Four Assets, Two Inspectors, One Jurisdiction
A refinery's mechanical integrity group must set the inspection program for four items. Item A: an air receiver, 6 ft³, built in 1995 to ASME VIII Div. 1, MAWP 250 psig. Item B: a chemical mixing tank stamped VIII Div. 1 with a design pressure of 10 psig. Item C: a fired heater with 400 psig tubes. Item D: a TEMA shell-and-tube exchanger with a U-stamped shell, MAWP 300 psig. The group has two candidate inspectors: R. Ortiz, whose API 510 certification expired four months ago but who has 20 years of vessel experience, and S. Kaur, a mechanical engineer with 12 years in vessel design and fabrication plus 2 years performing in-service inspections, who is not yet certified. The jurisdiction requires external inspections at 3-year intervals; the site procedure cites 5 years per API 510 Table 1.
1. Which of the four items fall within API 510 scope, and why?
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In scope: A and D.
- A (air receiver): an unfired pressure vessel with design pressure well above the 15 psig threshold, built to a recognized construction code. Fully covered.
- D (exchanger): the U-stamped shell and heads are pressure boundary and are covered. The tube bundle and tubesheets are not the subject of API 510; tube inspection belongs to the exchanger's own maintenance program (e.g., TEMA).
Out of scope: B and C.
- B: API 510 excludes vessels with a design pressure of 15 psig or less. A 10 psig stamped tank is outside the code regardless of its code stamp - the stamp does not pull it into scope.
- C: fired vessels are excluded. The heater's pressure-containing tubes are covered by other documents, not API 510.
The logic tested here: scope is set by the exclusion list and design pressure, not by whether a piece of equipment looks like a vessel or happens to carry a code stamp.
2. Who may act as inspector of record today, and what must happen before either person signs an inspection?
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Neither can sign today.
- Ortiz: API 510 defines the inspector as a person holding a current certification. Experience does not substitute for an expired credential. He cannot be the inspector of record until recertified; his 20 years can support a recertification application and can let him work under a certified inspector's direction, but the judgment calls and records remain the certified inspector's.
- Kaur: her engineering background and 12 years of design/fabrication experience are strong preparation, but she is not certified, so she is not an API 510 inspector.
Before work proceeds the owner/user must also confirm:
- The inspector's employer is the owner/user or an authorized inspection agency acceptable to the owner/user - an inspector cannot be employed by the repair organization doing the work.
- Qualifications and certifications are documented and on file.
- Any additional jurisdiction-specific inspector credential is satisfied, since the jurisdiction's rules apply on top of API 510.
A practical mitigation is to contract a certified inspector for the interim while Kaur completes certification.
3. The site procedure says external inspections every 5 years; the jurisdiction says 3 years. Which interval governs, and how should the procedure be written?
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Three years governs. API 510 sets maximum intervals but does not override a jurisdiction. Where a jurisdiction's requirement is more stringent, the more stringent requirement applies; an owner/user may always choose a shorter interval than the code maximum, never a longer one without a recognized alternative (e.g., a risk-based inspection program per API 580/581) that the jurisdiction accepts.
Procedure language should therefore read: external inspection at an interval not exceeding the lesser of (a) half the remaining life, (b) 5 years per API 510 Table 1, or (c) the jurisdiction's 3-year requirement.
A second trap: the 5-year external limit and the 10-year internal limit are caps, not entitlements. If the calculated remaining life at a CML is short, half-life governs and the interval collapses to well under 5 years regardless of what the procedure says.