PD 5500:2009 - Benefits and challenges of unfired fusion welded pressure vessels
PD 5500:2009 Specification for unfired fusion welded pressure vessels.pdf
Introduction
PD 5500:2009 Specification for unfired fusion welded pressure vessels.pdf
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If you are involved in the design, manufacture, inspection or testing of unfired pressure vessels, you might have heard of PD 5500. But what is it exactly and why is it important? In this article, we will explain what PD 5500 is, what are unfired fusion welded pressure vessels, and why you should use PD 5500 as a reference tool for your projects.
What is PD 5500?
PD 5500 is a published document by the British Standards Institution (BSI) that specifies requirements for the design, construction, inspection and testing of new unfired fusion welded pressure vessels. It was first published as BS 5500 in March 1976 and then as PD 5500 in January 2000. The latest edition is PD 5500:2009, which was published in January 2009 and amended in September 2012.
PD 5500 covers unfired pressure vessels made from carbon, ferritic alloy and austenitic steels, as well as material supplements containing requirements for vessels made from aluminium, copper, nickel, titanium and duplex. It also includes guidance on the use of alternative materials and design methods.
PD 5500 is not a British Standard, but it is widely recognized and accepted as a code of practice for unfired pressure vessels in the UK and internationally. It is also harmonized with the European Pressure Equipment Directive (PED) and can be used to demonstrate compliance with its essential safety requirements.
What are unfired fusion welded pressure vessels?
Unfired pressure vessels are containers that are designed to hold fluids (liquids or gases) under pressure without being exposed to direct heat from a combustion process. They are used for various applications such as storage, transport, processing and power generation.
Fusion welding is a process that joins two or more metal parts by melting them together using an electric arc, a gas flame or a laser beam. Fusion welding creates a strong bond between the metal parts and reduces the risk of leakage or failure.
Unfired fusion welded pressure vessels are therefore unfired pressure vessels that are constructed using fusion welding techniques. They can have various shapes and sizes depending on their purpose and design criteria.
Why use PD 5500?
PD 5500 is an invaluable reference tool for the design and assessment of unfired fusion welded pressure vessels. It provides comprehensive and detailed requirements for all aspects of their design, construction, inspection and testing. It also offers best practices and recommendations based on the latest research and experience in the field.
By using PD 5500, you can benefit from:
Safer and more reliable pressure vessels that meet the highest standards of quality and performance
More cost-effective and efficient pressure vessels that optimize the use of materials and resources
Increased trust and confidence from your customers, regulators and stakeholders
Easier access to new markets and trade opportunities by demonstrating compliance with the PED and other international codes and regulations
Better management of risk and liability by following a recognized and accepted code of practice
Design requirements
General
The design of unfired fusion welded pressure vessels should be based on sound engineering principles and practices. The design should consider all the relevant factors that affect the safety and performance of the pressure vessels, such as:
The nature and properties of the fluid to be contained
The operating conditions and environment of the pressure vessels
The loads and stresses imposed on the pressure vessels
The corrosion, erosion and protection of the pressure vessels
The fabrication, inspection and testing methods to be used
The documentation and certification to be provided
The design should also comply with the applicable laws and regulations in the country or region where the pressure vessels are intended to be used.
Application
The design of unfired fusion welded pressure vessels should take into account the following parameters:
Design pressure: The maximum pressure that the pressure vessel is designed to withstand under normal operating conditions. It should be determined by the designer based on the fluid properties, the operating temperature, the safety devices and the allowable stress.
Design temperature: The maximum and minimum temperatures that the pressure vessel is designed to withstand under normal operating conditions. It should be determined by the designer based on the fluid properties, the heat transfer, the thermal expansion and contraction, and the material properties.
Thermal loads: The changes in temperature and pressure that occur during start-up, shut-down, normal operation, emergency situations and transient conditions. They should be considered by the designer to ensure that the pressure vessel can accommodate them without exceeding its design limits.
Wind and earthquake loads: The external forces that are applied to the pressure vessel due to wind or seismic events. They should be considered by the designer to ensure that the pressure vessel can resist them without compromising its stability or integrity.
Materials selection
General
The materials used for unfired fusion welded pressure vessels should be suitable for their intended purpose and service conditions. They should have adequate strength, ductility, toughness, corrosion resistance, weldability and compatibility with the fluid to be contained.
The materials should also conform to the specifications and standards referenced in PD 5500 or approved by the Inspecting Authority. The materials should be identified, tested, certified and traceable throughout their supply chain.
Materials for pressure parts
The materials for pressure parts are those parts of the pressure vessel that are directly exposed to the fluid under pressure, such as shells, heads, nozzles, flanges, supports and attachments. The materials for pressure parts should meet the following requirements:
They should have a specified minimum yield strength (SMYS) not less than 165 MPa.
They should have a specified minimum tensile strength (SMTS) not less than 1.15 times their SMYS.
