reduction of diameter before preure control valve

[lomli]

hi,

we have to install a pressure control valve of 10" with its tow block valves and its bypass on a natural gas line of 16",

the control valve will reduce preure from 55 bar to 43 bar, the flow rate i about 200 000 Nm3/hr.

so how to determine the bypass diametter ?

the block valves (to ioslate the PRCV) will be of 10" or 16" (it means the reduction (16"x10")will be befor the block valve or between the control valve and the block valves ) i there any norm or standard ?

thank you

 

[JLSeagull]

Some companies have standards. Lacking such standards one could check the capacity coefficient of the bypass valve. Lacking such data one could consider line NPS 16 or perhaps NPS 14 block valves and about 12 or 14 for the bypass valve. Start by looking within the organization for a piping or instrument standard that addresses the control valve manifold requirements.

 

[BigInch]

Or you could select the control valve that gives you the best characteristics of flowing 200,000 m3/hr over your range of inlet pressures, note the control valve size and select your reducers accordingly.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[zdas04]

Typically this sort of installation does not have a bypass at all. Putting one in with connections outside the block valves would allow the system to remain in service during maintenance on the PCV which may be worth the cost of installing it, you have to look at your processes to decide.

I'm with BigInch that you should look for a PCV that has your required flow rate in the middle of its operating range. My gut feel is that it will be smaller than 10-inch, but I haven't done the calcs. My tendency is make a bypass one size smaller than half the reducer. So if you end up with a 10-inch PCV then I'd go with a 4-inch bypass. If it is 8-inch I'd go with a 3-inch bypass. These values are based on acceptable velocities for full flow. While you might want to stay under 100 ft/s in normal, steady state operations going to twice this number for short transients in a short bypass line is not a physical problem in gas flow (but some company tech documents might prohibit it, best to check).

David

 

[BigInch]

Select the "bypass diameter" (not the control valve) that gives the same pressure drop as the control valve.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[lomli]

thank you very much

what about the reduction poition;

1) B vlve - reduction 16x10 - control valv - reduction 10x16 - Blc valv

or

2) reduction 16x10 - blc vlv - control valv - blc valv - reduction 10x16

if someone can give me the reference of codes or standards that treat such problems ?