In This Article
- 1.API 598 - The Primary Valve Test Standard
- 2.Leakage Classes - API 598 vs ISO 5208 vs FCI 70-2
- 3.Third-Party Witness Inspection
- 4.Documentation Package
Factory Acceptance Testing (FAT) is the final manufacturing quality gate before a valve is shipped to site. Unlike dimensional inspection or material verification, FAT proves that the assembled valve actually seals to the required leakage class under the specified test pressure. Missing, forged, or inadequate FAT certificates are a common source of valve rejection at project pre-commissioning.
API 598 - The Primary Valve Test Standard
API 598 (Valve Inspection and Testing) is the most widely cited valve test standard in the oil and gas and process industries. API 598 defines three test types: (1) Shell Test (hydrostatic): Test pressure = 1.5 times rated pressure (per ASME B16.34 at 100°F); Test fluid: water (cleanliness test for food/pharma); Duration: 15 seconds minimum for DN15-DN50; 60 seconds for DN65-DN150; 120 seconds for DN200 and above; Acceptance: no visible leakage. (2) Seat Test - Liquid: Test pressure = 1.1 times rated pressure; Duration same as shell test; Acceptance: leakage not to exceed the leak class specified (Class IV, V, or VI); Classes defined in API 598 Table 3: Class IV (metal seat) = 0.1 mL/min per inch of nominal pipe size; Class VI (soft seat) = zero bubbles for most sizes.
Leakage Classes - API 598 vs ISO 5208 vs FCI 70-2
| Standard | Leakage Class | Maximum Leakage |
|---|---|---|
| API 598 | Class IV (metal seat) | 0.1 mL/min per DN-inch |
| API 598 | Class VI (soft seat) | 0-0.45 mL/min by size (Table 3) |
| ISO 5208 | Rate A | No visible leakage |
| ISO 5208 | Rate B | 0.006 × DN drops/min |
| ISO 5208 | Rate D | 0.6 × DN drops/min |
| FCI 70-2 | Class IV | 0.01% of rated Cv |
| FCI 70-2 | Class VI | Bubble-tight (bubbles per min by size) |
Third-Party Witness Inspection
For critical service valves (ESD, SIL-rated, high-pressure Class 1500+, sour service), buyers typically specify third-party witness inspection at the manufacturer. Approved inspection agencies: Bureau Veritas, Lloyd's Register, SGS, Intertek, TÜV Rheinland, TÜV SÜD. The witness inspector reviews: manufacturing procedure specification (MPS) compliance; material test certificates (EN 10204 3.1 or 3.2) traceability; dimensional inspection report; API 598 test procedure and witnessed performance; final documentation package before release.
Documentation Package
A complete FAT documentation package should include: API 598 test certificate (serial number, valve size/class/material, test date, test pressures, test fluid, results, inspector signature and stamp); Material Test Certificates (EN 10204 3.1 for body, bonnet, ball/disc, stem; EN 10204 3.2 for critical service); Dimensional inspection report (face-to-face, bore, flange bolt circle, flange OD per ASME B16.5 or EN 1092-1); PMI (Positive Material Identification) report by handheld XRF gun for all stainless, duplex, and alloy steel valves; Hardness test report (Brinell or Rockwell) for NACE service; Fire test certificate (API 607 or ISO 10497) for fire-safe valves; Functional test report for actuated valves (actuator open/close cycle, torque measurement, limit switch calibration); Third-party inspection release note (if applicable).
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