Pipe inspection is the documented sequence of chemical, mechanical, non-destructive, pressure, visual and dimensional checks that proves every length of pipe meets its specification before it leaves the mill or enters a piping system. A typical mill sequence is: heat and product chemical analysis, tensile, flattening, bend and Charpy impact tests, NDT of the body and weld seam (UT, RT, ET or MT), a hydrostatic test at P = 2St/D held for at least 5 seconds (ASTM A530 / API 5L), visual and dimensional inspection against ASTM A530, A999 or API 5L tolerances, and finally stencil marking, a mill test certificate (EN 10204 type 3.1) and protective packing. Installed piping is then pressure-tested again to its construction code, for example 1.5 × design pressure for at least 10 minutes under ASME B31.3.
Standards referenced in this guide (reviewed October 2026)
- ASTM A530/A530M – general requirements for carbon and alloy steel pipe (hydrotest formula, OD and wall tolerances, NDE in lieu of hydro) used by ASTM A106 and others; ASTM A999/A999M is the stainless equivalent used by ASTM A312.
- ASTM A53/A53M, A106/A106M and A312/A312M – product specifications for carbon and stainless pipe.
- API Spec 5L (47th edition) / ISO 3183 – line pipe, PSL 1 and PSL 2, with Annex H (sour service) and Annex J (offshore).
- ASTM A370 (mechanical testing), ASTM A751 (chemical analysis), ASTM A262 (IGC), NACE TM0284 (HIC), NACE TM0177 (SSC) and ISO 15156 / NACE MR0175 (sour service materials).
- ASME B31.3, B31.1, B31.4, B31.8 and BPVC Section VIII Div 1 – fabrication examination, weld acceptance and system pressure testing.
- ASME B36.10M and B36.19M – pipe dimensions and schedules; EN 10204 – inspection documents (MTC 3.1 / 3.2).
Types of Pipe Inspection
Inspection starts before the pipe is formed and ends only when the certified length is accepted on site. Mill inspection proves the product meets its material specification; fabrication inspection under a piping code proves the welded system is fit for service. Confusing the two is one of the most common causes of rejected test packs, so the matrix below separates them. If you are still sizing the line, check flow and wall first with the Fluid Flow & Pipe Sizing Calculator and the pipe sizes & schedules chart.
| Inspection / test | What it proves | Typical governing requirement | Seamless | Welded | Frequency |
|---|---|---|---|---|---|
| Mill (product) inspection | |||||
| Heat & product chemical analysis | Composition, carbon equivalent (CE) | ASTM A751; product spec chemistry table; API 5L Table 4/5 | Yes | Yes | Per heat (+ product analysis per lot) |
| Tensile test | Yield, tensile strength, elongation | ASTM A370; API 5L 10.2.3 | Yes | Yes (body + weld) | Per test lot |
| Flattening test | Ductility, weld integrity | ASTM A530 / A999; API 5L (EW pipe) | Yes | Yes (critical for ERW/HFW) | Per lot / per coil end |
| Guided bend test | Weld ductility and soundness | API 5L (SAW pipe), ASTM A370 | – | Yes (SAW/EFW) | Per lot |
| Charpy V-notch impact | Toughness at design temperature | ASTM A370 / E23; mandatory for API 5L PSL 2 | PSL 2 / SR | PSL 2 / SR | Per heat / lot |
| Hardness survey | Max hardness of body, weld, HAZ | ISO 15156 (≤ 250 HV10 / 22 HRC typical) | Sour / SR | Sour / SR | Per lot |
| NDT of body and seam | Laminations, seam and surface defects | API 5L Annex E; ASTM E213, E273, E309, E570 | PSL 2 mandatory | Weld seam always | 100 % of lengths |
| Hydrostatic test | Leak tightness, proof of strength | ASTM A530 / A999; API 5L 10.2.6 | Yes | Yes | Every length |
| Visual & dimensional | Surface quality, OD, wall, ovality, straightness, mass | ASTM A530 / A999; API 5L 9.11 | Yes | Yes | Every length / sampling |
| Marking & certification | Traceability to heat and tests | Spec marking clause; EN 10204 3.1/3.2 | Yes | Yes | Every length |
| Fabrication / site inspection (piping codes) | |||||
| Weld visual examination | Weld profile, undercut, surface flaws | ASME B31.3 341.4; B31.1 136.4 | – | – | 100 % of welds |
| Weld RT / UT | Internal weld soundness | B31.3 Table 341.3.2; ASME VIII UW-51 | – | – | 5 % random (normal service) to 100 % |
| System pressure test | Leak tightness of the installed system | B31.3 345; B31.1 137; B31.4 437.4; B31.8 841.3 | – | – | Each test pack / test section |
Chemical & Metallurgical Tests (Product Analysis)
Chemical and metallurgical tests confirm that the steel is what the certificate says it is and that its microstructure suits the service. They are often called micro and macro examinations.
