Vacuum condensate return system 1

[maxchief]

Greetings,
Would like to know the reason for the inclusion of a bypass
line at the outlet of a L.P. steam coil on an AHU.
Obviously a strainer is in front of the F&T Trap on the
return piping but after the F&T a 3/4" line runs back to the
coil outlet. This line is fitted with a check which is opening
towards the steam coil.All the AHU's are piped this way and
the return main is running to the accumulator tank of a
65K Dunham Bush Vacuum Tank.Can anyone that is sure of the reason for the inclusion of this bypass take a few minutes
to explain.
Thanks,

 

[imok2]

I believe this it to releive the vacuum that is present when the control steam valve closes other wise the accumulated condensate would not be able to drain through the F&T

 

[BronYrAur]

As imok2 said, think of it as a vacuum breaker. If it were not on a vacuum return system, the check valve (vacuum breaker) would just be open to atmosphere, and there would not a "bypass" line run back to the condensate side of the trap.