Appliedby XPO EngineersEngineer review
Menu
Fabrication screening · AS/NZS 1554

GP or SP? Choose the weld category.

The weld category is a design decision that shows up as fabrication cost. GP is not no inspection, SP is not just better welding, and the category belongs on the drawing before the job is priced.

Start the checkWhat the category buys
Pathway at a glance

GP, SP or another welding pathway?

The category is a design decision. Static structural welds, fatigue-loaded details, lifting gear and pressure equipment do not all belong in the same GP/SP bucket.

GP or SP — weld category at a glance Three gates: pressure-retaining welds go to the AS 3992 pathway; cyclic or fatigue loading goes to AS/NZS 1554.5 where the detail governs; high consequence or highly stressed welds take category SP; the remainder can take GP with the decision documented. Weld on the drawing board Pressure-retaining weld? yes AS 3992 pathway pressure equipment rules no Cyclic or fatigue loading? yes AS/NZS 1554.5 the detail governs no High consequence or high stress? yes SP category qualified, inspected, traced no GP category document the decision The designer chooses the category — per weld, on the drawing, before pricing
Sponsor logo position availablePDF footer sponsor space for workshop print-outs.

How to use this summary

  • Pressure equipment and special materials route out of the simple GP/SP question.
  • Fatigue-loaded details need the fatigue pathway rather than a simple category upgrade.
  • High consequence or high utilisation points toward SP with a defined inspection scope.
  • Low consequence and low demand can screen as GP when the designer records the decision.

This is category screening only. It is not an inspection scope, weld procedure or design approval.

01

Screen the weld category

Start with scope, then loading and consequence. The result tells you whether GP, SP, fatigue or a different welding pathway is likely.

ScopeLoadingConsequenceResult
Scope

What is being welded?

02

What the category actually buys

Category is about acceptance limits, inspection intent and design consequence — not a magic weld-strength upgrade.

01

Category means acceptance + inspection intent

The weld metal may be similar; what changes is how imperfections are judged and how much inspection you commit to.

02

The designer owns it

Category follows consequence and demand. Silence on the drawing is a design-information problem.

03

SP without inspection scope is half a decision

State what NDT, what extent and which welds. SP alone does not communicate the whole inspection plan.

04

Fatigue outranks category

A perfect SP weld on a poor fatigue detail can still crack. Detail selection and cyclic loading drive the decision.

03

Worked screening examples

01
Mixed categories

Equipment support brackets

Context: A plant-room frame includes primary member splices and low-consequence attachments.

Screening view: SP may apply to primary load-path welds while GP can be documented for low-demand attachments.

02
Fatigue

Vibrating screen support frame

Context: The drawing calls for SP everywhere, but the cracked detail sees cyclic loading.

Screening view: The tool routes to fatigue assessment because detail geometry matters more than simply upgrading the category.

03
RFI

Drawing with no categories

Context: A fabricator is asked to price work where GP/SP is not nominated.

Screening view: The result is an RFI back to the designer, not a fabricator guess.

04

Reference basis

This page paraphrases category-selection concepts and does not reproduce acceptance criteria or clauses from the standards.

AS/NZS 1554.1Welding of steel structures — GP/SP categoriesAS/NZS 1554.5Welding subject to high fatigue loadingAS 4100 / AS 3990Design standards that call up category selectionAS 3992Pressure equipment welding qualification boundary
Important limitation

Screening guidance on how weld categories are chosen and what they imply, in original language — it does not reproduce acceptance criteria or clause content from any standard, and it is not a welding procedure, inspection scope or design approval. Category selection for real structures is a design responsibility carried out against the current editions of the relevant standards.

Get Engineering Help

Need the category put on the drawing properly?

XPO Engineers can help with weld category selection, fatigue-sensitive details, lifting-device welds and inspection scope notes before fabrication is priced.

Ask an engineer