Sometime back, I was working on a project where the licensor was UOP, and we found that even in specs where RTJ flanges were used, UOP would switch to RF flanges if the metallurgy was dissimilar at spec breaks. Some food for thought :-)
Mahavir
-----Original Message-----
From: Steve McKenzie [mailto:Mechproj@xtra.co.nz]
Sent: 04 July, 2002 2:06 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Flanged connections with dissimilar
Materials
Dear Nirmal Murarka
It is probably time for you to work it out. Put numbers against a few
things.
Look at the properties of the two flanges: dimensions, materials, pressure,
temperature range and loads. Estimate what the effect will be. If the
differential growth cannot be absorbed by the flexibility of the joint, then
a different solution will be required. This may be a different flange
connection or even a different pipe material (although this will just move
the problem to somewhere else). Remember that it is the same differential
expansion which needs to be accommodated, regardless of joint type. If you
have a high thermal cycle requirement then this will have an effect on both
a flanged joint and on a dissimilar metal welded joint.
If you have experienced a problem between equipment and flange suppliers,
then, as I have said, look at getting the equipment supplier to supply the
flange to your requirements. Or get better informed suppliers.
The best solution will depend on operating conditions, sizes and material
properties.
Cheers
Steve McKenzie
-----Original Message-----
From: NIRMAL MURARKA [mailto:Nirmal-Murarka@enc.ltindia.com]
Sent: Thursday, July 04, 2002 6:00 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Flanged connections with dissimilar
Materials
Steve,
The two types of material break, I hope, are essentially break at flange-pipe joint (weld break) and break at flange face (mechanical break). Or are you taking about some other types of breaks using additional components. I would like to know more about that.
Generally in such a situation the equipment supplier and flange supplier will put the blame on each other. Its the system (plant) designer who has to take a decision.
Your concerns about hardness, elasticity, galvanic/corrosion resistance always remains there. What I feel more critical here is the differential thermal expansion of the two flanges twisting the gasket after a few thermal cycles and leading to a leak. Ring material may not help much in this case.
What you say...
Nirmal Murarka
"Steve McKenzie"
<Mechproj@xtra.co To:
<PipingDesign@yahoogroups.com>
.nz> cc:
Subject: RE: [PipingDesign]
Flanged connections with
04/07/2002 10:59 dissimilar Materials
AM
Please respond to
PipingDesign
Hi Nirmal Murarka
It is normally more difficult to arrange the welding of two dissimilar
metals than it is to arrange a flanged joint. As you have stated that the
materials will be dissimilar, a material "break" joint is required
somewhere. It will be either mechanical or welded. Mechanical is more
common. With RTJ joint with two different flange materials, hardness,
elasticity, galvanic/corrosion resistance need to be considered carefully.
A
good selection of ring material may help. I would talk to your vessel
supplier and your flange supplier. Service and temperature cannot be
ignored.
Cheers
Steve McKenzie
-----Original Message-----
From: NIRMAL MURARKA [mailto:Nirmal-Murarka@enc.ltindia.com]
Sent: Thursday, July 04, 2002 5:00 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Flanged connections with dissimilar
Materials
Steve/Mahavir,
Do you tend to say that we should not use different material flanges for RTJ joints with solid metallic gasket?
Can I conclude that if the joint is RTJ go for spec break at weld and otherwise flange face without bothering much about service and temperature?
Any comments?
Nirmal Murarka
"Steve McKenzie"
<Mechproj@xtra.co To:
<PipingDesign@yahoogroups.com>
.nz> cc:
Subject: RE: [PipingDesign]
Flanged connections with
04/07/2002 09:28 dissimilar Materials
AM
Please respond to
PipingDesign
Hi Mahavir
your dilemma occurs sometimes with pumps. One way it is overcome is to have the equipment supplier provide flanged ends on his equipment and also to supply mating flanges (and gasket if necessary) to your pipe material spec.
Cheers
Steve McKenzie
-----Original Message-----
From: Prasad Mahavir/Piping [mailto:jainmp@eil.co.in]
Sent: Thursday, July 04, 2002 3:30 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Flanged connections with dissimilar
Materials
Hi folks,
I guess that type of flange facing would also play a role. For example if the flange is with RTJ ends and gasket being used is solid octagonal or oval, then I would not like to exercise option 2. Any Comments?
Mahavir
-----Original Message-----
From: NIRMAL MURARKA [mailto:Nirmal-Murarka@enc.ltindia.com]
Sent: Wednesday, July 03, 2002 5:55 PM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Flanged connections with dissimilar Materials
For a spec break with change in material near a flanged joint (may be equipment flange and piping flange) what should be the correct approach:
May be temperature and type of materials will play a key role. When can we
go with option # 2 safely ?
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