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[ayan_dg]

I am trying to size a condensate collection drum. The max inflow of sub-cooled condensate (water) is 68 m3/hr at 80 °C and 0 barg. I am not able to fix the hold up time for the vessel. should I take 2 min or 5 min or 10 min . What is the industry practice ?

[katmar]

There are two important parameters you need to take into account in determining the residence time. These are
1) The variability of the flow
2) The response time to rectify a trip/fault

If the flow were always exactly 68 m³/h there would in fact be no need for a tank at all. In order for your flow controller on the pump discharge (which would probably be linked to the drum level) to have time to react to a change in flowrate you need a minute or two. A change in flow could be up or down, so you need to run the drum level around 50%. The residence time based on this working volume tells you how long the controller has in order to be able to respond to a decrease in in-flow. On the other hand, the empty space above the working level is what you have to play with when considering an increase in in-flow.

If the pump fails or trips, does your system automatically switch over? Does an operator need to get out into the field to manually restart the pump or switch over? How long will this take?

Also consider - what is the impact if the tank overflows or runs dry?

A good starting point would probably be 10 minutes on full tank volume or 5 minutes at the working volume. But there is no "one size fits all" answer here.