99 Diseases of Pressure Equipment: Welding QA/QC

As one would expect, attention to the potential for the types of welding flaws and defects addressed in the previous “Disease” is very important to the overall prevention program for the 99 Diseases of Pressure Equipment. At the heart of this prevention program is the necessary quality assurance/quality control program (QA/QC) for welding described in the three API pressure equipment codes/standards for vessels, piping and tanks; API 510, API 570, and API 653. Additionally, there are two relatively new API recommended practices, API RP 577 and API RP 582 that contain more information that can be used to enhance welding QA/QC programs. All inspectors, engineers, and other folks involved in welding practices should have ready access to each of these documents and thoroughly understand and implement the welding QA/QC aspects contained in them. The bottomline is that I’ve never seen a welding flaw/defect that could not have been prevented by a relatively simple and economic welding QA/QC program.

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. Within the United States, the industry typically follows the ASME Boiler and Pressure Vessel Code, Section IX requirements, as referenced by the five API Codes/Standards for pressurized equipment mentioned above (API 510/570/653/577/582).

One of the important aspects of welding QA/QC is the need to keep up-to-date welder log sheets, to help ensure that welder qualifications stay current. The most effective welding QA/QC programs usually set a minimum amount of NDE, such as radiographic examination for every welder and track weld reject rates, to ensure that rework is kept to a minimum. The best programs I’m aware of stay routinely below a 1% weld reject rate. The welding defects and flaws (that can grow to the size of being a welding defect) are caused by a large variety of welding QA/QC issues, such as: inadequate preheat or PWHT, welding on equipment in-service, and inadequate repair welds made during fabrication.

With recognition to the potential for the “large variety of welding QA/QC issues”, whenever specialized or non-routine welding practices or materials are to be utilized, it pays to have a welding specialist involved to help specify the necessary QA/QC practices needed to avoid flawed welds that can act as initiators for the 99 Diseases. Those specialists can be a variety of types of people, who are knowledgeable and competent in welding QA/QC, such as certified welding inspectors (CWI), welding engineers, welding foremen, and those that will soon be certified by the new API Supplemental Inspection Program for API RP 577 (see article in Nov/Dec issue of the IJ.