Interpretation ID: nht76-3.46
DATE: 01/08/76
FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA
TO: B. F. Goodrich Engineered Systems Company
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your August 28, 1975, question whether use of compressed air from a trailer air brake system to supply non-brake equipment such as an air suspension would violate the requirements of Standard No. 121, Air Brake Systems.
The answer to your question is no. Standard No. 121 does not contain a prohibition on the use of air pressure from the air brake system for powering auxiliary devices. The vehicle must of course conform to Standard No. 121 following installation of the device, if the installation occurs prior to the first purchase in good faith for purposes other than resale. For example, the brake actuation timing would still be required to meet S5.3.3 of the standard.
Although not a requirement of the standard, the NHTSA does consider it appropriate that a pressure protective valve be placed in the line to the auxiliary device so that a rupture of an auxiliary line does not cause depletion of air pressure in the brake system.
With respect to your request for approval of four installations of auxiliary equipment, the NHTSA does not issue approvals of specific designs, and therefore cannot state that vehicles modified in the described fashion would or would not be capable of meeting all requirements of the standard.
YOURS TRULY,
B. F. Goodrich Engineered Systems Company
August 28, 1975
R. L. Carter Acting Administrator National Highway Traffic Safety Administration U.S. Department of Transportation
The B.F. Goodrich Company has received numerous requests from our trailer customers asking for our approval to obtain air for auxiliary items, such as air suspension bags from the anti-skid air system.
Attached is one copy each of four drawings, Nos. 1998-42-43-44-45 which shows four different places in the anti-skid air system that air could be obtained for auxiliary items. Drawing -45 shows taking air from the Sealco Ratio Relay Valve. To assist you in evaluating this drawing, we are attaching a Sealco pamphlet describing the operation of the Ratio Relay Valve. We would appreciate your review and interpretation as to whether any or all of these methods would violate the requirements of MVSS-121. We would appreciate an early review of these proposed methods of obtaining air for auxiliary systems so that we will be in a position to properly advise our customers.
If you have any questions concerning information on the attached drawings please do not hesitate to contact me. I will look forward to a response from you and thank you for your consideration.
D. L. Haines Divisional Manager, Quality Assurance
B.F. Goodrich Engineered Systems Company
December 1, 1975
R. L. Carter Acting Administrator National Highway Traffic Safety Administration U.S. Department of Transportation
Subject: Anti-Skid - Containment of Air for Auxiliary Items
Ref: My letter of August 28, 1975
Dear Mr. Carter:
Attached to referenced letter I sent one copy each of four drawings, Nos. 1998-42,43,44,45, showing four different areas in the anti-skid air system that air could be obtained for auxiliary items, such as air suspension bags.
As of this date, we have not received a response on your review and interpretation as to whether any or all of these proposed methods would violate the requirements of MVSS-121.
As I pointed out, B.F. Goodrich has received numerous requests from our trailer customers asking for our approval to obtain air for auxiliary items. Therefore, your prompt response to my August 28 letter will be greatly appreciated.
If you have any questions concerning this matter, please do not hesitate to contact me.
D. L. Haines Divisional Manager, Quality Assurance