Leakage in Ball vs Butterfly with regards to seal

[AlexOfNorway]

Hi,

I'm in the process of selecting valves for a plant handling LPG (both liquid and gas). Normally for larger sized valves (4" and up), the double eccentric, firesafe BF valve is a good choice, especially due to dimensions/weight and price-wise. Customer is worried that the seal on the BF is more exposed to impurities in the cargo than a BV would be. I have only experienced problems with seals due to poor cleaning of pipeline before start-up (welding threads/beads, particles).

I would imagine that the seals on the BV is as prone to damage as the BF when dealing with small impurities in the cargo? Any of you have any experience with this?

Brg,
Alex

 

[gerhardl]

If you check references from some of the well-reputed valve producers with many years experience from the fluid, you will find that your opinion is correct.

In my own opinion seals in a ball-valve would have limitations in construction to accept a very high degree of impurities where special consruction BFL-valves for the purpose probably will have better tolerance for impurities(Triple eccentric BFL, special sealings and other special constructions)

Cost, cost over lifetime and practical solutions will however (for both types) as for all valves be depending on the detailed process conditions and requirements at site, and availability and commercial price locally for the particular valve.

 

[AlexOfNorway]

Thanks for sharing your thoughts gerhardl!

 

[NGiLuzzu]

Alex,
I agree with GerardL...

Probably a very SPECIAL high performance butterfly valve and a quite STANDARD triple-offset metal-to-metal torque seated valve can both do the job; of course, it's up to You to take into account other factors (initial and maintenance costs, reliability and expected useful lifetime, etc...).

You may find much information about the above mentioned valve types (including the names and websites of the "top" Manufacturers) by searching posts within this Forum.


Best Regards,
'NGL
___________________

 

[tr1ntx]

The seal on a BF is indeed more exposed to impurities in the cargo. When the valve is Open, the seal is completely exposed. However, on a BV, the seal surface is only exposed to the cargo for the amount of time that the bore through the ball is over it during movement from Open-to-Closed. (or Closed-to-Open)

But on the BV, the surface of the ball has sliding contact with the seal surface, so weld beads, particles, etc., can possibly do more damage to it than to a BF seal.

 

[TOVmania]

>>tr1ntx's
- It concerns me that your comment is valid only when the seat ring is fixed on the disc since the medium flows perpendicularly to the exposed seat ring in an open position. In other TOV design, the valve will less exposed to such issues as the medium(including impurities) flows horizontally to the seat ring fixed on body.

Just as a side note, Industrial Plant Engineers are using BF more and more for its design(TOV) and weight(less stress to pipe = cost saving) advantages in large size especaiily. There are many companies in the market, which claim that they are TOV manufacturers, but once you look inside, there are only a few that can produce the authentic TOV in the industry.

 

[HitokiriAoshi]

Ball valve's biggest problem is once the seat is damaged (particles got into the seat), the damage will worsen in an exponential manner as the particle continue to scrape against both the ball and the seat during each actuation.

I would recommend looking at a good ToV with laminated seal ring. As long as the seal ring is softer than the seat, any damage done will be to the laminated rings, which is slightly resilient and replaceable. In addition, one can always apply more torque in an attempt to increase TOV sealing.

 

[hsbcn]

If you're looking at triple-BF valves, you might want to check with Velan. We do not represent them, you can call on them here:

http://www.velan.com

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