Slotted bolt end Saddle Support 2

[AK375]

Hi,

Can anyone advise on the basis of selecting which end of the saddle (left/right)shall be provided with slotted holes in heat exchangers?

Regards

AK375

 

[mk3223]

Basically, the HEX has the fixed saddle end close to the channel head and the slotted saddle end at the the other end.

 

[KevinNZ]

The slotted support moves with temperature, so will the nozzles and piping at this end. Makes a difference to the nozzle and pipe stresses. The fixed end support and foundation end will have higher design loads.

 

[Christine74]

Typically this is NOT specified and the manufacturer just assumes that the fixed saddle belongs at the front of the exchanger and the slotted saddle belongs at the rear of the exchanger. But this is almost always wrong. The piping that connects to the exchanger nozzles is typically anchored somewhere behind the exchanger, so if you put the fixed saddle at the front of the exchanger the thermal expansion of the heat exchanger will move in the opposite direction of the expansion of the piping, thereby increasing the stress on the pipe and the loads on the nozzles.

It's almost always best to put the slotted saddle support at the channel end of the exchanger.


-Christine

 

[SnTMan]

It's almost always best to put the slotted saddle support at the channel end of the exchanger.

True perhaps, but: it is always the responsibility of the buyer to either specify or to review and confirm.

Regards,

Mike

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

 

[r6155]

For removable tube bundle fixed saddle shall be near the channel side.

Regards

 

[SnTMan]

The shell doesn't really care.

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

 

[r6155]

Best information is in SHELL COMPANY
DEP SPECIFICATION
AMENDEMTS / SUPLEMENTS TO API STD 660
DEP 31.21.01.30-Gen
February 2017

Fixed saddle support is near the channel side.

Regards

 

[SnTMan]

Yes, IF that spec is invoked by contract. And still the buyer has the say.

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

 

[Christine74]

Exactly, one would expect an engineer to be able to come up with a coherent reason for mandating something rather than just parroting something from some other client's standard.

As far as I can tell there is no logical reason to locate the fixed saddle support near the channel head by default. The fixed and the sliding ends for heat exchangers should be assigned the exact same way they are assigned for horizontal vessels, i.e. the fixed saddle should be located on the side that's closest to the pipe rack.

-Christine

 

[SnTMan]

Nevertheless, fabricators almost always locate the fixed support this way by default. The justification is that that is the end where the most piping connections are, two on the channel, one on the shell. Very rare to know where the pipe rack (or anything else) is.

The client may or may not change it. I'd guess less than 50%.

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

 

[r6155]

The specification I mentioned is from SHELL COMPANY. It is the buyer, not the fabricator.

Regards

 

[Trestala]

@r6155, there is no such requirement in DEP 31.21.01.30-Gen.

 

[r6155]

@Trestala
Do you have DEP SPECIFICATION
AMENDEMTS / SUPLEMENTS TO API STD 660
DEP 31.21.01.30-Gen
February 2017?

Regards

 

[SnTMan]

Here we go with this kind of exchange again

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