- Heat analysis is reported by the steelmaker from the ladle; product analysis is taken from the finished pipe (two lengths per heat is common) and must fall within the specification limits plus the permitted product-analysis tolerance. Methods follow ASTM A751 (OES or XRF), and the carbon equivalent (CEIIW or CEPcm) is calculated for weldability.
- Macro-etch of a welded-pipe cross section shows fusion, penetration, alignment and the extent of the heat-affected zone (HAZ). ERW/HFW pipe is also checked to confirm the seam has been heat treated so that no untempered martensite remains.
- Micro-examination checks grain size (ASTM E112), banding, inclusions (ASTM E45) and, for stainless steel, delta-ferrite content (ASTM E562 point count or a calibrated ferritescope).
Pipe for corrosive, sour or high-temperature service usually needs additional tests. Use the table to see which ones apply before you write the purchase requisition. To evaluate the process chemistry driving these choices, the Advanced Process & Thermodynamic Suite and Solvent Property & Sizing Calculator can help.
| Test | Test method | Typical materials | Why it is specified | Typical acceptance (check project spec) |
|---|---|---|---|---|
| HIC – hydrogen-induced cracking | NACE TM0284 (96 h, solution A or B) | Carbon / low-alloy line pipe and plate for sour service | Prevents stepwise blister cracking in wet H2S | API 5L Annex H: CLR ≤ 15 %, CTR ≤ 5 %, CSR ≤ 2 % |
| SSC – sulfide stress cracking | NACE TM0177 Method A or four-point bend (ASTM G39) | Sour-service carbon and alloy pipe | Confirms resistance to cracking under tensile stress in H2S | No cracks after 720 h at the specified stress (commonly 72–90 % of SMYS) |
| Hardness survey | ASTM E384 / E92 (HV10 traverse) | Sour-service body, weld and HAZ | High hardness drives SSC susceptibility | ≤ 250 HV10 (≈ 22 HRC) per ISO 15156-2 for most carbon steels |
| IGC – intergranular corrosion | ASTM A262 Practice E (Strauss) or C (Huey) | Austenitic stainless (A312, A358) | Detects sensitisation (chromium carbide at grain boundaries) | No intergranular fissures on bend (Practice E) |
| Ferrite content | ASTM E562 or magnetic ferritescope | Austenitic and duplex stainless, welds | Too little ferrite: hot cracking; too much: embrittlement | Duplex commonly 35–65 % ferrite; austenitic welds per spec (FN range) |
| Grain size | ASTM E112 | Alloy and stainless pipe, boiler tubes | Creep strength and toughness depend on grain size | e.g. ASTM No. 7 or coarser for H grades (A312 TP304H) |
| Pitting corrosion (duplex) | ASTM G48 Method A | Duplex and super-duplex stainless | Verifies correct heat treatment and phase balance | Typically no pitting, weight loss ≤ 4 g/m² at 25–50 °C |
| Macro / micro examination | ASTM E340, E3, E407 | Welded pipe seams, all grades | Fusion, penetration, untempered martensite, inclusions | No lack of fusion, cracks or untempered martensite |
Mechanical (Destructive) Tests
Destructive tests cut coupons from the pipe body (and from the weld for welded pipe) and break them in the laboratory. Test methods follow ASTM A370 unless the product specification says otherwise; API 5L references ISO 6892-1 and ISO 148-1 equivalents. Results are reported per test lot on the MTC, so a single failure normally triggers retests of two further lengths from the same lot before the lot can be rejected.
