Interpretation ID: nht74-4.32

DATE: 07/03/74

FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA

TO: Alfred Teves GMBH

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your May 10, 1974, request for permission to stamp label information on hose assemblies in place of banding, and to reduce S9.2.5 burst pressure from 350 to 100 psi, and your further request for an interpretation of the status of an in-line check valve as part of a vacuum brake hose.

The in-line check valve is not subject to Standard No. 106, Brake hoses, as a brake hose and fitting. In this configuration, the couplers depicted in your drawing are the clamps, and the check valve is a separate component to which the hose assemblies are attached.

The issue of stamping instead of banding will be answered in our upcoming Notice 11 in response to petitions for reconsideration of the brake hose standard.

Your petition for a reduction in the burst strength requirement for vacuum hoses is denied. The minimum burst pressure of 350 psi was established by the Society of Automotive Engineers in 1942, taking into consideration the effects of backfire pressure and the severe underhood environment to which vacuum hose may be exposed. Hoses with this burst pressure have provided excellent reliability and durability. We have no data to justify a reduction in burst strength in view of the two hazards just cited.

MAY 10, 1974

National Highway Traffic Safety Administration US Department of Transportation

Subject: Motor Vehicle Safety Standard No. 106

(Docket no. 1-5, Notice 10

According to Notice 10 the designation of fittings was dropped due to objections raised by various manufactures because of insufficient clearness. For years we successfully used to emboss the date of manufacture on to the fittings (after the swaging process). We therefore ask you to extend item S 5.2.4 to the effect that in case of two-piece end fittings, which are attached by crimping or swaging, embossing of the designation on to the fittings will also be allowed instead of using a band.

The present standard according to which only a band will be allowed would be connected with a high degree of capital expenditure (reconstruction of entire assembly machinery) for the manufacturing department of Alfred Teves GmbH.

As far as vacuum brake hoses (see item S 9.2.5) are concerned, we think that a 350 psi burst strength is too high. The maximum operating pressure amounts to a vacuum of 0,80 bar, so that the required 350 psi would mean a 27-fold safety.

For this field of application a burst strength of 100 psi is sufficient. We therefore ask you to amend item S 9.2.5 to the effect that in the case of vacuum brake tubes the burst strength will be reduced to 100 psi.

Our production programm also comprises a vacuum check valve, which 1st mounted between two vacuum brake tubes, according to the attached sketch. We kindly ask you to inform us whether in the case of vacuum check valves the same requirements as are applicable for complete brake tubes regarding a burst strength of 350 psi (item S 9.2.5) and a minimum cross-section of 70% (item S 9.2.1) will be made.

Considering the near effective date of FMVSS, we would like to receive your answer concerning the three items mentioned above as soon as possible.

Yours sincerely

ALFRED TEVES GMBH

ppa.

i.V.

BELLER

Attachment

1 sketch

Ruckschiagventil

Schlauchhalter

Vakuumschiauch

(Graphics omitted)