VALVE TEST STANDARDS
COMMON VALVE TYPES & RELATED TEST STANDARDS
*ISO 5208 (EN 12266-1) supersedes BS 6755.
Main Valve Test Standards
API 598 Valve Inspection and Test
The most widely used test specifi cation in the world. The standard covers all types of valves (soft & metal seated)
in sizes up to 600NB (NPS 24). It also includes leakage rates and testing criteria for metal-seated and resilient-
seated valves. Also mirrored by ISO 5208 Test standard.
API6D Pipeline Valves Test Standard
Used for API 6D ball valves, plug valves and API 6D design pipeline check/gate valves (also now adopted as part
of ISO 14313). ISO 5208 leakage rate tables are often referred in conjunction with API 6D tests.
ISO 14313 (Section II) Valve Test Standard
Mirrors API 6D above.
ISO 5208 Valve Test Standard
Incorporates an adoption of API 598 test standard. In addition, ISO 5208 includes leakage rate tables. Example -
Leakage rate A is specifi ed for soft seated valves and plug valves (zero leakage*). ISO 5208 includes standards for
gate, globe and check valves (EN 122661-1).
BS 6755 Valve Test Standard
Previously used by some European Manufacturers, now superseded by ISO 5208 (EN 12266-1) standard. It
includes leakage rates and testing criteria for metal and resilient seated valves.
ASME B16.34 Valves - Flanged, Threaded and Welding End
The primary valve design standard, it also contains pressure/temperature charts for determining the working
pressures of valves to be used in conjunction with other test standards, such as API 598.
ASME PTC 25 Pressure Relief Devices
The main reference document for the testing of pressure relief valves, PTC 25 contains detailed procedures for
testing relief valves with air or steam.
API 527 Seat Tightness of Pressure Relief Valves
This covers the seat tightness of pressure relief valves. It also includes allowable leakage rates for testing with
steam, water and air.
FCI 70-2* Control Valve Seat Leakage
This document contains detailed test procedures and leakage rate classes for control valves. The leakage classes
are also occasionally referenced by other documents and used as acceptance criteria. Supersedes ANSI B16.104.
Class VI is the highest shut off class*.
ISA S75 Hydrostatic Testing of Control Valves
This standard provides a procedure for the hydrostatic shell testing of control valves. Seat testing and acceptance
criteria are out of the scope of this document and usually are covered by referencing FCI 70-2.
ISO 5208 Industrial Valves, Pressure Testing of Valves
ISO’s primary testing standard, this document covers all types of valves and has four levels of allowable closure
test leakage rates.
MSS SP70 Cast Iron Gate Valves, Flanged and Threaded Ends
The primary design standard for cast iron gate valves, it also contains testing procedures and acceptance criteria.
MSS SP71 Iron Swing Check Valves, Flanged and Threaded Ends
The primary design standard for cast iron check valves also contains testing procedures and acceptance criteria.
MSS SP61* Hydrostatic Testing of Steel Valves
Similar to API 598 (in the case of soft seated valves) this document has some minor variations in test holding times
and leakage rates. Metal seated valves the leakage can be a little higher than API598.
MSS SP78 Cast Iron Plug Valves, Flanged and Threaded Ends
The primary design standard for cast iron plug valves also contains testing procedures and acceptance criteria.
MSS SP80, Bronze Gate, Globe, Angle and Check Valves
The primary design standard for commodity bronze valves also contains testing procedures and acceptance criteria.
MSS SP85, Cast Iron Globe & Angle Valves
The primary design standard for cast iron globe valves also contains testing procedures and acceptance criteria.
* See next page “Explanation of Zero and Low Leakage Test Standards”.
EXPLANATION OF ZERO AND LOW LEAKAGE TEST STANDARDS
In general, specifi cation such as API598 or MSS SP-61 that govern leakage for soft seated valves call for ‘0’
bubbles of air or ‘0’ drops of water under the specifi ed test conditions over the minimum test time period. These
valves are therefore sometimes referred to as ‘zero leakage’ valves. In reality, there really is no such thing as ‘zero
leakage’, since microscopic amounts of material may indeed cross the seat or packing boundaries, especially if
helium or hydrogen or other small molecule gases are used. Another common term for soft seated valves is ‘bubble
tight’.
