Michael J. Porfilio, QA Manager - NDE Level III
As the deadline of May 29, 2002 approaches it is getting increasingly more important that all pressure equipment manufacturing companies that will need to comply with the requirements of the 97/23/EC PED get informed and prepared. The topic of approved materials for service and design has been for the last few years an area of great concern and interpretation. harmonized standards including material lists are in the process of being developed and ratified but the materials that your products are currently designed with may need special treatment for use in a PED environment. We will discuss the content of some of the harmonized material standards as well as the process of approval for currently unharmonized materials.
As of today's date the incorporation of many of the ASME material grades have not meet with acceptance to the CEN (European Committee's for Standardization). There have been some materials, which have been accepted into the harmonized material lists though. Many forms of wrought, cast, and forged grades of European materials have been adopted and approved for use in pressure containing equipment. The grades adopted are in Alloy families from brasses and bronzes to carbon steels, Alloy steels, Titanium, Nickel Alloys, as well as Stainless steels.
There are some general requirements and attributes that all PED harmonized materials must conform to. Carbon steels, ferritic steels, as well as Nickel Alloy steel materials need to demonstrate a level of ductility; generally 14% when not specified along with impact resistance of 27J at 20 degrees C or the lowest operating temperature that the pressure equipment was designed for. There are other draft EN codes that will have other metallurgical parameters that PED materials will have to meet due to higher stressed applications. The ASME code has numerous specifications that do not mandate impact testing. These specifications will need to meet all of the SA/SB requirements as well as the above mentioned impact properties. Most ASME grades of material will need to undergo material appraisals as specified below if the proposed ASME grades submitted the Harmonization committees are deemed rejected as of May 29, 2002.
This tool will be a mandatory part of doing business in the PED environment for an ASME pressure equipment producer. A PMA basically is a one time evaluation and approval of a material as it relates to the pressure equipments parameters it will be used in. Some typical questions and conditions on a basic PMA form are as follows but not limited to: heat treat condition, equipment final usage, the design parameters, various metallurgical data, material grade and specification, as well as special conditions. In all situations a notified body authorized in the state of final pressure equipment destination is the proper authority to forward PMA requests to. The PMA in all instances will be requested by the pressure equipment manufacturer not sub-tiered vendors. The PMA appears to be a good thing for ASME material designers and manufacturers as it will be your ticket to get the unharmonized materials into Europe.
The availability for manufacturers to use grades that are in the harmonized material lists sounds great but without the ASME, ASTM, and other non-European standards being approved and added to the CEN harmonized lists the PED will be less than user friendly. Constant requests of PMA's from notified bodies will be costly and dependant upon the documentation processing speed of the notified body may slow the startup times of some projects. Manufacturers of pressure equipment need to stay on top of the constantly evolving harmonized material lists as well as becoming familiar with the structure of the 97/23/EC PED.
As the 97/23/EC PED implementation date for full compliance is approaching fast ASME Code material designers and manufacturers. If the materials that you prefer and your customers prefer to use are not in the lists provided in the harmonized standards you still will be able to use them provided you have followed the aforementioned parameters of this paper. Not mentioned in this paper are other technical procedures that you have prepared such as welding procedures and process procedures will be able to be used following similar qualifications and justifications to appropriate notified bodies. These areas of concern were great for myself as many dollars and effort has been put into the development of technical documents and development of material grades in the Foundry that at this point look as if they may be allowed for use on 97/23/EC PED projects, or maybe not? We will have to wait for the final interpretation of the standard committees setting up the PED.