A weld defect found in the shop costs a grinder and a few hours. The same defect found after the spool is installed and waiting for hydrotest can mean scaffolding, permits, a cut-out, re-welding, re-inspection and a slipped test date. That difference is the whole argument for fabrication quality control. Below are the controls that most directly prevent field delays on industrial projects, and what project teams should insist on before they accept fabricated items.
Start with the inspection and test plan
The inspection and test plan (ITP) lists every check, its acceptance criteria, the record it produces and who inspects. Inspection points are usually classed as:
- Hold points: work stops until the client or third party inspects
- Witness points: the client is notified and may attend
- Review points: records are reviewed without attendance
An ITP agreed before fabrication starts prevents arguments later about what was supposed to be checked. Too many hold points slow the shop. Too few push inspection out to site.
Welding qualification
Three documents control welding quality:
| Document | What it proves |
|---|---|
| WPS (welding procedure specification) | The parameters to be used for a given joint |
| PQR (procedure qualification record) | That the procedure was tested and produced acceptable welds |
| WQT (welder qualification test) | That each welder can produce sound welds with that procedure |
Every production weld should trace back to a qualified welder working to a qualified procedure. Recording the welder ID against each weld number makes that possible. Gaps here are hard to repair after the fact and can lead to cut-outs.
Material traceability
Mill test certificates should match the heat numbers on the material, and when pipe or plate is cut, the heat number must be transferred to every piece. For alloy and stainless materials, positive material identification (PMI) confirms the alloy before welding. Mixed-up material is one of the costliest problems to discover on site because it can mean replacing whole spools.
NDT selection and repair rates
Radiography, ultrasonic testing, magnetic particle and dye penetrant testing each suit different joints and materials. The specified NDT percentage is normally applied per welder and per procedure, and rejections trigger additional testing of that welder’s work. Track welder repair rates every week. A rising rate is a training or supervision problem that needs action before it reaches site.
Dimensional and coating checks
Dimensional inspection catches the problems that stop field fit-up: wrong flange orientation, bolt holes a few millimeters out, spool lengths outside tolerance. Coating inspection records surface preparation, dry film thickness and adhesion. Damaged coating should be repaired before dispatch, not left for touch-up at site.
Release notes: the final gate
No item should ship without a release note signed against complete records. This single rule stops incomplete paperwork from reaching site, where it turns into punch items and delays mechanical completion. The same records later feed the dossiers described in managing handover documentation.
Handling non-conformances
When something fails, raise a non-conformance report (NCR), define the correction and the root cause, and track it to closure. An NCR log reviewed weekly shows whether problems are isolated or systemic.
Quality steps specific to piping are described in pipe spool fabrication, and those for steel in planning structural fabrication. For owner-level priorities across a petrochemical project, see quality and safety priorities in petrochemical projects.
Apex Core Engineering supports fabrication packages with QA/QC personnel and supervision, working within the management systems listed on its certifications page.
Frequently asked questions
What is the difference between QA and QC in fabrication?
Quality assurance is the system: procedures, qualifications and plans. Quality control is the inspection and testing that checks the work against them.
What is a hold point?
A step in the ITP where work cannot continue until the named inspector has checked and accepted it.
Why do heat numbers need to be traced?
So every piece of material can be linked to its mill certificate, which proves it meets the required grade and properties.
When should NDT be increased?
When a welder’s rejections exceed the project limit, additional joints by that welder are usually tested as set out in the applicable code or specification.
Need inspectors or QA/QC supervision for a fabrication package? Contact Apex Core Engineering.