Vulcanized liner VS rubber liner on butterfly valves

[CKchi]

From my knowledge, the rubber liner is replacable and Vulcanized liner is boned to the body by vulcanization. So in most cases i guess rubber liner is preferred as the liner can be replaced for cost saving.

My question is what is the main purpose of having these two designs? Generally in what circumstance do we use the rubber liner or Vulcanized liner?

 

[gerhardl]

Hello CKchi,

The short answer is the total cost over lifetime consideration: what will be best/cheapest in the long run (planned lifetime of the total piping installation)considering also cost of replacement, repair and downtime for the installation changing valves and/or sealing.

As both valve-types are produced and used for a vast number of pressure classes, sizes, geometrical forms, materials, qualities and for a vast typerange of fluids and applications the long answer is very long. For specific purposes vulcanized solutions could be preferred, for instance for very large dimensions (up to diameters of several meters) for low-pressure seawater.

Hence your first sentence is not necessarily correct, but more correct if you replace 'most' by 'many'.

 

[Danlap]

Fully agree with gerhardl comments.

Both design is driven by the manufacturer (its patented design; production line; etc.) and end user (how versatile the end user line/Plant is; how much money willing to spent for replacement/re-vulcanization/liner replacement; how big the line is; etc.).
For concentric and also double offset design. And seldom selected for non-toxic and non-flammable application. For special chemical application, PTFE liner may also be considered.

One suggestion that end-user often forget (normally fitter/operator) IS to install the Liner Butterfly valve at Open position (prior and while tightening the flanges' bolts).
At close (and free) position prior line installation, the seat will be bulge a bit. And tightening it (with sufficient seating force), will keep the bulge on. Therefore when Opening the valve, the disc's tip will obstruct the Seat and seldom rupture/torn the Seat after several Opening-Closing attempt.
And further provide miss-understanding of the Liner Butterfly valve quality. Usually every IOM will incorporate this instruction, and normally fitter don't read this

Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[CKchi]

Thank you gerhardl and Dalnap for your valuable input.