August 2002 • Modern Steel Construction

Codes, specifications, andcontract documents pro-vide fabrication require-ments that must bemaintained when ap-

plied to welded construction. How-ever, some provisions are perceived as“requirements” when they are not ap-plicable, or when alternatives are per-mitted. Under these conditions, it isprudent to carefully evaluate such “re-quirements” and, when appropriate,consider alternatives that may providefabrications of equal or better quality,and at reduced cost.

Consider, for example, the require-ments as they relate to Complete JointPenetration (CJP) groove welds madein accordance with the American Weld-ing Society Structural Welding Code –Steel (AWS D1.1). A review of the pre-qualified joint details in AWS D1.1, Fig-ure 2.4 reveals that all CJP groovewelds (with one exception which willbe discussed below) utilize either sin-gle-sided joints with steel backing, ordouble-sided joints that involve backgouging (see Figures 1 and 2). Eitheroption is permitted, and when prop-erly made, both should result in a weldthroat that is equivalent to the thick-ness of the thinner base metal joint.

The single exception to this is the B-L1-S detail (see Figure 3), which is lim-ited to a maximum thickness of 3/8 in(10 mm). This detail relies on the pen-etration of the submerged arc weldingprocess to achieve a CJP groove weld.

It would be easy to conclude thatAWS D1.1 requires either (a) steel back-ing for one-sided joints, or (b) double-sided joints that use back gouging.However, this conclusion would be in-

Practical Cost-Saving Ideas for the Design Professional: Welding No. 6

CAREFULLY EVALUATE “CODE REQUIREMENTS”

Duane K. Miller, P.E.

Figure 1. Single-sided CJP weld with steel backing.

Figure 2. Back-gouged double-sided CJP weld.

Figure 3. Prequalified AWS D1.1 joint detail B-L1-S (used with permission of the AmericanWelding Society).

correct, and a careful evaluation ofcode “requirements” with respect tothis criterion will reveal that the codepermits alternatives.

The key principle that provides un-derstanding in this particular instanceis the difference between prequalifiedWelding Procedure Specifications(WPSs) and those that are qualified bytest. In order for a WPS to be prequali-fied, it must comply with all the criteriaof Chapter 3 in the AWS D1.1 Struc-tural Welding Code. However, it isalso possible to qualify WPSs by test inconformance with AWS D1.1, Chapter

4 - Qualification. Such qualificationtesting could thereby permit the use ofother materials for backing, includingceramic, glass tape, copper and ironpowder (see AWS D1.1, Section 5.10).

Qualification testing could similarlypermit the use of double-sided jointswithout back gouging. This is specifi-cally addressed in AWS D1.1, Table 4.5 –”PQR Essential Variable Changes Re-quiring Requalification for SMAW,SAW, GMAW, FCAW, and GTAW,”Item 35. This provision states that “theomission, but not inclusion, of backing

or back gouging” would require quali-fication of the WPS.

CASE STUDY For many years, a fabricator had

made CJP groove welds in T-joints foroffshore applications, using double-sided joints with back-gouging, consis-tent with the prequalified AWS D1.1joint detail TC-U5-GF (see Figure 4).Rather than incorrectly assuming thatback gouging of two sided CJP groovewelds was a “requirement,” this fabrica-tor took advantage of the D1.1 Code al-ternative which permitted WPSqualification without the use of backgouging.

The alternative approach replacedthe back gouging operation with aunique root pass procedure that en-sured a CJP groove weld. The overalljoint was a tee, composed of two 3-in.(75 mm) steel members, and was pre-pared with a double bevel groovepreparation, using a 50° includedangle, no root opening and no rootface. Two pulsed GMAW arcs, operat-ing from opposite sides of the web, si-multaneously made the root passes.Longitudinal spacing for the opposedarcs was approximately 1/2 in. (12 mm).Figure 4 shows the root passes, withcomplete penetration. Figure 5 showsthe completed joint that was filled withpulsed GMAW as well.

Such techniques necessitated WPSqualification testing, but the potentialcost savings greatly outweighed the ex-pense of the WPS qualification testing.

CONCLUSIONSReevaluation of “requirements”

such as backing or back gouging forAWS D1.1 CJP groove welds may per-mit the use of cost-effective alterna-tives. Once a WPS is qualified, it thenmay be submitted to the Engineer forapproval, consistent with AWS D1.1,Section 4.1.1.

In other situations, Code provisionscan be waived and alternatives permit-ted when approved by the Engineer.For example, AWS D1.1, Section 6.8permits the Engineer to use alternativecriteria for specific applications. Ap-

Figure 5. CJP groove weld completed by pulsed GMAW without back-gouging.

Figure 4. Pulsed GMAW root passes on 3 in. (75 mm) thick members.

Modern Steel Construction • August 2002

proving alternatives should not be ca-sually approached, and the Engineer isencouraged to rely upon prior experi-enced engineering judgment, in addi-tion to analytical or experimental data.However, alternatives can be approvedin this manner, permitting viable alter-natives.

In the preceding case study, the costsavings achieved were impressive.Equally important, overall quality isexpected to be enhanced since relianceis made upon a system that includescareful control of the welding proce-dures for the root pass, rather than onback gouging operations that are inher-ently subject to variations in operatorskill. As is frequently the case, thiscost-saving effort also improved quality.

Duane K. Miller is a welding designengineer with The Lincoln Electric Com-pany, Cleveland, OH. This article isreprinted with permission from WeldingInnovation, a publication of the James F.Lincoln Arc Welding Foundation.

August 2002 • Modern Steel Construction