[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR36.23]

[Page 170-171]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 36--APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT--Table of Contents
 
             Subpart B--Construction and Design Requirements
 
Sec. 36.23  Engine intake system.

    (a) Construction. The intake system (exclusive of the air cleaner) 
shall be designed to withstand an internal pressure equal to 4 times the 
maximum pressure observed in explosion tests, which are described in 
Sec. 36.46, or a pressure of 125 pounds per square inch, whichever is 
the lesser. Joints in the intake system shall be formed by metal flanges 
fitted with metal or metal-clad gaskets, positively positioned by 
through bolts or other suitable means for secure assembly, or shall meet 
the requirements for flanged metal-to-metal flame-proof joints as 
required in Sec. 36.20(b). Either type of joint shall withstand repeated 
explosions within the intake system without permanent deformation and 
shall prevent the propagation of flame through the joint into a 
surrounding flammable mixture.
    (b) Intake flame arrester. (1) The intake system shall include a 
flame arrester that will prevent an explosion within the system from 
propagating to a surrounding flammable mixture. This flame arrester 
shall be between the air cleaner and the intake manifold and shall be 
attached so that it may be removed for inspecting, cleaning, or 
repairing. Its construction shall be such that it may be cleaned 
readily. The flame arrester shall be of rugged construction to withstand 
the effects of repeated explosions within the intake system, and the 
material of construction shall resist deterioration in service. It shall 
be so mounted in the equipment assembly that it is protected from 
accidental external damage.
    (2) The parts of any flame arrester shall be positively positioned 
to produce a flame path that will arrest the propagation of an explosion 
and shall be so designed that improper assembly is impossible. In flame 
arresters of the spaced-plate type, the thickness of the plates shall be 
at least 0.125 inch; spacing between the plates shall not exceed 0.018 
inch; and the plates forming the flame path shall be at least 1 inch 
wide. The unsupported length of the plates shall be short enough that 
deformation during the explosion tests shall not exceed 0.002 inch. 
Corrosion-resistant metal shall be used to construct flame arresters.

[[Page 171]]

    (c) Air shutoff valve. The intake system shall include a valve, 
operable from the operator's compartment, to shut off the air supply to 
the engine. This valve shall be constructed to permit its operation only 
after the fuel supply to the engine is shut off. In reverse operation 
the valve must open fully before fuel can be supplied to the engine.
    (d) Air cleaner. An air cleaner shall be included in the engine 
intake system and so arranged that only clean air will enter the flame 
arrester. The resistance to airflow shall not increase rapidly in dusty 
atmospheres. Filters of the self-cleansing (oil-bath) type will be 
considered satisfactory for this application. Provision, satisfactory to 
MSHA, shall be made to prevent overfilling the oil-bath air cleaner.
    (e) Vacuum-gage connection. A connection shall be provided in the 
intake system for temporary attachment of a vacuum gage to indicate the 
pressure drop under flow conditions. This opening shall be closed by a 
plug or other suitable device that is sealed or locked in place except 
when a gage is attached.