28 replies to this topic

[katmar]

Mahesh, I agree that you need to add a valve into the secondary condenser vapor circuit to equalize the pressure drops through the two parallel paths. The flow of air is so low that it probably would not work to put the valve in the vapor outlet from the second condenser, so I agree with your plan of putting a butterfly valve into the vapor line leading to the secondary condenser. It might be an idea to use a butterfly valve with a manual gearbox actuator so that you can adjust it finely and there will be less of a chance of it being bumped out of setting by accident.

[Mahesh@A&M]

I have attached a brief report on hydraulics for inlet vapor piping and condensate drain piping. Distance between these two condensers is less than 7' and they are pretty much at same elevation (1.5'difference).

With seal legs in place for drain lines, vapor will not flow through these lines. As you mentioned I have vapor equalization lines (2" SCh40) and anti syphon vent lines are connected to this line.

Only thing that worries me is height of seal leg. I included those calculations in this report. I would like to know if it is right as I am not sure if I have to size it for pressure difference between reflux drum and condenser inspite of pressure equalization line (here I assumed blocked line) or critical height required for self venting? Appreciate your kind help.

Attached Files

•  Condenser installation.pdf   273.75KB   106 downloads

[katmar]

Mahesh, the calculated pressure drops for the vapor lines are wrong. The term on the right hand side (in the big square brackets) should be squared. The pressure drops will be less than indicated in the report, but I do not think this difference will have any impact on the design or operation of the condensers.

As you have correctly concluded, vapor will be entrained down the condensate drains from the condensers to the reflux drum. This vapor will be entrained through the seals and result in potential losses as warned of previously by pawan. If the liquid is sub-cooled it may cause some vapor to condense in the drains or in the drum, but I would not rely on this. The only sure-fire answer to this is to increase the size of the drain lines but of course this means modifications to the condenser nozzles and may not be possible or practical.

The vapor entrained in the drains will decrease the density of the liquid in the seal and affects the calculation of the required height. However, you have based your height on the full pressure drop across the condensers so the height would be safe. But as noted above, because the liquid entrains vapor through the seal it is not really functioning as a seal to keep the vapor from the reflux drum.

[Mahesh@A&M]

We finally installed the condenser in the recommended configuration and it is working great. I had to pinch down pressure equalization line (non condensible vent) valve to subcool the liquid few degrees more.

Thank you and appreciate all your help.