Less frequently, the leakage performance for soft seated valves is referred to as Class VI, which is the tightest
leakage under FCI 70-2, and generally applies to resilient seated control valves (as opposed to metal seated
control valves or soft seated shut off valves). In fact, FCI 70-2 Class VI (formerly ANSI B16.104) allows a small
number of bubbles per minute, increasing with valve size, during the test, whereas API598 and MSS SP-61 do not
(for soft seat, but does for metal seat). FCI 70-2 Class VI is for soft seated control valves but is frequently used as
a leakage acceptance test criteria for metal seated isolation valves such as ball and butterfl y valves. FCI 70-2 only
requires a low pressure test, consequently closure and seat tests should also be done per API 598 or MSS SP-61.
In actual fact even for metal seat valves the API 598 leak acceptance criteria for metal seated valves allows less
leakage than FCI 70-2 Class VI above 150NB (6”) and 50NB (2”) and under. For zero leakage metal seated valves
API 6D or API 598 soft seated zero leakage criteria can be specifi ed (such as triple offset metal seated butterfl y
valves and some metal seated ball valves). Special provisions for zero leakage gate valves can also be specified
to BS 6755 and ISO 5208 under special zero leakage classes. Metal seated valves, on the other hand, usually (not
always, triple offset butterfl y and ball valves for instance are available bubble tight) have some level of acceptable
leakage when tested, defi ned fi rst as some acceptable amount of liquid, under test conditions and over the time
period of the test.
ISO 5208 (EN 12266-1) supersedes BS 6755-1 and specifies acceptable leakage rates such as Rate A and Rate
B. Rate A allows ‘no visible leakage’, similar to API 598 for resilient seated valves. Rate B is used for gate valves.
| Valve type | Common test standard |
| Steel ball, gate, globe and check valves | API 598 |
| Steel ball, gate, globe and check valves | BS 6755*, ISO 5208 (EN 12266-1) |
| Cast Iron gate valves | API 598, MSS SP-70 |
| Bronze gate, globe and check valves | MSS SP-80 |
| Steel gate, globe and check valves larger than NPS 24” | ASME B16.34 |
| Pressure seal gate, globe and check valves | ASME B16.34 |
| Pipeline valves | API 6D, ISO 5208 |
| Cast iron checks | API 598, MSS SP-71 |
| Cast iron globes | API 598, MSS SP-85 |
| Cast iron plugs | API 598, MSS SP-78 |
| Steel ball valves | API 598 |
| Steel butterfly valves | API 598 |
| Cryogenic valves | API 598, BS 6364 |
| Control valves | FCI 70-2, ISA-S75, |
| Pressure relief valves | API 527, ASME PTC 25 |
Main Valve Test Standards
API 598 Valve Inspection and Test
The most widely used test specifi cation in the world. The standard covers all types of valves (soft & metal seated)
in sizes up to 600NB (NPS 24). It also includes leakage rates and testing criteria for metal-seated and resilient-
seated valves. Also mirrored by ISO 5208 Test standard.
API6D Pipeline Valves Test Standard
Used for API 6D ball valves, plug valves and API 6D design pipeline check/gate valves (also now adopted as part
of ISO 14313). ISO 5208 leakage rate tables are often referred in conjunction with API 6D tests.
ISO 14313 (Section II) Valve Test Standard
Mirrors API 6D above.
ISO 5208 Valve Test Standard
Incorporates an adoption of API 598 test standard. In addition, ISO 5208 includes leakage rate tables. Example -
Leakage rate A is specifi ed for soft seated valves and plug valves (zero leakage*). ISO 5208 includes standards for
gate, globe and check valves (EN 122661-1).
BS 6755 Valve Test Standard
Previously used by some European Manufacturers, now superseded by ISO 5208 (EN 12266-1) standard. It
includes leakage rates and testing criteria for metal and resilient seated valves.
ASME B16.34 Valves - Flanged, Threaded and Welding End
The primary valve design standard, it also contains pressure/temperature charts for determining the working
pressures of valves to be used in conjunction with other test standards, such as API 598.
ASME PTC 25 Pressure Relief Devices
The main reference document for the testing of pressure relief valves, PTC 25 contains detailed procedures for
testing relief valves with air or steam.
