Concept · The inspector's job

Reference (control) areas

Why a small area prepared and coated to the agreed standard settles disputes on the whole job.

A reference area is a small part of the structure. It is prepared, inspected and accepted at the start of a job as the agreed standard. This standard covers the cleanliness, the profile and later the coating. ISO 12944-7 defines it as a defined part of the structure, coated to the specification and approved by all parties.

The why: words and photographs do not settle arguments

A specification says "Sa 2½", "uniform" or "free of runs". People read these words in different ways. A photograph in a standard shows another piece of steel, with another abrasive and another light. The owner, the contractor and the inspector can all be honest and still disagree.

A reference area removes the guess. All three parties look at the same piece of the real structure, and they agree that it meets the specification. From then on, nobody asks what the specification means. The question is whether this section matches the reference area and whether the readings agree.

This is dispute prevention. The agreement is made early, when nothing is at stake, and not in week six, when a rejected section costs money.

It is also evidence. The signed record shows what all parties accepted and when. A new owner's representative, a new foreman or an auditor can read it a year later and see the same standard.

In the field

1. Agree at the pre-job conference where the reference area goes, how large it is and which surfaces it covers. Choose a part that represents the job, with a weld and an edge if the job has them.
2. Prepare it with the same method and abrasive that production will use.
3. Inspect and measure it. Take the readings for cleanliness, dust, soluble salts, profile and climate (surface cleanliness and surface profile).
4. Coat it with the specified system. Measure the DFT of each coat.
5. Photograph it, record it and collect the signatures of all parties.
6. Mark its edges and protect it for the whole job. Show it to new crews and new site staff.

A worked scenario

A contractor repaints the outside of a storage tank. At the pre-job conference, the owner, the contractor and the inspector choose a section of the tank wall that includes a weld seam. The contractor blasts and primes it with the production abrasive and paint.

The inspector records the method, the abrasive, the climate and the profile and cleanliness readings. The three parties walk the section, take photographs and sign the record. The contractor marks the section with a painted frame and keeps it clean.

Weeks later, the owner's representative looks at a section of production work and says it looks rougher than the specification allows. The contractor says it is the same as before.

The inspector does not argue about words. She measures the profile and checks the cleanliness of the disputed section. She compares both with the readings and the photographs of the reference area.

The readings match. The owner's representative accepts that the section meets the standard that the owner signed. If the readings had not matched, the contractor would have repaired the section. In both cases the record decided, and not the opinion of one person.

What the inspector records

• The location and the size, marked on a drawing or a sketch.
• The preparation method, the abrasive and the coating products with their batches.
• The readings: cleanliness grade, dust, salts, profile, climate and DFT.
• Photographs that show the whole area and the close detail.
• The date and the signatures of the owner, the contractor and the inspector.

What it cannot do

A reference area shows what the specification looks like on this structure. It does not replace the measured limits. Production work still needs its own readings, such as the DFT limits. If the reference area and the specification conflict, raise the conflict with all parties at once.

For the related stripe coat requirement, see stripe coat. The same standard, ISO 12944, covers both. The hold points in the plan say when the parties must inspect the production work against the reference area.

Exam traps

• Trap: "The inspector alone chooses and approves the reference area." All parties approve it, and they sign the record.
• Trap: "The reference area replaces the specification." It shows how to read the specification. Measured limits still apply.
• Trap: "It is a test panel in the workshop." A reference area is part of the real structure. A mock-up or test panel is a separate item.
• Trap: "Remove it once the first coat is accepted." Keep and protect it for the duration of the work.
• Trap: "A photograph is enough." The record needs the readings, the methods and the signatures too.
• Trap: "A reference area in ISO 1461 galvanizing is a sample patch." There it means the area for magnetic thickness readings on an article.

5 practice items in the members area mention this topic (CIP 1: 1 · CIP 2: 1 · FROSIO written: 3).

Related

• Standards: SSPC-PA 9
• Defects: Orange peel
• The inspector's job: Hold points, witness points and the ITP · Reports, nonconformances and traceability