DE Determination of Retest Periods of Composite Pressure Receptacles by the competent authority including the re-assessment of service live after 15 years for UN-composite pressure receptacles The revised and restructured procedure described in the following serves the multimodal determination of retest periods for composite pressure receptacles in Germany as stipulated by regulations relevant for the transport by road/rail, sea and air. It particularly accounts for the multitude of design variables and complexity of the behaviour of composite pressure receptacles designed in accordance with accepted standards, as well as the specific properties of composite materials regarding prediction of service life and periodic inspection and testing. The provided procedural method replaces the previous procedure from the 31 st October 2008 (version 4.0 EN). Contact: RegDir Dr.-Ing. Georg W. Mair georg.mair@bam.de Dr.-Ing. Pascal Pöschko pascal.poeschko@bam.de Dipl.-Ing. (FH) Manfred Spode manfred.spode@bam.de Informative translation of version 6.0 DE 31 st March 2012 Safety in technology and chemistry
Retest periods of composite pressure receptacles version 6.0 EN from 31 st March 2012 Content 1 Conceptual description...3 1.1 Basics on the determination of retest periods...3 1.2 Legal basis...3 1.3 Competence of the Federal Institute for Materials Research and Testing...4 1.4 Scope...4 1.5 Safety goal...5 1.6 Regulation stipulating the safety goal to be achieved...5 1.7 Connections with other regulations...5 2 Determination of the retest periods of composite pressure receptacles...6 2.1 Background on the safety concept...6 2.2 General explanations concerning the concept of Xy-composite pressure receptacles up to 450 litres...7 Appendixes: Appendix VA: Composite Pressure Receptacles with a nominal water capacity up to 450 l - procedure, criteria, and requirements - from the 31 st March 2012 Technical Appendix CAT (Concept Additional Tests): Concept of complemented tests for the registration and preservation of the status as a Xy-composite pressure receptacle (Xy-CRP) from the 31 st March 2012 Technical Appendix LCT (Load Cycle Test): Procedure and assessment of hydraulic load cycle tests on Xy-composite pressure receptacles (Xy-CPR) from the 31 st March 2012 Technical Appendix SBT (Slow Burst Test): Procedure and assessment of hydraulic slow burst tests on Xy-composite pressure receptacles (Xy-CPR) from the 31 st March 2012 page 2 of 8
1 Conceptual description 1.1 Basics on the determination of retest periods Pressure receptacles made of composite materials are structures exhibiting a multitude of parameters and design variables, the likes of which are not present in monolithic gas cylinders. Dependent on the type of liner, fibre type, and layer composition, the attributes relevant for the determination of a safety-technically valid retest period may vary significantly. Therefore the retest periods or inspection intervals of composite pressure receptacles for the transport of dangerous goods are not as yet being determined based on the transported substance (as is described in 4.1.4.1 P200 RID/ADR for metal cylinders). Instead, the determination of adequate retest periods in accordance with 4.1.4.1 P 200 (9) RID/ADR has to be done individually for each design type by the competent authority. (Quote: "By derogation from this paragraph, the periodic inspection of pressure receptacles which make use of composite materials (composite pressure receptacles) shall be carried out at intervals determined by the competent authority of the Contracting Party to ADR which has approved the technical code for the design and construction." ) In Germany, this task is in the area of transport by road/rail performed by the Zentralstelle der Länder für Sicherheitstechnik (ZLS) in Munich after consulting with the Federal Institute for Materials Research and Testing (BAM) according to the national regulation RSEB. For all other modes of transport and UN pressure receptacles (also in the area of transport by road/rail), the BAM is the competent authority. In an effort to provide a uniform procedure, the BAM and the ZLS agree upon the following procedural method until revoked. It is being conducted by the BAM. Until now, it was common practice in Germany that new design types were initially granted a retest period of 3 years. Later on, with positive in-service experience, this retest period would often be extended to 5 or 10 years. However it can now be assumed that, if appropriate documentation is performed (scatter, cf. Appendix CAT), a retest period of 5 years may be viewed to be the future rule, and 10 years may be granted in exceptional cases. This is due to increasingly better understanding of the particularities of these kinds of pressure receptacles, and accumulated practical experience in operating and testing. The procedure described here is based on the assumption that the retest period for a design type/design variant will be determined usually within the frame of type approval. It is nevertheless applicable for initial determinations as well as for extensions of retest periods of design types/design variants already in operation. 1.2 Legal basis Sections 4.1.4.1 P 200 (9) of RID/ADR/ADN 2011 and 4.1.4.1 P 200 (2) d of the IMDG Code (Amdt. 35-10) do not specify retest periods of pressure receptacles made of composite materials, but instead stipulate that they shall be determined specifically for each design type by the competent authority. There are no comparable requirements in the area of transport by air (ICAO Technical Instructions 2011-2012 and IATA Dangerous Goods Regulations (DGR), 53rd Edition 2012). However, ICAO-TI 5.2.6.2.1 and IATA 6.4.1.6 require that the system of periodic inspection and testing be approved by the competent authority. Since pressure receptacles are generally considered, in contrast to tanks and MEGCs, as a form of packaging, the BAM determines retest periods of composite cylinders for transport by air along with granting a type approval for that mode of transport. page 3 of 8
