Pipe Fitting Inspection and Test Plans: Setting Hold Points, Witness Points, and Review Points
An Inspection and Test Plan (ITP) is the quality management document that defines what inspections are performed on a batch of pipe fittings, who performs them, and — critically — whether the process stops for TPI witnessing or can proceed after notification. The three categories of inspection activity — Hold Points, Witness Points, and Review Points — carry very different obligations. Setting them incorrectly results in either over-inspection (wasted cost) or under-inspection (unacceptable risk on critical equipment). Understanding the hierarchy allows procurement engineers to write ITPs that are proportionate, cost-effective, and enforceable.
The Three Inspection Activity Categories
- Hold Point (H): Production stops until the TPI (or client representative) physically attends, inspects, and signs off. The manufacturer cannot proceed past this point without the witnessed signature. Used for activities that cannot be verified after the fact — e.g. dimensional inspection before heat treatment (heat treatment changes dimensions), bevel inspection before welding (the weld covers the bevel). If the TPI does not attend within an agreed time window (typically 5–10 working days), the client must either release the hold or agree to postpone production.
- Witness Point (W): The TPI is notified and invited to attend, but production may proceed if the TPI does not attend within the agreed notification window. The manufacturer records the result regardless of TPI attendance. Used for activities where the result is independently verifiable after the fact — e.g. hydrostatic pressure tests (the chart record is the evidence), PMI testing (the XRF printout is the record).
- Review Point (R): The manufacturer performs the activity and submits the record for document review. No physical TPI attendance is required. Used for activities that are entirely document-based — e.g. certificate review, dimensional records, heat treatment records submitted with the delivery package.
Standard ITP Structure for Critical Pipe Fittings
| Activity | Standard Service | PED Cat III–IV / NACE / Cryo |
|---|---|---|
| Raw material certificate review | R | R (3.1) / W (3.2) |
| PMI / XRF verification | W | W or H (depends on client) |
| Dimensional inspection | R | W |
| Heat treatment chart review | R | H (P91/P92) / R (others) |
| NDE (PT/MT/UT/RT) | R | W or H |
| Hardness testing (NACE) | N/A | W |
| Charpy impact testing | N/A | W |
| Final visual and marking check | R | W |
| Pre-shipment inspection | N/A | H (client or TPI) |
TPI Agencies
Common TPI agencies used for pipe fitting inspection: TÜV Rheinland, Bureau Veritas (BV), DNV GL, Lloyd's Register (LR), SGS, Intertek. For PED CE marking, the Notified Body (NB) must perform or approve the 3.2 countersignature — not all TPI agencies are EU Notified Bodies for pressure equipment. Confirm the TPI's NB number in the NANDO database before appointing them for PED work. For IBR in India, the Inspecting Authority must be recognised by the Chief Inspector of Boilers of the relevant state — a foreign TPI is not automatically acceptable.