Interpretation ID: nht81-1.17

DATE: 02/19/81

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Mercedes-Benz of North America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your recent letter asking whether certain flexible air pressure hoses for use on trucks would be subject to the requirements of Safety Standard No. 106, Brake Hoses. The hose in question would be used to transfer pressure from the air reservoir of the brake power assist unit (of the hydraulic service brake system) to a cylinder that actuates the exhaust brake control.

Safety Standard No. 106 defines "brake hose" as: "A flexible conduit, other than a vacuum tubing connector, manufactured for use in a brake system to transmit or contain the fluid pressure or vacuum used to apply force to a vehicle's brakes."

The hose that your company desires to use is not a part of the service brake system or the power assist system, either directly or indirectly. If pressure should be lost in the exhaust brake circuit of which the subject hose is a component, the loss would be isolated from the performance of the service and power assist circuits by means of a check valve. Therefore, the hose does not transmit the pressure or vacumm used to apply force to the vehicle's brakes, and it would not be considered a "brake hose" subject to the requirements of Safety Standard No. 106.

Sincerely,

ATTACH.

MERCEDES - BENZ OF NORTH AMERICA. INC.

December 17, 1980

OFFICE OF CHIEF COUNSEL -- National Highway Traffic Safety Administration

Re: Request For Interpretation; FMVSS 106, Brake Hoses

Dear Madam or Sir:

Mercedes-Benz of North America, Inc. hereby requests an interpretation as to whether or not certain flexible air pressure hoses proposed for use on our truck models would be subject to the requirements of FMVSS 106, brake hoses. The hose in question would serve to transfer pressure from the air reservoir of the brake power assist unit (of our hydraulic service brake system) to a cylinder that actuates the exhaust brake control. The brake power assist unit reservoir is protected against pressure loss in this exhaust brake circuit by means of a check valve located directly on the reservoir. All pertinent components are identified on the attached drawing No. BL046/80.

Inasmuch as the hose used in this exhaust brake circuit is neither within the hydraulic service brake circuits, nor within the brake power assist unit circuit (air), and should pressure be lost in this exhaust brake circuit it would be isolated from the performance of the service and assist circuits by means of a check valve, Mercedes-Benz of North America, Inc. believes that this hose is not subject to the requirements of FMVSS 106.

Should you have any questions regarding this request, do not hesitate in contacting this office,

Best regards,

HEINZ W. GERTH -- VICE PRESIDENT, ENGINEERING AND SERVICE