Using Butterfly Valves

[Narbij]

Hello Community. This is an excellent site which has helped me tremendously when researching potential solutions. This is my first post however, and am looking forward to many more.

I am a Mechanical Engineer who has dealt with a lot of various types of equipment but have limited experience (especially from an operator perspective) with valves. I have a question about Butterfly Valves:

I am trying to specify a valve for Hot Air Service (Temp = 370 deg C; Press = 700 kPa). The valve is to be used for isolation purposes only (i.e. not intended to be used for throttling). Normally, I would specify a gate valve but due to significant space constraints (trying to install this valve inside an already crowded enclosure) gate valve is out.

This leaves two options (that I know of): Ball Valve or Butterfly Valve.
BALL VALVE: Great choice but the flange I am connecting to is 5" - not easy (if even possible) to get a valve in that size as it is not a common size. Would need a reducer to go to 6" or 4". As space is already tight, it's not ideal.
BUTTERFLY VALVE: I can get this in a 5" size. However, every Operator tells me Butterfly Valves leak and have caused nothing but problems. However, a quick search on Google finds me a number of manufacturers that claim "zero leakage" or "leak-free service". They also talk about "double-offset" and "triple-offset".

Question to you all: What kind of experience have you had with Butterfly Valves? Recommendations on type (i.e. double/triple offset, no offset?) Know of any other types of "compact" design valves?

Thanks in advance for your help. Greatly appreciated.

Regards,
JA

 

[zdas04]

In my class, I refer to butterfly valves as "junk service" valves for systems that need flood protection, not leak protection. I don't like them in gas service because the velocities tend to be high enough to set up harmonics in the disk and I've had a few break off and lodge in an inconvenient (and hard to find) place downstream. Temperatures much above 100C are very difficult on the elastomers and by 370C the valve seats wouldn't last an hour.

The double and triple offset varieties are simply trying to create a more symetric seating pattern (i.e., the disk tends to slide into the seat instead of rotating into the seat), they help, but not enough.

At your temperature, you are going to want a metal-to-metal seat which puts you in special order territory. If you are special ordering a valve, it would shock me if one of the ball valve manufacturers didn't have the molds and jigs for a 5-inch valve.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[gerhardl]

For this temperature you will want (as for all other applications) a valve that is factory approved for the application; leaks, dependability (standtime / quality) to be OK regarding cost and consequences if anything goes wrong.

You have a world-wide commercial available 'standard' product range to choose from, where both ball-valves and BFL valves are available in certified quality.

There is nothing against using a BFL valve for the purpose, provided it meets the requirements. Valves for steam and overheated steam in the temperature and pressure range will be suitable. Cheap BFL valves not constructed for the purpose will of course give you problems, as unsuitable ball valves will do, both normally with sealing problems as the first failing point.

Examples (many competitors) of quality valves:

https://www.velan.com/en/products/t...l-seated-ball-valves.html/1/52?product_id=111

http://www.wilson-co.com.tw/File/1.Product/1.1.Metso/1.1.1.Neles/1.1.1.6.pdf

 

[Narbij]

Thanks zdas04 and gerhardl. Appreciate your responses and input. I checked out some suppliers and it appears that metal-to-metal seats or not that uncommon; however, a 5" with metal-to-metal IS uncommon.
I guess I will make the ball valve work. This isn't an application where we are willing to spend a lot of money as all I'm doing is making provision for a future tie-point for a solution we may or may not implement (likely the latter).

Thanks for your prompt responses.

JA

 

[gerhardl]

OK, thanks!

As an afterthought if 5" is 'uncommon': have you checked out if there is any cheaper total solution with a 6" valve if you weld on a 6"
pipe-bit?

 

[Narbij]

gerhardl: I have and am pursuing exactly that. The space constraints pushed me to look for other options (or at least, not eliminate options due to inexperience) but it seems that we may be able to make the 6" w/ reducer and pup work - my piping designer is awesome.

Thanks again.

JA

 

[LittleInch]

If its to allow connection at a future date without shutting down have you considered using something like a Lock-o-ring flange from TD williamson? Or Sureloc which is another version

http://www.weldfit.com/sureloc-line-stop-tees.html

If you can get access in the future to install a valve and a tapping machine, this might be a cost effective way to seal it off. They do tend to use O rings though so you would need to contact the vendor to see if they make a high temp version and they probably would need to make a special in 5", but worth thinking about IMO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Narbij]

That's actually a pretty good idea LittleInch. I will investigate this. Does anyone have any experience with this?

 

[LittleInch]

It's common practice for any stople tees no longer needed and I've seen it used on tee connections for pig taps where they didn't want the expense of a valve or something that could be opened

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.