As per api 598, zero drops means no visible leakage per minimum specified test duration for liquid test and zero bubbles means less than one bubble per minimum specified test duration for gas test. Leakage allowed is limited to 5 x 104 ml per minute per inch of orifice diameter per psi differential. Technical bulletin valve seat leakage standards and. For metal seated valves, allowable leakage rate values are taken from api 598. For zero leakage metal seated valves api 6d or api 598 soft seated zero leakage criteria can be specified such as triple offset metal seated butterfly valves and some metal seated ball valves. Class i is an agreed upon leakage rate between the customer and the vendor. Blockandbleed valve 2valve manifold models iv20 and iv21.
Technical bulletin valve seat leakage standards and related. Most industrial valves, such as our high performance butterfly valve, flanged ball valves, cast steel valves, etc. It may leak as little as a few molecules of hydrogen a year to several gallons of fluid per minute. Permissible leak rate from atmosphere to jacket in case of. No visually detectable leakage for the duration of the test.
Leak rate ml per minute leak rate bubbles minute 3 76 0. Api 598 covers the inspection, examination, and testing requirements for resilientseated, nonmetallicseated, and metaltometalseated gate, glove. A full copy of api 527, with complete testing procedures and specifications, can be purchased from the american petroleum institute. Shaft speed 24 000 rpm was monitored by a magnetic pickup. For metalseated valves the maximum allowable leakage rate is half that of the standard procedure, while for softseated valves it remains the same i.
Share this page bubbles per minute as tabulated are a suggested alternative based on a suitable calibrated measuring device, in this case a 0. Api598en122661 seat leak free download as pdf file. Ansi fci 702 is for internal testing only and refers users to api 598 for testing isolation valves. Api 527 specifies procedures for testing with air or nitrogen, steam, and water. After these constants, the remaining test parameters of packing material, test temperature, and test pressure are dependent on the valve design and intended use. No test required provided user and supplier so agree. Leakage was measured by a wettest gas flowmeter, and the torque was continuously recorded on magnetic tape. The purpose of establishing a leak rate specification is to define the maximum. This standard is extremely common when a floating ball valve is specified. On the other hand, api 598 details both seat leakage tests and hydrotests along with other tests. Ob obtuator ti tightness h t test l leakage k r rate 1 2 rate b. Unbalanced, single port, lapped metal seats, high seat load. Nov 01, 2011 today, most valve manufacturers strive for and achieve a zero closure test leakage rate during initial factory testing of their metal seated gate and globe valves.
Technical bulletin gate valve installations and leakage. Api 624 leak measurement packing leakage measurements around the full circumference of the stem od and packing od and the highest reading is recorded. Api598 is not specific to control valves and there is no mention of classwise segregation of valves and the corresponding allowable leakage rates. A premium valve manufacturer specifies always leak rate a highest level. Leakage of valves testing api 598, ansi fci 702, msssp61. Tests api 598, valve inspection and testing iso 5208, pressure testing of metallic valves with leakage rate a mss sp61, pressure testing of valves material requirements nace mr0175 iso 15156, use in h. Any other type valve designed to meet resilient seat leakage rates as speci. Oct 28, 2014 api 527 covers seat tightness testing of metal and softseated pressure relief valves, including conventional, bellows, and pilotoperated designs. There are two things that the test standards have in. It contains charts that identify the working pressures used in conjunction with other test standards, such as api 598. For standard valves, you prove the tight shut off acc.
Iso 5208 pressure testing of valves leakage valvias. Scontaining environments in oil and gas production norsok m630, specificaiton for. Testing procedures required for establishing rating. Api 598 is not specific to control valves and there is no mention of classwise segregation of valves and the corresponding allowable leakage rates. Offshore metaltometal seated, trunnion type riser valve 24 nps to api 598. Comparison of leakage rates between api standard 598 and api specification 6d iso 143. Class d leakage rate equivalent to class c where the accumulation bagging method is specified the vacuum method is. Qualification requirements api 591 this standard is a quality qualification whereas the others are performance qualifications. The standard is currently in the 9th edition, which was released in 2009.
Control valve and regulator section notes that fci 702 has been intended to apply to control valve seat leakage. Special notes api publications necessarily address problems of a general nature. Valve is factory tested per api 598 then based on a suggested sized a quantity is disassembled. Measurement of starting torque and leakage provided a relative gage of lip contact force. The test medium for determining the seat tightnessair. For gas test, o bubble means less than 1 bubble per minimum specified test duration. For check valves larger than nps 24, the allowable leakage rate shall be per agreement between purchaser and manufacturer. This test is optional depending on size, class and type but is carried out for standard. In actual fact even for metal seat valves the api 598 leak acceptance criteria for metal seated valves allows less leakage than fci 702 class. The valve size less or equal 2 inch the test duration will be 15 seconds, between 2 12 and 6 inch 60 seconds, between 8 and 12 inch 120 seconds and above 14 inch will be 300 seconds. In both cases, seat leakage tests are performed on factory new valves with the stem vertical and the maximum handwheel torque applied, with measurable leakage allowed at the test pressures involved.
