Does AWS D1.1 require the weld pass sequence to be on the WPS?

Yes. Both prequalified WPS (Clause 5) and tested WPS (Clause 6) must document the pass sequence or pass arrangement. For complex joints with multiple passes, a numbered pass diagram on the WPS is the clearest way to comply and give welders unambiguous guidance.

What makes a structural joint 'high restraint'?

A joint is high restraint when the surrounding structure significantly restricts thermal expansion and contraction during and after welding. Common examples include column-to-base plate CJP welds on thick plates, corner welds of box columns, T-joint connections with heavy flanges, and weld joints blocked by adjacent structures that prevent free movement.

Can incorrect weld sequence cause cracking?

Yes. An incorrect sequence in a high-restraint joint concentrates residual tensile stress at the root or along a single axis. Combined with elevated hydrogen levels from low-hydrogen electrode exposure or inadequate preheat, this creates the conditions for delayed hydrogen cracking, which may not appear until hours after welding completes.

Who is responsible for specifying the weld sequence—the engineer or the fabricator?

AWS D1.1 places responsibility on the fabricator to document the pass sequence on the WPS. The engineer of record may impose sequence requirements through contract specifications or WPS approval comments, but the default code expectation is that the fabricator's CWI or welding engineer develops and documents the sequence.

Weld Sequence Documentation for High-Restraint Structural Joints

AWS D1.1 requires the pass sequence on every WPS. For high-restraint connections, documenting the right sequence prevents hydrogen cracking, lamellar tearing, and costly rework.

Weld sequence is one of the most consequential decisions made during fabrication of structural connections — and one of the most frequently underdocumented items on a WPS. In a simple fillet weld on a free-standing bracket, sequence matters little. In a moment-frame beam-to-column connection, a gusset plate on a braced frame, or a column base plate with full-penetration groove welds, the order in which beads are deposited determines the residual stress distribution, the distortion pattern, and the risk of hydrogen-assisted cracking.

AWS D1.1 does not prescribe a single weld sequence for most structural connections — the code trusts the fabricator's engineering judgment — but it does require that whatever sequence is used be documented on the WPS. The CWI's job is to verify that welders follow the documented sequence, not to develop it on the floor during production.

What AWS D1.1 Requires

Both prequalified WPS (Clause 5) and tested WPS (Clause 6) require documentation of the pass sequence as part of the WPS content. The Annex M form — the standard WPS format endorsed by the code — includes a section for pass arrangement/sequence and a space for a sketch or pass-number diagram.

The code language does not specify how detailed the pass diagram must be. A simple two-pass fillet weld WPS might indicate "Pass 1: root pass, Pass 2: cover pass" in text. A multi-pass groove weld in a heavy box column might require a dimensioned sketch showing numbered bead locations across the joint cross section. The level of detail must be sufficient for a qualified welder to reproduce the sequence without interpretation.

For high-restraint joints specifically, "sufficient detail" typically means a numbered pass diagram, not just a pass count. Rule library based on AWS D1.1:2025; verify against your governing edition.

What Makes a Joint High Restraint

Restraint in welding is the degree to which surrounding structure prevents the joint from moving as weld metal cools and contracts. High restraint correlates with higher residual tensile stress in the finished weld, which is directly linked to hydrogen cracking susceptibility and lamellar tearing risk in through-thickness loading.

Several structural configurations consistently produce high restraint conditions:

Column base plates. A wide-flange or hollow section column anchored to a thick base plate creates extreme restraint in the flange-to-plate CJP welds. The plate is rigid against the column axis, and the anchor rod layout prevents rotation. Residual stress after welding without a planned sequence can be very high.

Box column corner welds. The four corner welds of a built-up box section are each restrained by the other three panels. Welding all four corners simultaneously in a balanced sequence is standard practice; welding them sequentially without balancing locks in significant distortion and transverse residual stress.

Moment frame beam-column connections. CJP groove welds in the beam flanges at column faces are restrained by the column, the continuity plates, and the stiffeners already in place. The sequence of continuity plate welds relative to the beam flange welds matters.

Heavy T-joints in column stiffeners. A doubler plate or continuity plate welded to a column web is highly restrained by the surrounding flanges and existing web-to-flange fillet welds.

Sequencing Principles for High-Restraint Joints

The following principles apply broadly to high-restraint structural connections. Always consult your shop's welding engineer or CWI for joint-specific guidance; these are not code-mandated sequences but engineering best practices widely applied under AWS D1.1 work.