According to section 6.2.2.1.1 Note 2 in RID/ADR/ADN as well as in the IMDG Code, and according to the note in section 5.2.1.1 of the ICAO-TI or to Note 2 in 6.4.2.1.1 of the IATA DGR, the maximum service life is limited to 15 years despite the mandatory design as pressure receptacle for non-limited life. The competent authority may, however, allow further use. For this purpose the procedure described below will also be applied in principle. By analysing the data obtained in accordance with the Technical Annexes, it serves to evaluate whether safe continued operation in excess of 15 years can be reasonably expected. 1.3 Competence of the Federal Institute for Materials Research and Testing The competence of the BAM in Germany with respect to the determination of retest periods is laid down in the following national regulations: Transport by road/rail, inland waterways: According to 8 section 1 c) of the Gefahrgutverordnung Straße, Eisenbahn und Binnenschifffahrt (GGVSEB) in the announcement from 16 th December 2011, the competence for 4.1.4.1 P200 (9) RID/ADRADN is not regulated in the GGVSEB. Thus the joint competence of the BAM and the ZLS results from section 4-4.4 of the RSEB Richtlinien zur Durchführung der GGVSEB from 29 th April 2011. Transport by sea: 6 section 5 of the Gefahrgutverordnung See (GGVSee) from 16 th December 2011 Transport by air: Fourth Section, 5. 78 (3) of the Luftverkehrs-Zulassungs-Ordnung LuftVZO from 10 th July 2008, amended on 22 nd February 2011 1.4 Scope This document is applicable to composite pressure receptacles designed, approved and tested in accordance with a standard referenced in regulations pertinent to the respective mode of transport. Specifically, the following standards shall be referred to: EN 12257:2002 Transportable gas cylinders Seamless hoop wrapped composite cylinders EN 12245:2002 Transportable gas cylinders Fully wrapped composite cylinders EN 14427:2004 + A1:2005 Transportable refillable fully wrapped composite cylinders for liquefied petroleum gases Design and construction ISO 11119-1:2002 Gas cylinders of composite construction Specification and test methods Part 1: Hoop wrapped composite gas cylinders ISO 11119-2:2002 Gas cylinders of composite construction Specification and test methods Part 2: Fully wrapped fibre reinforced composite gas cylinders with load sharing metal liners page 4 of 8
ISO 11119-3:2002 Gas cylinders of composite construction Specification and test methods Part 3: Fully wrapped fibre reinforced composite gas cylinders with non load sharing metallic or non metallic liners This excludes neither older versions of respective design standards nor design variant approvals according to the German national DruckBehVO. Also, newer versions of the standards may be used, provided that corresponding changes in legal requirements are already decided and the standard is being used in anticipation of these new regulations. 1.5 Safety goal The protection against detriments with regard to health and property of owners, possessors, operators and of unintended bystanders during unaffected and normal operational conditions shall be ensured in accordance with the accepted residual risk level. 1.6 Regulation stipulating the safety goal to be achieved The retest periods of pressure receptacles shall be determined according to the-state-of-theart in such a way that no unacceptable residual risk, especially with respect to burst, will occur. Particularly, neither extensive use (frequent filling) nor lack of use (i.e., no emptying of pressure receptacles after transport, or of pressure receptacles forgotten after partial emptying) may lead to a hazardous state. On the part of the competent authority the state-of-the-art of science and technology is hence being considered. 1.7 Connections with other regulations The determination of retest periods is carried out with regard to safety requirements concerning the transport of dangerous goods in pressure receptacles. Hence, only transport conditions are being considered for safety. In case of pressure receptacles being intended also for use under different circumstances (e.g., temporary or permanent stationary use in facilities with operating parameters differing from normal transport conditions, like filling procedure and frequency), additional provisions of other regulations (e.g. concerning handling, storage, use and re-filling) must be taken into account. This may cause the necessity of additional tests, shorter retest periods or of service lives being determined in a different manner. Provisions not concerning the transport of dangerous goods are not being reviewed or evaluated for the purpose of determining retest periods. page 5 of 8
2 Determination of the retest periods of composite pressure receptacles 2.1 Background on the safety concept Pressure receptacles made from fibre-reinforced composite materials are, like any other kind of pressure receptacles, subject to ageing processes. In terms of development and evaluation, these processes are more complex than is the case for metallic pressure receptacles. Internationally, contradictory experiences have hence been gathered, and there is as yet no conclusive picture concerning the behaviour of composite pressure receptacles. As a result, the respective national competent authority is required to participate in terms of individual examination. Generally, the relevance of periodic inspection and testing has changed. With 10 to 15 years retest periods being now common for many gases, it has broadened from mere individual surveillance to that of entire design type populations with regard to systematic problems. At present, individual safety of pressure receptacles in operation is achieved largely through inspections prior to filling. Based on this tendency, the concept introduced below focuses on recognising possible systematic deficiencies concerning the service strength of a given design type. The underlying principle is that populations of pressure receptacles may be granted a prolonged retest period only if the service life prognosis of that design type for the relevant time span can be ascertained in praxis. 