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High temperature Exhaust Piping -Bolts and Gaskets

High temperature Exhaust Piping -Bolts and Gaskets

High temperature Exhaust Piping -Bolts and Gaskets

(OP)


 Dear members

 In one of our construction , we have 32 In Carbon steel line used in a exhaust line of a diesel engine.
 Design temp: 460 Deg C, Design pr: 10 bar.
 
 The following are our queries

 1) In the dissimilar flange joint between Expansion bellow ( Material ASTM A 182 gr F 316L)and Pipe flange ( Material ASTM A 105) the supplied fasteners are of ASTM A 193 Gr B7 and A 194 Gr 2H material.

 Since the CS fasteners will bein contact with SS flange,
 we would like to know the types of isolation kits available in the market which can withstand the design temp of 460 Deg C or any other suitable methods to prevent galvanic corrosion because of SS to CS contacts.

2) Secondly we are looking for a suitable non asbestos gasket to be used at the dissimilar flange joint which can withstand the same design temperature of 460 Deg C

Any help or suggestions to the above queries from experts in this forum will be appreciated

Sree60

RE: High temperature Exhaust Piping -Bolts and Gaskets

Try this website.  It lists a number of companies that make high temp gaskets.

RE: High temperature Exhaust Piping -Bolts and Gaskets

(OP)

Penpiper
Can u give the link  which u mentioned?
Thanks
sree60

RE: High temperature Exhaust Piping -Bolts and Gaskets

Typically SS to CS is not an issue for galvanic corrosion.

I'm not a corrosion expert but I thought you needed the presence of electrolytes for galvanic corrosion and I can't see that happening at 460 deg. C.

In any case CS to SS is common in piping with out isolation.

Hopefully your flange is not going to be insulated but if it is, I would recommend using B16 bolts and Gr. 4 nuts instead of the ones you mentioned.

Also, a reinforced graphite gasket will be suitable for your service. Get with a gasket manufacturer as there may be cheaper alternatives. I've pasted a couple of gasket links below.

http://www.lamonsgasket.com/

http://www.flexitallic.com/

NozzleTwister
Houston, Texas

RE: High temperature Exhaust Piping -Bolts and Gaskets

Stainless steel bolts (B8) will gall and/or seize at 460F, and you'll never get them off without cutting after running them hot.

RE: High temperature Exhaust Piping -Bolts and Gaskets

Also, chanches are your B7 or B16 bolting will not loosen due to differential thermal expansion.

Regards,

Mike

RE: High temperature Exhaust Piping -Bolts and Gaskets

Uh, TEN BAR design pressure?  Seems a little high.

Diesels half that size limit exhaust backpressure to five inches of water.  You don't need heavy pipe or ANSI flanges to deal with that little pressure.

You won't have galvanic corrosion.  You will need anti-seize on the bolts no matter what material they are.

Mike Halloran
Pembroke Pines, FL, USA

RE: High temperature Exhaust Piping -Bolts and Gaskets

DARCO SOUTHERN INC manufactures high temperature gasketing material
The catalog that I have is dated January 1996

253 Darco Drive
Independence VA 24348
800-327-2610
540-773-2711

RE: High temperature Exhaust Piping -Bolts and Gaskets

(OP)

Dear members

Thanks to all for your valuable inputs

sree60

RE: High temperature Exhaust Piping -Bolts and Gaskets

Don't use a flexible graphite sheet type gasket at that temperature as the gasket will fail prematurely due to oxidation.  If the pressure is >30 psig and you have plenty of bolting available, use Flexitallic Thermiculite sheet gaskets.  If the pressure is <30 psig, you can also use Cogebi Mica sheet gaskets.  These are both used extensively in diesel exhasut systems with both B7 and B16 bolts.

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