Bulletin feature - May/June 2011
Pressure equipment and critical welded structures - safety compromised by rogue materials
Industrial users of imported pressure equipment and other welded structures worldwide are reporting a significant increase in the number of cases of rogue materials and fabrications that are found to be non-compliant to specification, defective or with fraudulent documentation. John Wintle gives examples of the kinds of problems experienced, together with consideration of the origins and causes. Ways to improve quality management of the whole procurement process and supply chain are suggested and other initiatives highlighted.
Typical problems
Users of pressure equipment and materials, together with inspection organisations, certification and official bodies in the UK are discussing the problems of rogue materials and fabrications. Industry sectors affected include oil refining, power generation, and chemicals industries as well as engineering contractors.
Companies are finding problems with the quality of materials and fabrications purchased from new sources that have not historically supplied world markets. Whereas the total amount of imports has remained reasonably constant, since about 2003 the volume of materials purchased from such sources has increased progressively. In the same period, the number of instances of rogue materials and fabrications has increased significantly and is continuing to do so. The problems are not isolated occurrences, but part of a trend that is already causing significant loss and, if not checked, could lead to disastrous consequences.
In the absence of industry-wide data, the scale of the problem in global terms is uncertain. There is evidence that rogue materials and fabrications are a problem with an international dimension. It is unclear to what extent the problems are confined to suppliers from certain regions, or even specific suppliers, or whether there has been a general decline in standards.
Rogue materials and fabrications are often discovered late in the procurement chain after delivery to site and sometimes during installation. They have had a major impact on the companies affected in terms of delays and the costs of remediation. In some cases had they not been discovered, they could have given rise to early failure in-service with serious safety and production consequences.
A wide range of quality problems is being reported. Issues include:
- Parent material that did not meet chemical specification
- Castings and forgings that contained unacceptable defects
- Instances of a specified material substituted by another inappropriate material
- Incorrect or no heat treatment when specified
- Failure to meet tensile strength, ductility or creep strength requirements
- Welded fabrications and repairs with significant welding defects
In many instances, the information in the paperwork supplied does not correspond to the condition of the materials or fabrications supplied. Sometimes a different material or fabrication would have been substituted for an original somewhere along the supply chain.
Typical problems that have come to light include:
- Flanges that arrived with the material not meeting the chemical composition requirements and containing cracks, despite documentation claiming that the material met the specification
- Fabricated tees with lack of weld line fusion defects (Fig. 1.)
- Valve bodies supplied for refinery use containing obvious casting defects (Fig. 2.).
- Titanium heat exchanger tubing supplied for refinery use that failed the hydrotest under tap pressure (Fig. 3.)
- P91 tubing required for a fired heater at a refinery had been replaced with the less heat resistant alloy P9.
- Valve bodies that were required to be heat treated had clearly not been.
- Casting defects that had been repaired using mixed welding rods without evidence of a repair procedure.
- B7 Bolts that failed during normal tightening and found on sectioning to have serious laminations (Fig. 4.)
- Bolts which had been necked to an unacceptable reduced diameter.
- Substantial welded fabrications for fatigue service that contained numerous serious hydrogen cracks and other welding defects when delivered to the UK.
In some instances the materials supplied from alternative sources, while meeting the basic specification, are not of the quality that procurers and users expect. Properties such as fracture toughness cannot be assured from previous favourable experience with established suppliers. Manufacturing processes may not be as advanced, and materials are being manufactured solely with the aim of meeting the basic specification.
Interpretations of standard specifications and extra requirements specified by the procurer can be very variable. This arises particularly when these documents are not translated, or not fully communicated or understood, by the material manufacturer or the fabricator. Some materials specifications have not kept pace with improvements in the quality of materials that are achievable with modern steel making practices.
Possible origins and causes
The origins of the problems are often difficult to ascertain when the supply chain between material manufacturer and end user is long and involves many different parties. At different stages the material and the paperwork are subject to quality control systems, checks and inspection by further organisations. The data on original test certifications are frequently copied onto new paperwork, sometimes not always accurately and sometimes fraudulently. When problems arise, it is clear that these control systems are not functioning correctly.
