Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (13)
- Zeitschriftenartikel (7)
- Beitrag zu einem Tagungsband (7)
- Beitrag zu einem Sammelband (3)
- Buchkapitel (1)
- Dissertation (1)
Schlagworte
- Pneumatic impact (5)
- Flammability (4)
- Berstscheibe (3)
- High pressure oxygen (3)
- Adiabatic compression (2)
- Aluminium (2)
- Brandgefahr (2)
- Coatings (2)
- Ignition source (2)
- Metallic materials (2)
Eingeladener Vortrag
- nein (13)
Gaseous oxygen impacts may occur in high-pressure oxygen systems whenever oxygen equipment is pressurized too fast. This is one of the main causes of fires in such systems. Therefore, equipment for high-pressure oxygen that contains nonmetallic sealing materials should be tested for burn-out safety. This is required by numerous international standards such as ISO, CEN or national standards as DIN in Germany. Because of new technical developments in industrial uses of oxygen, higher operating pressures up to 500 bar are becoming more and more frequent. With regard to this need, a new 500 bar gaseous oxygen impact tester has been designed and built at the Federal Institute for Materials Research and Testing (BAM) in Berlin (Germany). This paper describes all elements of this test system. The most important element of this BAM test apparatus is a new hydraulically operated quick opening valve that meets all international standards. First experiences on performance and maintenance of the new test apparatus are given.
Autoignition temperature (AIT) round robin tests were conducted by seven laboratories on eight polymeric materials. A statistical analysis was conducted that focused on investigating data variability both within and between test methods. With some exceptions, the methods ranked the materials consistently and as expected from their chemical makeup. There was no consistent difference between AIT values determined at 6.9 and 10.3 MPa. BAM and ASTM G72 consistently provided lower, more conservative AITs at both 6.9 and 10.3 MPa. Within an estimated accuracy obtained from all methods from this round robin, data from the following methods appeared to be more accurate than the rest: NF E 29763/88 and Parr Bomb at 6.9 MPa; automated ASTM G72 at 10.3 MPa. The following methods provided lower within-method variability than the average for all methods: BS 3N 100 and ASTM G72 at 6.9 and 10.3 MPa; Parr Bomb at 6.9 MPa. At 6.9 MPa the BAM method provided data with greater within-method variability than the average for all methods. For most materials, the automated ASTM G72 method at 10.3 MPa provided data with greater within-method variability than the average for all methods. Two data points for this method, Zytel? and Teflon? FEP, exceeded critical . At 6.9 MPa, the largest within-method variability resulted from NF E 29763/88 on Zytel, the only data that exceeded critical . Two extreme results were caused by significant effects of method-specific test parameters: BAM on Zytel at 6.9 MPa and BS 3N 100 on Viton? at 10.3 MPa. Statistically these results had a probability of less than 5 percent of occurring by chance.
Combustion Tests under High Pressure Oxygen: Metals- vs. Component-Related Test Specifications
(2006)
Armaturen und Anlagenteile für Hochdruck-Sauerstoff enthalten meistens nichtmetallische Materialen als Sitz- und Dichtungswerkstoffe. Die Gefahr eines Ausbrands dieser Armaturen; ist grundsätzlich vorhanden, jedoch relativ gering, wenn neben dem richtigen Design geeignete metallische und nichtmetallische Materialien für die vorgesehenen Betriebsbedingungen von Druck und Temperatur gewählt werden. Aus sicherheitstechnischer Sicht sollte daher für Armaturen und Anlagenteile, die komplett aus Metall gefertigt und metallisch abgedichtet werden, eine noch geringere Gefahr eines Ausbrands bestehen. Während einer Versuchsreihe auf dem BAM-TTS- Frei Versuchsgelände mit Hochdruck-Sauerstoff brannte jedoch unerwartet ein solches - rein metallisches Anlagenteil - komplett ab. Bei diesen Versuchen platzt eine metallische Membran wie eine Berstscheibe bei einem bestimmten Sauerstoffdruck auf.
