1、 THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION VALVE PURCHASERS GUIDE TO THE EUROPEAN PRESSURE EQUIPMENT DIRECTIVE PUBLICATION N196 : 1999 (Incorporating Amendments Nos 1 to 3 (Nov 00, Feb 02 furthermore the draft documents referenced are those whose eventual publication is considered a
2、certainty. Documents in draft are clearly indicated in the list of references in Sec. 15. A glossary of terms and abbreviations is given in Sec. 16. Use of Language The auxiliary verb must is used to indicate a statutory requirement. Units Consistent with the Pressure Equipment Directive, bar signif
3、ies gauge pressure (above atmospheric). 12ONE PAGE GUIDE TO THE PED WHAT IS THE PURPOSE OF THE PED? Removal of barriers to the free trade in pressurised equipment within the European Union (EU)*. HOW DOES IT DO THIS? By specifying minimum requirements which must be met by such equipment. TO WHAT DOE
4、S IT APPLY? The design, manufacture and conformity assessment of pressure equipment and assemblies with an allowable pressure greater than 0.5 bar placed on the market and put into service in the European Economic Area (EEA)* whether new equipment, or second hand imported from outside the EEA. It is
5、 understood that Switzerland is also likely to adopt the Directive. HOW DOES IT APPLY TO VALVES? Valves, although not specifically referenced, are considered as either pressure accessories or safety accessories. Pressure accessories have an operational function and pressure bearing parts, e.g. valve
6、s and pressure regulators. Safety accessories are designed to protect pressure equipment against allowable limits being exceeded e.g. safety valves, bursting discs and controlled safety pressure relief systems. TO WHICH VALVES DOES IT APPLY? Most valves used by the chemical, oil and gas production,
7、petrochemical and power generation industries. There is a list of exclusions, some of which are significant (e.g. oil and gas well-head valves). WHAT DOES IT CONTAIN? A list of essential requirements which must be complied with. Classification rules (related to level of hazard). Rules for assessing
8、conformity. WHO IS RESPONSIBLE FOR MEETING ITS REQUIREMENTS? The manufacturer of the equipment. (Note that compliance with harmonised CEN standards gives presumption of conformity.) WHO IS RESPONSIBLE FOR ASSESSING CONFORMITY? (1) Notified Bodies (Inspection bodies independent of manufacturers and p
9、urchasers approved by national governments and employed by the equipment manufacturer at his expense). (2) User Inspectorates who may undertake the inspection activities of the Notified Body in certain circumstances (approved by national governments and employed by the purchaser for his own procurem
10、ent only). HOW DO WE KNOW EQUIPMENT CONFORMS? Most equipment will carry a CE mark affixed by the manufacturer and have an EC declaration of conformity drawn up by the manufacturer; where appropriate a certificate of conformity will be issued by the Notified Body. WHEN WILL IT BECOME EFFECTIVE? Volun
11、tary from 29thNovember 1999, mandatory from 30 May 2002. 3* The PED has the force of law in the 15-state EU. Its recognition by the non-EU members of the EEA (Iceland, Liechtenstein and Norway) is subject to a decision by the EEA Joint Committee. 41 INTRODUCTION The European Pressure Equipment Direc
12、tive (Directive 97/23/EC) is a New Approach directive intended to harmonise the laws of member states concerning the design, manufacture and conformity assessment of pressure equipment with the objective of facilitating trade in this equipment. It becomes mandatory on 30 May 2002 and manufacturers m
13、ay offer to supply in accordance with its requirements from 29 November 1999. The requirements will apply to most valves purchased for use in the European Economic Area (EEA) whether for application in new construction or in existing plant, including valves which have been refurbished and placed on
14、the market or which are being imported from outside the European Union. Valves are classified by the PED as pressure accessories or as safety accessories. This means that they are accessories to a piping system (usually) or vessel (less frequently) and follow the classification and conformity assess
15、ment rules for these items and the relevant working fluid. A safety accessory is one which protects other pressurised equipment against the allowable limits being exceeded. Thus, a spring loaded or pilot operated safety relief valve will always be classified as a safety accessory but so will shut-do
16、wn valves in high integrity pressure protection systems and valves in certain other specialised safety applications. In general, safety accessories are given a higher classification category than other accessories operating in comparable conditions. With regard to pressure accessories, the PED is pr
17、imarily concerned with their pressure containing aspects rather that their function; however see Appendix A for a qualification of this statement. The PED places more responsibility on the manufacturer than has traditionally been the case (e.g. he is required to assess the hazard associated with the
