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Condensate return lines between the steam trap and the condensate recovery system should be carefully engineered to ensure minimum back pressure is created on the steam trap to ensure effective condensate evacuation.

Condensate is valuable resource. An effective condensate recovery system that collects the hot condensate from the steam using equipments and returns it to the boiler feed system needs to be carefully designed. Broadly, Condensate return lines can be classified into three categories: drain lines to traps, trap discharge lines and pumped return lines.

At the outlet of the steam trap, the line must carry not only the condensate and any air or other condensable gases, but also any flash steam released from the condensate. Wherever possible, these lines connecting to a flash steam recovery vessel of a condensate pump or even directly to the boiler feed water tank, should fall with a slope of 1/70.

At startup the condensate will be relatively cool and there will be little or no flash steam. But the condensing rate will be at maximum, and also any air discharged through the trap will have to pass along the line with the condensate. The pipes must then be at least equal in size to those at the inlet side of the traps. Usually the inlet lines are sized for twice the running load of the equipment.

If care is not observed in this designing, the line may be undersized thereby increasing back pressure on the steam traps, hampering condensate evacuation.  This condition may impact the process and results can include reduced heat transfer or increased process time.