Lock-Out Traps For Start-Up Loads - Xylem Bell & Gossett Hoffman Speciality Series Engineering Data Manual

Lock-out Traps For Draining Condensate
Under Low Pressure.
In the discussion of trap operation, we point-
ed out that if the differential pressure across
the trap seat exceeds the trap pressure rat-
ing, the trap will fail closed. This occurs when
the differential force across the seat and pin
exceeds the drop-away force created by the
weight of the float or bucket and linkage.
Under certain conditions we can use a trap
with a low differential pressure in a high pres-
sure application to drain condensate during
start-up or operation at reduced pressure.
Low pressure F & T or Bucket Traps may be
used for lock-out applications.
Lock-out trap used to drain underground steam main
POWER
PLANT
Lock-out Trap Used to Drain
Underground Steam Main.
One application of a lock-out trap is to drain
condensate from underground steam lines
during start-up. The low pressure trap con-
nected to an open drain or sump drains con-
densate during start-up. When the steam line
pressure exceeds the trap rating it will close
and remain closed. The differential pressure
will then allow the condensate to flow through
the high pressure drip trap and be recovered
through the return line.
This method may also be used where a modu-
lating temperature regulator may reduce pres-
sure ahead of the trap. When the regulator
reduces the flow of steam, the pressure in
the steam space drops due to the condensing
rate in relation to steam flow. The low pres-
sure trap connected to a sump or drain will
then operate when the pressure drops approx-
imately to the rated pressure of the trap.
UNDERGROUND WET
RETURN LINE
UNDERGROUND
STEAM LINE
LOCKOUT
TRAP TO DRAIN
HIGH PRESSURE
DRIP TRAP
Lock-Out
Traps for
Start-Up
Loads
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