18、 application, and is responsible for compliance with the requirements of the PED). Also, Notified Bodies (NoBos) have been introduced. These are inspection bodies which are independent of purchasers and manufacturers and appointed by the EU member governments and employed by manufacturers. The degre
19、e of involvement of the notified body varies according to the chosen route of conformity assessment which is itself determined by the classification category of the valve. This presumes that the category, and hence the limits of application, of the valve are known at time of purchasea major change t
20、o current practice in the case of valves manufactured or purchased for stock. (See the recommendation on page 29 concerning marking valves with their appropriate category.) It would be a mistake to assume that application of the PED will result in valves being manufactured to higher quality standard
21、s than are currently applied. For example many valves (more for liquid service than for gas and more for Group 2 fluids than for Group 1) are not required to be produced in accordance with the conformity assessment modules of the PED (Annex III). Instead they are to follow the sound engineering prac
22、tice (SEP) of member states, an undefined term which could allow a manufacturer to reduce standards below those commonly insisted on at present. The purchaser should ensure that his contractual requirements continue to specify the degree of quality which he currently finds acceptable. A working grou
23、p set up by the Commission (Working Group (Pressure)WGP) is currently charged with establishing standard interpretations of the PED. Interpretations adopted by WGP are being formally issued as Guidelines, which in effect bear the imprimatur of the European Commission, but do not have the force of la
24、w. The WGP has in turn set up a subsidiary working party (Working Party on GuidelinesWPG) to act as a first assessor of detailed questions. Nevertheless it is important to recognise that, under the rules established, the NoBo 5is the ultimate arbiter of conformance. 62 SCOPE This EEMUA publication o
25、ffers guidance on the application of the PED to the purchase of (a) block valves, check valves and control valves which may be considered as pressure accessories and (b) safety relief valves and such other valves which may be considered as safety accessories. 783 EXCLUSIONS Not all valves are requir
26、ed to conform to the PED. Principal relevant exclusions are: Pipeline valves, including the first/last isolation valves located within the confines of the facilities or sites connected by the pipeline. Note that valves associated with pumping and compression stations are included in the scope of the
27、 Directive. Valves associated with oil, gas or geothermal exploration and production and underground storage equipment including Christmas tree, work-over equipment and piping manifold. (Valves downstream of the manifold are included in the scope of the Directive.) Valves associated with water suppl
28、y, distribution and discharge of water including penstocks, and valves for hydroelectric power systems. Valves designed and constructed for military purposes. Valves designed for nuclear use, failure of which might cause an emission of radioactivity. Valves for ships, rockets, aircraft and mobile of
29、fshore units (e.g. drilling rigs). Valves used in warm water heating systems (110C). Valves covered by Directive 87/404/EEC on Simple Pressure Vessels. Valves designed to operate at pressures no higher than 0.5 bar. Valves purchased within the EEA but put into service elsewhere, or imported for re-e
30、xport elsewhere. Valves, the use of which is in the interests of experimentation. In addition, where valves would be classified as no higher than category I under the PED and are covered by another, listed directive, they are excluded from the scope of the PED. These other directives are those cover
31、ing: Machinery (98/37/EC) Low Voltage Equipment (73/23/EEC) Equipment used in explosive atmospheres (94/9/EC) Equipment associated with burning of gaseous fuels (90/396/EEC) Medical devices (93/42/EEC) Lifts (95/16/EC). 9104 CLASSIFICATION OF EQUIPMENT (Articles 3 highly flammable; extremely flammab
32、le; toxic; very toxic oxidising. Group 2 comprises: all other fluids (note that this includes steam). The appropriate group can usually be determined from the safety data sheet. If not, the site safety specialist should be consulted. With this information, the supplier can access the tables (in effe
33、ct charts) in Annex II of the Directive to determine the category. Linearlinear plots of these tables have been included in Appendix B of the present document to better illustrate the classification for typical sizes and pressure ratings. When valves are purchased for stock, a sufficiently high cate
