Butterfly Valves : Single Eccentric vs Double Eccentric
Butterfly Valves : Single Eccentric vs Double Eccentric
(OP)
Dear All,
I am trying to understand the preference on double eccentric over single eccentric.
Especially Awwa designs are single offset. Whereas Europen prefer
double eccentric. (what I see)
Options,
1.better sealing (any concrete number for proof?)
2.less wear on seal(any concrete number for proof?)
3.better control performance
4.Double one should need higher torque?(disadvantage)
5.Any other?
Thanks in advance
I am trying to understand the preference on double eccentric over single eccentric.
Especially Awwa designs are single offset. Whereas Europen prefer
double eccentric. (what I see)
Options,
1.better sealing (any concrete number for proof?)
2.less wear on seal(any concrete number for proof?)
3.better control performance
4.Double one should need higher torque?(disadvantage)
5.Any other?
Thanks in advance





RE: Butterfly Valves : Single Eccentric vs Double Eccentric
there are many threads on the forum that deal with this, cf. http://www.eng-tips.com/viewthread.cfm?qid=313416 and http://www.eng-tips.com/viewthread.cfm?qid=126483, and http://www.eng-tips.com/viewthread.cfm?qid=145006, some also dealing with triple offset butterfly valves.
good luck with the investigations!
Corrosion resistant, exotic alloy valves from The Alloy Valve Stockist in Barcelona, Spain http://valvestockist.com
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
some of them are not even aware of signle offset.
I read all of them coule of times.
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
Good luck.
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
Another advantage of the dbl offset is the difference of the pressure-area on the disc. Since the shaft is offset to one side the pressure area will be slightly bigger on one side of the shaft. If the valve is installed in the preffered direction the process pressure will help the valve making a better sealing.
I dont think a double offset valve needs higher torque than single offset valves. I have not checked any calculations, but I cant see why that should be necessary.
I can think about two disadvantages for a double offset vs a single offset. One is price and availability. The other disadvanteg is a slightly higher pressure drop on the double offset valve.
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
So what you are saying is there is no wear between disc and seal by double eccentric design?
I dont understand why the 2nd offset (shaft offset position off the valve centerline) results this.
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
That is the reason why we have to rely on triple offset design.
RE: Butterfly Valves : Single Eccentric vs Double Eccentric
RE: Butterfly Valves : Single Eccentric vs Double Eccentric