They should have a specified minimum elongation at fracture (A) not less than 14% for carbon and low alloy steels, 20% for austenitic steels, 12% for aluminium alloys, 15% for copper alloys, 20% for nickel alloys, 10% for titanium alloys and 25% for duplex steels.
They should have a specified minimum Charpy V-notch impact energy (CVN) not less than 27 J at -20C for carbon and low alloy steels, 40 J at -196C for austenitic steels, 15 J at -80C for aluminium alloys, 15 J at -40C for copper alloys, 40 J at -196C for nickel alloys, 40 J at -60C for titanium alloys and 40 J at -50C for duplex steels.
They should have a specified maximum carbon equivalent (CE) not greater than 0.43% for carbon and low alloy steels, 0.35% for austenitic steels, 0.40% for aluminium alloys, 0.30% for copper alloys, 0.35% for nickel alloys, 0.10% for titanium alloys and 0.40% for duplex steels.
Construction and workmanship
General
The construction and workmanship of unfired fusion welded pressure vessels should be carried out in accordance with the approved design and welding procedures. The construction and workmanship should ensure that the pressure vessels are free from defects, distortions and residual stresses that could impair their safety and performance.
The construction and workmanship should also comply with the applicable laws and regulations in the country or region where the pressure vessels are intended to be used.
Welding
Welding is a crucial part of pressure vessel construction, as it joins the various components of the pressure vessel together. Welding should be performed by qualified welders using suitable welding techniques and equipment. The welding process should ensure that the welds are strong, durable and compatible with the base materials.
Some of the common welding techniques used in pressure vessel construction are:
Shielded Metal Arc Welding (SMAW): This welding process uses a flux-coated consumable electrode. This is often thought of as the default form of arc welding. It is versatile and can be used for various materials and positions. However, it produces slag that needs to be removed after welding, and it may not be suitable for thin materials or high-quality welds.
Gas Metal Arc Welding (GMAW): This welding process uses a continuously fed solid wire electrode and an inert gas shield. It is also known as metal inert gas (MIG) welding. It is fast and efficient, and it produces clean welds with minimal spatter. However, it requires a constant power source and gas supply, and it may not be effective for thick materials or vertical positions.
Flux-Cored Arc Welding (FCAW): This welding process uses a continuously fed tubular wire electrode filled with flux and an external gas shield. It is similar to GMAW but with more flexibility and penetration. It can be used for various materials and positions, and it can tolerate some contamination on the base metal. However, it also produces slag that needs to be removed after welding, and it may generate more fumes than GMAW.
Gas Tungsten Arc Welding (GTAW): This welding process uses a non-consumable tungsten electrode and an inert gas shield. It is also known as tungsten inert gas (TIG) welding. It is versatile and can be used for various materials and positions. It produces high-quality welds with excellent appearance and strength. However, it is slower and more complex than other welding processes, and it requires a high level of skill and precision.
Plasma Arc Welding (PAW): This welding process uses a non-consumable tungsten electrode and a plasma gas shield. It is similar to GTAW but with more heat and speed. It produces high-quality welds with deep penetration and low distortion. However, it is more expensive and less flexible than other welding processes, and it may require special equipment and safety precautions.
The choice of welding technique depends on various factors such as the material type, thickness, shape, position, joint design, quality requirements, cost and availability. The welder should select the most appropriate technique for each situation and follow the approved welding procedure specification (WPS).
The welder should also ensure that the welds are properly prepared, aligned, cleaned, preheated, post-heated, cooled and inspected according to PD 5500 requirements.
Heat treatment
General
Heat treatment is a process of heating and cooling metal parts to alter their physical and mechanical properties. Heat treatment can be used to improve the strength, ductility, toughness, hardness, corrosion resistance or stress relief of metal parts.
Non-destructive testing
General
Non-destructive testing (NDT) is a process of inspecting and evaluating the quality and integrity of pressure vessels or their components without causing any damage or alteration to them. NDT can be used to detect and characterize defects such as cracks, porosity, inclusions, lack of fusion, lack of penetration, corrosion, erosion, wear and fatigue.
NDT can be applied to pressure vessels during or after their fabrication, as well as during their service life. The purpose of NDT is to ensure that the pressure vessels meet the specified requirements and standards, and to prevent any potential failures or accidents.
The choice of NDT method depends on various factors such as the material type, thickness, shape, defect type, location and size, accessibility, cost and availability. The NDT method should be selected and performed by qualified personnel using suitable equipment and procedures. The NDT results should be recorded and reported according to PD 5500 requirements.
Some of the common NDT methods used for pressure vessel inspection are:
Visual Testing (VT): This NDT method involves observing the surface and appearance of pressure vessels or their components using the naked eye or optical aids such as magnifiers, mirrors, cameras or borescopes. VT can be used to detect defects such as cracks, dents, scratches, corrosion, distortion and misalignment. VT is simple, fast and inexpensive, but it has limited sensitivity and accuracy, and it cannot detect internal defects.