| Test | Method | What it proves | Typical requirement / acceptance |
|---|---|---|---|
| Tensile (body) | ASTM A370; ISO 6892-1 (API 5L) | Yield, tensile, elongation | ≥ SMYS and SMTS of the grade, e.g. A106 Gr B: YS ≥ 240 MPa (35 ksi), TS ≥ 415 MPa (60 ksi). PSL 2 adds maximum YS/TS and Y/T ≤ 0.93 |
| Transverse weld tensile | ASTM A370; API 5L | Weld strength across the seam | Fracture strength ≥ specified minimum tensile strength |
| Flattening | ASTM A530 / A999; A370 Annex | Ductility of body and ERW/HFW seam | No cracks until distance H between plates is reached (H = (1+e)t / (e + t/D)) |
| Guided bend | API 5L (SAW), ASTM A370 | Soundness of SAW/EFW welds | No crack or opening > 3.2 mm in the weld or HAZ |
| Charpy V-notch | ASTM A370 / E23; ISO 148-1 | Toughness at minimum design temperature | API 5L PSL 2: e.g. ≥ 27 J (avg) at 0 °C for grades up to X52, higher for higher grades; projects often specify −20 to −46 °C |
| DWTT (drop-weight tear) | API RP 5L3 | Fracture arrest in gas pipelines | ≥ 85 % shear area (PSL 2 gas, D ≥ 508 mm) |
| Hardness | ASTM E18 / E10 / E92 | Uniform heat treatment; sour limits | Product spec maxima; ≤ 250 HV10 sour |
| Reverse bend / flare | ASTM A370; A450 (tubes) | Weld and tube ductility | No cracks on the bent / flared surface |
API 5L Line Pipe: PSL 1 vs PSL 2
API Spec 5L (identical in technical content to ISO 3183) defines two Product Specification Levels. PSL 2 is the default for most hydrocarbon transmission, offshore and sour projects because it tightens chemistry, adds toughness and maximum-strength limits and makes NDT and traceability mandatory. Annex H (PSL 2S, sour service) and Annex J (PSL 2O, offshore) add further tests.
| Requirement | PSL 1 | PSL 2 |
|---|---|---|
| Grade range | L175 (A25) to L485 (X70) | L245 (B) to L830 (X120) |
| Carbon (max, seamless) | 0.28 % (grade dependent) | 0.24 % |
| Carbon equivalent | Not specified | CEIIW ≤ 0.43 % or CEPcm ≤ 0.25 % (grade dependent) |
| Max S / P | 0.030 % / 0.030 % | 0.015 % / 0.025 % |
| Yield and tensile strength | Minimum only | Minimum and maximum, plus Y/T ratio ≤ 0.93 |
| Charpy impact | Not required | Mandatory (body, weld and HAZ) |
| DWTT | Not required | Required for gas pipelines D ≥ 508 mm |
| NDT of seamless pipe | Not required (unless SR) | Mandatory full-body (Annex E) |
| NDT of weld seam | Required | Required, full length, with tighter acceptance |
| Weld repair | Permitted on pipe body under conditions | Not permitted on pipe body; restricted on SAW seam |
| Traceability | Heat traceability until tests pass | Heat and test-unit traceability maintained after tests |
| Certification | Inspection document on request | EN 10204 / ISO 10474 3.1 (or as agreed) mandatory |
Non-Destructive Testing (NDT) Methods for Pipe
NDT checks the full length of the pipe without damaging it. At the mill it is automated and in-line; at fabrication it is applied to girth welds, branch connections and bevels. Choose the method by the defect you need to find: volumetric methods (UT, RT) for internal flaws, surface methods (MT, PT, ET) for cracks open to or just below the surface.
