Most ecnomical shut-off valve 1

[simplemath]

What is the most economical shut-off valve suitable for my application?
Service: water @ 50degF, 50psig,
Connection: 6" 150# RFSO flange, Tank drain nozzle, A105.

On my list are:
1. Bfly valve: may not fit because of slip-on flange. No sure.
Cost : 200-300
2 Gate Valve: Trim 8 or any other cheaper choice?
Cost: 500-600
3 Ball valve

Any other type might fit?

Thanks in advance.

 

[pennpiper]

Your # 1 choice is the best choice from a cost standpoint and from both a weight and space standpoint.
Your concern about the fact you have slip-on (SO) flanges is a non-issue.
Any qualified piper will tell you (and show you) that the disk of the butterfly valve will clear the inside diameter of the pipe which is inserted into the SO flange.

 

[zdas04]

The most expensive valve in the world is the one that fails to isolate a line when it is needed.

Butterfly valves have their place and it is pretty wide, but I don't like them in high velocity flow (much above 5 ft/sec in water) because the disks tend to vibrate near their harmonic frequency and I've seen more than a few break off. I also like them better in service where they are exercised periodically. If they are "always open" then I've seen solids build up on the seating surface and they won't close tight when needed.

Gate valves are often a good choice, but a 6-inch rising-stem gate valve requires almost 100 turns to go from fully open to fully shut. The guys in the field tend to hate them.

Ball valves are often the highest purchase price, but they avoid the problems of the other two.

David

 

[simplemath]

Regarding butterfly valve, one of Milwaukee Valve engineer confirmed that slip-on FLG and bfly do not work well together and could cause leak because the seal is dependent on bfly lining and thus the smaller contact area with slip-on.

 

[rconner]

I don't know if it would be suitable for your application/purpose, but I see at

http://www.acipco.com/afc/gate_valves/series_2500/2500-brochure.pdf

a 6" resilient wedge gate valve would appear to match your bolt hole drilling (and takes only about 20 turns to open).

 

[IVNJ]

We have a Lug Style Butterfly valve that sells for well under $100, rated for dead end service, use with slip-on or weld-neck flanges. Ideal for mounting actuation, unlike a gate valve.

 

[Gator]

meanstone, are all butterfly valves lined?

 

[gerhardl]

No, not all butterfly valves are lined. Ideal would be a double-eccentric, double flanged butterfly valve with solid construction. Sealing with holding ring mounted on disc. Seating against housing, seat often walzed in stainless steel.

http://www.erhard.de

For this small size, price would however be at least 2-3 times, or even considerably more compared to a standard centric butterfly valve. (Prices even out at about 12 inches depending on operator type)

Theese types of valves are commonly used and specified in Europe for long-term water service, with lifetime requirements 25 years and up. This type of valve will close or open dependably after long-time permanently posed in opposite position.

Alternative (depending on lifetime requirement) to a standard centric bfl valve could also be a centric butterfly valve of good construction of chemical or food process qualification standard with FKM or Viton lining, again price going up.

Ballvalves have to be stainless, costs normally to much, and have 'pockets' between ball and seals where smudge can gather.

Gatevalves allowed for drinking water is OK, but more common for buried lines, heavier, and not so easy to operate if on/off is often repeated.

Selection of a valve is always depending both on type of service and quality and dependabillity requirement and cost over lifetime. NB! Downtime-cost taken into consideration!

 

[simplemath]

Thanks all for your input. I would like to go with gate valve. As gerhardl stated, the on-off here is supposed to be once several months when maintenance. However, I am still not sure why bfly valve(with lining and no gasket) can not seal tight with slip-on flg as the valve vendor claimed. I think the sealing condition(area)would be the same when mating with gate valve flg, the only difference is the gasket replaced by lining.

Thanks for more enlightening.

 

[gerhardl]

A centric butterfly valve with lining is always dependent of sealing with the disc (circular side-force) pressing into the softer lining to obtain a drop tight sealing.

As the (relatively large amount of) soft sealing material alter quality over time (age hardening, swelling over time absorbing fluid, abration of sealing area, altered material properties in general) you will come to a point where drop-thight sealing no longer is effective or the valve has grown stuck in closed position.

For a gate-valve the sealing is effecuated by linear force, not depending in the same degree of lasting elastic properties.