Vent lines

Posted by: honest_stressman

Vent lines - 02/06/07 09:58 AM

I am presently working on one 40" vent line running from top of column which is around 30m high. This line is connected to an exchanger which is on a structre around 4.0 m away from column in horizontal direction and structre TOS is 26.0 m. The line operating temperature is 200 Deg. C, Line is SS material. The column temperature varies along its height. At column nozzle lvl I have a vertical expansion of around 62.0 mm The line comes from top of column , runs vertically around 3-4 m. and then gets connected runs horizontally around 4.0 m , then goes down 3.5 m and reaches exchanger top nozzle. I have put a pressure balanced expansion joint in vertical on column nozzle to absorb column growth ( which is vertical). The client is insisting on putting the joint in horizontal, and making it tied universal to reduce cost. But the processos licensor has objection to putting it in horizontal since that will lead to condensation of vapour.
I have few questions-
1. Is it abnormal to put pressure balanced bellow as I have put on column top ?
2. If the exchanger is put on springs then the bellow can be removed ( not needed in horizontal or vertical), but then the exchanger needs to be put on constant springs. Also other nozzles also move with the exchanger. The exchanger nozzle has 55.0 mm upward movement which gets transferred to exchnager lifting it up. All the connected piping will have to be made extensively flexible as the excahnger will pull the connected pipes upward by 55.0 mm. Is this option tried by anyone anywhere ?
Regards,
honest_stressman
Posted by: CraigB

Re: Vent lines - 02/06/07 10:38 AM

You might want to try putting a tied expansion joint in each of the two risers. This may allow the horizontal run to move out of a horizontal plane to compensate for the differential movement without incurring the wrath of your process engineer.

Otherwise, it sounds like the process guys will veto the owner's suggestion and you will have to use a pressure-compensated joint as you describe. This seems like a classic application for such hardware.

Putting an entire exchanger on springs will probably create more problems than it solves. It's not recommended unless you have no possiblity of transient loads of any sort (including wind, seismic, and fluid transient loads). Any sort of forcing function applied to such a setup would create a dynamic analysis nightmare.
Posted by: NozzleTwister

Re: Vent lines - 02/06/07 04:47 PM

They sure didn't do you any favors with the equipment locations.

Let me add a couple more things to consider.

Do you have any Wind or Seismic conditions? If so, the lateral deflections at the top of your tower and the top of your structure can be quite large and unless the tower and structure are tied together your vent line and any expansion joints you have are going the see the wrath of these movements, which could be out of phase with each other.

Good luck,
Posted by: Jouko

Re: Vent lines - 02/07/07 02:14 AM

Pressure balanced units are expensive, can be heavy and are specials. Before you use one get required movements and contact your supplier.