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External-Style Pressure Relief Valve A-1402C Series
6 SPECIAL GUIDELINES AND PRECAUTIONS
ON PRESSURE TESTING AND ADJUSTMENT
6.1.1
Determining Applicable Pressure Values
Refer to AAR publication “Regulations for Tank Cars.” Appendix A applies specifically to
valves. This section prescribes the start-to-discharge pressure" to start-to-discharge (STD)
pressure and their tolerances.
6.1.2
Test Stand and Gauge Requirements
It is recommended that the test stand mounting must be equivalent to the AAR M1002
figures E19.14 through E19.23 for the valve being tested. The pressure gauge must meet
the requirements of D4.5 Test Gauge Standards and must be date-tagged.
CAUTION: Safety Protection.
Wear appropriate safety glasses or face-shield and protective clothing when
conducting this procedure. Valve testing involves high-velocity air and water flow that can cause injury.
CAUTION
NOTE:
A “popping pressure” is not specified. It is only necessary to ascertain the STD pressure as pressure is
increased, and to establish the vapor-tight pressure as pressure is being reduced. (STD is defined as a continuous
discharge in contrast to the start-to-leak pressure, which is defined as the first bubble leak. Vapor-tight is defined
as the pressure at whch no further fluid is detected. Midland recommends that no bubbles be observed for 2
minutes at vaport-tight.)
NOTE