Welding inspection involves much more than checking the accuracy of welds. Inspectors must know codes, standards, materials, and other fabrication processes.
Welding inspection is not something to take lightly. Lives can depend on the accuracy of the inspection. Failed welds that cause the loss of life or property make the news and technical journals. Unfortunately, these failures are sometimes blamed on the welding inspector. However, you can avoid the harmful event if the inspector had done it correctly.
This claim is sometimes justifiable. Inspectors make mistakes like any other person in the fabrication chain. However, an inspector cannot inspect the quality of the product. Inspectors must establish the quality of a weldment at the beginning of the project and follow through to the end. If any step in the job is not established and carried out with quality as the top priority, the possibility of failure exists.
In years past, poor welds caused many more catastrophic failures than today. Boilers exploded, ships sank, buildings and bridges collapsed, and pipelines blew up frequently. As they established codes and standards, these disasters became far less frequent.
Which Code or Standard?
The ASME worked to establish rules for fabricating boilers, pressure vessels, and piping. The ASME is the American Society of Mechanical Engineers. The American Welding Society (AWS) established structural fabrication and erection rules. The American Petroleum Institute (API) is quality and safe for pipelines and related facilities.
An inspector must know which code or standard to use for the inspection criteria. Both the code of construction and the code to qualify the welding procedures and welders. They must have these requirements outlined in the job specifications. The inspector should not make assumptions or rely on his judgment to set the standard. The inspector should not proceed without clarification if it is not written in the specifications or on the drawings.
They must note that the ASME Section IX is only for welding procedures and welder qualification. It may not be in use as a code of construction. The AWS D1.1 code may be in use for welding procedures and welder qualification and as a construction code. The API 1104 is for welding and nondestructive testing of pipelines and related facilities.
The inspector must verify that the welding procedures comply with the applicable code or standard. This must happen before welding begins. Sometimes a customer establishes a standard not referenced to a particular code. This is often the case with substantial companies, such as Siemens and General Electric. In these cases, the customer standard prevails.
Each contractor or company is responsible for establishing welding procedures. No code that I am aware of allows a company to outsource a test for welding procedures. However, prequalified welding procedures are available from AWS. The user must demonstrate that the company can perform these procedures. Most companies require fabricators to establish and test their procedures. The API 1104 code does not recognize prequalified procedures. All codes require destructive tests for the qualification of procedures. And each code has different procedure testing requirements (Figure 1)
Welders must have the qualifications and certifications to the proper code or standard. This is what the welding inspector must verify. Testing is how to establish a welder’s qualifications. A welder who successfully performs a test and receives a certification document is now a certified welder.
Essential and nonessential variables in a list in each of the codes. Some essential variables that are common to all the:
- Codes are position
- Vertical progression
- Weld deposit thickness
- Others related to the specific process
Nonessential variables do not require requalification, but essential variables do. For example, the inspector may need a welder to perform a demonstration for a reasonable cause. Such as multiple failures and poor workmanship.
The inspector must observe the joint design to ensure that the procedures cover the type of weld specified on the drawing. For example, if the procedures and welders are only qualified for welds with backing, no open-root welds are the permits. On the other hand, if the procedures and welders qualify for welds without backing, then welds with or without backing can be used. This variable is common to all the codes (Figure 2).
Figure (2)
Material Information
Material traceability is an absolute necessity for all jobs. If a failure occurs and involves liability, proof of material quality can hold the key to the cause of the failure. The inspector can only recommend specific additional tests to ensure that the material is of sufficient quality. I advise a client to require an ultrasonic examination on any material that is 1 inch thick or thicker.
Detection should be in the report for a plate with lamellar inclusions before any work starts on the material. Material suppliers must replace defective material. But convincing a supplier to pay for any work done before finding flaws is difficult.
The inspector must check the material test report (MTR) to ensure it meets the code requirements. Usually, the ASTM is referenced for AWS work, and the ASME Section II, Parts A, and B, are referenced for ASME fabrications. Even when low-carbon materials are being welded, care must be taken. This is to compare the chemical, physical, and mechanical properties to the proper standard. For example, the API piping standard is API 5L.
The inspector may question the material selection but accept the material if it meets the job specifications. The customer should determine the specification for the material type.
Tracking the Job
The inspector should request a shop traveler. A step-by-step guide that begins when the job is designed by engineering and proceeds through packaging and shipping. The guide enables the inspector to establish hold points when necessary for tracking inspections in the process. An inspector should sign off on each step of the fabrication. If they cut, bend, or roll incorrectly, the condition must be recorded and held as nonconforming until the customer decides. The decision may be to rework, use as is, or scrap. This decision is not for the inspector to make, but the inspector must record the matter and secure it in the permanent job records.
Inspection Tools
Inspectors use tools such as these recommended and assembled in a kit by AWS. These tools and the inspector’s knowledge of codes, standards, materials, and processes help. They help determine welded products and structures’ quality, durability, and safety.