Control Valve Minimum Pressure Rating

[Steve010]

Apart from companies'/owners' standards, is their any technical reason (valve cracking, mechanical integrity ..... etc.) or any obligatory code or standard that prohibits the use of control valve rating 150# for raised face flanged control valves (Globe Style) smaller than 2 inches in oil and gas applications?

 

[MickMc]

Steve010,

The pipe schedule in small bore piping is normally specified for mechanical protection and coversely above the calculated thickness as per your example in Class 150. You would also specify the corrosion allowance in your valve data sheet/description and if this in the unlikely event then exceeded the minimum thickness as per ASME B16.34 the manufacturer would have to add additional thickness. The minimum Class 300 control valve is irrelevant in this context and a quick search on google will give plenty examples of Class 150 control valves.

http://www.flowserve.com/files/

http://www/Literature/ProductLiterature/FlowControl/Valtek/VLENTB0060.pdf

 

[Steve010]

Vendors do not include corrosion allowances in their manufacturing process. They manufacture valves with fixed thicknesses. Due to their standard machining processes, what i know is that they will never add more thickness. I asked masoneilan and they confirmed that valve thickness is standard according to the valve size and rating.
Does this mean that corrosion allowance may require increasing the rating? Especially in small valve sizes due to low valve thickness?

 

[BigInch]

No. Ask for the appropriate trim to resist corrosion.

 

[Steve010]

The trim is 316 ss so it will resist corrosion, but the body is cs like the pipe. Trim does not require corrosion allowance but valve body may require. Loosing thickness from the body by time will derate the valve. What is your opinion?

 

[BigInch]

You won't be able to get extra wall on a valve.
Chances are that it will be thicker than the pipe. Check the dimensions.

If the body corrodes, I'd just replace it.

 

[MortenA]

I would also refrian from using less than 2" piping, mainly because of a concern wrt operators stepping on the pipig, and less than 2" dosnt have sufficient strength - and the savings from going down in size is insignificant?