Sizing Vent Pipe
Sizing Vent Pipe
(OP)
Hi all,
we have a vent pipe that we use to warm up the main pipe (steam to the turbine).
This vent pipe is just a pipe with an isolating valve and it discharges to the atmosphere (we are thinking about getting a silencer).
I'm trying to calculate the flow that will be evacuated trough this line (and also the pressure drop), taking into account the conditions in the main pipe.
I have never done this and I'm not sure that the common formulas will apply in this case (with such high velocities).
Any suggestions will be welcome.
Thank you!
we have a vent pipe that we use to warm up the main pipe (steam to the turbine).
This vent pipe is just a pipe with an isolating valve and it discharges to the atmosphere (we are thinking about getting a silencer).
I'm trying to calculate the flow that will be evacuated trough this line (and also the pressure drop), taking into account the conditions in the main pipe.
I have never done this and I'm not sure that the common formulas will apply in this case (with such high velocities).
Any suggestions will be welcome.
Thank you!





RE: Sizing Vent Pipe
Good luck,
Latexman
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers
RE: Sizing Vent Pipe
I am a bit confiused as to what exactly you are trying to calculate as you say have this pipe but only now you're trying to calcualte the flow and velocity - why? If the pipe is open to atmosphere and has a simple isolating valve, the flow control is then somewhere else, i.e at the valve from the boiler to the main pipe. If there is a real velocity problem, just go up a couple of line sizes which makes a huge difference in pressure drop and velocity for the same flow rate.
What sort of sizes are we talking here?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Sizing Vent Pipe
will have a look at the Crane. Thanks.
LittleInch,
I have a presurized system (40 bar) which is the pipe (8") from a boiler to the steam turbine (ST). The ST end of the pipe is blocked. To warm up this main line, we install a vent to the atmosphere (2"~4"). This vent has just an on/off valve (no control valve). I assume the flow through this line will be directly proportional to the difference of pressure between the main line (40 bar) and the atmosphere. The Boiler will produce the amount of steam that can be evacuated through this vent line (this flow remains unknown and I want to calculate it).
I don't really have a request for the flow. But the more, the better (the warming up will take less time).
Hope you can see the image here http://img703.imageshack.us/img703/1397/sinttulozz...
So, to summarize, my data is a pipe of 2" (or 4"), that connects 40 bar to 1 bar. How do I calculate the flow? What happens if the velocity is near critical?
RE: Sizing Vent Pipe
Good luck,
Latexman
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers
RE: Sizing Vent Pipe
Plug that into an orifice calcualtion and find the biggest vent pipe you can. Attach the orific plate immeadiately downstream of the valve. This will give you some sort of control over what currently sounds like a fairly brutal and very noisy venting system. Your vent pipe design in the current scheme would be subject to huge loads and thermal shock and also needs to be rated at the header pressure as the pressure d/s of the isolation valve will be close to or at header pressure. Your valve also probably won't last very long as isolation valves are not much good at opening and closing against flow
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Sizing Vent Pipe
Maybe then you could use the Cv and the pressure drop across the valve to find the flow.