2 replies to this topic

[ChemE04]

Hi everybody,

I have a question. I have to rerate three condensers in series for proper design conditions, considering the loss of cooling water.

Tube side: cooling water
Shell side: steam and hydrocarbon vapors

The request is very general, because they don't say how much cooling water could be lost compared to the design conditions. My solution would be pretty general as well, either decrease the flowrate of steam and vapors or increase the number of tubes for greater removal of heat. I need to be more specific though and I was wondering that I might have to take a look downstream or upstream of the condenser, but I don't have a clue what parameters to start looking for . Any suggestions are greatly appreciated. Thanks!

ChemEGirl.

[Diederik Zwart]

Loss of cooling water normally means complete loss. (e.g. failure of the main cooling water pumps, or loss of power in the plant). So the answer to your first question: "How much cooling water is lost?" is: All cooling water.

What I would look at is the design temperature and pressure of the condensors. Probably the first one is designed for the correct maximum temperature and pressure of the vapor and steam feed. The two condensors downstream (and other downstream equipment and downstream piping as well) may be designed for lower pressure and temperature, but will see the same pressure and temperature as the first one if no cooling takes place. If that's the case try to calculate if the equipment/piping is suitable for the new design conditions and if not take measures to decrease the effects of the cooling water loss (install relief valves, or shut-off the feed if that is possible).

I hope this helps,
Diederik Zwart

[ChemE04]

Thanks! It really helped. That's what I sorta had in mind. These condensers were not rated for the design temperature of the steam even though other drums and piping downstream were in fact rated for this temperature, which is the highest to consider in this case, so I rerated them for this temperature. Thanks again!