In This Article
- 1.API 598 — Valve Inspection and Testing
- 2.API 598 Seat Leakage — Permissible Drop vs No Drop
- 3.ISO 5208 Leakage Rate Classes
- 4.EN 12266 — European Valve Testing Standard
- 5.Test Certificate Requirements
Factory Acceptance Testing (FAT) of industrial valves is the final quality gate before shipment. Every industrial valve shipped from Vajra Industrial Solutions' supply chain undergoes hydrostatic pressure testing per the applicable standard — API 598 for most industrial valves, ISO 5208 for international projects, or EN 12266 for EU/PED projects. Understanding the test procedures helps procurement engineers, project engineers, and inspection teams verify valve quality and interpret test certificates.
API 598 — Valve Inspection and Testing
API 598 (Valve Inspection and Testing) is the most widely specified valve testing standard worldwide, covering shell (body) pressure tests, seat tightness tests, and backseat tests for gate, globe, plug, ball, butterfly, and check valves. API 598 is referenced by API 600 (gate valves), API 6D (pipeline valves), API 609 (butterfly valves), and most other API valve design standards as the default FAT standard.
| Test Type | Test Pressure | Test Duration (DN ≤ 50) | Test Duration (DN > 50) | Acceptance Criterion |
|---|---|---|---|---|
| Shell (body/bonnet) hydrostatic | 1.5× rated pressure at 20°C | 15 seconds | 30–60 seconds (size-dependent) | No visible leakage from body/bonnet |
| Low-pressure seat (closure test) | 80 psi (5.5 bar) water or 60–100 psi air/N2 | 15 seconds | 30 seconds | See Table 2 (size & seat-type dependent) |
| High-pressure seat (closure test) | Rated pressure (1.1× rated for API) | 15 seconds | 30–60 seconds (size-dependent) | See Table 2 — drops for soft seat = 0 |
| Backseat test (where applicable) | 1.1× rated pressure | 15 seconds | 30 seconds | No visible leakage through packing area |
API 598 Seat Leakage — Permissible Drop vs No Drop
API 598 Table 1 defines seat leakage allowances by valve type, size, and seat material: Soft-seated valves (PTFE, elastomer, or polymer seat contact): zero allowable leakage for both low-pressure and high-pressure seat tests (0 drops for liquid test, 0 bubbles for gas test); Metal-seated valves (metal-to-metal seat contact): allowable measured leakage per Table 1 of API 598, which permits a small number of drops per minute depending on valve size (larger valves allow more drops). Example: DN50 metal-seated gate valve: 1 drop/minute; DN300 metal-seated gate valve: 6 drops/minute; DN600 metal-seated ball valve: 12 drops/minute. Zero drops mandatory for all API 598 tests on soft-seated valves regardless of size.
ISO 5208 Leakage Rate Classes
ISO 5208 (Industrial Valves — Pressure Testing of Metallic Valves) uses a leakage Rate system: Rate A — no visible leakage (equivalent to zero drops/bubbles); Rate B — 0.006 × DN drops per minute (very low; typically required for gas service); Rate C — 0.06 × DN drops per minute (low leakage, general service); Rate D — 0.6 × DN drops per minute (standard metal seat); Rate E — 6 × DN drops per minute (high; for coarse metal seats only); Rate F — 60 × DN drops per minute (highest; not often specified in practice). Rate A is mandatory for gas service valves, toxic service, and all soft-seat designs. Rates D-F are only acceptable for metal-seated valves in general liquid service.
EN 12266 — European Valve Testing Standard
EN 12266 (Parts 1 and 2) is the EU equivalent of API 598/ISO 5208, required for PED 2014/68/EU compliance in European projects. Part 1 covers standard pressure tests; Part 2 covers supplementary tests (high/low temperature seat tests, fugitive emission tests). EN 12266 uses the same Rate A through F leakage classification as ISO 5208. For PED Category II, III, and IV valves, the manufacturer must hold an EU Declaration of Conformity and the FAT test certificate must reference EN 12266. Third-party witness testing by a Notified Body (TÜV, Bureau Veritas, Lloyd's Register) may be required for high-risk applications.
Test Certificate Requirements
A complete API 598 / ISO 5208 / EN 12266 Factory Acceptance Test certificate should contain: Valve identification (tag number, serial number, size, class, material, end connection type); Purchase order number and customer name; Test standard referenced (API 598 6th Ed., ISO 5208:2015, EN 12266-1); Shell test pressure, test fluid (water or N2), test duration, result (pass/fail); Seat test pressure (low-pressure and/or high-pressure), test fluid, leakage observed (drops or bubbles per minute), acceptance criterion, result; Backseat test result (where applicable); Test date, test technician signature, QC manager countersignature; For third-party witnessed tests: inspector name, witnessing company, inspector's certificate number.
Request Valves with API 598 FAT Certs
API 6D certified. Ships worldwide. 24-hour quote response.
Need industrial valves for your project?
API 6D, ASME B16.34 certified. 120+ cities served. 24-hour quote response.