Reading Welding Symbols, WPS Documents, and AWS/ABS Code Basics

Why Welding Symbols and WPS Documents Matter

Every weld on a ship begins as ink on paper. Before you strike an arc, you must read two documents accurately: the engineering drawing (which uses standardized welding symbols to tell you what the joint must look like) and the Weld Procedure Specification (WPS) (which tells you exactly how to make that weld). Misreading either document can produce a weld that fails classification society inspection, forces costly repairs, or — in the worst case — fails at sea. Accuracy at this stage protects your crew, your ship, and your career.

The AWS A2.4 Welding Symbol System

AWS A2.4 is the standard that defines welding symbols used on US shipbuilding drawings. Every welding symbol is built from the same skeleton:

• Reference line — a horizontal line that anchors all other elements.
• Arrow — points from the reference line to the joint being described.
• Arrow side / Other side — information placed below the reference line applies to the arrow side of the joint; information placed above applies to the other (far) side.
• Weld symbol — a graphic shape in the junction of the arrow and reference line that identifies groove type (V, bevel, J, U, square), fillet, plug, slot, or other weld type.
• Dimensions — weld size appears to the left of the weld symbol; length and pitch appear to the right.
• Finish symbol — a letter (C = chipping, G = grinding, M = machining) placed above or below the contour symbol tells the welder how the face must be finished.
• Contour symbol — flat (straight line), convex (curve above), or concave (curve below).
• Tail — a forked tail at the opposite end of the reference line from the arrow. The tail holds supplementary information: the welding process, specification reference, WPS number, or special notes. No tail is drawn when no supplementary information is needed.
• All-around symbol — a small circle at the arrow/reference line junction means the weld encircles the joint completely.
• Field weld flag — a filled flag at the same junction means the weld is to be made in the field (on board the vessel), not in the shop.

When a drawing shows a double-V groove weld, both arrow-side and other-side weld symbols appear on their respective sides of the reference line. Always check both sides before you decide whether the joint is single- or double-sided.

Reading a Weld Procedure Specification (WPS)

A WPS is a written document that a welding engineer qualifies through testing or through prequalified status under AWS D1.1. It is your legal and technical authority for making each weld. When you pick up a WPS, locate these items first:

1. Base metal P-number — AWS/ASME group designation for the steel or aluminum alloy. Structural ship steel commonly falls under P-1 (carbon steel). Knowing the P-number confirms the WPS covers your material.

2. Welding process — SMAW, GMAW, FCAW, GTAW, SAW, or a combination. The process on the WPS must match the process you intend to use.

3. Filler metal classification — the AWS filler classification (e.g., E7018 for SMAW) and, where applicable, the ABS-approved filler grade. Using an unspecified filler is an essential variable change that invalidates the WPS.

4. Preheat minimum temperature — the lowest temperature the base metal must reach before welding begins. For carbon steel in marine work, preheat prevents hydrogen-induced cracking. Never weld below the stated minimum.

5. Interpass temperature limit — the maximum temperature between passes. Exceeding it can degrade toughness, especially in higher-strength steels used in hulls and bulkheads.

6. Essential variables — changes to essential variables (base metal, filler, position, heat input limits, preheat, etc.) require requalification of the procedure. A prequalified WPS under AWS D1.1 is only prequalified when all prequalification limits are strictly followed.

AWS D1.1 and ABS Rules: How They Relate

AWS D1.1 is the structural welding code for steel; it governs workmanship, qualification, and inspection on most shipbuilding steel structures. The American Bureau of Shipping (ABS) Rules for Materials and Welding add classification-society requirements: ABS approves welding procedures and may require additional testing beyond D1.1 minimums. In practice, a shipyard's WPS must satisfy both documents. When the two conflict, the more stringent requirement governs. ABS also independently qualifies welders — your ABS/USCG welder qualification card confirms you can produce acceptable welds under classification oversight, separate from the shop qualification your employer may hold on file.

Safety Points

Engineering drawings and WPS documents are sometimes reviewed in areas adjacent to active welding. Wear your PPE (safety glasses minimum) in any shop space. Never prop a drawing against a hot weldment or near arc flash zones. Confirm that any drawing or WPS you use is the current revision — outdated documents are a common source of nonconformance. If a drawing symbol or WPS requirement is unclear, stop and ask your supervisor before welding. Making a weld based on a guess creates rework at best and a classification rejection at worst.

Putting It Together

A competent shipfitter or marine welder reads a drawing callout in seconds and immediately knows: what joint geometry to prepare, which side to weld first, what filler to pull from the cage, whether to preheat, and how to finish the weld face. That fluency starts here — with disciplined practice on symbols and WPS documents until the process is automatic.