| Method | Detects | Where used | Reference standard | Practical notes |
|---|---|---|---|---|
| Ultrasonic testing (UT / PAUT) | Laminations, inclusions, longitudinal and transverse flaws, wall thickness | Seamless body, ERW/HFW and SAW seams, girth welds | API 5L Annex E; ASTM E213, E273, E797; ASME V Art. 4 | Best for planar defects and laminations; PAUT/TOFD often replace RT on site |
| Radiographic testing (RT / DR) | Porosity, slag, lack of penetration, burn-through | SAW seams, pipe ends, girth welds | ASTM E94; ISO 10893-6/-7; ASME V Art. 2 | Film or digital; radiation safety controls required |
| Electromagnetic / eddy current (ET) | Surface and near-surface defects, seam flaws | Small-bore seamless and welded pipe, tubes | ASTM E309, E426, E570; A530 / A999 NDE in lieu of hydro | Fast in-line test; accepted in lieu of hydrotest when specified (“NDE” marking) |
| Flux leakage (MFL) | Pits, wall loss, surface cracks | Seamless carbon steel pipe and OCTG | ASTM E570 | Ferromagnetic materials only |
| Magnetic particle (MT) | Surface and slightly sub-surface cracks | Bevels, ends, carbon steel welds | ASTM E709; ASME V Art. 7 | Ferromagnetic only; wet fluorescent is most sensitive |
| Liquid penetrant (PT) | Surface-breaking cracks and porosity | Stainless and non-magnetic pipe, bevels, welds | ASTM E165; ASME V Art. 6 | Clean, dry surface is essential |
| Visual testing (VT) | Surface finish, weld profile, undercut, dents | All pipe and all welds | ASME V Art. 9; ASME B31.3 344.2 | The first and cheapest method; always done first |
Weld Acceptance Criteria: ASME VIII Div 1 vs ASME B31.3
Weld acceptance depends on the code that governs the item. Pressure vessels follow ASME Section VIII Division 1 (UW-51 for full radiography, Appendix 4 for rounded indications, UW-35 for undercut). Process piping follows ASME B31.3 Table 341.3.2, where limits depend on the fluid service category. The comparison below uses B31.3 Normal Fluid Service girth welds; Category M and severe cyclic conditions are stricter. For vessel thickness checks, see the ASME VIII Pressure Vessel Calculator.
| Imperfection | ASME VIII Div 1 (full RT, UW-51 / App. 4 / UW-35) | ASME B31.3 Table 341.3.2 – Normal Fluid Service girth weld |
|---|---|---|
| Cracks | Not permitted | Not permitted |
| Lack of fusion | Not permitted | Not permitted |
| Incomplete penetration | Not permitted | Depth ≤ lesser of 1 mm and 0.2Tw; cumulative length ≤ 38 mm in any 150 mm of weld |
| Elongated indications (slag) | Length ≤ 6 mm for t ≤ 19 mm; ≤ t/3 for 19 < t ≤ 57 mm; ≤ 19 mm for t > 57 mm. Aligned groups: total length ≤ t in 12t (unless spaced > 6L) | Individual length ≤ Tw/3; width ≤ lesser of 2.5 mm and Tw/3; cumulative length ≤ Tw in any 12Tw |
| Rounded indications (porosity) | Max size ≤ lesser of t/4 and 4 mm; isolated indication (≥ 25 mm from next) ≤ lesser of t/3 and 6 mm (10 mm for t > 50 mm); distribution per Appendix 4 charts | Per BPVC VIII Div 1 Appendix 4 for Tw ≤ 6 mm; 1.5 × those values for Tw > 6 mm |
| Undercut | ≤ lesser of 0.8 mm (1/32 in) and 10 % of nominal thickness (UW-35) | ≤ lesser of 1 mm and Tw/4 |
| Surface porosity / exposed slag | Not permitted on finished surface | Not permitted for Tw ≤ 5 mm |
| Weld reinforcement (each side) | Per UW-35(d) table, increasing with thickness (circumferential joints allowed more than longitudinal) | ≤ 1.5 mm (Tw ≤ 6), 3 mm (≤ 13), 4 mm (≤ 25), 5 mm (> 25) |
| Concave root / internal protrusion | Total joint thickness ≥ t | Total joint thickness incl. reinforcement ≥ Tw |
Hydrostatic Test Pressure & Hold Times
The hydrostatic test fills the pipe with water, expels all air and raises the pressure to a value that proves strength and leak tightness. Two different tests are often confused: the mill hydrotest of each length (a proof test lasting seconds) and the system pressure test of the installed piping or pipeline (minutes to hours). Both are required; one does not replace the other.
- P = hydrostatic test pressure, psi or MPa
- S = fibre stress = test factor × SMYS (ASTM A106 via A530: 60 % SMYS; API 5L: 60–90 % SMYS depending on grade and size)
- t = specified wall thickness, in or mm
- D = specified outside diameter, in or mm
Worked example – ASTM A106 Grade B, NPS 6 Sch 40
D = 168.3 mm (6.625 in), t = 7.11 mm (0.280 in), SMYS = 240 MPa (35,000 psi), S = 0.60 × 240 = 144 MPa.