An analysis of the problems has identified several root causes. In some cases there is clearly a lack of competence of manufacturers and fabricators to produce material and constructions to the appropriate standards of quality, even when using their best efforts. In other instances, there appears to be a lack of commitment to inspection and quality in a production driven culture. This is aggravated by economies driven by cost considerations.
Long supply chains may be responsible for a lack of accountability and responsibility to the end user. This is a particular risk if the end user does not have representation on site or is not involved in the original contract. While the liability and legal responsibility of suppliers of faulty goods to the ultimate end users is an important principle established in English law, even when no legal or direct commercial contract exists, it is often difficult to enforce on suppliers outside the European Union.
Procurers and users perceive a lack of competence and commitment in some local statutory inspection bodies and international independent inspectorates, particularly where the latter are locally managed or outsourced. Some companies do not have confidence in local inspection bodies and send their own representatives to oversee the manufacture of critical components. In the worst cases there is the perception of a purposeful intent to deceive for monetary gain or other motives.
Some of the problems are due to a lack of clarity of the procurer's specifications and quality plans. While some companies are providing very detailed specifications, others are of a view that such detail could confuse suppliers. In other instances short or abbreviated specifications do not carry the implied meaning that procurers or users expect. Achieving clear communication of specifications to materials manufacturers and fabricators and ensuring understanding is a major challenge, particularly where supply chains are long.
Part of the problem lies with the differences between national standards for similar materials resulting from variations in national practices and construction codes. Manufacturers who are not conversant with these standards can easily make mistakes. In some instances materials standards have not been updated for many years to align with modern practice.
View from inspection organisations
Inspection organisations recognise the problem of rogue materials and fabrications and are equally concerned. They accept their responsibility in the supply chain and believe they have an important role in improving matters. Many inspection organisations have a global network and any changes would have far reaching consequences.
Inspection organisations are also victims of malpractice. There are instances of signatures being forged and certification altered to imply a higher level of approval. Local agency inspectors that do not come up to the company's normal high standards and control are a particular problem. A high turnover rate of local agency inspection staff and a lack of local control, particularly in some countries, are a matter of concern, but reflect the reality of the inspection market. The practice of subcontracting inspections to agency staff weakens the supply chain, and is a risk factor that procuring companies should take into account.
The culture in some parts of the world makes raising issues with fabricators difficult. Communication and surveillance is more difficult when fabricators subcontract work and inspections to others. Traceability of materials to source is a key issue: equipment ordered from European suppliers often has parts manufactured in countries outside Europe. Original certification for fasteners such as bolts is frequently unavailable.
The approval of materials and of materials certificates is a difficult area, particularly when the original certificates are not available. There is a need to clarify which material certificates can be accepted and when they might be refused. There is a perceived difficulty with specifying the brief of inspection bodies by the procuring companies. Inspection organisations believe that the extent of the problems is not huge but cannot quantify it.
Official position
While there have not been any in-service failures of UK pressure equipment that have been clearly attributed to rogue materials and fabrications, there are examples when equipment has failed under pressure test. There is understandable concern within the pressure systems community that rogue materials and fabrication pose a serious issue for safety.
In UK law, it is the user's duty to take all necessary measures to guard against rogue materials and fabrications before equipment enters service. This might include supplier vetting, more rigorous quality assurance during fabrication, and post manufacturing inspections when there is a potential risk that material may be suspect. Where suppliers put their own brand name on products made elsewhere they take on the manufacturer's liability.
It is accepted that there are weaknesses in the ISO 9000 certification system. While under the European Pressure Equipment Directive (PED) there is a requirement for the fabricator's quality system to be approved by an inspection body established in the EU, some inspection bodies are not properly established in this way. This problem extends much wider than pressure equipment. The assurance of quality management that should be provided with ISO 9000 certification sometimes does not exist.
In the event of a damaging failure, a claim that a piece of equipment was ordered to meet a national standard is not always sufficient evidence that it was manufactured fit for purpose. Similarly, product certification alone would not be accepted as giving automatic compliance with health and safety legislation if the documentation was subsequently found to be incorrect. Due diligence of the user is expected that is commensurate with the possibility of a problem arising and the scale of hazards that would occur in the event of failure.
