Collar Thread for Shell and Tube Heat Exchanger 2

[Hari1207]

Hi!

Currently I'm taking care of Shell and Tube Heat Exchanger design and this is new to me.

For the BKU TEMA type, as per project specification, Full-diameter stationary tube sheet to provided with 25% Collar bolts.

I found in the calculations that Channel Side test pressure is more than the Shell side test pressure (As Channel side Design Pressure is more than Shell side and considered DP as MAWP). I suggested that collar bolts and other channel flange bolts can be used to hold bundle and Channel together during hydro test and no need to use Test Rings for Channel Test.

But this had been rejected from my counter-part by saying that Collar bolts are used to hold Tube and Shell only during removal of bonnet.

I got a doubt that why my idea was not acceptable?

Could anyone explain me why I should not use the collar bolts in that way? what is the logic behind it?

Also, I would like to ask that are we allowed to hydro test the kettle? since one of my exchanger manufacturers suggested me that we can use dummy shells to check for shell side gasket leaks. No need to go for Kettle, as the volume of kettle is more, tubes and other internals may fail during test, he says.

Please comment your views on this too.

Thanks in advance.

 

[SnTMan]

Hari1207, collar studs are ordinarily used only with B-type channels, as in your case. As you have noted they are used with full diameter tubesheets. They really only have one purpose: To prevent breaking the gasketed joint between the tubesheet and shell flange, when the bonnet is removed. This is so the shell gasket need not be replaced when the bonnet is removed for whatever reason. The collar studs are only intended to maintain a minimal contact force on the gasket, not full design seating force. This is more or less what your counter-part is saying.

If the tubesheet rim is designed so, hydrotest of the shell side may be conducted with the bonnet removed. BUT, all service bolting including nuts must be in place. As well, it can be possible to hydro the tubeside with bundle removed from the shell and the channel attached. Same cautions as before, tubehseet rim is designed so, all service bolting in place.

Having said all that, if the tubesheet rim is not thick enough to withstand the hydro stresses a test ring must be used.

As for hydrotest for kettles, in my experience this is very common, specially constructed test shell are very uncommon. Due to the added expense. If there is some reason the shell cannot be flooded, such as internals that cannot be adequately dried, the bundle could be hydro'd in a test shell. But the shell most likely would still need to be pressure tested in some way, pnuematically I'd guess, what other way is there?

Regards,

Mike

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

 

[r6155]

1.Shell flange (before welded to the shell) may be used for hydrostatic test of tube side.

2.Shell side shall be hydrostatically tested with the tube bundle installed

Regards

 

[Hari1207]

Thank you so much Mike.