On/off valves leakage class standard

[aidini]

Ansi FCI 70-2 covers leakage test and classes for control valves, what would you choose for on/off valves leakage standard?
API 598, ISO 5208 or another standard?
Since API 598 does not have a classification chart like FCI 70-2, how is it possible to write the required leakage class when preparing data sheets?

[prajule]

All above referred standards used for leakage class requirement based on their metal seat or soft seat type On/Off valves.
Please check with your end user for preferred standard that to be followed for this project.
Refer individual standard for Tables to specific max. allowable closure test leakage rate/leakage class.

[prajule]

All above referred standards used for leakage class requirement based on their metal seat or soft seat type On/Off valves.
Please check with your end user for preferred standard that to be followed for this project.
Refer individual standard for Tables to specific max. allowable closure test leakage rate/leakage class.

[aidini]

Prajule,
Since we are the consulting company of the project, it is our responsibility to define the appropriate standard.

[aidini]

Prajule,
Since we are the consulting company of the project, it is our responsibility to define the appropriate standard.

[prajule]

Ok.

For most of case , process demands the tight shut off on/off valve then go as per ANSI FCI leakage class. Based on ur process condition go ahead as per ANSI standard and most of client accept the same.

I suggest u to discuss this with ur subvendor for more clarity and understanding point of view.

[prajule]

Ok.

For most of case , process demands the tight shut off on/off valve then go as per ANSI FCI leakage class. Based on ur process condition go ahead as per ANSI standard and most of client accept the same.

I suggest u to discuss this with ur subvendor for more clarity and understanding point of view.

[aidini]

FCI 70-2 :

The standard was revised in 2003 to add the option to permit low pressure gas testing to
determine Class V leakage. During the canvass of the 2003 version, one respondent asked for
the standard to be modified to specifically exclude on/off valves used for tight shut-off. The FCI
Control Valve and Regulator Section notes that FCI 70-2 has been intended to apply to control
valve seat leakage. If line isolation and/or absolute tight shut-off 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.”

So, FCI seems not to be the correct reference standard for on/off valves.

[prajule]

Though FCI exclude the on/off , but the procedure provided in FCI is generally used to test the on/off leakage class and also approved by most clients/consultants.Else client specify the standards that to be followed for same in bid document. So once any i suggest check with your end user.

If u are more concern on same then i suggest refer API 6D tight shut off guidelines.

[prajule]

Though FCI exclude the on/off , but the procedure provided in FCI is generally used to test the on/off leakage class and also approved by most clients/consultants.Else client specify the standards that to be followed for same in bid document. So once any i suggest check with your end user.

If u are more concern on same then i suggest refer API 6D tight shut off guidelines.

[aidini]

But the permissible leakage rates are not equal between FCI and API 598/ISO 5208.

[prajule]

The three most commonly used for valve leakage are:

API (American Petroleum Institute) 598 – this document covers valves of all types, metal and soft seated, and is the industrial valve seat leakage baseline.
FCI (Fluid Controls Institute) 70-2 (also called ANSI/FCI 70-2) – this document is specifically for control valves, and in general allows higher leakage as a result.
MSS (Manufacturer’s Standardization Society) SP-61 – this document is similar to API 598 in that it applies to metal and soft seated valves. For soft seated valves, it converges with API 598, while for metal seated valves it may allow a little more leakage than API 598 would.

In general, specifications such as API 598 or MSS SP-61 that govern leakage for soft seated valves call for ‘0’ bubbles of air or ‘0’ drops of water under the specified 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 allows some small number of bubbles per minute, increasing with valve size, during the test, whereas API 598 and MSS SP-61 do not.

Metal seated valves, on the other hand, usually (not always) have some level of acceptable leakage when tested, defined first as some acceptable amount of liquid, under test conditions and over the time period of the test. Gas is an alternate test media for metal seated valves, as liquid can be easier to measure, especially for larger valves.