49 C.F.R. § 232.710 – General rules; locomotives.

(a) Air brake and hand brake equipment on locomotives including tender must be inspected and maintained in accordance with the requirements of the Locomotive Inspection and United States Safety Appliance Acts and related orders and regulations of the Federal Railroad Administrator (FRA).
(b) It must be known that air brake equipment on locomotives is in a safe and suitable condition for service.
(c) Compressor or compressors must be tested for capacity by orifice test as often as conditions require but not less frequently than required by law and orders of the FRA.
(d) Main reservoirs shall be subjected to tests periodically as required by law and orders of the FRA.
(e) Air gauges must be tested periodically as required by law and orders of the FRA, and whenever any irregularity is reported. They shall be compared with an accurate deadweight tester, or test gauge. Gauges found inaccurate or defective must be repaired or replaced.
(f) (1) All operating portions of air brake equipment together with dirt collectors and filters must be cleaned, repaired and tested as often as conditions require to maintain them in a safe and suitable condition for service, and not less frequently than required by law and orders of the FRA.
(2) On locomotives so equipped, hand brakes, parts, and connections must be inspected, and necessary repairs made as often as the service requires, with date being suitably stenciled or tagged.
(g) The date of testing or cleaning of air brake equipment and the initials of the shop or station at which the work was done shall be placed on a card displayed under transparent covering in the cab of each locomotive unit.
(h) (1) Minimum brake cylinder piston travel must be sufficient to provide proper brake shoe clearance when brakes are released.

(2) Maximum brake cylinder piston travel when locomotive is standing must not exceed the following:

	Inches
(i) Steam locomotives:
(A) Cam type of driving wheel brake	3 1⁄2
(B) Other types of driving wheel brakes	6
(C) Engine truck brake	8
(D) Engine trailer truck brake	8
(E) Tender brake (truck mounted and tender bed mounted)	8
(F) Tender brake (body mounted)	9
(ii) Locomotives other than steam:
(A) Driving wheel brake	6
(B) Swivel type truck brake with brakes on more than one truck operated by one brake cylinder	7
(C) Swivel type truck brake equipped with one brake cylinder	8
(D) Swivel type truck brake equipped with two or more brake cylinders	6

(i) (1) Foundation brake rigging, and safety supports, where used, must be maintained in a safe and suitable condition for service. Levers, rods, brake beams, hangars and pins must be of ample strength and must not bind or foul in any way that will affect proper operation of brakes. All pins must be properly applied and secured in place with suitable locking devices. Brake shoes must be properly applied and kept approximately in line with treads of wheels or other braking surfaces.
(2) No part of the foundation brake rigging and safety supports shall be closer to the rails than specified by law and orders of the FRA.
(j) (1) Main reservoir leakage: Leakage from main air reservoir and related piping shall not exceed an average of 3 pounds per minute in a test of three minutes' duration, made after the pressure has been reduced 40 percent below maximum pressure.
(2) Brake pipe leakage: Brake pipe leakage must not exceed 5 pounds per minute after a reduction of 10 pounds has been made from brake pipe air pressure of not less than 70 pounds.
(3) Brake cylinder leakage: With a full service application of brakes, and with communication to the brake cylinders closed, brakes must remain applied not less than five minutes.
(4) The main reservoir system of each unit shall be equipped with at least one safety valve, the capacity of which shall be sufficient to prevent an accumulation of pressure of more than 10 pounds per square inch above the maximum setting of the compressor governor fixed by the chief mechanical officer of the carrier operating the locomotive.
(5) A suitable governor shall be provided that will stop and start the air compressor within 5 pounds above or below the pressures fixed.
(6) Compressor governor when used in connection with the automatic air brake system shall be so adjusted that the compressor will start when the main reservoir pressure is not less than 15 pounds above the maximum brake-pipe pressure fixed by the rules of the carrier and will not stop the compressor until the reservoir pressure has increased not less than 10 pounds.
(k) The communicating signal system on locomotives when used in passenger service must be tested and known to be in a safe and suitable condition for service before each trip.
(l) Enginemen when taking charge of locomotives must know that the brakes are in operative condition.
(m) In freezing weather drain cocks on air compressors of steam locomotives must be left open while compressors are shut off.

(n) Air pressure regulating devices must be adjusted for the following pressures:

	Pounds
(1) Locomotives:
(i) Minimum brake pipe air pressure:
(A) Road Service	70
(B) Switch Service	60
(ii) Minimum differential between brake pipe and main reservoir air pressures, with brake valve in running position	15
(iii) Safety valve for straight air brake	30-55 30-68
(iv) Safety valve for LT, ET, No. 8-EL, No. 14 El, No. 6-DS, No. 6-BL and No. 6-SL equipment	30-75
(v) Safety valve for HSC and No. 24-RL equipment	30-50
(vi) Reducing valve for independent or straight air brake	50
(vii) Self-lapping portion for electro-pneumatic brake (minimum full application pressure)	30-50
(viii) Self-lapping portion for independent air brake (full application pressure)	40-60
(viiii) Reducing valve for air signal	50
(x) Reducing valve for high-speed brake (minimum)
(2) Cars:
(i) Reducing valve for high-speed brake	58-62
(ii) Safety valve for PS, LN, UC, AML, AMU and AB-1-B air brakes	58-62
(iii) Safety valve for HSC air brake	58-77
(iv) Governor valve for water raising system	60
(v) Reducing valve for water raising system	20-30