Liquid Penetrant Testing (PT): This NDT method involves applying a liquid penetrant (usually a colored or fluorescent dye) to the surface of pressure vessels or their components and allowing it to seep into any surface defects. After a dwell time, the excess penetrant is removed and a developer (usually a white powder) is applied to draw out the penetrant from the defects. The defects are then revealed by the contrast between the penetrant and the developer. PT can be used to detect defects such as cracks, porosity and lack of fusion. PT is sensitive, simple and inexpensive, but it has low selectivity and reliability, and it cannot detect subsurface defects.
Magnetic Particle Testing (MT): This NDT method involves magnetizing pressure vessels or their components made from ferromagnetic materials (such as iron or steel) and applying fine magnetic particles (usually iron filings) to the surface. The magnetic particles are attracted to any surface or near-surface defects that interrupt the magnetic field. The defects are then revealed by the accumulation of the particles. MT can be used to detect defects such as cracks, inclusions and lack of penetration. MT is sensitive, fast and reliable, but it has low penetration depth and resolution, and it cannot detect non-magnetic defects.
Documentation and certification
General
The documentation and certification of unfired fusion welded pressure vessels are essential to demonstrate their compliance with PD 5500 and other applicable codes and regulations. The documentation and certification should provide sufficient information and evidence to verify the design, construction, inspection and testing of the pressure vessels.
The documentation and certification should also comply with the applicable laws and regulations in the country or region where the pressure vessels are intended to be used.
Data report
The data report is a document that contains the essential details and data of the pressure vessel, such as its identification, description, dimensions, materials, design conditions, test results and certification. The data report should be prepared by the manufacturer or contractor of the pressure vessel using the appropriate form specified in PD 5500.
The data report should be signed by the manufacturer or contractor and by an authorized inspector who has witnessed and verified the fabrication, inspection and testing of the pressure vessel. The data report should be submitted to the Inspecting Authority for registration and approval.
Some of the common data report forms used for pressure vessels are:
Form U-1: Manufacturer's Data Report for Pressure Vessels. This form is used for general pressure vessels that are not completely shop- or field-fabricated.
Form U-1A: Manufacturer's Data Report for Pressure Vessels (Alternative Form for Single-Chamber, Completely Shop- or Field-Fabricated Vessels Only). This form is used for single-chamber pressure vessels that are completely shop- or field-fabricated.
Form U-2: Manufacturer's Data Report for Pressure Vessel Parts Fabricated by Welding or Brazing. This form is used for pressure vessel parts that are fabricated by welding or brazing and supplied to another manufacturer for final assembly.
Form U-2A: Manufacturer's Partial Data Report. This form is used for pressure vessel parts that are not fabricated by welding or brazing and supplied to another manufacturer for final assembly.
Form U-3: Manufacturer's Certificate of Compliance. This form is used for pressure vessels that are manufactured in accordance with a standard design approved by an Inspecting Authority.
Conclusion
Summary of main points
In this article, we have explained what PD 5500 is, what are unfired fusion welded pressure vessels, and why you should use PD 5500 as a reference tool for your projects. We have also discussed the main requirements and best practices for the design, materials selection, construction, workmanship, inspection, testing, documentation and certification of unfired fusion welded pressure vessels according to PD 5500.
We hope that this article has given you a clear overview of PD 5500 and its significance for unfired fusion welded pressure vessels. By following PD 5500, you can ensure that your pressure vessels are safe, reliable, cost-effective and compliant with the relevant codes and regulations.
Benefits of PD 5500
As we have seen, PD 5500 offers many benefits for unfired fusion welded pressure vessels, such as:
Safer and more reliable pressure vessels that meet the highest standards of quality and performance
More cost-effective and efficient pressure vessels that optimize the use of materials and resources
Increased trust and confidence from your customers, regulators and stakeholders
Easier access to new markets and trade opportunities by demonstrating compliance with the PED and other international codes and regulations
Better management of risk and liability by following a recognized and accepted code of practice
Call to action
If you are interested in learning more about PD 5500 or obtaining a copy of it, you can visit the BSI website at https://www.bsigroup.com/en-GB/ . You can also contact us at [insert contact details] if you need any assistance or advice on PD 5500 or any other aspect of unfired fusion welded pressure vessel design, fabrication or inspection. We are a team of experienced and qualified engineers who can help you with your pressure vessel projects from start to finish. We look forward to hearing from you soon.
FAQs
Here are some frequently asked questions and answers about PD 5500 and unfired fusion welded pressure vessels:
Q: What is the difference between PD 5500 and ASME BPVC?
A: PD 5500 and ASME BPVC are both codes of practice for unfired pressure vessels, but they have some differences in their scope, structure, content and application. PD 5500 is a published document by the BSI that covers unfired pressure vessels made from various materials and supplements. It is harmonized with the PED and can be used to demonstrate compliance with its essential safety requirements. ASME BPVC is a set of standards by the ASME that covers various types of boilers and pressure vessels, as well as nuclear components, piping, transport tanks and valves. It is not harmonized with the PED and cannot be used to demonstrate compliance with its essential safety requirements. However, it is widely recognized and accepted as a code o