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In checking a trap ultrasonically, a continuous rushing sound will often be the key indicator of live
steam passing through. There are subtleties for each type of trap that can be noted.
Use the sensitivity levels of the Sensitivity election Dial to assist your test. If a low pressure system
is
to be checked, adjust the sensitivity UP toward 8; if a high pressure system (above 100 psi) is to be
checked, reduce the sensitivity level. (Some experimentation may be necessary to arrive at the most
desirable level to be tested.) Check upstream and reduce the sensitivity so that the meter reads about
50% or lower, then touch the trap body downstream and compare readings.
General steam/condensate/flash steam confirmation
In
instances where it may be difficult to determine the sound of steam, flash steam or
condensate,
1. touch at the immediate downstream side of the trap and reduce the sensitivity to get a mid-line
reading on the meter (about 50%).
2. Move 15-30 cm downstream and listen. Flashing steam will show a large drop off in intensity
while leaking steam will show little drop off in intensity.
Inverted bucket traps
INVERTED BUCKET TRAPS normally fail in the open position because the trap loses its prime. This
condition means a complete blow-through, not a partial loss. The trap will no longer operate
intermittently. Aside from a continuous rushing sound, another clue for steam blow-through is the
sound of the bucket clanging against the side
of the trap.
bucket trap drawing
Float and thermostatic
A FLOAT AND THERMOSTATIC
trap normally fails in the "closed" position. A pinhole leak produced
in the ball float will cause the float to be weighted down or water hammer will collapse the ball float.
Since the trap is totally closed - no sound will be heard. In addition, check the thermostatic element in
the float and thermostatic trap. If the trap is operating correctly, this element is usually quiet; if a
rushing sound is heard, this will indicate
either steam or gas is blowing through the air vent. This
indicates that the vent has failed in the open position and is wasting energy.
Thermodynamic
THERMODYNAMIC
(
DISC) traps work on the difference in dynamic response to velocity change in
the flow of compressible and incompressible fluids. As steam enters, static pressure above the disc
forces the disc against the valve seat. The
static pressure over a large area overcomes the high inlet
pressure of the steam. As the steam starts to condense, the pressure against the disc lessens and
the trap cycles. A good disc trap should cycle (hold-discharge-hold) 4-10 times per minute. When it
fails, it usually fails in the open position, allowing continuous blow through
of steam.
