what should be the gate valve class for the pipe design pressure of 25 bar ?

Question

I wanted to know the rating for post indicator valve whose dia is 500mm in a firewater pipeline in petrochemical plant. The material of the pipe is carbon steel, CLASS 150, design pressure is PN 25, working pressure is 12 bar.
Can anyone specify me the guideline to decide the flange rating for gate valve?

Answer 1

In fire hydrant line , you are using water almost at a ambient temperature.
The gate valve class for the pipe design pressure of 25 bar SHOULD be more than 300#.
150# means , it is suitable for working pressure upto 150 psi gauge pressure.that means 10.54 kg/cm^2 pressure( 10 bar).

If you consider design parameter as you have given-25 bar, then you must go for 450 class.So, in case extreme condition , your gate valve will work without fail.
Please refer:
ASME/ANSI B16.5-1996 Pipe Flanges and Flanged Fittings - Class 300 Flanges - outside and inside diameters, bolt circles, numbers and diameters of bolts at ,
http://www.engineeringtoolbox.com/asme-carbon-stainless-steel-flanges-d_302.html

Answer 2

25 bar is a lot of water pressure. What is the actual operating pressure? For 25 bar, I would make the jump to 300# flanges. What code are you building to. I would suggest ASME/ANSI B31 for petrochemcial work. That standard contains a chart to tell exactly what the ratings are for each situation.

Answer 3

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Answer 4

http://en.wikipedia.org/wiki/Gate_valve
i'm not too sure but here is some info that MIGHT help