Api 6d and api 598 both call for a tight shut off if the valve is soft seated, the leakage rate differs between the specifications when you move to metal seat designs. America seat leakage guide page 2 aug 28, 2009 guide to api 598 eighth. All valves built to the various api standards are required to meet api 598 leakage criteria prior to shipment from the. The rr calculation includes the likelihood and amounts of. Today, most valve manufacturers strive for and achieve a zero closure test leakage rate during initial factory testing of their metal seated gate and globe valves. Misconceptions regarding control and isolation valve standards. Special provisions for zero leakage gate valves can also be specified to bs 6755 now en 122661 and iso 5208 under special zero leakage classes. Api standard 598 supplements the api standards that. For zero leakage metal seated valves, api 6d iso 5208 rate a or api 598 soft seated zero leakage criteria can be specified such as triple offset metal seated butterfly. Leakage rate lr when testing with liquid lr x dn cc min m i maximum allowable all bl leak l k rates r t for f closure cl tests t t. In fact even for metal seat valves the api 598 leak acceptance criteria for metal seated valves excluding check valves allows less leakage than fci 702 isas75. If greater seat tightness is required, the purchaser shall specify it in the purchase order. Leakage rates the tests are carried out as per tables 1 to 4 on previous page. Valve leakage classifications contractors unlimited.
Qualification standards on performance type testing for. The first principle that must be understood is that all materials permit some leakage through them over a period of time. Api std 598 valve inspection and testing, tenth edition. There are two things that the test standards have in common. No packing adjustment during type testing is permitted. Leaks through the pressure retaining parts are not permitted, except through the temporary joints. Api 598 is an isolation valve test for seat leakage and body shell testing that requires the valve to pass both a highpressure test at 110% of maximum cold working pressure and a low pressure test. Api std 598 supplements the api standards that reference it, but it may also be applied to other types of valves by agreement between the purchaser and the valve manufacturer. Control valve seat leakage classifications ansi fci 702 superseding ansi b16. In the following it is seen that the conditions for tests are quite similar for the two leakage test standards as the high pressure liquid test will. Api 6d makes reference to iso 5208, but in practice api 6d valves are often in europe specified with allowable leakage rates as per en 122661. The api std 598 provides the allowable amount of leakage in table 6, and it is measured based on drops per minutes. This valve will require a leakage rate a according to en 122661. Oct, 2014 api standard 598, from the american petroleum institute, provides industry standards for valve ratings and valve leakage.
If line isolation andor absolute tight shutoff is a normal expectation of the valve application, the fci control valve and regulator sections recommend specifying another standard, such as api 598, valve test and inspection. American petroleum institute api 598, valve inspection and test. This means, that there is no visible leakage during a defined testing period. Standards for acceptable rates of valve leakage there are many standards for classification of valve leakage rates e. Leak measurements are sniffed using a detection probe. Balanced, single port, polytetrafluoroethylene ptfe piston rings, soft seats, low seat load. Valve leakage classifications this page on control valve leakage is an excerpt from the original and is reproduced courtesy of control and types of valve leakage there are two types of leakage from a valve, namely. Ansi fci 702 is for internal testing only and refers users to api598 for testing isolation valves. Seat tightness of pressure relief valves api standard 527. It has acceptable leakage rates for liquid as well as gas testing.
Din en 917 covers thermoplastics valves, bs 6364 covers cryogenic valves, however the three standards used most in the oil and gas, and petrochemical industry are api 598, ansi fci 702 and msssp61. Consistent performance for industries that demand reliability. It has six different leakage levels from class i up to class vi. However, the predominant valve testing standard, api 598, valve inspection and test, does have allowable leakage rates for these types of valves in sizes above nps 2.
For a softseated valve, there shall be no leakage for one minute 0 bubblemin. The steel valves are designed and built in accordance with american petroleum institute api 600, and tested per the applicable sections of api 598. In actual fact even for metal seat valves the api 598 leak acceptance criteria for metal seated valves allows less leakage than fci 702 class vi above 150nb 6 and 50nb 2 and under. There are many standards for classification of valve leakage rates e.
Especially for the oil and gas market, the most important ones are api 6a, api 6d and api 598. This is the most widely used test specification in the world. In above example, the valve shall be tested at 6880. Valve inspection and testing, covers the testing and inspection requirements for gate, globe, check, ball, plug and butterfly valves. Fci 702 only requires a low pressure test, consequently closure and seat tests should also be done per api 598 or mss sp61. The api 598 lowpressure seat closure test can be performed on any size valve. On the other hand, api598 details both seat leakage tests and hydrotests along with other tests. V alve testing standards msssp61 ansi fci 702 every valve testing standard has an acceptable leakage rate. For a valve with a metal seat, the leakage rate in bubbles per minute shall not exceed the appropriate value in table 1. Material is examined per table 1 stemdrive train is. Leakage of valves testing api 598, ansi fci 702, msssp. These are normally tested per mss sp61 pressure testing of steel valves. The maximum acceptable leakage rates are defined for pressure relief valves with set pressures from 103 kpa gauge 15 psig to 41,379 kpa gauge 6000 psig. Valve inspection and testing global ihs ihs markit.
The amount of leakage also depends on the valve size. Api std 598 supplements the api standards that reference it, but it may. The following tables detail for each valve seat leakage class the allowable leakage rate, and the seat leakage test procedure. Static and dynamic stem leakage measurements are be taken. Fci 702 only requires a low pressure test, consequently closure and seat tests should also be done per api 598 iso 5208 leakage acceptance rates or mss. Long term leakage rate performance is dependent on the valve and application. Api 598 does incorporate a zero leakage requirement for soft seated valves used in. Every valve testing standard has an acceptable leakage rate. Oct 01, 2016 api std 598 valve inspection and testing, tenth edition on. Seat tightness of pressure relief valves api ballots.
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