Triple offset butterfly valve vs double offset butterfly valves for throttling the flow of gas. 3

[viki100]

Hello all,

For control / throttling the flow of gas, what is a better solution : triple or double offset butterfly valve (high performance) ? At the inlet low pressure, high flow, size 18'' - 24'' . What are your opinion?

Thanks a lot

Viki

 

[hsbcn]

Do you require positive isolation? Then triple offset. You prefer a low risk of disc jamming over the long run: double offset. But the answer really depends on the process conditions. What are you dealing with? Also, triple offset and high performance are not the same, thought I'd mention.... What about seats/sealing (a majoy issue with buttefly valves): metallic or soft? You'll need to fill the forum in on many details to get a reliable answer.

I work with valves in exotic alloys at The Alloy Valve Stockist. This is our blog, and this is me on Twitter and LinkedIn. Let's connect!

 

[gerhardl]

Agree with hsbcn: To specify valvetypes without having exact conditions is wasted time. At least the 'usual' conditions must be given: all fluid conditions (type of gas, temperature, pressure, pressure upstream, downstream, flow and at least, max, min, and medium flow, requirementts for leakage and tests etc. etc.)

Giving that this is throtteling valves, the valves geometry (ability to give laminar flow and smallest pressure lost under the given throtteling data, as opposed to turbulent or cavitation conditions and high pressure loss) will count far more than tripple or double construction.

First when you have one valve of each construction (almost) equally suitable, can you start discussing details such as triple or double construction.

 

[viki100]

ok
medium: nitrogen gas
flow range: min 10 000 normal from 20 000 to 32 000 max 52 000 Nm3/h (control flow).
pressure P1: 0,7 barg.
pressure P2: don't know (no pressure gauge), outlet to the atmosphere through the chimney.
at the normal working, temperature ca. 20 degC.
at the abnormal working of process / at the stop process, temperature ca. minus 90 degC.
at the stop process, butterfly valve closed - closes cold.
at the normal working of process butterfly valve control of flow / throttling of flow.
pipeline inlet / outlet DN600
failure: valve open.
air to actuator: 4-5 barg.

Viki

 

[viki100]

Hello

Could you help me in this topic?

Viki

 

[NGiLuzzu]

viki100.
I’d suggest to submit Your service condition data to some Manufacturers (of both types of valves).
As already mentioned in thread408-360754 within this Forum, in the major Companies even the Sales Representatives should be able to run sizing calculations based on Your input and recommend the best solution (including economic considerations, of course)… ;-)

Regards,
’NGL