by Doug Berger
This planet is blessed with an abundance of steel, one of the most versatile materials you could dream of. Slight changes in composition or heat treatment allow us to create structures designed to permanently deform and absorb energy, or resilient springs which snap back every time. The material is relatively inexpensive, recyclable, durable, form-able and machinable. From an engineering standpoint,
design methods are well established. A wide variety of material specifications are available. There are warehouses of data regarding properties. It is no wonder that it is the material of choice for structural design.
Another huge benefit of a construction with steel is that connections can be welded. Welding is a process by which two pieces of material are fused together. The most critical aspect of a weld is that it develops the strength required by the design of the structure. Because of this many building codes and design specifications require certified welders to perform the welds and certified weld inspectors to verify the work performed.
A Weld Procedure Specification (WPS) is a document the designer of a structure can use to communicate to the welder about how to make a weld. It doesn’t specify where the weld is or how big it is, like a design drawing would. The information in a WPS describes a range of specifications which, when used together by a competent welder may produce a quality weld. The format of a WPS isn’t as important as the information it contains. Some of the information found in a WPS may include the following:
- Weld type: fillet, groove, as well as complete or partial joint penetration
- Weld process: GMAW, GTAW, SMAW, among others
- Base metals - along with allowable thickness
- Filler metal and electrode information
- Shielding requirements: gas, flux
- Fit up of the joint - including end treatment, root opening, requirements for backer material and angles between base metals
- Process information such as preheating requirements current type and level, voltage range, number and size of passes, speed of passes, welding position, cleaning position, technique information and post weld treatments
Many jurisdictions require a weld to be inspected by an AWS (American Welding Society) Certified Inspector. As part of our commitment to public safety, our clients’ peace of mind and customer service, NTA has Certified Weld Inspectors on staff. A CWI will review the WPS, welder qualification records, equipment calibrations and welding materials. They will inspect the base and consumable materials, as well as check various cutting methods, joints and alignment. The City of Houston, Clark County Nevada, the State of Washington and City of Los Angeles are just a few who require an inspection by a CWI.
For more information on having a Certified Weld Inspection performed, please feel free to contact NTA.