Interpretation ID: nht75-4.13

DATE: 08/25/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Dana Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Dana Corporation's July 11, 1975, question whether a system which controls a truck engine throttle from a remote location by means of compressed air from the truck's brake system 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 compressor build-up pressure would still be required to meet S5.1 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.

SINCERELY,

DANA CORPORATION . TECHNICAL CENTER

July 11, 1975

Chief Council U.S. Department of Transportation

We are presently involved with the design and development of a system used in the control of truck engine throttles. The system will require compressed air for its actuation which will be obtained from the air supply used in the vehicle's air brake system. This system will primarily be used on refuse packers during the pack cycle. The time per pack cycle will be one minute or less with a system's air consumption of .375 cubic feet at a regulated pressure of 35 pounds per square inch and having a free air flow of .358 cubic feet.

With data available to you, I would like to know if, when using our system, the manufacturers will be in any violation of the FMVSS No. 121, Air Brake Systems. I am mostly concerned with paragraphs S5.1.1, S5.1.2, and S5.1.2.1 referring to compressors and reservoirs.

Having this information, we can assure the truck manufacturers that our system will not in any way put them in jeopardy of any vehicle safety standards set forth by the U.S. Department of Transportation.

If you have any questions, please feel free to contact me.

Robert J. Ostrander Development Engineer