Butterfly valve for steam service

[AminSaalaar]

Hi

Does a butterfly valve for steam service need to have metal seats?

Design conditions:
Saturated steam, 200 psig and 400F

I'm looking at high-performance butterfly valves with the following specs:
carbon steel body (WCB), ANSI class 150 to B16.34 (200 psig, 400F)
Lug style

Not sure if I could use seats other than metal for these service conditions. I keep hearing soft seats won't survive the temperature.

Does anyone have experience with TFM (second generation polymer) seats?
Metal seated butterfly valves have long lead time.

I'd appreciate Any help, comments, recommendations and advice

Thanks in advance

 

[gerhardl]

Steam will always need steam-expert advice.

You do not give the reason for your question, or where you have got the specifications. My advice is to go to your source for more information and ask for the detailed backgrond.

My suspicion is that this is either a specification that are based on wrong or uncomplete information (there is no such animal) or that the originator is referring to a special valve from a specific producer.

I would never have offered or supplied a valve for such conditions without a longtime reference history for use.

Doublecheck: reliable steam-valve suppliers!

 

[Danlap]

Steam characteristic (to name a few among others)are as follow:
a. Relatively high temperature (shall compared with the design temperature of the Polymer)
b. Steam is considered as a gas. With respect to its pressure (and temperature), it will flows at relatively high velocity
c. Steam consist of condensates (phase between liquid and gas). At high velocity, condensates act as 'bullets'.

And its target are anything on its flow path (read: Seat, Ball / Plug / Disc /etc.)​

d. Some steam services (sulfuric) + ideal condition may initiate SSC (sulfuric stress cracking), thus damage the valve.

Therefor, its not just about the temperature. If your steam service condition consist of any one of the above, you need a 'hard' material as base material for your trim.
Most steam services are not even recommend a bare SS316 and SS410 as trim material. It should meet some hardness criteria (overlay, HF, etc. or even a very good quality SS410).
Conservatively I would say no also for any Soft goods (aside from Stem packing material) to be used in Steam service.

Align with gerhardl, either you have missing information (e.g. this is only normal steamed cooling water) or something that is overseen by the manufacturer. I would be interested in the outcome/result, shall you deciding to choose this type of material.

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[AminSaalaar]

Thank you all for the helpful information

The saturated steam service will be delivered to a building for their space heating. The pressure is reduced in the building from 185 psig to 50 psig. The low pressure steam service then goes through a temperature control valve and then to a heat exchanger.

As for isolating the heat exchanger we usually provide a gate valve; however, due to space limitation I'd have to use a butterfly valve. We don't have too many butterfly valves on our system that's why I asked the question. The pressure and temperature design for our system are 200 psi and 400 F, that's why we'd like the butterfly valve to be rated for these conditions.

Thanks

 

[gerhardl]

See for instance:

http://www.metso.com/products/butterfly-valves/series-800-butterfly-valve/

as one of a number of (several competing) high-class producers.

Muktiadi: Some small corrections, your points:

b) Steam is a gas (of the liquid H2O).
c) (Check the steam table. Overheated steam is pure gas.) When there is not sufficient extra heat at a given pressure to vaporize present water droplets (condensate is the water, not somthing in-between water and gas or the mixture) pipelines and vessels will contain both phases, steam and water droplets (water droplets called condensate because it most often comes from condensated steam).

(There is often some mix-up of precision here as for instance a so called 'condensate vessel' is built and placed to contain both steam and the steam condensated to water together) I fully support you regarding necessary lay-out with correct steaamtraps to drain out condensate, to avoid water-hammer from condensate assembled at lowpoints. Possible acids is always an issue.

AminSaalar: In addition precise and 100% closing and sealing of valves is important, as crack openings to lower pressure will give high-velocity escaping gas speed, very soon tearing groves in the sealings.

I think you will be able to solve your practical problem with a suitable butterfly valve. Good Luck!

 

[AminSaalaar]

Thanks for the info gerhardl

 

[Danlap]

Thank you for the feedback gerhardl.
Very constructive and highly appreciated.

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments