Overview of Welding
Welding is the process of joining separate metals together using extreme heat. Welding can be used for a number of different purposes. For example, repair welds are minor welds that are applied to structures to repair areas of minor surface damage. Weld overlay, on the other hand, is a process that is used to add an outer layer to a piece of equipment.
There are multiple different welding processes. Some of the more common types of welding are shielded metal arc welding, CO2 welding, Metal Inert Gas (MIG) welding, Submerged arc welding, and Plasma Transferred Arc (PTA) welding.
After performing any weld. it is important to perform a post weld heat treatment (PWHT) on the weld area to reduce residual stresses. If this is not done, then the weld is more likely to experience brittle fracture. PWHT is also able to reduce the chances of hydrogen induced cracking (HIC) in the weld as well.
Hot Work
Hot work refers to any work involving electric or gas welding, cutting, brazing, or similar flame or spark-producing operations. In many oil and gas or chemical processing enviroments, hot work has the potential to ignite a combustible material and cause significant process safety incidents. Extreme caution must be used whenever planning and performing any hot work.
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FFS Forum: Creep in Heater Tubes and Other Components – Part II: Strategies for Evaluating & Managing Remaining LifeJuly/August 2019 Inspectioneering JournalBy Greg Garic at Stress Engineering Services, Inc.
This is the second of a two-part column on “Creep.” This second part discusses the approach to creep assessment in plant equipment.
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May/June 2019 Inspectioneering JournalBy Greg Garic at Stress Engineering Services, Inc.
This is the first of a two-part column on “Creep”. It presents an engineering overview of the phenomena, answers the question: “What is Creep?”, and provides readers with foundational knowledge for evaluating and managing remaining equipment life.
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Assuring Pressure Part Manufacturing & Repair Quality - Has ticking the box become more important than the end product?March/April 2019 Inspectioneering JournalBy Andreas Fabricius at Tetra Engineering, James Malloy at Tetra Engineering, and Mark Taylor at Tetra Engineering
The quality of the thousands of factory and field welds present in pressure part modules is critical for assuring reliable operation over the life of a plant. Companies should be doing more than paying lip service to quality. Don't just tick a box.
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January/February 2019 Inspectioneering JournalBy Qasem Fandem at Saudi Aramco
Welding imperfections vary in impact from being acceptable to requiring repair. It is important to ensure the quality of welds using NDT and to ensure the strength of the entire piping system with hydrotesting.
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January/February 2018 Inspectioneering JournalBy Phillip E. Prueter at The Equity Engineering Group, Inc.
Given the concern throughout industry regarding the potential for brittle fracture failures, PWHT guidance to address potential issues arising from the recent changes in PWHT code requirements for carbon steel is examined in this article, and commentary on the potential reduction in fracture toughness due to PWHT is provided based on a review of published literature.
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July/August 2016 Inspectioneering JournalBy Sanjoy Das at Bhabha Atomic Research Centre, and D. Mukherjee at Bhabha Atomic Research Centre
The structural integrity of components is controlled by material properties, the presence of flaws, and levels of applied stress. Several factors such as temperature, type of loading, toughness, corrosion resistance, micro-structural stability, cost etc. dictate the suitable material for the desired application.
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July/August 2016 Inspectioneering JournalBy Mark Geisenhoff at Flint Hills Resources, Jonathan D. Dobis at The Equity Engineering Group, Inc., Phillip E. Prueter at The Equity Engineering Group, Inc., and Dr. Michael S. Cayard at Flint Hills Resources
This article summarizes a recent finite element analysis (FEA)-based study that employs creep simulation techniques to investigate the elevated temperature response of piping with peaked longitudinal weld seams.
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March/April 2015 Inspectioneering JournalBy Connie LaMorte at EWI, and Jon Jennings at EWI
Weld inspection using lasers is not new, but doing it 75 meters inside a pipe or streaming inspection data wirelessly is new. As laser technology has improved, more industries such as oil & gas are beginning to require laser inspection as part of their specifications. This non-contact method can help catch an unacceptable condition before it becomes too late to remedy the weld.
