Oxygen Endurance Testing of Oxygen Cylinder Valves

Cylinder valves for oxygen service that meet the standard DIN EN ISO 10297 should be safe, if properly handled by the user. In the last few years, however, the number of safety incidents with oxygen valves that has been reported to the Federal Institute for Materials Research and Testing (BAM) has increased. According to the incident reports, incorrect handling can be ruled out. People were seriously injured and, in most cases, the causes of these incidents were not clear. Very often such incidents occurred during opening and closing of the valves. Therefore, the technical-scientific community has put the existing methods for type testing more and more into question. Besides other mandatory tests, the aforementioned standard allows the endurance test to be performed with air or with nitrogen. This is appropriate for all other gases but not for oxygen. Up to now, this test did not consider the fact that cylinder valves also contain nonmetallic seat materials and lubricants that may react with oxygen in a dangerous way. Because of this unsatisfactory situation, BAM initiated a research project to perform endurance testing of cylinder valves for oxygen service with oxygen. This test accurately simulates real-life situations when the cylinder valve is opened or closed. The first part of this project was the development of a new oxygen operated endurance tester in accordance with DIN EN ISO 10297. In the second part, endurance testing of valves with air and with oxygen was performed and the results were compared. In addition, another mandatory test of the standard, the oxygen pressure surge test, was carried out on new valves and on valves that had undergone endurance tests with air or oxygen to see the influence on the burn-out safety of such pre-stressed valves. This paper presents the main results of the project. The findings clearly speak for implementing the oxygen endurance test not only with DIN EN ISO 10297 but also with various other standards to increase the burn-out safety of oxygen cylinder valves.