Interpretation ID: nht92-5.10

DATE: July 28, 1992

FROM: Tom Mario -- Vice President Sales, Sealco Air Controls, Inc.

TO: Steve Wood -- Office Staff Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 9/25/92 from Paul Jackson Rice to Tom Mario (A39; Std. 121)

TEXT:

I had a recent phone conversation with Mr. Richard Carter about trailers using the "protected separate reservoir", which has a 60 P.S.I. pressure protection valve built in it.

With 60 P.S.I. in the supply line and 60 P.S.I. on top of the piston in the spring brake control valve, you will have a 90 P.S.I. holding the spring brakes off, because of the built in ratio feature, when the protected reservoir is fully charged.

We are requesting your interpretation of the current regulation as to the following item-

If a O.E.M. decides to use the system with a protected reservoir, what pressure must be retained in the supply line with any single leakage type failure in the service brake system?