Use of Butterfly Valves
Use of Butterfly Valves
(OP)
I am installing automatic valves on one of our propylene refrigeration compressor to isolate the unit in case of a compressor shaft seal leak, in order to isolate the casing and vent the casing gas to the flare. One of our engineers here recommended using full port ball valves instead of butterfly valves for better valve cv. The cost of ball valve (8", 10" and 12", 300# flange) is much higher than a butterfly valve. These valves would not be directly installed on the compressor nozzles, but would be located about 10 feet away on the piping feeding the compressor (suction, discharge and 2nd stage). The engineer's concern was about disturbing the flow of gas to the compressor in case if a butterfly valve was used. This is a 3000 HP horizontally split case centrifugal compressor.
I personally would like to use the butterfly valves. Does anyone see any issues with this approach?
I personally would like to use the butterfly valves. Does anyone see any issues with this approach?





RE: Use of Butterfly Valves
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Use of Butterfly Valves
RE: Use of Butterfly Valves
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Use of Butterfly Valves
Your point is also clear to me why the butterfly valve would not be smart choice. I have some questions that would extend the subject of the topic.
What is your experience with big butterfly valve used as suction control valve (say with a CV from 10000-15000 usgpm and higher)?
I am interested to know about reliability of such big sizes and about the dynamic characterstics when they are actuated (e.g. quick opening)?
I have also no idea if on this range of diameters the most encoutered/reliable actuators are motor type or pneumatic.
I also wonder what would would be the main difference in terms of reliability and suitability when using the valve for insulation or for process control.
Also when you say that these valves are not up to task, could you please elaborate a bit on this ?
Beside this, I have personal experience with the selection of a suction throttle valve about 8'' size for a cent. compressor where minimizing dP losses with valve fully open was a critical project requirement. Both angle valve and globe valve turned out not to be a good choice with respect to dP at full passage. It appeared that only the butterfly type satisfied the low dP losses requirements also at low costs. In that project, the use of flangeless valve driven the cost down even further.
RE: Use of Butterfly Valves
You keep talking about price. It sounds to me like you are interested in saving a few hundred dollars on a half million dollar machine. I've inherited a few of those machines over the years and they are truly difficult to operate. I generally ended up throwing the cheap crap away and installing a proper valve.
If I have to do big inch suction control and want a zero dP when fully open, I'll use one of the "profile ball" valves like a Fisher V-Ball. When fully open it has about a zero dP, but has great linearity over most of the range.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Use of Butterfly Valves
Thanks again!
RE: Use of Butterfly Valves