49 CFR Appendix B to Part 180 - Acceptable Internal Self-closing Stop Valve Leakage Tests for Cargo Tanks Transporting Liquefied Compressed Gases
For internal self-closing stop valve leakage testing, leakage is defined as any leakage through the internal self-closing valve or to the atmosphere that is detectable when the valve is in the closed position. On some valves this will require the closure of the pressure by-pass port.
1. An operator of a cargo tank equipped with a calibrated meter may check the internal self-closing stop valve for leakage through the valve seat using the meter as a flow measurement indicator. The test is initiated by starting the delivery process or returning product to the cargo tank through the delivery system. This may be performed at an idle. After the flow is established, the operator closes the internal self-closing stop valve and monitors the meter flow. The meter flow must stop within 30 seconds with no meter creep within 5 seconds after the meter stops.
2. On pump-actuated pressure differential internal self-closing stop valves, the valve must be closed with the remote actuator to assure that it is functioning. On other types of internal self-closing stop valves, the valve(s) may be closed using either the normal valve control or the discharge control system (e.g., remote).
3. Rejection criteria: Any detectable meter creep within the first five seconds after initial meter stoppage.
An operator of a cargo tank that is not equipped with a meter may check the internal self-closing stop valve(s) for leakage as follows:
1. The internal self-closing stop valve must be in the closed position.
2. All of the material in the downstream piping must be evacuated, and the piping must be returned to atmospheric temperature and pressure.
3. The outlet must be monitored for 30 seconds for detectable leakage.
4. Rejection criteria. Any detectable leakage is considered unacceptable.