API 527 Seat Tightness of Pressure Relief Valves
This covers the seat tightness of pressure relief valves. It also includes allowable leakage rates for testing with
steam, water and air.
FCI 70-2* Control Valve Seat Leakage
This document contains detailed test procedures and leakage rate classes for control valves. The leakage classes
are also occasionally referenced by other documents and used as acceptance criteria. Supersedes ANSI B16.104.
Class VI is the highest shut off class*.
ISA S75 Hydrostatic Testing of Control Valves
This standard provides a procedure for the hydrostatic shell testing of control valves. Seat testing and acceptance
criteria are out of the scope of this document and usually are covered by referencing FCI 70-2.
ISO 5208 Industrial Valves, Pressure Testing of Valves
ISO’s primary testing standard, this document covers all types of valves and has four levels of allowable closure
test leakage rates.
MSS SP70 Cast Iron Gate Valves, Flanged and Threaded Ends
The primary design standard for cast iron gate valves, it also contains testing procedures and acceptance criteria.
MSS SP71 Iron Swing Check Valves, Flanged and Threaded Ends
The primary design standard for cast iron check valves also contains testing procedures and acceptance criteria.
MSS SP61* Hydrostatic Testing of Steel Valves
Similar to API 598 (in the case of soft seated valves) this document has some minor variations in test holding times
and leakage rates. Metal seated valves the leakage can be a little higher than API598.
MSS SP78 Cast Iron Plug Valves, Flanged and Threaded Ends
The primary design standard for cast iron plug valves also contains testing procedures and acceptance criteria.
MSS SP80, Bronze Gate, Globe, Angle and Check Valves
The primary design standard for commodity bronze valves also contains testing procedures and acceptance criteria.
MSS SP85, Cast Iron Globe & Angle Valves
The primary design standard for cast iron globe valves also contains testing procedures and acceptance criteria.
* See next page “Explanation of Zero and Low Leakage Test Standards”.
EXPLANATION OF ZERO AND LOW LEAKAGE TEST STANDARDS
In general, specifi cation such as API598 or MSS SP-61 that govern leakage for soft seated valves call for ‘0’
bubbles of air or ‘0’ drops of water under the specifi ed test conditions over the minimum test time period. These
valves are therefore sometimes referred to as ‘zero leakage’ valves. In reality, there really is no such thing as ‘zero
leakage’, since microscopic amounts of material may indeed cross the seat or packing boundaries, especially if
helium or hydrogen or other small molecule gases are used. Another common term for soft seated valves is ‘bubble
tight’.
Less frequently, the leakage performance for soft seated valves is referred to as Class VI, which is the tightest
leakage under FCI 70-2, and generally applies to resilient seated control valves (as opposed to metal seated
control valves or soft seated shut off valves). In fact, FCI 70-2 Class VI (formerly ANSI B16.104) allows a small
number of bubbles per minute, increasing with valve size, during the test, whereas API598 and MSS SP-61 do not
(for soft seat, but does for metal seat). FCI 70-2 Class VI is for soft seated control valves but is frequently used as
a leakage acceptance test criteria for metal seated isolation valves such as ball and butterfl y valves. FCI 70-2 only
requires a low pressure test, consequently closure and seat tests should also be done per API 598 or MSS SP-61.
In actual fact even for metal seat valves the API 598 leak acceptance criteria for metal seated valves allows less
leakage than FCI 70-2 Class VI above 150NB (6”) and 50NB (2”) and under. For zero leakage metal seated valves
API 6D or API 598 soft seated zero leakage criteria can be specifi ed (such as triple offset metal seated butterfl y
valves and some metal seated ball valves). Special provisions for zero leakage gate valves can also be specified
to BS 6755 and ISO 5208 under special zero leakage classes. Metal seated valves, on the other hand, usually (not
always, triple offset butterfl y and ball valves for instance are available bubble tight) have some level of acceptable
leakage when tested, defi ned fi rst as some acceptable amount of liquid, under test conditions and over the time
period of the test.
ISO 5208 (EN 12266-1) supersedes BS 6755-1 and specifies acceptable leakage rates such as Rate A and Rate
B. Rate A allows ‘no visible leakage’, similar to API 598 for resilient seated valves. Rate B is used for gate valves.