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To Test or Not to Test: A Comparison of the Pressure Testing Requirements between ASME B31.3 and ASME Section VIII, Division 1January/February 2015 Inspectioneering JournalBy Hugo Julien, P.E. at GCM Consultants, and Serge Bisson at GCM Consultants
Are you still hitting the welded joints of pressure vessels with a hammer during hydrostatic testing? If yes, then you’re due for a refresher on the pressure testing requirements of ASME Section VIII Division 1 since this requirement was for pressure vessels back in the mid 1940’s. This article will help you by highlighting the main requirements of, and differences between, the hydrostatic test for new pressure vessels fabricated according to ASME Section VIII, Division 1 and the hydrostatic leak test for new piping systems made under ASME B31.3.
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BlogNovember 10, 2014 By Nick Schmoyer at Inspectioneering
One of the more insidious problems within the industry is the issue of atomic hydrogen dissolving into steel equipment. This can happen to some steel components under certain circumstances and can cause weld failure, or what is known as “hydrogen cracking.” These cracks can occur during the welding process itself, but sometimes they can occur up to 48 hours later.
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Abnormal Cracks Led to Premature Decommissioning of Boiler Feed Water Exchanger – What Happened and Why?
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May/June 2014 Inspectioneering JournalBy Neil Ferguson at Hydratight
In November 2013, ASME released its updated PCC-1 guidelines for pressure boundary bolted flange joint assemblies. Contained within the document is Appendix A, which represents a major change from the previous 2010 release and is considered to be one of the most critically important changes for BFJA technicians, operators, and other industry professionals.
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January/February 2014 Inspectioneering JournalBy Marc McConnell, P.E. at Pro-Surve Technical Services, Josh Yoakam at Holly Refining and Marketing - Tulsa, LLC, and Frank Dean at Ion Science, Ltd.
This is the second of two articles published in Inspectioneering Journal discussing the value of hydrogen bake-outs. Our first article was published in the May/June 2013 issue and received a great response from the Inspectioneering community. In this piece, we will continue the discussion and touch on some new technologies used to enhance the bake-out process.
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January/February 2014 Inspectioneering JournalBy Neil Ferguson at Hydratight
If necessity is the mother of invention, then the American Society of Mechanical Engineers (ASME), the Occupational Safety and Health Administration (OSHA), and the Environmental Protection Agency (EPA) are the parents of guidelines, standards, and regulations that help keep industrial operations safe for humans and the environment.
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January/February 2013 Inspectioneering JournalBy Ana Benz at IRISNDT
In this article you will find the failure investigations of six 0.094 inch thick carbon steel vessels. These vessels were in service in natural gas well facilities; some functioned as dryers and were subjected to cyclic loads. Metallographic tests, hardness tests, and fracture surface scanning electron microscopy (SEM) examination results are presented for each of the vessels.
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September/October 2010 Inspectioneering Journal
For years the WRC has provided the documented technical basis for many decisions made regarding design, repair, remaining life estimation, and fitness for service of pressure equipment in our industries. Many codes and industry recommended practices are based on the information found in these bulletins, globally.
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March/April 2007 Inspectioneering JournalBy John Reynolds at Intertek
In the welded condition many stainless steels are susceptible to rapid intergranular corrosion or stress corrosion cracking. This is because the heat from welding sensitizes the base metal heat affected zone (HAZ) and the weld.
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March/April 2007 Inspectioneering JournalBy John Reynolds at Intertek
A myriad of issues need to be considered before welding to or repairing weld overlayed or clad equipment. (By clad we mean roll-bonded or explosion bonded, i.e. basically 100% metallurgically bonded, and not a loose or seam-welded liner, e.g., not strip lining.)
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March/April 2007 Inspectioneering JournalBy John Reynolds at Intertek
When we talk about welding QA/QC we typically focus on the technical requirements and what QA/QC is needed to assure that the technical requirements are met. Examples include the preheat, interpass, and PWHT temperatures and how to assure that the correct temperatures and hold times are used.
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May/June 2006 Inspectioneering JournalBy John Reynolds at Intertek
As noted in the discussion on delayed cracking, when the steel contains hydrogen as a result of service exposure (or corrosion, or high temperature - high pressure hydrogen processing) then a hydrogen bake out may be needed to avoid cracking problems during or after welding.
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January/February 2006 Inspectioneering JournalBy John Reynolds at Intertek
After a pressure equipment or piping failure, it’s not uncommon to find out during the failure analysis part of the investigation that the failure initiated at a welding flaw of some sort.
