EVALUATION OF DANGEROUS GOODS PRESSURE RELIEF VALVE PERFORMANCE : PHASE 2, AIR TEST RESULTS : ADDENDUM : SERIES C312-1 SERIES RESULTS AND ANALYSIS

Results of the BLEVE (Boiling Liquid Expanding Vapour Explosion) study conducted by Queen's University have shown that energy storage in a pressure vessel is a prime factor in predicting the severity of a catastrophic vessel failure. During these tests, a number of unusual behaviours were observed in the PRVs (pressure relief valves) installed on the test vessels. Since these valves play a large role in the control of energy accumulation and storage in a pressure vessel, it was determined that there was a need to study their dynamic behaviours in detail and quantify their effect on energy storage. As an initial step, 40 small (1-inch NPT) PRVs such as those used on automotive propane tanks and representing equivalent designs from each of two manufacturers were procured through a third party and tested on DuPont Canada's air test bench in Maitland, Ontario. These tests were conducted in accordance with the certification procedures specified by various agencies (ASME, UL, CSA, CGA). Four characteristic pressures were measured - simmer (start-to-discharge), pop (full open), reseat, and reseal (bubble-tight reclosure). After initial testing, the valves were stored for various periods of time and retested. A third batch of 20 small valves of another commercially available design was subsequently tested. This report details the results of this testing as well as a significant discussion about the expected operation of relief valves. The results are discussed in three parts: qualitative analysis of the test results, statistical distribution of the results, and comparison to code requirements.