4 replies to this topic

[steve73200]

Hi,

 

I'm a part-time student in need of some help with a work based problem.

 

I have a steam bleed line that starts from a HPS turbine inlet pipe (70.5 barg) and leads down to an atmospheric expansion vessel around 15m away. Within this steam line, located next the vessel is first an open/shut control valve and then a restriction orifice plate.

 

I am trying to calculate the steam flow rate through a valve when it is opened in order to gain the pressure downstream of the valve and upstream of an orifice plate in the same line. I then need to calculate the steam flow rate after the orifice plate and into the expansion vessel.

 

Is anybody able to help with this problem? The only formulas I can find require a pressure downstream of the valve to calculate the flow rate.

 

The only information that I have is attached on the drawing; this will probably make more sense.

 

Help will be much appreciated...Thanks in advance.

 

 

Attached Files

•  Steam Expansion Vessel Set-Up.jpg   76.85KB   5 downloads

[ahmadikh]

 Steve73200,

 

I do not think that the valve is a control valve if it is installed on a bleed system following by an orifice (I might be wrong, please confirm and correct me if I am wrong). If this is an On/Off valve then when it is open it has no pressure drop and that is why the orifice is installed to restrict the flow. Since the pressure drop across the orifice is huge, "Choked" condition occurs in the orifice and for calculating the flowrate you only need your upstream condition and properties and also the orifice dimension and coefficient of discharge chosen by Vendor (check orifice datasheet).

 

For more information check the formulas given in AGA 3.1. 

 

Hope that helps...

 

Best,

Milad 

[steve73200]

Admadikh,

 

Thanks for the reply. You are correct in thinking that this is an on/off valve due to the nature of the system. I will look into the choked conditions that you speak about and see what I can come up with.

 

Regards,

 

Steve

[Brocklesnar]

Steve 73200,

You should see the Crane Technical Paper 410 (2009) / Eq. 4-14, 4-15 and Example 7-20.

Studying above will help you address the issue.

[breizh]

Steve 73200

Other resource to support your work .

 

 

Hope this helps

 

Breizh