Balance across axes of symmetry. When a joint has two sides (flanges, opposing fillet welds), weld both sides alternately rather than completing one side before starting the other. This distributes shrinkage forces symmetrically and minimizes net angular distortion.

Work away from high-restraint points. In a multi-pass groove, depositing the first passes adjacent to backing or at the root — rather than starting at the mid-thickness — can reduce triaxial stress concentration at the most restrained zone. This is especially important in joints with steel backing bars where the root is difficult to re-examine.

Use backstep or skip-sequence technique on long welds. For longitudinal welds exceeding 18–24 in. (460–610 mm), a backstep pattern — depositing short segments from right to left while overall progression moves left to right — reduces the net longitudinal shrinkage and the tendency for the joint ends to pull together.

Maintain continuous preheat through the sequence. High-restraint joints that cool to ambient between passes allow hydrogen absorbed during welding to migrate to the root and high-stress zones. The WPS must specify a minimum interpass temperature, and that temperature must be maintained throughout the entire sequence — including during inspection holds, coffee breaks, and shift changes.

Avoid completing one quadrant or zone at full thickness before the adjacent zone is started. In box column welds, this means bringing all four corners to approximately equal fill height before any one corner is completed, rather than running corner 1 to finished height, then starting corner 2.

Documenting the Sequence on the WPS

For simple welds — two-pass fillet, single-pass fillet, root-and-one-fill groove — a text description in the pass sequence section is adequate. For complex joints, consider the following approaches:

Numbered pass diagram. A cross-sectional sketch of the joint showing weld beads numbered in sequence is the most inspection-friendly format. A CWI can reference the diagram during production without looking up text. This approach also prevents ambiguity: "Pass 7" on the diagram means a specific bead in a specific location, not the seventh bead the welder deposits in whatever order they choose.

Quadrant or phase notation. For box sections and similar symmetric joints, "Phase A / Phase B" notation can organize passes by symmetry group rather than absolute number. Example: "Phase A = passes on flanges 1 and 3; Phase B = passes on flanges 2 and 4; alternate phases until joint is complete."

Reference to a welding sequence drawing. For connections designed by the engineer of record with specific sequence requirements (common in AISC 341 seismic work under AWS D1.8), the WPS may reference a sequence drawing by number. The referenced drawing becomes part of the WPS package.

Whatever format is used, the WPS must stand alone as a document — a welder or CWI must be able to pick it up and understand the required sequence without needing an oral explanation from the shop foreman.

What the CWI Verifies

The CWI's role during weld sequence inspection is not passive. Before welding starts, the CWI should confirm the welder has the current WPS revision and understands the pass sequence. During welding, the CWI spot-checks that passes are being deposited in the documented order, particularly at the critical early passes (root and first fill) where deviation is most common and most consequential.

Specific CWI checkpoints for high-restraint joints:

Confirm preheat is achieved and interpass temperature is maintained across all elements of the joint (not just at the start point).
Verify that the welder is not jumping ahead to a pass or zone not yet called for by the sequence.
Document time-stamped notes for each phase of a multi-shift weld that runs across a shift boundary. Record who welded which passes and what the interpass temperature was at handoff.
For demand-critical welds under AWS D1.8 (seismic), verify that any owner-specified sequence restrictions from the connection design are reflected on the WPS and followed in production.

After welding, the CWI should record that the documented sequence was followed. A simple notation on the inspection record ("pass sequence per WPS [number] observed and confirmed") is sufficient for most projects; seismic and bridge work may require more detailed reporting.

When the Engineer Imposes Sequence Requirements

Some project specifications — particularly AISC 341 seismic moment frame connections — require the engineer of record to review and approve the weld sequence for demand-critical connections. In these cases, the fabricator's WPS must reflect the approved sequence, and any deviation requires EOR approval before production restarts.

The fabricator CWI's job in this scenario is to enforce the approved sequence as a code requirement, not as a suggestion. If a welder deviates and the deviation is caught, the sequence must be corrected (or the deviation documented and submitted for EOR disposition) before continuing.

For a detailed look at how essential variables like pass sequence interact with PQR qualification scope, see essential variables vs. non-essential and weld distortion control and sequence planning. Shops managing multiple complex connections across a project can track WPS revisions and sequence documentation in the welding procedure library tool.