1 The following description of degradation behaviour is built on a criterion of minimal residual strength in conjunction with a 99.9999% survival probability, or 10-6 probability of failure, until the end of service life in principle. Sample sizes which can be viewed as feasible with regard to practicality are however insufficient in order to guarantee such a level of reliability. The procedure thus aims at providing add-on-information without abstaining from the usual tests, as long as these can be said to generate substantial knowledge. This is why in spite of statistical uncertainties it is assumed to enhance the safety level through knowledge on the interaction of design and operation of composite pressure receptacles. This knowledge on design type specific safety behaviour is the necessary compensation for extended retest periods. The general reliability requirements presented herein do not yet factor in aspects of proven fail-safe behaviour, which could lead to higher accepted failure probabilities with regard to leakage. Such alleviations would come into effect if in addition, because of neither toxicity nor flammability of gases used, comparably much less serious consequences had to be expected. This does not preclude the competent authority from choosing different (higher or eventually lower) underlying survival probabilities in individual cases, based on the potential consequences. 1 Comment: This approach is based on state of the art scientific knowledge, and is designed to allow for ongoing optimisation through further research as well as scientifically founded individual case decisions, at least in its early stages. page 6 of 8
If the above mentioned safety-technical prerequisites for pressure receptacles up to 450 litres are evaluated and fulfilled, they will be marked as Xy-pressure receptacles 2 upon application by the manufacturer or the operator, and be subjected to testing parallel to operation as per the Appendices. Evaluation of composite pressure receptacles with volumes greater than 450 litres is based on the same principles but is conducted according to an individual procedure for the demonstration of their relevant properties. 2.2 General explanations concerning the concept of Xy-composite pressure receptacles up to 450 litres 2.2.1. Because of the high numbers of required test specimens, this concept is mainly meant for cylinders and tubes which are manufactured in large serial production. For design types with higher volumes, which are usually manufactured in relatively small numbers, it is assumed that due to economic considerations, proof of safety will rather be achieved by means of NDT (online) methods. Hence retest periods for composite tubes over 450 litres are not determined using the test concept at hand, but according to an individual procedure. 2.2.2 The term Xy-pressure receptacles applies to all pressure receptacles made from fibre-reinforced composite materials which fulfil the requirements as per VA 1.2 of Appendix VA, and which have been and are continuously subjected by the operator to the procedure as per chapter VA 2 of Appendix VA. 2.2.3 The term Xy-pressure receptacle expresses that a design type of a pressure receptacle made from fibre-reinforced composite materials is addressed in accordance with the definition given above. Therefore the design type is tested more extensively than is required in design standards, in accordance with this concept and it has been granted a 10 years retest period due to the demonstrated properties. 2.2.4 If the requirements of chapter VA 2 are no longer fulfilled, the status as Xy-pressure receptacle expires immediately. These composite pressure receptacles shall then to be treated as per chapter VA 1 of Appendix VA, or, depending on the evaluation of the last test results with respect to the end of service life, be rendered unserviceable. 2.2.5 The necessary tests are stipulated according to the criterion of load cycle sensitivity. A design type will be classified as non load cycle sensitive if it has no metal liner and if none of the test specimens from the sample show evidence of a failure during a cycle test of at least 50,000 load cycles to test pressure. In the case of metal liners, it is assumed that the material per se is load cycle sensitive. If pronounced overdimensioning may be the reason for high cycle strength, the individual case would have to be evaluated as to what further criteria should apply. 2.2.6 The component authority reserves the right to deviate from the rules laid town in this concept as equates to the state-of-the-art of science and technology. This includes higher or and exceptionally lower minimum reliability (survival rate) values depending on pressure-volume-product and the gas(es) intended for service. 2.2.7 Initial performance of these tests, while constituting additional effort for testing, does not call for minimum requirements in addition to design standards. The results from initial performance of these tests represent properties meant for comparison with those determined in repetitions of theses tests parallel to operation at a later point. 2 Comment: X stands for Roman 10, y stands for years ; cf. Appendix VA. page 7 of 8
2.2.8 Test specimens taken from service as test sample shall first be subjected to periodic inspection and testing as the operator is used to do. This is to ensure that the specimens are above reproach concerning their being representative for all pressure receptacles of that design which remain in service after periodic inspection and testing. 2.2.9 A test result may only be condemned and testing of a design type be repeated if there is no doubt that the test procedure has failed to meet the test specifications due to e.g. massive fault in load application caused by the test equipment. page 8 of 8