34、gory must be selected to allow maximum freedom of application. When stock valves are used as safety accessories the user should check that the classification is equal to or higher than that of the equipment being protected. * This is the minimum information necessary to enable the manufacturer to co
35、mply with the requirements of the PED. In order to be able to ensure that the valve being offered will perform satisfactorily, he should be provided with the maximum possible information relating to the valve duty and function. 11125 REVIEW OF CONFORMITY ASSESSMENT MODULES (Article 10) Conformity as
36、sessment modules are the means by which the manufacturer demonstrates compliance with the requirements of the Directive, and they effectively determine the level of quality assurance applied. Table 1 lists the conformity assessment modules which are available for each classification category. The ba
37、sic philosophy is that full (independent) inspection and full (independently assessed) QA systems provide an equivalent level of assurance, and that the two systems can be combined in varying degrees. Table 1 Summary of the conformity assessment modules Category I Category II Category III Category I
38、V Module Modules Modules Modules A A1 B1 + D B + D D1 B1 + F B + F E1 B + E G B + C1 H1 H Table 2 indicates the design and production requirements associated with each module. For a given category the manufacturer is responsible for selecting the module to be applied. The different modules in any on
39、e category are supposedly intended to guarantee the same degree of quality and conformity (and involve the NoBo to varying degrees) but a brief examination of Table 2 will reveal that this is not the case. For example for category III, the highest normally applied to valves (as pressure accessories)
40、, a manufacturer may select B1 + D (design examination by NoBo together with a QA system covering production, final inspection and test) or B + E (where the QA system is not required to cover production). It should be noted that the price of the valve is likely to reflect the degree of direct involv
41、ement by the Notified Body and that it may be in both manufacturers and purchasers interests to select modules which minimise this. Module H (effectively full QA system assessed and approved by the NoBo) most closely represents the procurement practice of recent years, and is likely to be the most e
42、conomic overall. Note that there is nothing which prevents a purchaser contractually requiring a particular (permitted) module and/or imposing and carrying out his own supplementary 13inspection requirements (for which there may be an increased cost). Note also that the use of a module appropriate t
43、o a higher category does not change the category of the item to which it is applied. 14Table 2 Key to the requirements of conformity assessment modules Module Design Production A Technical documentation Internal production control A1 Technical documentation Internal production control with monitorin
44、g of the final assessment. B Type examination B1 Design examination C1 Monitoring of final assessment D Quality assurance for production, final inspection and test D1 Technical documentation Quality assurance for production, final inspection and test E Quality assurance for final inspection and test
45、 E1 Technical documentation Quality assurance for final inspection and test F Product verification G Unit verification Unit verification H Quality assurance for design, manufacture, final inspection and test H1 Quality assurance for design, manufacture, final inspection and test with design examinat
46、ion and monitoring of final assessment Reference to the charts in Appendix B will reveal that there will be some relatively critical valves which could be manufactured in accordance with module A1 (category II). This does not require the manufacturer to have a QA system, only to keep appropriate tec
47、hnical documentation (how the veracity of this can be guaranteed in the absence of some sort of quality system is not explained) in addition to which he will be subject to unannounced visits by the NoBo. Module A (category I) dispenses with the unannounced visits. In such cases the 15purchaser is re
48、commended to apply normal commercial prudence and impose (via his order) such minimum standards as he has traditionally considered necessary. 166 MATERIALS 6.1 General In theory, the shells of all valves covered by the PED (including those made to SEP) may be manufactured from any suitable material
49、meeting the essential requirements for ductility and toughness. In practice, considerable obstacles are placed in the way of non-harmonised materials. It should be noted that there are no specific requirements in the PED covering materials for seals, gaskets, etc. At the time of writing, the position with regard to materials for valve internal parts is that they will in most cases be excluded from the remit of the PED (see Appendix A). 6.2 Routes to Compliance There are three routes to compliance: use a material listed in a harm