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January/February 2006 Inspectioneering JournalBy John Reynolds at Intertek
Among other things, a welding QA/QC program needs to ensure that only qualified welders, utilizing qualified procedures are allowed to weld on any pressurized equipment, including storage tanks and piping.
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July/August 2005 Inspectioneering JournalBy Jonathan D. Dobis at The Equity Engineering Group, Inc., and David N. French
This bulletin is part of a series of WRC Bulletins that contain the technical background and other information to evaluate damage mechanisms in various industries to facilitate the use of API 579. These bulletins, shown below, will be updated based on the latest knowledge and technology developed for identification of damage mechanisms.
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May/June 2005 Inspectioneering JournalBy Julian Speck at TWI Ltd., and Amin Muhammed at TWI
Current BSI and ASME codes for the construction of pressure vessels, boilers and piping specify that post-weld heat treatment is required if the thickness of the components being welded exceeds a specified value. This value depends on the type of material being used, and varies from code to code. An alternative procedure is available for deciding whether or not PWHT is necessary to avoid the risk of failure by fracture. This involves conducting a fracture mechanics assessment using procedures such as those in BSI 7910, or API 579. The use of these procedures is permitted in the British pressure vessel standard BS PD 5500:2003.
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January/February 2004 Inspectioneering JournalBy John Reynolds at Intertek
Repair welds can be another undetected and insidious "fabrication defect" that eventually results in equipment failure. Any experienced metallurgist that has completed numerous failure analyses over the years will tell you that periodically they see failures that initiated at the site of a repair weld. Sometimes those repair welds are field repairs, but not infrequently they occurred during original fabrication and were unknown to the purchaser. Typically our standards and specifications do not cover repairs completed by the fabricator, so they believe they are free to do whatever they want to repair a manufacturing or fabrication defect, then grind it flush, finish the fabrication and ship the product.
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January/February 2004 Inspectioneering Journal
When we specify that some equipment (vessels, flanges, fittings, etc.) be overlaid with a corrosion resistant alloy, we need to pay attention to making sure that the chemistry of the top layer of alloy welding, that will be exposed directly to the process fluid, is sufficient to resist degradation from the process environment. This may sound logical, but I’m aware of several cases where weld overlaid surfaces are ground or machined to meet specification tolerances, and in so doing the most resistant part of the alloy overlay is removed.
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January/February 2004 Inspectioneering Journal
DMW cracking is another fabrication issue that can and does result in equipment failure. It usually occurs at the weld juncture where carbon steel or low alloy steels are welded to austenitic (300 series) stainless steels in high temperature applications. The large difference in coefficient of expansion of the two steels, sometimes exacerbated by thermal cycling, results in cracking at the toe (HAZ) of the weld joining the two materials. Using an austenitic stainless filler material for the DMW junction also increases the stress intensification on the toe of the weld on the ferritic side of the weldment. This type of cracking is most common when temperatures above 800F (425C) are involved, such as in FCCU reactor/regenerations systems, superheaters, reheaters, fired heaters, and hydroprocess equipment. Use of bolted joints, if possible, or nickel base filler materials helps to avoid the DMW cracking problem.
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Partner Content
ASTM International in partnership with the Codes and Standards Training Institute (CASTI), launched an eLearning course to provide individuals with a general knowledge relating to maintenance, inspection, repair, and alteration of pressure vessels as outlined in the API RP 510 code. Click to find out more.
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January/February 2004 Inspectioneering JournalBy John Reynolds at Intertek
Cracks along the toe of a weld are not uncommon during fabrication, and can occur for a wide variety of reasons involving the metallurgy and process control of the the same issues covered above on repair welds can apply to repair welds on castings; especially if you are unaware that the foundry or fabricator is trying to salvage a defective casting by covering up porosity and shrinkage cracking with a big glob of weld metal.
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January/February 2004 Inspectioneering JournalBy John Reynolds at Intertek
Inadequate PWHT is one of our pressure equipment nemeses. We normally specify PWHT for a variety of pressure equipment integrity reasons including when we need to lower residual stresses, increase resistance to cracking or soften weld hardness. All for the purpose of prolonging the service life of our equipment and preventing unexpected failures. But this issue is clearly where those old sayings of "Buyer beware" and "You don't get what you expect, you get what you inspect" apply quite often.
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May/June 2003 Inspectioneering JournalBy John Reynolds at Intertek
A new recommended practice from the API is in the final stages of preparation before publications. It is API RP 577 on Welding Inspection and Metallurgy.
