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Flanged and flued vs bellows

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waliq

waliq

Mechanical
Joined
Jan 28, 2019
Messages
53
Location
PK
Hi all,

Can anyone explain the difference between flanged and flued expansion joints and bellow type expansion joints. ASME sec VIII, Div.1, mandatory appendix 26 talks about bellows expansion joints while, in mandatory appendix 5, it talks about flanged and flued type expansion joints. If both of them are different, then I get confused when I find it written as flanged and flued expansion bellows on the internet.

 
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waliq, the term you cited "flanged and flued expansion bellows" is generally incorrect. Both flanged and flued joints and bellow joints are expansion joints, but of very different types. The two appendices 5 & 26 illustrate the differences very well, but:

A flanged and flued joint is a relatively thick expansion joint, usually made from two F&F heads. Usually a single convolution, usually the same material as the vessel shell cylinders. Accommodates only a small movement. Simple.

A bellows joint is a relatively thin joint, formed from sheet, many convolutions, usually high alloy or non-ferrous, accommodates larger movements. May be more than one ply. With stub ends, and optional features such as protective covers, shipping bars, etc, more complex

Rule of thumb: If you don't really need an expansion joint, use a flanged & flued. If you do, use a bellows :)

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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@snTman: This is such a helpful reply. Thumbs up!!!

Can a flanged and flued head have more than one convolution??
 
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waliq, yes it is possible, there are no "rules" limiting the number of convolutions. I have in the past designed an exchanger with 2 convolutions (four F&F heads). It gets messy though. For example, for a horizontal unit each convolution needs a vent and drain connection. "Real estate" may become a problem. Fabrication is difficult. I'd avoid more than one convolution if at all possible.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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snTman: Actually my vendor is giving a F&F joint with two convolutions (thickness 18 mm each)

It is for a vertical vessel of thickness 8 mm and design temperature 230 Deg C

Now, by drain and vent for every convolution, I assume that they are required to drain off any working fluid trapped in the flanged portion of the expansion joint?? And why is a vent required?

Moreover, a vertical vessel wont require these drain and vents for expansion joint convolutions??
 
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waliq, a vertical vessel will not need the V&D, only if horizontal. (Vent for hydro). Best of luck :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
Upvote 0 Downvote
@sntman: Can a flanged and flued expansion joint cater lateral stresses or is it good for only axial stresses??
Actually, the vessel is flanged to two vessels through nozzles located on their shells (one above and one below it). The expansion joint is there to cater the stresses that may arrive when sliding saddle of one of these vessels moves. So, the stresses resulting will come on this vertical vessel sandwiched in between. In order to cater these lateral stresses, expansion joint should be there
As per my research, flanged and flued are good for axial movements.
I want to ask if they can cater lateral stresses also?
 
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waliq, typically designed for axial movements only, and so stated per Apx 5-1(a). Designing for lateral displacements would be per U-2(g).

Comments: In my opinion, traditional expansion joints are a poor choice to accommodate primarily lateral displacements. Designing a vessel for lateral displacement seems to me a poor choice as well. I'd think you would need to assure yourself the vendor knows what it's doing.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
Upvote 0 Downvote
@sntman: Well, thats the first time I have encountered such a design situation. Maybe, an FEA needs to be done here as well.
 
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Somebody needs to do something :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
Upvote 0 Downvote
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