August 26, 2008
Welding codes are designed to improve the quality and efficiency of welding and are used to qualify welders. Predominate among welding codes in the U.S. are those authored by ASME and AWS. This article provides a brief overview of the similarities and differences in these codes.
The most commonly used codes for qualifying welders are the American Society of Mechanical Engineers (ASME) Section IX and American Welding Society (AWS) D1.1. Committees and subcommittees comprising volunteer workers interested in furthering the quality and efficiency of the welding industry work together to develop these codes.
We all have heard that ASME codes are more stringent than AWS codes and vice versa. In some areas both are the same. In others they are very different.
The most obvious difference between ASME Section IX and AWS D1.1 is that D1.1 addresses fabrication, erection, inspection, and welder and welding procedure qualification. ASME is specifically for welder and welding procedure qualification. A "code of construction," such as ASME Section VIII, Division I, must be used in conjunction with Section IX for fabrication.
Some work contracts require that a specific code be used for qualifying the welders, but in many cases either code is sufficient. If the job consists totally of structural welding and the contract specifies the AWS Structural Code, then that is the code that must be used for all aspects of the job.
If the job entails pressure vessels or piping, the ASME Boiler and Pressure Vessel Code must be used.
If the job is related to ductwork associated with a boiler, the contract usually allows qualification with either code. Choosing a specific code when one is not specified in the contract often involves a fine line.
The basic contents of a procedure qualification are the same in both programs.
The welding procedure specification (WPS) is a document that is intended to provide direction for the welder. It also depicts the joint design and welding materials, parameters, and technique and code requirements.
The procedure qualification record (PQR) is a record of test results for the welds made in accordance with the WPS. Destructive testing (tensile pulls, bends, etc.) is required for PQRs in all codes. AWS D1.1 also requires nondestructive testing for procedure qualification. ASME Section IX does not.
The welder qualification test record (WQTR) comprises the results of a test to prove that a welder is qualified to weld to a certain WPS. It includes qualification of the range of base materials, weld materials, positions, and so forth. These tests consist of guided bends, breaking of fillet welds, and macroetching. In some cases, the test coupons may be radiographed in lieu of destructive testing.
The AWS D1.1 code qualification is specifically for carbon and low-alloy metals. The minimum thickness addressed is 1/8 in. The maximum yield strength addressed is 100 KSI.
This code, generally used for buildings and support structures, is useful for fabricating and erecting any welded structure.
The prequalification Section 3 of AWS D1.1 lists materials for prequalifying the WPS. These materials are listed in groups that are assigned Roman numerals. Although the groups reflect a somewhat ascending alignment as to the yield strength, there are instances of overlapping within three of the four groups.
Group I lists the lowest-yield-strength materials from 30 KSI to 46 KSI. Group II lists materials at 36 KSI to 80 KSI. Group III, 46 KSI to 90 KSI. Group IV, 70 KSI materials only. Each material list shows matching electrode, and filler metal, to be used to establish prequalified procedures.
If a fabricator wants to use a material that is not listed in the table, a procedure must be qualified by testing and with a written PQR.
ASME materials are listed by "P" and "S" numbers. There are very few restrictions as to size and strength of material. This is a reason for qualifying welders and procedures to the ASME Section IX when possible.
Welding codes are intended to improve skills, processes, materials, and equipment. They are important in achieving maximum quality and efficiency.