P = 2 × 144 × 7.11 / 168.3 = 12.2 MPa (≈ 1,775 psi). ASTM A106 caps mill test pressure at 2,500 psi for NPS 3 and smaller and 2,800 psi for larger sizes, so 1,775 psi applies.
| Code / standard | Application | Test pressure (typical) | Minimum hold time |
|---|---|---|---|
| Mill test (each length) | |||
| ASTM A530 / A106, A999 / A312 | Carbon, alloy and stainless pipe | P = 2St/D (A106: S = 60 % SMYS; caps per spec) | ≥ 5 seconds |
| API Spec 5L | Line pipe | P = 2St/D, S = 60–90 % SMYS by grade and size | ≥ 5 s (seamless; welded D ≤ 457 mm); ≥ 10 s (welded D > 457 mm) |
| System / field test | |||
| ASME B31.3 | Process piping | 1.5 × design pressure × ST/S (not to exceed yield) | ≥ 10 min, then examine all joints |
| ASME B31.1 | Power piping | 1.5 × design pressure (not to exceed 90 % yield) | ≥ 10 min, then examine at ≥ design pressure |
| ASME VIII Div 1 (UG-99) | Pressure vessels | 1.3 × MAWP × stress ratio | No fixed duration; inspect at ≥ test pressure / 1.3 |
| ASME B31.4 | Liquid pipelines | ≥ 1.25 × internal design pressure | ≥ 4 h; plus 4 h at 1.1 × design for sections not visually inspected |
| ASME B31.8 | Gas transmission pipelines | Factor by location class (e.g. 1.25–1.5 × MAOP) | ≥ 2 h strength test (US 49 CFR 192.507: 8 h for lines ≥ 30 % SMYS) |
| DNV-ST-F101 | Offshore / subsea pipelines | Typically 1.05 × incidental pressure (system test) | Holding period typically ≥ 8 h (many operators specify 24 h) |
Hydrostatic Test Pressure Calculator (P = 2St/D)
Because hydrotest volumes and fill times drive temporary-pump selection, estimate them with the Vessel Volume & Calibration Calculator, and confirm overpressure protection for the test with the Relief Valve Suite (API 520/521).
Visual Inspection & Surface Defect Acceptance
Visual inspection is the first line of defence and is carried out on the outside surface of every length and, as far as practical, the inside surface. Inspectors look for laps, seams, slivers, laminations at the bevel, scabs, gouges, dents, arc burns, hard spots and, on welded pipe, weld-seam off-set, trim and reinforcement. ASTM A530 and A999 treat surface imperfections deeper than 12.5 % of nominal wall as defects; they may be removed by grinding provided the remaining wall is not below the specified minimum. API 5L adds specific limits, for example dents deeper than 6.4 mm (or with sharp-bottom gouges) are rejectable and arc burns are defects.
Site teams tracking these checks on punch lists can use the Field Safety & Construction Utility Suite.
Dimensional, Straightness & Mass Tolerances
Dimensional inspection ensures fit-up with fittings, flanges and adjacent spools. Nominal dimensions come from ASME B36.10M (carbon and alloy) and B36.19M (stainless); permitted variations come from the general-requirements specification (A530, A999) or API 5L. See our pipe dimensions chart for nominal OD and wall values.
