3 replies to this topic

[Terry T]

 Hello Everyone,

 

We are looking to take natural gas from two suppliers, but the pressure needs to be reduced to our required pressure of 300 psig.   Both suppliers have their own letdown stations and then it ties into one pipeline that feeds the factory.   See attached sketch of the proposed piping.  I am looking for some thoughts on the following. 

 

1.       Would we be able to take natural gas from both suppliers at the same time?  Is there a possibly for the two pressure reducing valves to fight?

2.       Can the two reducing valves operate at the same time?  Would there be a possibility for one of the valves slamming shut if the pressure changes on the other let down station? 

3.       There are flow meters on the lines, but they are not used for flow control.  Should we consider the use of a flow controller on one of the reducing stations?

 

Any thoughts would be greatful.

 

Thanks, 

Attached Files

•  Visio-Letdown Station.pdf   30.02KB   71 downloads

Edited by Terry T, 21 December 2014 - 02:36 PM.

[Bobby Strain]

Try again to attach the sketch.

 

Bobby

[Marian1]

one of the two parallel CV has to be operated to control the flowrate setpoint (standard flow control loop), the other has to keep the balance "gas supply vs variable gas demand", which means to control the downstream header pressure at its setpoint.

 

Of course the cheapest supply should me maximized!

[fallah]

Terry T,

 

Appears you need to control the pressure and flow in a line (common line after two parallel pressure reducing valves) simultaneously, then you should use a flow control valve at common line downstream of the two pressure reducing valves. Indeed, if such pressure reducing valves have been accurately specified for the conditions you described, they would operate at the same time and don't fight against each other...