Interpretation ID: nht76-4.16

DATE: 11/10/76

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Midland-Ross Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Midland-Ross' September 30, 1976, question whether the "method" specified by Compliance Testing, Inc., in its December 8, 1975, Technical Proposal for Solicitation NHTSA-6-A212 is consistent with the laboratory procedure contemplated by the NHTSA for its test contractors in evaluating the compliance of air-braked vehicles with Standard No. 121, Air Brake Systems. The NHTSA laboratory procedure for compliance contractors in the case of Standard No. 121 states in relevant part:

PROCEDURE:

A. Physically locate check valve or equivalent device.

B. Following manufacturer's recommendation, check the check valve or equivalent device for proper function without disconnecting any air line or fitting. Describe method and technique used.

The Compliance Testing, Inc. (CTI) solicitation was evaluated along with other proposals and has been accepted by the NHTSA. The "method" set forth by CTI as its intended course of action in evaluating the compliance of valves in accordance with the requirements of S5.1.2.3 will not appear in the manual produced for NHTSA compliance testing.

I would like to note in closing that this letter does not constitute an interpretation of the requirements of Standard No. 121. Although the laboratory procedure sets forth the method by which contractors satisfy NHTSA contracts, it does not mean that a vehicle need not meet the requirements of the standard when tested according to its terms by other methods.

MIDLAND-ROSS

September 8, 1976

Salvatore J. Nicolosi -- Office of Contracts and Procurement, National Highway Traffic Safety Administration

Gentlemen:

Subject: Laboratory Procedures for Air Brake Systems, Federal Motor Vehicle Safety Standard No. 121, Report #TP-121-00

Midland-Ross Corporation is a manufacturer of air brake actuation equipment for heavy duty trucks. We therefore manufacture components which are used by truck manufacturers for compliance with FMVSS 121. We are asking for interpretation of the requirements for check valves.

In the subject procedures, issued by the U.S. Department of Transportation, National Highway Traffic Safety Administration, Office of Standards Enforcement Motor Vehicle Programs, Section 1.3.2 states:

"This procedure must be followed by any contractor conducting FMVSS 121 tests for the National Highway Traffic Safety Administration."

Section 5.7 REQUIREMENT S5.1.2.3 -- SERVICE RESERVOIR SYSTEM AIR LOSS TEST states"

"Each service reservoir system shall be protected against loss of air pressure due to failure or leakage in the system between the service reservoir and the source of air pressure, by check valves or equivalent devices whose proper functioning can be checked without disconnecting any air line or fitting."

Under the same section PROCEDURE A and B:

"A. Physically locate check valve or equivalent devices.

B. Following the Manufacturer's recommendation, check the check valve or equivalent device for proper function without disconnecting any air line or fitting. Describe method and technique used." (Underscoring added.)

In the submission by Compliance Testing Inc., which we understand was accepted, the Contractor states:

"Method:

1. Build up air in system to maximum

2. Open bleed valve in supply tank

3. Monitor for 10 minutes pressure in primary and secondary tanks - no loss of air allowed"

We submit that on the surface this appears to be not in compliance with requirements of TP121.00 and we would like to have a clear interpretation of what the contractor plans to do with these valves in checking them for leakage. We submit that zero leakage is a physical impossibility and must be interpreted in terms of the accuracy of the equipment being used for measurement.

Further we submit that the contractor is obligated to test for compliance "following the Manufacturer's recommendation" which we in turn would consider to be the engineering specification for the appropriate valve.

We request that this question be clarified and the NHTSA position be stated so that erroneous claims of non-compliance can be avoided. An early response would be appreciated.

Sincerely,

M. J. Denholm -- Director of Engineering, Power Controls Div.

cc: J. Brewster, M-R; D. Gross, M-R; F. Nawalanic, M-R; A. Beier, IHC; R. MADISON