what is high performance type for butterfly valve?

[ryanhu]

hello,everyone

I want to kown what is the high performance type for

butterfly valve?can someone explain to me?

regards

ryan

 

[gerhardl]

A high performance butterfly valve is normally a triple or occasionally double eccentric butterfly valve (could be centric???) but where the valve in all cases is metal to metal seated. The sealing construction might be 'laminated': several layers of metal or carbon (or metal and teflon), but where the metal construction also normally will give a firesafe design. ( If the valves are firesafe tested with valid certification is a separate issue)

The sealing has a mechanical sealing function (not depending on helping pressure or forces from the fluid) where the torque forcing the seat sealing into the seat is giving the sealing effect.

The sealing is either from the formed edge of the metal disc itself, but normally a mounted on disc sealing ring construction where at least the main and backup sealing is metal.

 

[hsbcn]

Better seal, less wear...

High performance butterfly valves often incorporate a an offset in the disc position, which in turn increases the valve's sealing ability. Wear and tear are therefore decreased.

Heather Smith
Alloy valves from The Alloy Valve Stockist

http://duplex-valves.com

 

[gerhardl]

Comment to above: offset = double or triple eccentric, and yes, a valve with this description will have an almost plan-parallell movement the first degrees of the disc movement in and out of the seat, contributing to less wear than a valve without offset.

Eccentric: stem is 'off to one side' from the center of the disc.

Double eccentric : stem is in addition slightly off to one side from the center of the valve (pipeline)

Triple eccentric : the seatsealing construction or seat is slightly off from plan parallell to the valve/pipeline. (Giving even better geometrical plan-parallell movement of seat-sealing in and out of the seat)

Tee HP-valve however would always have the metal to metal sealing as the necessary item to be deemed a 'HP' valve.

I have not seen any official standard describing a HP valve, but the name is commonly used, and has probably an origin in a factory trying to describe 'a better quality metal-seated constructed valve' in a shorter and more commercial way, and then being used further by others.

Other opinions?

 

[NGiLuzzu]

ryanhu,
please take also a look at thread408-126483 and thread408-257196 within this Forum.


Hope this helps, 'NGL

 

[ryanhu]

anegri,gerhardl and hsbcn

thanks a lot!

for you explain ,maybe I catch something

The high performance type of butterfly valve

It must be eccentric design,one ,two or third

and sealing face will be metal

Is that right? And the seal of PTFE is also consist.

okay,thankyou?

 

[itascot]

ryanhu,
There are also high performance butterfly valves that are soft seat with metal seat back-up (in case of fire, soft seat melts away & metal seat comes into action). Check out K-lock (Keystone valves) as an example of soft+metal seated configuration.
Ciao

 

[JLSeagull]

Start with a conventional butterfly for comparison.

Conventional butterfly valves include a hollow body enclosing a thin disc that rotates on an attached shaft. The disc is not offset from the centerline. The shutoff seal and throttling performance is poor. Actuator forces can reverse above 60 degree open.

See page 17 at the following link for a symmetrical example:

http://www.kalsi.com/NRC-ASME-P&V-8...-Periodic-Verification-margin-improvement.pdf

 

[itascot]

JLSeagull,
Conventional butterfly (centered) are normally rubber or Teflon seated, and although limited in applications (heat, medium & pressure), normally give THE best sealing performances (for their intended service).
I would disagree with "the shutoff performance is poor", I may have less to say about throttling (as this is not the intended service), I may even agree with torque curve requirements (vortex, that changes with shape of disc); But generally they are good for what they have been intentionally designed to do.
Ciao

 

[ryanhu]

so good,all

thanks a lot for you attend

I catch more

 

[bcd]

Just to clarify, the term "high-performance" has nothing to do with the seat material. It was first used to describe a valve with an offset shaft. The shaft did not pass through the seat. Single offset, double offset, triple offset terms came later. High performance ment the valve had a higher pressure rating than rubber or polymer lined valves where the shaft does pass through the seating surface. Refer to API or MSS valve standards for more details.

 

[unclesyd]

You might want to look at the offerings by Hy-Grade.
We used a lot of these valves.

http://www.hy-grade.com/index.html

 

[780812]

for example