Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Butterfly Valve Seat Pressure Testing

Status
Not open for further replies.

dynamics2004

Mechanical
Jan 12, 2013
6

hello,

i am new to the valves engineering market and i am trying my best to check for different matters pertaining to this field.

within my reading of API-598 i noticed that the seat test for the butterfly valves (API-609 Category A) can be performed from only one side though its not marked (arrow indicated), here for the bi-directional valves how can be sure that we tested the correct side where the flow is creating the most/severer conditions which is the up-stream side?

can you please advise

thanking for your answers

 
Replies continue below

Recommended for you


I am not familiar with the API tests in detail, but:

For new valves, this should be no problem (already tested, drawings/instructions from supplier, tests already described and done, normal seat testing above maximum allowable line pressure, but below body/shell test, quality valves tested both ways at equal pressure, quality valves with arrow indicating preferred flow direction).

Line testing? Correctly mounted valves?

If older valves, or valves taken out of line, and geometry (seating and disc) are completly symmetric (no differences in sealing edges either): test one way and mark, or preferably both ways, use described tests from API.

Note: any 360 degree BFL should be limited mechanically (gear or handle) to 180 deg (or some few degrees more).

What is yoor exact problem?

 
Hello,

API-598 is written so that Category A type valves with concentric liners only need to be tested in one direction. These are the standard rubber lined butterfly valves where test pressure direction makes no difference. You can do the low pressure test in either direction and the valve is OK as long as it passes. You do not need a flow direction arrow on this type of valve because they are symmetric.

If the buttefly valve has an offset seat, then the pressure direction affects the seat loading so you must test in both directions unless the valve is marked with a flow direction.
 

thanks bcd for your reply and as gerhard i will over-say its short, direct and super! just to validate my understanding for the situation that these valve will experience the same load on both sides in which it wont make any difference if only one side is tested but what if we tested one valve on both sides and succeed from one side and leaked from the another one in your opinion what is the reason/s behinds such?

would you please advise?

Thanking for your cooperation


 

Such a valve has only two states, good or bad. There is no such thing as 'half good' or 'half bad'. By ethical standard logic: any series of tests on a product where the product can be given the approval by disregarding one or more test(s) in a series is both a risk and a swindle.

(Note: some quality approval tests describes renewed tests if the first falls below a given value. Same here, if you have to disregard disregard test(s) to reach a valid range of tests)

By failing one side the valve have to be inspected for foreign elements, damages (hairline cracks) in sealing surfaces or else), cleaned, repaired if necessary and tested again, both sides.

 
Exactly as gerhardl says. The valve should pass leak testing in both directions even though the standard only requires one direction. The purpose of testing is a quality check. If all the parts are good, and the valve is assembled correctly, then you only need to test in one direction to verify the quality is OK. If the valve is not passing in both directions, then I would carefully look at the design and the test method. Is the seat deforming during the test so that when pressurized in the opposite direction, it allows leakage? Is the disc and or shaft bending? Is there residual water or trapped air pressure that is leaking out when testing in the opposite direction? These are some of the common reasons why a butterfly valve will leak when pressure tested in both directions.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor