureau of Mines. This setting is made to limit the fuel injected at full throttle and to prevent operation of the engine on the rich side (insufficient air for complete combustion) with the attendant production of dangerous quantities of carbon monoxide. After this adjustment is made the fuel pump is sealed or locked to prevent alteration.

It should not be necessary to reset the fuel pump unless some part breaks or unless the pump is disassembled for a complete overhaul. When it is necessary to set the fuel pump the seal or lock should be broken by an authorized person and the final adjustment should be made under the supervision of this person. After this adjustment has been made the fuel pump should be sealed or locked by an authorized person.

(iii) Method of adjusting fuel pump. When it is necessary to reset the stop limiting the fuel injector at full throttle, it is absolutely essential that some means be available for reproducing the original setting. Failure to reproduce the original setting might lead to the production of dangerous quantities of carbon monoxide if too much fuel were injected at full throttle.