Choke valve test 1

[Ali F.]

Does anyone know why choke valves (specifically adjustable choke valve) does not have a seat test?According to the standard api 6a, Table 30 of the 2018 edition, only the body test is defined for them. (Api 6a-2018,Section 14.15.4 refers to Section 11, which sets the test priority according to Table 30).Please guide me in this case.

 

[LittleInch]

Because they are designed to control not seal.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Ali F.]

Thx for your tips.
1. That is, it never closes completely? Even in the adjustable type that 'removable seat' has?
2. So my conclusion from the standard(api 6a) is correct that it only has a body test(hydrostatic test)?

 

[SPDL310]

As LI has stated by definition chokes are not shutoff devices. It depends on the design but most manufactures will set the 0 position of the trim at slightly above the seated position, particularly in actuated valves. In a manually operated choke if you turn the handwheel far enough the trim will reach the seated position, though you will probably still see some flow. There are no 6A testing requirements for a positive shutoff in chokes. Some choke designs are capable of a positive shutoff and the manufacture can provide a seat test upon request. That being said there is no guarantee that the shutoff capability will persist once it has been put into service.

 

[Ali F.]

Thanks to SPDL310 for their guidance. The oil operator in our company emphasizes the repair of some choke valves due to passing leaks in the workshop. Arguing that they are ultimately VALVE emphasizes that they should be tested. My source was api 6a. And to some extent I agreed. I have worked with 598 and other specific valve standards but it was very interesting to me that according to 6a only body(and drift) test is mandatory..I searched a lot but did not find a standard that made seat test mandatory.

 

[jbeckhou]

See API 6A Performance requirements (PR)table 57
This includes H2 (adjustable and positive)style chokes. Fluid is not allowed to pass thru the seat to body seal area on any choke per API 6A /16C

Petrotrim Services, LLC

http://www.petrotrim.com

 

[jmec87]

Does anyone know why choke valves (specifically adjustable choke valve) does not have a seat test?

As others have noted, this is because chokes are for controlling the flow and not for shutoff.
API 6A 21st Edition no longer refers to "choke valves" but only to "chokes" to reduce the false perception that chokes are intended to be shut-off valves.

See API 6A Performance requirements (PR)table 57
This includes H2 (adjustable and positive)style chokes. Fluid is not allowed to pass thru the seat to body seal area on any choke per API 6A /16C

Note that the seat-to-body seal is not the same as a seat test for a valve - the seat to body seal does not prevent flow through the seat, but only around the seat. Furthermore, this is a performance requirement (which should be validated) but not a production test required on every choke.

 

[Ali F.]

jbeckhou & jmec87 thank you for your tips.