§ 393.50 Reservoirs required.
Current wording, in the annual edition revised as of Oct. 1, 2005.
(a) General.Reservoir Everycapacity commercialfor motorair-braked vehiclepower usingunits airmanufactured on or vacuumafter forMarch breaking1, shall1975, beand equippedair-braked withtrailers reservemanufactured capacityon or aafter reservoirJanuary sufficient1, to1975. ensureBuses, atrucks, fulland servicetruck-tractors brakemanufactured applicationon withor theafter engineMarch stopped1, without1975, depletingand the air-braked pressuretrailers ormanufactured vacuumon below 70 percent of that pressure or degreeafter ofJanuary vacuum1, indicated1975, bymust themeet gauge immediately before the brakereservoir applicationrequirements isof madeFMVSS No. For121, purposes of this sectionS5.1.2, ain fulleffect serviceon brake application is considered to be made when the servicedate brake pedal is pushed to the limit of its travelmanufacture.
(b) SafeguardingReservoir ofcapacity for air-braked andvehicles vacuum.not (1)subject Everyto bus,FMVSS truck,No. and121 truckon tractor,the whendate equippedof withmanufacture airand orall vacuum reservoirsbraked andvehicles. regardlessEach ofmotor datevehicle ofusing manufacture,air shallor havevacuum suchbraking reservoirsmust sohave safeguardedeither byreserve acapacity, check valve or equivalenta devicereservoir, that inwould enable the eventdriver ofto failuremake ora leakagefull inservice itsbrake connectionapplication towith the sourceengine ofstopped compressedwithout airdepleting or vacuum the air pressure or vacuum supplybelow in70 thepercent reservoirof shallthat notindicated be depleted by the leakair or failure.vacuum
(2)Meansgauge shallimmediately bebefore provided to establish the checkbrake valveapplication tois be in working ordermade. OnFor andthe afterpurposes Mayof 1,this 1966paragraph, meansa otherfull thanservice looseningbrake orapplication disconnectionmeans ofdepressing any connection between the sourcebrake ofpedal compressed air or vacuumtreadle and the check valve, and necessary tools for operation of such means, shall be provided to prove that the checklimit valve is in working order. The means shall be readily accessible either from the front, side, or rear of theits vehicle, or from the driver's compartmenttravel.
(ic) InSafeguarding of air brakeand systemsvacuum. withEach oneservice reservoir, thesystem meanson a motor vehicle shall be protected against a cock,loss valve,of plug,air pressure or equivalentvacuum devicedue arranged to vent a cavityfailure havingor freeleakage communicationin with the connectionsystem between the checkservice valvereservoir and the source of compressed air pressure or vacuum.,
(ii)Whereby aircheck isvalves deliveredor byequivalent adevices compressorwhose intoproper onefunctioning tankcan orbe compartmentchecked (wetwithout tank),disconnecting andany air foror brakingvacuum isline, taken directly from another tank or compartment fitting.
(dry tankd) only,Drain withvalves thefor requiredair checkbraked valvevehicles. betweenEach thereservoir tanksmust orhave compartments, a manuallycondensate operated drain cockvalve onthat thecan firstbe (wet)manually tankoperated. orAutomatic compartmentcondensate willdrain servevalves asmay abe meansused hereinprovided required(1) ifthey itmay conformsbe tooperated themanually, requirementsor herein.(iii2) Ina vacuummanual systems stopping the engine will serve as the required means, theof systemdraining remaining evacuated as indicated by the vacuumreservoirs gaugeis retained.
[3370 FR 1973548052, DecAug. 2515, 1968, as amended at 53 FR 49400, Dec. 7, 19882005]
(a) Reservoir capacity for air-braked power units manufactured on or after March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975. Buses, trucks, and truck-tractors manufactured on or after March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975, must meet the reservoir requirements of FMVSS No. 121, S5.1.2, in effect on the date of manufacture.
(b) Reservoir capacity for air-braked vehicles not subject to FMVSS No. 121 on the date of manufacture and all vacuum braked vehicles. Each motor vehicle using air or vacuum braking must have either reserve capacity, or a reservoir, that would enable the driver to make a full service brake application with the engine stopped without depleting the air pressure or vacuum below 70 percent of that indicated by the air or vacuum gauge immediately before the brake application is made. For the purposes of this paragraph, a full service brake application means depressing the brake pedal or treadle valve to the limit of its travel.
(c) Safeguarding of air and vacuum. Each service reservoir system on a motor vehicle shall be protected against a loss of air pressure or vacuum due to a failure or leakage in the system between the service reservoir and the source of air pressure or vacuum, by check valves or equivalent devices whose proper functioning can be checked without disconnecting any air or vacuum line, or fitting.
(d) Drain valves for air braked vehicles. Each reservoir must have a condensate drain valve that can be manually operated. Automatic condensate drain valves may be used provided (1) they may be operated manually, or (2) a manual means of draining the reservoirs is retained.
[70 FR 48052, Aug. 15, 2005]
Amendment history
2 distinct wordings on file since Oct. 1, 1996- [70 FR 48052, Aug. 15, 2005]
- Oct. 1, 1996 → Oct. 1, 2005annual editions 1996–2004[33 FR 19735, Dec. 25, 1968, as amended at 53 FR 49400, Dec. 7, 1988]
A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section. Set a case date in the header to read any earlier wording.