Valve leakage class and rate for ball valve, gate, globe, check valve, butterfly, and plug valves according to the latest international standards ISO 5208, API 598, EN 12266-1, and ANSI/FCI 70-2 for all grades: A, AA, A, B, C, CC, D, E, EE, F, G, and the rate A.
ISO 5208 specifies examinations and tests that a valve manufacturer needs to act upon in order to establish the integrity of the pressure boundary of an industrial metallic valve and to verify the degree of valve closure tightness and the structural adequacy of its closure mechanism.
There are 10 leakage rates specified in ISO 5208: A, AA, A, B, C, CC, D, E, EE, F, G and the rate A is the highest grades.
ISO 5208 Maximum allowable closure test leakage rate
|Test fluid||Unit leakage rates||Rate A||Rate AA||Rate B||Rate C||Rate CC||Rate D||Rate E||Rate EE||Rate F||Rate G|
NOTE 1 No visually detect- able leakage for the duration of the test.
NOTE 2 The leakage rates only apply when discharging test fluid to the atmosphere.
NOTE 3 The closure leakage rate that applies is either that identified in a valve product standard or a leakage rate identified in a purchaser’s valve procurement purchase order that is more stringent than that specified in the product standard.
NOTE 4 For the definition of visually detectable leakage see 2.12.
NOTE 5 There is a correspondence between the leakage rate acceptance values of API 598 and the leakage values Rate A as applied to DN≤50, Rate AA-Gas and Rate CC-Liquid for other than metal seated check valves and for check valves Rate EE-Gas and Rate G-Liquid. Rates A, B, C, D E, F and G correspond to values in EN 12266–1.
API 598 is the most commonly used test standard for American standard valves. It is applicable to the following API standard valve sealing performance tests:
API 6D - Axial, ball valve, check valve, gate, plug valves for application in the petroleum and natural gas industries
API 594 - Flanged, lug, wafer and butt weld connection check valves
API 599 - Flanged, threaded and butt-welded metal plug valves
API 602 - Steel gate valve and check valves DN 100 and below for the oil and natural gas industry
API 603 - Flanged and butt-welded corrosion-resistant bolted cover gate valves
API 608 - Flanged, threaded and butt-welded metal ball valves
API 609 - Double flanged, lug and wafer butterfly valves
API 598 Maximum Allowable Leakage Rates for Closure Tests c
|Valve Size||All Resilient
|Metal Seated Valves
Except Check Valves
|Metal Seated Check Valves|
|DN (mm)||NPS (inch)||Liquid Test a (drops/min)||Gas Test a (bubbles/min)||Liquid Test (cc/min)||Gas Test (m3/h)||Gas Test (ft3/h)|
|≤ 50||≤ 2||0||0b||0b||6||0.08||3|
- a - For the liquid test, 1 mL is considered equivalent to 16 drops. For the gas test 1 mL is considered equivalent to 100 bubbles.
- b - There shall be no leakage for the minimum specified test duration (see Table 4). For liquid test, 0 drops means no visible leakage per minimum specified test duration. For standard gas test, 0 bubbles means less than 1 bubble per minimum specified test duration. For high-pressure pneumatic closure test refer to paragraph 5.4.
- c - Leakage rates for sizes above DN 1200 (NPS 48) shall be calculated by the following formulas: Liquid Test for Metal Seated Valves except Check: 2 x NPS (drops/min) Gas Test for Metal Seated Valves except Check: 4 x NPS (bubbles/min) Liquid Test for Metal Seated Check Valves: 3 x NPS (cc/min) Gas Test for Metal Seated Check Valves: 0.042 x NPS (m3/h) Gas Test for Metal Seated Check Valves: 1.5 x NPS (ft3/h)
- Refer to ISO 5208 leakage rate.
EN 12266-1 Standard specifies requirements for tests, test procedures, and acceptance criteria for production testing of industrial valves made of metallic materials.
EN 12266-1, Tests on Industrial Valve Part l, specifies the pressure tests, test methods, and acceptance criteria—mandatory requirements. EN 12266-1 meets the requirements of ISO 5208 for seal classification but lacks AA, CC, and EE ratings. The new edition of ISO 5208 adds six levels of AA, CC, E, EE, F, and G and gives comparisons with several seal levels of API 598 and EN 12266.
EN 12266-1 Maximum allowable seat leakage for each leakage rate
|Test fluid||Rate A||Rate B||Rate C||Rate D||Rate E||Rate F||Rate G|
|Liquid||No visually detectable
leakage for the duration of the test
|0.01 x DN||0.03 x DN||0.1 x DN||0.3 x DN||1.0 x DN||2.0 x DN|
|Gas||0.3 x DN||3.0 x DN||30 x DN||300 x DN||3000 x DN||6000 x DN|
NOTE 1: The leakage rates only apply when discharging to room temperature.
NOTE 2: Table A.1 shall be used to establish the equivalent DN number for those valves which are designated other than by DN.
NOTE 3: "No visually detectable leakage" means no visible weeping or information of drops or bubbles. If leakage rate measurements are carried out by automatic means, this should be qualified by the manufacturer's quality system.
ANSI/FCI 70-2 (ASME B16.104) is applicable to the control valve seal grade requirements. A metal-elastic seal or metal seal should be selected in engineering design according to the characteristics of the medium and the opening frequency of the valve. Metal-seated valve seal grades should be stipulated in the order contract; rates I, II, and is used less due to requests for a lower level; generally, choose IV at least and V or VI for higher requirements.
ANSI/FCI 70-2 Leakage Rates Class VI (EN 60534-4)
|Nominal Port Diameter
(ml Per Minute)
(Bubbles Per Minute)
Bubbles per minute is a suggested alternative to ml per minute; in which a 0.25 inch OD x 0.032 inch wall tube is submerged in water to a depth of 1/8” to 1/4”. The tube is to be cut square and smooth with no imperfections and should be perpendicular to the surface of the water.