| NPS | ASTM A106 (A530) | ASTM A53 | ASTM A312 (A999) |
|---|---|---|---|
| ⅛ to 1½ | +0.4 / −0.4 mm (±1/64 in) | ±0.4 mm | +0.4 / −0.8 mm |
| Over 1½ to 4 | ±0.8 mm (±1/32 in) | ±1 % | ±0.8 mm |
| Over 4 to 8 | +1.6 / −0.8 mm | ±1 % | +1.6 / −0.8 mm |
| Over 8 to 18 | +2.4 / −0.8 mm | ±1 % | +2.4 / −0.8 mm |
| Over 18 to 26 | +3.2 / −0.8 mm | ±1 % | +3.2 / −0.8 mm |
| Over 26 to 34 | +4.0 / −0.8 mm | ±1 % | +4.0 / −0.8 mm |
| Over 34 to 48 | +4.8 / −0.8 mm | ±1 % | +4.8 / −0.8 mm |
| Characteristic | ASTM A106 / A53 | ASTM A312 | API 5L |
|---|---|---|---|
| Wall thickness | Minimum wall ≥ 87.5 % of nominal (−12.5 %) | Minimum wall ≥ 87.5 % of nominal | Seamless: +15 / −12.5 % (typical); welded: ±10 % or as table |
| Mass (weight) | A106: +10 % / −3.5 % (NPS ≤ 12); A53: ±10 % | Not specified unless ordered | Single length +10 % / −3.5 % |
| Length | Single random 4.8–6.7 m; double random ≥ 6.7 m (avg 10.7 m) | Per order (typically 6 m random) | Per order; e.g. 12 m nominal with min/avg limits |
| Straightness | “Reasonably straight” (projects often specify ≤ 0.2 % of length) | Welded: ≤ 3.2 mm in 3 m (1/8 in in 10 ft); finished pipe reasonably straight | Total ≤ 0.2 % of length; local ≤ 3.2 mm in 1 m at each end |
| Ovality (out-of-roundness) | Within OD tolerance | Thin-wall pipe: ≤ 1.5 % of OD (A999) | Pipe ends: ≤ 0.015 D (D/t ≤ 75) – see Table 10 |
| Ends | Plain end; when bevelled: 30° +5/−0°, root face 1.6 ± 0.8 mm | Plain or bevelled per order | Bevel 30° +5/−0°, root face 1.6 ± 0.8 mm |
Pipe Marking, MTC & Traceability
Once a length has passed every test it is marked so that it can be traced back to its heat, test lot and certificate for its whole life. Paint stencilling (or ink-jet) is the default. Die stamping, where the specification permits it, must use low-stress (round-nosed or dot) dies and is commonly prohibited on thin-wall pipe and on most stainless and sour-service pipe because sharp stamps create stress raisers. Pipe that has been tested by NDE instead of a hydrotest is marked “NDE”, and pipe supplied without a hydrotest is marked “NH”.
| Marking element | Example | Purpose |
|---|---|---|
| Manufacturer name or mark | MILL-LOGO | Identifies the producing mill |
| Specification & grade | ASTM A106 Gr B / API 5L X42 PSL2 | Confirms material standard; dual certification shown together |
| Size and schedule or wall | 8 in Sch 40 or 219.1 × 8.18 mm | Confirms dimensions to ASME B36.10M / B36.19M |
| Product type | SMLS, ERW, HFW, SAWL, SAWH | Identifies manufacturing route and weld joint factor |
| Heat number | HT 6A0447 | Links the length to its chemistry and mechanical test results on the MTC |
| Length | L 11.80 m | Stock control and take-off |
| Hydrotest pressure / NDE / NH | HYDRO 1500 PSI, NDE or NH | Shows how the length was proof-tested |
| Supplementary marks | S1, S7, NACE, PSL2S, cold-service | Shows extra requirements met |
| Colour code (if specified) | Stripe per owner spec | Rapid material identification in the stockyard; see pipe colour codes |
Pipe Packing & Handling
Good pipe can be ruined between the mill and the site. Bevel protectors or end caps keep bevels and threads clean; small-bore pipe is bundled with steel or polyester strapping and timber spacers; large-diameter thin-wall pipe receives internal spiders to hold circularity. Coated pipe is lifted with wide nylon slings or padded end hooks, never chains, and stacked on sand-bag or timber sleepers with stopper blocks. Stainless pipe is kept apart from carbon steel to avoid iron contamination.
Supplementary Requirements
Supplementary requirements (SRs) are optional tests that apply only when the purchaser names them in the order. They are a cost-effective way to buy extra assurance only where the service needs it, for example S7 internal cleanliness or HF acid alkylation requirements on ASTM A106. See also our ASTM A53 pipe guide and pipe materials guide.
| ASTM A106 (carbon steel) | ASTM A312 (stainless steel) |
|---|---|
| Product analysis | Product analysis |
| Transverse tension test | Transverse tension test |
| Flattening test, standard or enhanced | Flattening test and etching tests |
| Metal structure and etching test | Radiographic examination of welded pipe |
| Carbon equivalent restrictions | Stabilising heat treatment (Ti / Nb grades) |
| Heat-treated test specimens | Intergranular corrosion test (ASTM A262) |
| Internal cleanliness (government orders) | Weld decay test |
| Requirements for HF acid alkylation service | Minimum wall pipe |
Receiving Inspection Checklist (Site / Warehouse)
Use this checklist when pipe arrives on site. It is printable with the rest of the page.
- Packing list, PO and MTC match: specification, grade, size, schedule, quantity and heat numbers.