The new promoted ignition combustion test apparatus at BAM matches the requirements of ASTM test method G 124 [ASTM G 124, Standard Test Method for Determining the Combustion Behavior of Metallic Materials in Oxygen-Enriched Atmospheres, 2003] and of EIGA publication, IGC Doc 13/02/E [EIGA Gas Association Document IGC Doc 13/02/E, Oxygen Pipeline Systems, 2003]. The test apparatus is most likely the only one in Europe. The test chamber allows investigations with pure oxygen or oxygen mixtures at pressures up to 500 bar and at temperatures up to 400°C at static or flowing gas conditions. The ignition device consists of an electrical ignition wire and a promoter. IR-sensors, distributed over the whole length of the rod, measure and record the burning temperature and allow measurement of the burn rate. A video system records the experiment for visual characterization of the burning behavior. BAM test results are compared with published data. Results on investigations with coated rods are presented. Ceramic coatings seem to be a solution for the use of certain less compatible metallic materials at higher oxygen pressures.
Two different test apparatuses are used at BAM to evaluate the safety of oxygen components: First, the promoted ignition combustion test according to ASTM G 124 [1] and to EIGA IGC Doc 13/02/E [2], and second, the new metallic disk ignition test that has not been standardized yet. The standard test method ASTM G 124 allows a ranking of metallic materials for use at high pressure oxygen. However, the transfer of those test results to valves and fittings in real-life situations is rather complex. The metallic disk ignition test, developed at BAM, is more practice oriented and uses metallic disks of different thicknesses of the investigated material. A commonly used nonmetallic sealing ring is placed in front of this disk and serves as an igniter. This test array is then exposed to high pressure gaseous oxygen impacts in a standardized pneumatic impact tester according to DIN EN 1797 [3].
Nach nationalen und internationalen Vorschriften müssen
Armaturen und Anlagenteile für hoch verdichteten Sauerstoff
ausbrennsicher sein. Diese Forderung kann technisch dadurch
erreicht werden, dass sicherheitstechnisch geeignete
nichtmetallische und metallische Werkstoffe verwendet werden.
Für die Auswahl geeigneter metallischer Werkstoffe sind
der Verwendungszweck der Armatur, die Betriebsbedingungen
sowie werkstoffspezifische Parameter zu berücksichtigen.
Einige metallische Werkstoffe besitzen gute Materialeigenschaften,
lassen sich leicht be- bzw. verarbeiten und
sind kostengünstig in der Beschaffung, dürfen aber aufgrund
ihres ungünstigen Abbrandverhaltens in Sauerstoff nicht eingesetzt
werden. Es besteht daher ein großes Interesse, den
sicherheitstechnischen Beschränkungen dieser Werkstoffe
durch geeignete Maßnahmen entgegenzuwirken. Eine mögliche
Lösung stellt die Beschichtung dieser Werkstoffe beispielsweise
mit Keramik dar, um den unmittelbaren Kontakt
mit dem Sauerstoff zu verhindern. Um den Einfluss dieser
Keramikschichten auf das Abbrandverhalten metallischer
Werkstoffe zu untersuchen, wird die im Standard ASTM G124
[1] beschriebene Apparatur und das in der einschlägigen
Literatur beschriebene Bewertungsverfahren verwendet. Die
Ergebnisse zeigen, dass für keramikbeschichtete metallische
Werkstoffe ein Abbrand erst bei höheren Sauerstoffdrücken
erfolgt.
Die Gefahr eines Ausbrandes bei Armaturen und Anlagenteilen für Sauerstoff ist latent vorhanden wenn ungeeignete nichtmetallische Dichtungsmaterialien eingesetzt werden. Aus sicherheitstechnischer Sicht sollten daher komplett aus metallischen Materialien gefertigte und gedichtete Sauerstoffkomponenten kaum die Gefahr eines Ausbrands aufweisen. Auf dem 'BAM Testgelände Technische Sicherheit' (BAM-TTS) erfolgte der Ausbrand eines derartigen Sauerstoff-Anlagenteils daher völlig unerwartet. Neben dem heftigen Metallabbrand wurde glühendes metallisches Material bis zu 70 m weit geschleudert und führte zu mehreren Grasbränden. Die anschließenden Untersuchungen konzentrierten sich insbesondere auf die beiden Metallsorten Aluminium und Stahl, aus denen der Großteil der kommerziell erhältlichen Berstscheiben besteht.
