Steam system pipe sizing inquiry

[mandoto]

Good day,

My question relates to the use of a pressure reducing station (pressure reducing valve) in a steam system. As those involved in the design know, pipe sizing is carried out starting with the furthest point (the most demanding point of consumption) and sizing shall start from that point on till we reach the boiler following the different standrads guide lines based on velocity or pressure drop. In case there was no pressure reducing valve(s) fitted on the line we can continue our sizing procedure without any troubles. The problem I face is when there is a pressure reducing station, in this case shall I start sizing in a reveresed mannar starting from the nearest point where pressure and pipe size is known (given that we have started with the most demanding point which typically shall not need any kind of pressure reduction and that line extending from the most demanding point is sized) then carry on till we reach the pressure reducing valve, and then starting our sizing procedure after the pressure reducing valve with the new pressure value approched via the pressure reducer. Also I noted that any pipes downstream the pressure reducing stations are larger than those pipes upstream (feeding) the pressure reducing station.

I'd appreciate it if anyone got a clue if what I've said makes sense? any ideas?

 

[anorlunda]

You are asking about a calculation strategy. Presumably, no matter where in the line you start, or which direction you go, there is only one correct result. A software program may iterate moving up the line then down the line, over and over.

So sorry, I can't guess which strategy works best for you.

 

[jrmichler]

You are on the right track. A problem such as this is really two separate problems, one downstream of the PRV, the other upstream. You solve each problem by itself without consideration of the other problem. You do have a common steam flow rate, but everything else is independent.

The PRV is a third sizing problem. Be sure to calculate if the valve needs a linear or equal percentage response.