Commercial Vessel Compliance

3/8/2017: MSIB 004-17 Testing of pneumatic system vapor pressure relief valves

Due to a mishap from improper testing of a vapor safety relief valve on a compressed air system, the Coast Guard Office of Commercial Vessel Compliance reminds all those concerned of the risks and best practices when conducting or witnessing the testing of relief valves. While this information is based on testing compressed air systems using vapor relief valves, the guidance is also relevant to safety valves in other pressure systems, except boilers.

Marine inspectors should be aware of the following:

1) A marine inspector should not allow removal or alteration of a secondary safety device to facilitate a test of the intended safety device

2) All systems are different, and the attending marine inspector should become familiar with each system and the valve settings before testing

3) The attending marine inspector is observing the test only, and the appropriate vessel representative should perform all functional tests

4) The attending marine inspector should verify that all relief valves meet the design, installation, and performance criteria in 46 CFR Subchapter F

This safety bulletin is issued after, in preparation for a test, the relief valve on the associated compressor was removed because it had a lower set-point than the relief valve on the air receiver being tested. The isolation valve between the compressor and the air receiver was mistakenly left closed during the test, resulting in a dead-head situation, causing the compressor to rupture, and sending shrapnel throughout the space. Fortunately, no one was injured.

More information is available in the full MSIB-004-17.

This blog is not a replacement or substitute for the formal posting of regulations and updates or existing processes for receiving formal feedback of the same. Links provided on this blog will direct the reader to official source documents, such as the Federal Register, Homeport and the Code of Federal Regulations. These documents remain the official source for regulatory information published by the Coast Guard.