Manual Valve API 623 VS ASME B16.34

[johnthebest]

We are on the go of a central processing facility project.

our contractor claims that in order to match the CV of the conrol valves (as per ASME B16.34) and the manual globe valves (as per API 623) (which serves as a by-pass of the control valves and will be operated only in case of maintenance of the control valve), both valves shall be procured from the same vendor.

the control valves are already procured. however, when they want to procure the manual valves from the same vendor, they came with these deviations (see attached file).

Is it true that in order to get the same CV you have to buy manual and control valves from the same vendor? if yes, what are your thoughts about the deviations.
Thx in advanve

 

[gerhardl]

Hi,

Valves are normally supplied with a measured and certified Cv, either from direct measurement from an identical valve, or on exception calculated from the nearest dimension of an equal valve.

A certified Cv will be a certified Cv.

Bypass stop valves will seldom be critical if near or equal to the regulating Cv. There is however a but. If the stopvalves are supposed to work as throttling by-pass vales, the valves must be constructed for the actual flow, pressure and throttling application. This is much more essential then supply from a single producer, or also as the described types (globealves?).

The (material and test) deviations are a completely separate issue. Producing and testing standards will very often deviate if the selected supplier/factory uses another system than an earlier used factory.

The answer will be a combination from of how easy/cheap the correct standards will be supplied from original/other sources, and the end users willingness to change. Advice is to avoid change if it is not obvious reasons to do so.