Low Air Warning Device and Air Loss Rate Tests

The OOSC and The North American Standard Level I Inspection Procedure related to the Low Air Warning Device and the Air Loss Rate tests need to be more specific in stating that both primary and secondary reservoir gauges need to be observed during these tests and that if either gauge drops below the specified level the vehicle is OOS.

NTSB Safety Recommendation HS-97-032 states that CVSA should "....develop an inspection protocol that could be easily administered by inspection personnel for detecting either reversed air brake lines or inoperative air pressure switches on commercial vehicles equipped with dual airbrake systems". In it's recent response to NTSB on this recommendation, CVSA stated that at the next meeting (March '08) "...the Vehicle Committee will review the language in the OOSC and consider adding additional language to clarify that the Low Air Pressure Warning Device and the Air Loss Rate tests apply to both the primary and secondary systems". While this will not completely address the NTSB recommendation, it will help the situation they describe in the report. Completely addressing the NTSB recommendation would require testing that is not practical at the roadside.

Add wording to the OOSC and the North American Standard Level I Inspection Procedure for both the Low Air Warning Device and Air Loss Rate tests to clarify that they apply to both the primary and secondary air systems. Suggested Wording for OOS as Follows: 1(h) Low Pressure Warning Device Low pressure warning device missing, inoperative, or does not operate if either the primary or secondary reservoir is at 55 psi (379 kpa) and below, or 1/2 of the governor cut-out pressure, whichever is less. NOTE: If either an audible or visual warning device is working as required, vehicle should not be placed Out-of-Service (393.51) 1(i) Air Loss Rate Test If an air leak is discovered and either the primary or secondary reservoir pressure is not maintained when: (1) Governor is cut-in; (2) Reservoir pressure is between 80 & 90 psi (551-620 kpa); (3) Engine is at idle, and (4) Service brakes are fully applied. (396.3(a)(1)) Suggested Wording for Level I Procedure STEP 33 INSPECT BRAKE SYSTEM WARNING DEVICES ABS MALFUNCTION LAMP(S) Ask the driver to turn the key to the "on" position. Observe the dash panel area when the key is turned on for the function test of the ABS malfunction lamp(s) (when applicable). NOTE: The trailer ABS malfunction lamp(s) may also be checked during this step utilizing the procedure above if not inspected in Step 21 (if applicable). LOW AIR PRESSURE WARNING DEVICE Instruct the driver to deplete the air supply until the low air pressure warning device activates. Observe the primary and secondary air reservoir gauges on the dash. The low air pressure warning must activate before either gauge drops below 55 psi or one-half the compressor cutout pressure, whichever is less. STEP 34 TEST AIR LOSS RATE If you detected an air leak at any point in the inspection, you should: Now check the vehicles air loss rate. Have the driver run the engine at idle, ensure brakes have been released. Observe the primary and secondary air reservoir pressure gauges on the dash. Have the driver pump the pressure down to 80 p.s.i.on the gauge with the highest reading (Compressors do not activate until system pressure drops below a certain level) at about 80 p.s.i., most compressors should be operating. With the engine idling and the air pressure between 80 - 90 p.s.i. instruct the driver to make a full brake application. Check the air pressure gauges after initial application air loss. Air pressures in both reservoirs should be maintained or increased. A drop in pressure in either reservoir indicates a serious air leak in the brake system.