The PED is seen as having achieved its objectives in ensuring a good market in pressure equipment in Europe. The Directive allows companies to market equipment without knowledge of material processes where a materials manufacturer has an appropriate QA system certified by a Conformity Assessment Body established in the EU. Having undergone a specific approval for materials, certificates issued by the materials manufacturer are presumed to ensure conformity even though quality may deteriorate over time. Instances where specific materials approval has been withdrawn without reinstatement are rare.
NDT certification bodies report that there is misinterpretation among some overseas fabricators about the scope of EN 473. This is a standard for bodies certifying NDT personnel qualification, not an NDT certification for individuals. Sometimes fabricators can self-certify NDT personnel under the so called second party route but there are limits to the equipment that can be inspected by such individuals. Where equipment is inspected by NDT personnel holding personal certification for NDT (PCN), it is possible to check their qualification relatively easily on-line.
Organisations that provide certification, testing, inspection and calibration services (ie those with Competent Body or Notified Body status) are required in the UK to be accredited by UKAS against international Standards. As these organisations can be global and have local subsidiaries, it is difficult for the accreditation services (and even the inspection bodies themselves) to cover and guarantee every part of the organisation. While an organisation might have good procedures and intentions, there is sometimes an inadequate level of control and internal audit of remote operations, outstations and subsidiaries.
Controlling the problems
The ability of end users to control the quality problems of materials and fabrications from remote suppliers is limited by the logistics of the purchasing processes and the length of the supply chain. Special care is required when purchasing pressure parts and materials from new markets since conventions and expectations that are well recognised in traditional markets are not necessarily understood elsewhere. There should not be over-reliance on the paperwork and data supplied without its authenticity being validated.
Leading companies are taking special measures to safe-guard themselves. Some have lists of selected countries, suppliers or manufacturers, either because they have a proven good track record of quality, or because they are regarded as potentially unreliable. Careful selection and pre-qualification of suppliers is beneficial, but can be time-consuming and expensive. Other end users have their own inspectors on site to oversee the manufacture and material supply at every stage. Although this is also expensive it is an effective approach. It is good practice to ask for the original test certificates, but these are often difficult to obtain. Independent post-manufacturing inspections (PMI) and material validation at selected stages are considered to be valuable alternatives.
Procurers and users are recommended to make their specifications clearer and unambiguous, separating the engineering and procurement parts, and supplementing national materials standards with additional requirements as appropriate. Reliable translation of the specification into the local language could also help. Ensuring the communication and understanding of the specification and quality plan by the local fabricators is essential, even if this means more time spent on site. It is important to engage and explain requirements to senior management at an early stage. Particular care by the procuring engineer is needed when suppliers offer substitute materials, different from those specified.
Overseeing fabrication is necessary in line with the perceived risk. Fabricators with limited experience of delivering to European standards are more of a risk, as are those who use outsourced local inspection agencies. The communication of the quality plan to inspection organisations is a key aspect, and there is a need to invest more in training local inspectors.
From the limited information available it would appear that the problem of rogue materials and fabrications has its roots in the control of inspection of both materials and fabricated equipment at different points in the supply chain. A clear process and standards for controlling inspection on site that is both practical and not prohibitively expensive is required. Accountabilities and responsibilities in the supply chain need to be clarified and strengthened so that there is more chance of detecting rogue materials and fabrications at an early stage.
Local culture and customs also influence the working practices of suppliers and fabricators. Although these cannot be controlled by purchasers and users, generating a greater understanding of where problems may arise is a good step forward. More communications and personal contact throughout the supply chain is beneficial, but requires the necessary investment and effort in manpower and logistics.
Next steps
The Engineering Equipment and Materials Users Association (EEMUA) is producing an information sheet on the issue of rogue materials. Beyond this the need for more detailed guidance is being determined. This could include a wider consultation with industry to gather data on the full extent of the problem and with different parts of the international supply chain.
TWI is planning to launch a Group Sponsored Project (GSP) in this area. The aim will be to compile a list of the factors that increase the risk and a summary of best practice on how the risk can be mitigated and problems detected at an earlier stage. TWI Members that would like to register an interest should contact the author by e-mail john.wintle@twi.co.uk