- MTC is the required type (EN 10204 3.1 or 3.2), signed, and results meet the specification (chemistry, CE, tensile, impact, hardness, hydro/NDE).
- Stencil on every length is legible and matches the MTC; heat number is transferred before any cutting.
- End caps and bevel protectors are present; bevels free of dents, laminations and corrosion.
- No dents, gouges, arc burns, coating damage, or mixing of stainless with carbon steel.
- Spot-check OD (circumference tape), wall (UT gauge at four quadrants), ovality and straightness against the tolerance tables above.
- PMI (positive material identification) of alloy and stainless pipe where the project requires it.
- Record nonconformances, quarantine and tag rejected lengths, and update the material traceability register.
Frequently Asked Questions
What is pipe inspection?
Pipe inspection is the set of chemical, mechanical, non-destructive, hydrostatic, visual and dimensional checks that prove each length of pipe meets its material specification (ASTM, ASME or API) before dispatch, followed by fabrication examination and pressure testing of the installed system under codes such as ASME B31.3.
How do you calculate hydrostatic test pressure for pipe?
Use P = 2St/D, where S is the fibre stress (a percentage of SMYS, 60 percent for ASTM A106 and 60 to 90 percent for API 5L), t is the specified wall thickness and D is the specified outside diameter. For A106 Grade B NPS 6 Sch 40 this gives about 12.2 MPa (1,775 psi).
How long must a hydrostatic test be held?
A mill hydrotest under ASTM A530 or API 5L is held for at least 5 seconds (10 seconds for API 5L welded pipe over 457 mm OD). An ASME B31.3 or B31.1 system test is held for at least 10 minutes, ASME B31.4 pipelines for at least 4 hours, and gas pipelines under US DOT rules typically for 8 hours.
What is the difference between API 5L PSL 1 and PSL 2?
PSL 2 adds mandatory Charpy impact testing, maximum yield and tensile strength limits, carbon equivalent limits, lower sulfur and phosphorus, mandatory NDT of seamless pipe and full traceability. PSL 1 is a basic quality level without these requirements.
What does NH or NDE mean in pipe marking?
NH means the pipe was not hydrostatically tested. NDE means a non-destructive electric test (eddy current, ultrasonic or flux leakage) was performed in lieu of the hydrotest, which ASTM A530 and A999 permit when allowed by the product specification or purchaser.
What is the wall thickness tolerance for ASTM A106 pipe?
The minimum wall thickness at any point must not be more than 12.5 percent below the nominal wall, so the minimum wall is 87.5 percent of nominal. There is no specific plus tolerance on wall, but mass is limited to plus 10 percent.
Which NDT method is best for pipe?
Ultrasonic testing is the most widely used method for pipe body laminations and weld seams. Radiography is used for SAW seams and girth welds, eddy current for small-bore pipe and tubes, and magnetic particle or penetrant testing for bevels and surface cracks.
What is an EN 10204 3.1 certificate?
It is a mill test certificate issued by the manufacturer and validated by its own authorised inspection representative, independent of production, stating the actual test results for the delivered heat and lot. A 3.2 certificate is additionally verified by the purchaser or a third-party inspector.
Test Your Knowledge: Pipe Inspection & Testing Quiz
1. According to ASTM A530, which formula is used to calculate mill hydrostatic test pressure?
2. What is the minimum hold time for an ASME B31.3 hydrostatic leak test?
3. Which requirement is mandatory for API 5L PSL 2 but not PSL 1?
4. Under ASME VIII Div 1 UW-35, what is the maximum undercut?
5. What does the marking “NDE” on ASTM pipe indicate?
6. What is the minimum wall for ASTM A106 pipe with 10.0 mm nominal wall?
7. Which test detects sensitisation in austenitic stainless pipe?
8. HIC testing for sour-service line pipe is carried out to which standard?
Conclusion
Reliable piping starts with disciplined inspection: verify chemistry and mechanical properties on the MTC, confirm NDT and the mill hydrotest, check dimensions against the right tolerance table, and keep heat-number traceability from stockyard to test pack. Specify PSL 2, Annex H or supplementary requirements only where the service needs them, and never treat the mill hydrotest as a substitute for the code-required system pressure test.
Written by Muhammad Raza
Founder of Aienginear. Engineering and digital solutions professional with 26+ years managing projects, plant shutdowns and turnarounds in oil & gas, petrochemical and power generation.