In oxygen components, even for high pressure oxygen service, it is possible to use organic seals, lubricants, or filling liquids, provided their oxygen compatibility has been checked. However, fire incidents in oxygen systems still occur because these materials ignite and burn. There are many reasons, such as incorrect design, contamination, faulty operation, unsuitable materials, etc., why this happens. Another cause that is overseen very often is proper maintenance on the user´s side. It is very important to replace in a component a worn out seal by the same one with identical oxygen compatibility properties. On the part of the producer or distributor of materials, batch testing and also a quality assurance system play a key role in the safety of an oxygen component. Any change in the manufacturing process of a material, or in its composition, and even its further processing may have an impact on its oxygen compatibility and finally on the component in which it is used. Numerous investigations by BAM over decades reveal the influence of minor constituents and fillers on a material´s oxygen compatibility. The test results in this paper show how important it is to regularly perform batch testing on nonmetallic materials used for oxygen service and to have a quality assurance system that helps minimize incidents where unsuitable materials are chosen by accident.
Self-contained underwater breathing apparatus (SCUBA) divers use different mixtures of nitrogen and oxygen as breathing gas. The so-called NITROX mixture often contains more oxygen than is contained in air and may increase the fire hazard in diving equipment. The SCUBA diving community, however, still differentiates between NITROX mixtures that contain more than 40 % oxygen or less. They consider a mixture with up to 40 % oxygen often as regular air. In filling operations of SCUBA cylinders, gas flows from high pressure to low pressure. Because of compressive heating, a sudden temperature rise in the gas occurs and nonmetallic materials, e.g., seals may ignite. BAM has used the pneumatic impact test to investigate the ignition sensitivity of ethylene propylene diene monomer (EPDM), fluorelastomer (FPM), polytetrafluorethylene (PTFE), polyetheretherketone (PEEK), and nylon (PA 6.6) to gaseous impacts in synthetic air, in various NITROX mixtures, and in pure oxygen. The test results clearly show that for nonmetallic materials, the maximum pressure of nonreaction in NITROX mixtures decreases at a content of 29 % oxygen in comparison to those in air. In addition, autoignition temperatures of the nonmetallic materials were also determined. The findings of this investigation support very well the results of other publications on oxygen enrichment. As a consequence of this study, in SCUBA diving, the same safety requirements for NITROX mixtures with more than 21 % oxygen should be applied as for pure oxygen in the industry.
Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies; however, a thorough evaluation of the test parameters and test system influences on the thermal energy produced during the test has not yet been performed. This paper presents a background for adiabatic compression testing and discusses an approach to estimating potential differences in the thermal profiles produced by different test laboratories. A "thermal profile test fixture" (TPTF) is described that is capable of measuring and characterizing the thermal energy for a typical pressure shock by any test system. The test systems at Wendell Hull and Associates, Inc., in the United States and at the BAM Federal Institute for Materials Research and Testing in Germany are compared in this manner and some of the data obtained are presented. The paper also introduces a new way of comparing the test method to idealized processes to perform system-by-system comparisons. Thus, the paper introduces an "idealized severity index" (ISI) of the thermal energy to characterize a rapid pressure surge. From the TPTF data a "test severity index" can also be calculated so that the thermal energies developed by different test systems can be compared to each other and to the ISI for the equivalent isentropic process. Finally, a "service severity index" is introduced to characterize the thermal energy of actual service conditions. This paper is the second in a series of publications planned on the subject of adiabatic compression testing.
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.
Oxygen Compatible Materials & Burn-Out Safe Oxygen Components Approach and Test Methods by BAM
(2013)
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 incidents with oxygen valves that has been reported to 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 test methods for type testing more and more into question. Besides other mandatory tests, the above-mentioned standard allows to perform the endurance test with air or with nitrogen. This is appropriate for all other gases but not for oxygen. Up to now, this test does 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 much more practice related with oxygen. This test simulates very well 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 a 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 to DIN EN ISO 10297 but also to various other standards to increase the burn-out safety of oxygen cylinder valves.