Check valve differences

[curlyjackme]

I need some clarification help on wafer check valves.

I speced some short pattern wafer check valves for a job and the purchasing agent bought regular wafer check valves and when they realized those were wrong they bought a wafer style swing check valve and now I am getting questioned because I did not specify a manufactor or model number. My question is not the short pattern wafer check valve a distinctive style or am I wrong?

 

[eadwine]

Wafer style check valves are a breed unto themselves and manufacturer. On specials, it's alwyas best to spec. a manufacturer and model number. Then you can get into the "or approved equal" clause. Don't ever expect Purchasing to get the right thing when a generic descriptor is used.

 

[rneill]

There are a number of different styles of wafer check valves and it would be best to clearly indicate the specific style of wafer valve you were looking for. For example, you can get wafer single plate (swing) check valves or wafer dual plate check valves. Myself, I would specify the specific type I was looking for an then list API 594 as the applicable standard to which the valve was required to comply.

API 594 defines Type "A" check valves as being "short face to face" and Type "B" check valves as being "long face to face". Tables of dimensions for Type A are provided in 594 and for Type B, reference is made to the ASME B16.10 standard valve dimensions.

API 594 does go on to say that Short pattern are not permitted except by agreement between the purchaser and the manufacturer.

Anyway, if you specified "short" pattern then the valve should have meet the short pattern dimensions of API 594. If the valve purchased by your purchasing department meet these dimensions then the supplier complied with the PO. If you wanted something that was shorter than the defined "short face to face" specified in API 594, then you would be going to a manufacturer specific custom valve dimension and you would really need to specify a specific make and model of valve.