construction is more complex than inverted bucket
type but is suitable for applications having wide
variation of load and pressure, and is recommended
for constant pressure systems. Bucket sinks into
condensate when condensate reaches top of trap and
the discharge port opens. After discharge, the
bucket floats on incoming condensate keeping the
discharge port closed.
c. Impact-Operated Traps: These traps depend on
steam velocity to keep the disc closed. As steam
velocity decreases, the disc lifts off the seat and
allows flow of condensate. These traps allow some
steam leakage and do not vent air at low pressure.
They are not recommended for service lower than 70
kPa (10 psig) or where back pressure may exceed 50
percent of inlet pressure. These traps are less
expensive and have poor performance in the presence
of dirt.
d. Thermostatic Traps: These traps are
bellows-actuated and contraction of bellows at a few
degrees below saturated steam pressure allows
condensate air and noncondensable gases to be
discharged. As steam reaches the bellows, the
expansion of the bellows closes the discharge port.
These traps can also be utilized to vent air from a
steam system and can be used in conjunction with an
inverted bucket type steam trap previously described.
e. Float and Thermostatic Trap: These traps
provide optimum performance on modulating systems at
lowest first cost. Where steam pressures modulate
down to zero, large amounts of air may be liberated.
They are ideal for dripping ends of steam risers,
heels of up-feed steam risers, bottoms of down-feed
steam risers. These traps are also ideal for fan
coil units and unit heaters.
f. Any trap selected must be sized for the expected
condensate load with an applicable safety factor
applied for the particular type of equipment
serviced. Manufacturer's application manuals should
be consulted to assist in sizing traps. Safety
factors vary from 2:1 to 10:1. An average 3:1
safety factor value will cover most applications.
g. Service life between repairs or replacement of
traps may be a determining factor in the choice of
traps. One manufacturer of all types of traps
offers the following experience record:
Average Service Life
Between Replacement
Type of Trap
or Repairs
Inverted bucket traps
42 months
Float and thermostatic traps
24 months
Thermostatic traps
24 months
SECTION 15559A
Page 65
Previous Page
