For many overseas buyers, especially in oil & gas, infrastructure and government projects, a shipment is not ready until an independent inspector says so. Third-party inspection (TPI) gives the buyer confidence that what leaves your plant matches the purchase order — without having to fly their own engineer across the world. For exporters, a smooth TPI is the fastest route to getting paid.
What third-party inspection is
TPI is an independent check of materials or products by an inspection agency appointed by the buyer (or sometimes by the seller at the buyer's request). The inspector visits your plant or warehouse, witnesses tests, checks documents and issues a report or release note.
Well-known international agencies include SGS, Bureau Veritas, TÜV, Intertek, DNV and Lloyd's Register, along with many reputable regional firms. Buyers usually name the agency in the purchase order.
When buyers ask for TPI
- Pressure and process applications (oil & gas, petrochemicals, power)
- Project orders with an EPC contractor or consultant
- New supplier relationships, where the buyer has not yet audited you
- Letters of credit that list an inspection certificate as a required document
- High-value or critical items such as large-bore pipes, forged flanges and valves
TPI is closely linked to the EN 10204 3.2 certificate, which must be validated by both the manufacturer's inspector and the buyer's or third-party representative.
What the inspector checks
1. Documents
- Purchase order and technical specification
- Mill test certificates and heat number traceability
- Approved quality plan or inspection and test plan (ITP)
- Calibration certificates for gauges and test machines
- Welding procedures and welder qualifications, if applicable
2. Visual and dimensional inspection
- Surface condition — no cracks, laps, pits or heavy rust
- Outside diameter, wall thickness, length, straightness and ovality
- End finish, bevel angle and threads
- Flange dimensions, facing and bolt holes
3. Material verification
- Positive Material Identification (PMI) with a handheld analyser to confirm grade — for example checking molybdenum to separate 316 from 304
- Hardness testing
4. Witnessed testing
Depending on the order:
- Tensile, yield and elongation tests
- Impact (Charpy) tests at specified temperatures
- Hydrostatic pressure tests
- Non-destructive testing (ultrasonic, radiography, eddy current, magnetic particle or dye penetrant)
- Flattening, flaring and bend tests for pipes and tubes
- Intergranular corrosion tests for stainless steel
5. Marking, packing and quantity
- Stencil or stamp marking as per standard and PO
- Correct end caps, bundling, crating and ISPM 15 compliant wood
- Piece count and weight against the packing list
Inspection stages
- Raw material inspection — before manufacturing starts
- Stage or in-process inspection — during forming, welding or heat treatment
- Final inspection — on finished goods, before packing
- Pre-shipment / loading inspection — during container stuffing
Hold points in the ITP tell you when you must stop and wait for the inspector.
How to prepare for a smooth TPI
- Agree the ITP early. Know exactly which tests are witnessed and which are reviewed from records.
- Pre-inspect internally. Do your own full check a day before the inspector arrives.
- Keep documents in order. MTCs, calibration records and test reports should be printed and indexed by heat number.
- Segregate material. Keep inspected lots separate and clearly tagged.
- Give clear notice. Agencies usually need several working days' notice. Confirm the date in writing.
- Provide access and equipment. Space, lighting, calibrated tools and a helper make the visit faster.
- Fix and record non-conformities. Close every observation with evidence before the release note is issued.
Avoid these common causes of rejection
- MTC values outside the standard's limits
- Heat numbers on material that do not match certificates
- Missing or illegible marking
- Expired calibration on test equipment
- Wrong end finish or bevel
Clean certificates make inspectors' work easier. MTCMitra generates EN 10204 3.1 certificates with grade limits built in and every value checked before printing, so errors are caught at your desk, not at the inspection table.
Who pays for TPI?
Usually the buyer pays the agency, but re-inspection after a failure is often charged to the seller. Make this clear in your quotation and contract. Also add the inspection time to your delivery schedule.
Frequently asked questions
How much notice does a TPI agency need?
Most agencies need a few working days' notice. For remote locations or busy periods, give more time and confirm the date in writing.
What is the difference between 3.1 and 3.2 certificates?
A 3.1 certificate is validated by the manufacturer's independent inspection representative. A 3.2 certificate is also validated by the buyer's representative or a third-party inspector.
Can the inspection be done remotely?
Some buyers accept remote or video inspections for simpler items. Critical tests and witness points usually still need an inspector on site.
What happens if the material fails inspection?
The non-conformity is recorded, the material is segregated, and the issue is corrected or the material replaced. Re-inspection costs are often charged to the supplier.
Key takeaways
- TPI gives buyers independent proof of quality and often unlocks payment.
- Inspectors check documents, dimensions, material, tests, marking and packing.
- An agreed ITP, internal pre-inspection and clean certificates make TPI smooth.
Suppliers who pass inspection the first time stand out. Buyers remember who delivers without surprises — and that is how one export order becomes many. See how we help metal companies show that reliability online on our services page.
