Control Valve Minimum Pressure Rating
Control Valve Minimum Pressure Rating
(OP)
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?





RE: Control Valve Minimum Pressure Rating
If you're going to double post - http://www.eng-tips.com/viewthread.cfm?qid=386167 at least reference the previous one in your post.
did you not like the answers you got in that post?
Codes and standards are not normally in the business of prohibiting one size of something that is allowed in a different size.
AFAK there is no technical or code reason behind this, simply economics and practicality
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Control Valve Minimum Pressure Rating
what do you mean by practicality ? I found that most vendors manufacture them (so it seams that nothing inhibits their use).
I am concerned if there may be any mechanical concern on control valves (globe valves) with small sizes, like cracking or mechanical integrity ... etc. in fuel gas applications.
The valve is already present with a flange and body rating 150# (size 1 inch) but i am thinking to bring another one (with 300#) because of the sentence i find in most owner companies' specifications " control valves with sizes below 2" should have a minimum rating of 300#"
Have you ever used one?
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
I have seen that most companies standards alow the use of control valves' with sizes not smaller than 1".
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
isn't the rating determined solely by the design pressure and temperature ?
What is the relation between size and rating and such service ?
RE: Control Valve Minimum Pressure Rating
While RPs are fine as general guides, I do not think following their recommendations are mandatory in all circumstances.
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
I know how to calculate the cooling effect from depress. Using the jt effect. But how can i decide whether vibrations are going to happen or not ?
RE: Control Valve Minimum Pressure Rating
This might help,
http://turbolab.tamu.edu/proc/turboproc/T19/T19119...
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
Although the Piping Spec stipulates globe valves at Class 150 & Class 800 these are manual valves and control valves are usually by Instrument Group and if Class 300 selected Piping will provide Class 300 flanges to mate. There have been previous posts on this topic of minimum Class 300 control valves and the general consensus I believe is that there is no technical reason just manufacturers preference.
RE: Control Valve Minimum Pressure Rating
For Small valve sizes, the body wall thickness is small unlike larger valve sizes. For example as per ASME B16.34 the minimum body wall thickness for 1" valve with rating 150# is 3.9 mm.
Maybe the minimum rating of 300# is specified for small valve sizes is to cover this issue. Any idea ?
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
This means that the pipe wall thickness is greater than the valve body thickness ???
RE: Control Valve Minimum Pressure Rating
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/www/Literature/Prod...
RE: Control Valve Minimum Pressure Rating
Does this mean that corrosion allowance may require increasing the rating? Especially in small valve sizes due to low valve thickness?
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
RE: Control Valve Minimum Pressure Rating
Chances are that it will be thicker than the pipe. Check the dimensions.
If the body corrodes, I'd just replace it.
RE: Control Valve Minimum Pressure Rating