Chemical Engineering October 2020 - 40

Test point 4 (T4) should be equal to
or less than Test point 3 (T3). If T4
is higher than T3, then the air vent
mechanism has failed.
Test point no. 3
" 64 " DB
Test point no. 1
" 25 " DB
Test point no. 2
" 32 " DB
FIGURE 14. Measurements at three test points
indicating a failed steam trap
Proper Operation (PO). Using Figure
12 as a guide, consider the following
three measurements:
Test point 1:
Test point 2:
Test point 3:
32 dB
34 dB
34 dB
If a steam trap is operating properly,
the ultrasound level at Test
point 3 will not be higher than at
Test points 1 or 2.
NOTE: The reading at Test point 3
will be equal or less than the readings
at Test points 1 or 2. The highfrequency
ultrasound readings, in
addition to a temperature measurement
that is appropriate for the system
pressure, will indicate a properly
operating steam trap.
NOTE: If the ultrasound reading
at Test point 3 is higher than
the readings at Test points 1 or 2,
wait for 45 seconds to ensure that
the steam trap was not in a cycle
mode. During the cycle mode, the
ultrasound reading at Test point 3
will be higher, which is the proper
operation of a steam trap with on/
off discharge cycle.
Float and thermostatic steam
traps: Four test points. The float
and thermostatic steam trap has
two orifices: one orifice for discharging
the condensate and the
other orifice for the air vent mechanism
that discharges air and noncondensable
gases.
The four test points, shown in Figure
13, are as follows:
T1 - upstream of the steam trap
station,
T2 - downstream of the steam trap
station,
T3 - at the discharge side of the
steam trap condensate orifice, and
T4 - at the discharge side of the
steam trap air vent.
NOTE: If the air vent is operating
properly, the ultrasonic level at
40
Temperature
transmitter
Heat exchanger
T4
T2
T1
T3
1. 25 db
2. 32 db
3. 49 db
4. 40 db
FIGURE 15. Measurements at these four test
points indicate a steam trap leaking steam
Blowing or completely failed
steam trap (BLW). For this example,
the three test points indicated
on Figure 14, are as follows:
Test point 1:
Test point 2:
Test point 3:
25 dB
32 dB
64 dB
A significant increase (greater
than two times the base level reading)
in the decibel level at test point
3 indicates that the steam trap is
failed open and allowing steam
to pass. Continue to monitor the
steam trap at test point 3 to see
whether the steam trap cycles according
to its design.
Steam leakage. When a steam trap
system is leaking steam, the following
test points, shown in Figure 15,
should be considered:
Test point 1:
Test point 2:
Test point 3:
Test point 4:
25 dB
32 dB
49 dB
40 dB
An increase in the decibel level at
Test point 3 indicates leaking steam
through the steam trap. Again, if this
increase is observed, take additional
time at test point 3 to determine
whether the steam trap is in the middle
of a discharge cycle. If the decibel
level at Test point 3 does not return
to the baseline value established
at test point 1, then the steam trap is
leaking steam.
Competing
downstream
ultrasounds.
Consider the five test-point
measurements shown in Figure 16,
in which all the steam components
are tested:
Test point 1:
Test point 2:
Test point 3:
Test point 4:
Test point 5:
22 dB
42 dB
28 dB
28 dB
52 dB
Temperature
transmitter
Heat exchanger
T5 T4
T2
T1
T3
1. Upstream
2. Downstream
3. Steam trap discharge
orifce
4. Steam trap air vent
5. ** check valve
FIGURE 16. Utrasound testing of all steam components
requires these five test points
The above readings show that ultrasound
is being produced downstream
of the steam trap. Check
valves can be a source of additional
ultrasound in the piping system.
Perform further testing at the other
components in the steam trap station
(Test point 5) if the assessor
determines that the check valve in
the system is generating the high
ultrasound levels. If the decibel
value is higher at Test point 5, then
there are competing ultrasounds
in the system. If the value is lower
at Test point 5, conduct further examination
of the piping and steam
trap to determine the source of the
higher ultrasound.
Sound characteristics
While using ultrasound listening devices,
the tester should be made
aware of a few distinct sounds that
he or she may hear while testing
steam traps:
* Crackling - This sound signature
is generated by condensate
flowing through a steam trap with
flash steam occurring after the discharge
orifice of the steam trap
* Whistling - A whistling sound is
a characteristic of steam passing
through a steam trap orifice ■
Edited by Gerald Ondrey
Author
Kelly Paffel is the technical manager
at steam-engineering firm
Inveno
East Fletcher Ave,
Email:
Engineering, LLC (7320
Tampa, FL
33637; Phone: 239-289-3667;
Website:
www.invenoeng.com;
kelly.paffel@invenoeng.
com). Paffel has 42 years of experience
in steam and power operations,
and is an experienced lecturer
who has published many technical papers on the
topics of steam system design and operation. He is
known for writing " Steam System Best Practices, " which
are used by plants and engineers globally to ensure
proper operation of steam and condensate systems.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM OCTOBER 2020
http://www.invenoeng.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering October 2020

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