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The widely held incorrect belief in the self-contained underwater breathing apparatus (SCUBA) diving community, that oxygen-enriched gas mixtures, so-called NITROX, with an oxygen content of up to 40 vol. % can be considered as regular air, has already been refuted in many papers. Now, another dangerous practice has drawn the attention. In a market study, more than 60 representative SCUBA cylinder valves were examined. Sales offices claim that all of those valves can be used for oxygen-enriched gas mixtures. The fact is that some of these cylinder valves are for air use only. By exchanging the nonmetallic materials and applying additional cleaning procedures, these air valves become so-called “oxygen clean.” Then, the valves are on sale for oxygen-enriched service. This procedure is dangerous because the labeling pretends a pseudo-safety. All of the 60 SCUBA cylinder valves were tested applying the standardized oxygen pressure surge tester at BAM. As suspected, many of the cylinder valves are not burn-out safe. In addition, different test results were received for actual new valves, for so-called new but temporarily stored valves, and for used valves. This paper reveals another dangerous practice and wants to alert the SCUBA diving community.
Die meisten Sauerstoffarmaturen und -anlagenteile bestehen aus Metallen und enthalten nichtmetallische Materialen als Sitz- und Dichtungswerkstoffe. Die Gefahr eines Ausbrands ist grundsätzlich vorhanden, jedoch relativ gering, wenn neben der richtigen Konstruktion geeignete metallische und nichtmetallische Materialien für die vorgesehenen Betriebsbedingungen gewählt werden. Aus sicherheitstechnischer Sicht sollten Sauerstoffarmaturen und -anlagenteile, die komplett aus metallischen Materialien gefertigt und abgedichtet werden, ein noch geringeres Risiko eines Ausbrands aufweisen. Bei einer Versuchsreihe auf dem BAM-TTS-Freiversuchsgelände brannte unerwartet ein rein metallisches Anlagenteil komplett ab. Bei dieser Versuchsanordnung platzt eine metallische Berstscheibe bei einem bestimmten Sauerstoffdruck auf. Die anschließenden Untersuchungen konzentrierten sich auf die Frage, wie es bei diesem Versuch zu einem Ausbrand des massiven Anlagenteils kommen konnte. Im Vortrag werden die Ergebnisse der Untersuchungen diskutiert und die Sauerstoffverträglichkeit der verwendeten Metalle auf Grundlage des Abbrandverhaltens nach ASTM G 124-95 verglichen. Es wird versucht, die Frage zu beantworten, ob der Einsatz metallischer Berstscheiben zu einer Erhöhung der Brandgefahr in Sauerstoffanlagen führen kann.
The general requirement, that nonmetallic materials for oxygen service must be tested and found suitable for their intended use in plants and components is the current state of technical safety. However, numerous requests of manufacturers, sales offices, and users show, that there is still a strong need for information on how these materials are tested and evaluated. Based on more than 60 years of expertise, this paper provides background information on BAM’s test approach. It explains why BAM applies additional assessment criteria on nonmetallic materials for certain use conditions. Hence, the test schedule as well as the final evaluation shall reflect the practical application in a more customer-related way in combination with a higher safety level. That is the demand of BAM’s safety philosophy.
The general requirement, that nonmetallic materials for oxygen service must be tested and found suitable for their intended use in plants and components is the current state of technical safety. However, numerous requests of manufacturers, sales offices, and users show that there is still a strong need for information on how these materials are tested and evaluated. Based on more than 60 years of expertise, this paper provides background information on BAM’s test approach. It explains why BAM applies additional assessment criteria on nonmetallic materials for certain use conditions. Hence, the test schedule as well as the final evaluation shall reflect the practical application in a more customer-related way in combination with a higher safety level. That is the demand of BAM’s safety philosophy.
The Oxygen Pressure Surge Test (OPST) is considered to be best practice for evaluating the burn out safety of plant components and testing the compatibility of nonmetallic materials for oxygen service. Nevertheless, there are only a few laboratories worldwide performing the OPST. The Federal Institute for Materials Research and Testing (BAM) already operates oxygen pressure surge test facilities with maximum OPST pressures of 450 bar.
However, to ensure technical innovation and to enhance research and development, the decision was made to develop a new and large-scale oxygen pressure surge test facility. Due to the size and the high potential impact energies, the test facility is located outside of Berlin at BAM Test Site for Technical Safety (TTS), where large scale testing is carried out. In addition to an intended maximum OPST pressure of 750 bar, there is the possibility of testing industrial equipment with large inner volumes and diameters. The new quick opening valve constitutes the core of the system and was developed by BAM. It allows to perform tests with the standardized pressure rise times of 15 ms to 20 ms or with adjustable pressure rise times at higher or lower values. As a result, it is possible to provide customized test parameters for specific practical applications as well as research projects.
This presentation shows the status quo of this unique test facility, its performance, its technical specifications, and its new possibilities for research and development for a long term enhancement of burn out safety in oxygen application.