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November/December 2000 Inspectioneering JournalBy John Reynolds at Intertek
Part 4 of this article continues to outline the 101 essential elements that need to be in place, and functioning well, to effectively and efficiently, preserve and protect the reliability and integrity of pressure equipment (vessels, exchangers, furnaces, boilers, piping, tanks, relief systems) in the refining and petrochemical industry.
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September/October 1999 Inspectioneering JournalBy Reggie Cross at ND Tech
This paper describes the use of a UT fixture for detection of stress corrosion cracking in ferrous heat exchanger tube-to-tubesheet welds and external tube corrosion or pitting near the tubesheets including crevice OD corrosion.
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July/August 1998 Inspectioneering JournalBy Constance Reichert at Edison Welding Institute
Visual inspection is the most common nondestructive testing method. For critical applications, machine vision technology provides advantages over visual inspection.
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July/August 1998 Inspectioneering Journal
The debate about advantages and drawbacks of the application of the TOFD (time of flight diffraction) approach for ultrasonic weld inspection should not forget the original reasons for its introduction in the 1960s. The major advantage at that time had been the better crack detection in comparison to x-ray techniques, especially in view of an increased use of steels and welding technologies with a the presence of diverse cracking phenomena (e.g. cold cracking, transverse cracks etc.).
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May/June 1997 Inspectioneering Journal
Case 1: Fuel Gas to Boilers in boiler house: in 1992 two flanges were installed for installation of knock blinds. No degassing was completed. Both welds were radiographed and noted as acceptable. Case 2: Alky Unit Flare Header: No degassing completed in 1993 on multiple tie-ins. All of these tie-ins were radiographed and noted as acceptable. Case 3: Alky Unit flare Header: No degassing completed in 1993 on multiple tie-ins, all of these tie-ins were radiographed and noted as acceptable.
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November/December 1996 Inspectioneering JournalBy Shaun W. Lawson at Mechatronic Systems and Robotics Research Group, University of Surrey
The basic approach to the inspection and repair procedure for welding has barely altered for three decades. The normal practice has continued to be to inspect a weld only after the welding programme is complete. Thus by the time a defect is detected, considerable time and money has been spent on completing the welding of a rejectable component. Furthermore, a large number of additional weld runs will generally have been deposited over the defect, thus increasing the cost of repair and decreasing the quality of the component.
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May/June 1996 Inspectioneering JournalBy Del Underwood at Det Norske Veritas
This final issue on gusset problems will discuss why gussets are "stiffeners" rather than "strengtheners." The effective load bearing capacity of a member of given strength is based upon how large a cross-sectional area is carrying the load. Gussets are commonly welded to tubular members to reduce their flexure under a bending load.
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January/February 1996 Inspectioneering JournalBy Del Underwood at Det Norske Veritas, and Tim Munsterman at Det Norske Veritas
Last issue, in keeping with the evaluation that "gussets are stiffeners, not strengtheners," we discussed welding around the ends of the gusset plate instead of just along the sides in order to reduce the stress concentration. A further improvement in the gusset life can be obtained by welding it to a reinforcing plate and/or a fitting instead of directly to the pipe.
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September/October 1995 Inspectioneering JournalBy Del Underwood at Det Norske Veritas
A key to any piping evaluation program is to understand where problems can occur. Vibrating piping can propagate a crack relatively quickly. Have you ever installed gussets to stabilize a vibrating pipe situation only to find, shortly thereafter, that the gussets have cracked the pipe? If so, you've got lots of company.
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May/June 1995 Inspectioneering JournalBy Bob Browne at ERA Technology
For reason of economy, the hot reheat pipework in many US power plants is fabricated from seam-welded low chrome-moly carbon steel spools. Unlike girth butt welds, where the critical weldment microstructures can off-load stress to the stronger parent material, seam welds are subject to the full pressure hoop stress. A number of failures have occurred, some of which have been evidenced by fast fracture over extended lengths of the seam weld with a massive and violent steam release.
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Published on April 24, 2018The CSB has released an animation detailing the events leading up to the February 8, 2017 explosion at the Packaging Corporation of America's DeRidder, Louisiana, pulp and paper mill. The incident killed three contract workers and injured seven.
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Published on June 7, 2010U.S. Chemical Safety Board safety video discussing key lessons to prevent flammable vapor explosions caused by welding and cutting.
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