Michael J. Porfilio, QA Manager - NDE Level III
Pressure equipment manufacturing companies must comply with the requirements of the EU Directive 97/23/EC PED if they wish to participate in the pressure equipment products realization arena. As always the topic of approved materials for service and design is of great concern and interpretation. Harmonized standards including material lists are constantly evolving with newly ratified materials that your products are currently designed to. Special treatment of materials for use in a PED environment requires verbatim compliance and manufacturing diligence. 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 todays date many of the ASME material grades from the Boiler and Pressure Vessel Code (B&PVC), Section II, parts A and B have not meet with acceptance to the CEN (European Committee's for Standardization). There is a continuing stream of 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 most Stainless steel grades.
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° C or the lowest operating temperature that the pressure equipment was designed for. There are other EN codes that will have other metallurgical parameters that PED materials will have to meet due to higher stressed applications. The ASME B&PVC 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 specific material appraisals as specified below if the proposed ASME grades submitted to the Harmonization committees are deemed acceptable.
This material acceptance 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 equipment’s 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 EU 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 suppliers. The PMA appears to be a good avenue for ASME material designers and manufacturers as it will be your ticket to get the unharmonized materials into the EU,
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 can become less than user friendly. Constant requests of PMA's from notified bodies will be costly and dependent 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.
The 97/23/EC PED program and notified body that a material organization has implemented for full compliance is an evolving process. ASME Code pressure material designers and manufacturers need to be knowledgeable. The materials that you prefer to design with and your customer’s preference to use are not in the lists provided in the harmonized standards you still are 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 special process procedures will be able to be used following similar qualifications and justifications to appropriate notified bodies. These areas of concern were great for Stainless Foundry & Engineering, Inc. when we became the most complete materials verified foundry in North America and many dollars as well as effort has been put into the development of technical documents and development of many material grades in our foundry. We have processed many customer orders and projects for the 97/23/EC PED to date. We are definitely up for the challenge to assist your needs.