At the valve seat leakage test (also called closure test), one side (valve inlet) shall be subjected to the test pressure and amount of leak shall be measured on the opposite side of the valve.
The seat leakage of control valve is the quantity of test fluid passing through an assembled valve in the closed position.
Timing of seat tests
Usually the valve seat leakage test is to be performed after successful completion of valve shell test.
Table: Standards and specification of valve seat test
| Standard/ Specification | Titel | Scope/Application |
|---|---|---|
| ISO 5208 | Industrial valves – Pressure testing of metallic valves | ISO 5208 specifies valve closure tests of an industrial metallic valve to verify the degree of valve closure tightness. ISO 5208 is listed as a reference in the following valve product standards such as ASME B16.34, API SPEC 6D, ISO 13942. Valve Type: – Gate valves – Globe valves – Plug valve – Check valve – Floating ball valve – Diaphragm Valve – Butterfly valve – Trunnion mounted valve The test fluid shall be a liquid and/or gas. Acceptance criteria: ISO 5208 contains 10 leakage rate classes. Read More ISO 5208: Valve seat leakage rate |
| EN 12266-1 | Industrial valves – Testing of metallic valves – Part 1: Pressure tests, test procedures and acceptance criteria – Mandatory requirements | The test (P12) shall confirm the capability of the seat(s) to conform to the specified leakage rate in the direction(s) for which the valve is designed. The test fluid shall be a liquid or gas. The test pressure shall be a minimum of 1,1 times the allowable differential pressure at room temperature. If the test fluid is a gas, the test pressure may be the lower of 1,1 times the allowable differential pressure at room temperature or (6 ± 1) bar for valves : -sizes up to DN 80 for all pressure ratings ; -sizes above DN 80 and up to DN 200 for pressure ratings up to PN 40 and up to Class 300. Valve Type: – Gate valve – Ball valve – Globe valves – Plug valve – Diaphragm valve – Butterfly valve – Check valve Acceptance criteria: The leakage rates shall not exceed the rate specified in the corresponding product standard. Leakage rates A to G are given for each liquid and gas test fluid and will be calculated with a factor multiplied by DN. |
| EN 13942 | Petroleum and natural gas industries – Pipeline transportation systems – Pipeline valves | Hydro test pressure for all seat tests shall not be less than 1,1 times the pressure rating determined in accordance in EN 1092-1 (PN) or ASME B16.34 (Class) for material at 38 °C. Valve Type: – Gate valve – Ball valve – Plug valve – Check valve Acceptance criteria: Leakage for soft-seated valves and lubricated plug valves shall not exceed not exceed ISO 5802 Rate A. For metal-seated valves the leakage rate shall not exceed ISO 5208 Rate D, except that the leakage rate during the seat test in Clause B.4 (high-pressure seat test by using an inert gas) the test shall not be more than two times ISO 5208, Rate D, unless otherwise specified. |
| API STD 598 | Valve Inspection and Testing | Low and/or high pressure closure tests depending the size/class and optional order request. The maximum allowable leakage rates are specified for liquid tests (ml/min or drops/min) and gas tests (ml/min or bubble/min) depending the valve size. Valve Type: – Gate valve 1, 2 – Globe valve 1, 2 – Parallel slide gate valve 1, 2 – Plug valve 1, 2 – check valve 1, 2, – floating ball valve 1, 2 – Butterfly valve 1,3 – Trunnion mounted valve 1, 2 1) Low pressure closure test at 5.5 bar (80 psi) 2) High pressure closure test at 110 % of maximum allowable pressure at 38 °C (100 °F); not valid for check valves with casting materials) 3) 110 % of design differential pressure at 38 °C (100 °F) |
| API SPEC 6D | Specification for Pipeline and Piping Valve | Valve Seat Test with acceptance criteria (leakage rate) agreed in accordance with the order, as specified in ISO 5208: 1. The test pressure for all hydrostatic seat tests shall not be less than 1.1 times the pressure rating at 100 °F (38°C): a) Soft seated valve: Rate A b) Lubricated plug valve: Rate A c) Metal-seated valve (except check valve): Rate D d) Metal-seated check valve: Rate G 2. High-pressure Gas Seat Test (may be performed in lieu of the hydrostatic seat test by agreement) by the minimum test pressure shall be 1.1 times the pressure rating for the material at 100 °F (38°C): a) Soft seated valve: Rate A b) Lubricated plug valve: Rate A c) Metal-seated valve (except check valve): Two times Rate D d) Metal-seated check valve: Rate EE Valve type: – Ball valve, – Check valve, – Gate valve, – Plug valve. Read More ISO 5208: Valve seat leakage rate |
| ANSI/FCI 70-2 (IEC 60534-4) | Control Valve Seat Leakage | The seat leakage of control valve is the quantity of test fluid passing through an assembled valve in the closed position under the test conditions as defined. The acceptance criteria (Leakage Class) defined the maximum allowable seat leakage as specified for each class (Class I to VI): – Designed intend the same as the basic class II, III or IV; by agreement; without test (Class I) – Percent rated valve capacity (Class II to IV) or – ml per minute of water per inch of seat diameter per psi differential pressure (Class V) or – ml per minute of air per inch of seat diameter (Class V) or – ml per minute value depending a list depending nominal seat diameter (Class VI) Control valve type: – single seat control valve – double seat control valve – balanced single seat control valves with a piston ring seal and metal-to-metal seat – balanced single seat control valves with extra tight piston rings or other sealing means and metal-to-metal seat – resilient seating control valve with unbalanced and balanced single-seat with O-ring |
| ASME B16.34 | Valves — Flanged, Threaded, and Welding End | Valve Closure Test with acceptance criteria (leakage rate) agreed in accordance with the order, as specified in ISO 5208 or API STD 598. Valve type: – All shut-off valve – Stop valve – Check valve The test pressure shall be not less than 110% of the 38°C (100°F) pressure rating except that, at the manufacturer’s option, a gas closure test at gauge pressure not less than 5.5 bar (80 psi) may be substituted for valve sizes and pressure classes as follows: NPS ≤ 4 (Pressure Class ≤ 2500) and NPS ≤ 12 (Pressure Class ≤ 300). The standard fluid is water. Read More ISO 5208: Valve seat leakage rate |
| ISO 17292 | Metal ball valves for petroleum, petrochemical and allied industries | For valve designs having resilient seats, the closure tightness test shall be a gas test with the test gas at a pressure between 400 kPa (4 bar) and 700 kPa (7 bar). For valve designs having metal or ceramic seats, the closure tightness test shall be a liquid test with the test fluid at a pressure not less than 1,1 times the rated pressure at 38 °C (100 °F). Valve type (size range DN ≤ 600): – Floating ball valve – Trunnion-mounted valve |
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