Interpretation ID: nht78-2.48

DATE: 05/23/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: The Johnson Manufacturing Co.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Johnson Manufacturing's May 4, 1978 request for confirmation that the requirement in Standard No. 121, Air Brake Systems, that reservoirs "withstand" specific pressure does not require testing of a multi-compartment reservoir compartment-by-compartment.

Your understanding of the "withstanding" requirement in S5.1.2.2 and S5.2.1.3 is correct. Although the agency sought to clarify that compartment-by-compartment testing was the proper interpretation of this requirement (42 FR 64630; December 27, 1977), problems with the interpretation resulted in its withdrawal (43 FR 9149; March 6, 1978) and adherence to the existing interpretation that there be no rupture or permanent circumferential deformation of the reservoir. Under this interpretation only the circumference of the outer reservoir shell is measured, and internal baffles are not stressed by separate compartment-by-compartment testing.