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YarwaY water column
InstallatIon, operatIon and maIntenance InstructIons
3 Startup aNd OpEratION
to place the water column in service the
following procedure is recommended:
1. Inspect the water column to ensure that all
the probes are installed and the associated
wiring is correct and all connections are
secure. wiring Should be neatly routed and
any contact between the high temperature
water column body or the probe cover
should be avoided.
2. open the blowdown valve.
3. crack the steam block valve and warm
up the water column for a period of 3 to 5
minutes with low velocity steam.
4. at the end of the warm-up period, close
the blowdown valve and then fully open the
steam valve.
5. the water connection block valve should now
be opened, or alternately, if this valve is left
closed, the vessel will fill with condensate
allowing the operating range to be verified.
6. the water block valve must then be fully
opened.
7. Visually check all the probes for any sign of
leaks. replacement of the probe cover using
the ¼" socket head cap screws will complete
the commissioning of the water column.
8. the metallic sensing tip of any probe
may self-passivate or the probe insulator
may retain a slightly conductive film from
processing. a "hot start" as outlined
above will clear any residual passivation
or coating. attempting to commission
a water column with probes using cold
water, such as during a hydrostatic test,
cannot guarantee proper probe wetting.
the display/relays may therefore generate
a random output commonly called
"checkerboarding". Pre-cleaning the probes
(see section 4.2 (3)) will also eliminate this
potential commissioning problem.
9. Isolation and blowdown valves should be
carefully selected and installed as outlined
in aSme Boiler & Pressure Vessel code,
Section I. Yarway welbond valves, Series
5600, are recommended.
10. During vessel blowdown, isolation or
testing, some form of interlocking bypass of
the high and low water control outputs may
be required to avoid boiler tripping.
4 MaINtENaNCE
each boiler installation is subject to varying
operating and water conditions. Generally, the
higher operating pressure units (>1800 psig
[125 barg]) have improved water treatment and,
as such, maintenance is minimized.
4.1 water column
a specific maintenance program is difficult to
detail but the following outlines the minimum
required: the water column should be blown
down periodically and visually inspected for
leaks every 3 months.
4.2 probes
warNINg
Before servicing the probes, ensure that the water
column is properly isolated from the system, all
pressure has been relieved and the unit cooled
to an acceptable level, otherwise severe personal
injury and property damage may occur.
NOtE
the voltage to the probes from the electronic module
is 24 Vac rmS or less for all Yarway remote level
indicating devices. the power, therefore, does not
have to be turned off when working with the probes.
Probe tips may be shorted to ground but should never
be subjected to another voltage source. assuming
trouble-free operation, probes should be inspected
after the first 12 months. thereafter, they should be
inspected as required, depending upon the degree of
contamination found at first inspection.
1. Hp probe: loosen the probe retaining nut
approximately 1 turn and then free the probe
to verify all pressure has been relieved. the
metal to metal sealing surface initially may
cause the probe to stick, so carefully free
the joint by tapping the probe on the metal
body. Do not strike the zirconia insulator
and do not turn the probe hex head nuts or
the probe will be destroyed. after the probe
becomes free, loosen the probe retaining nut
fully and remove the probe.
Lp probe: loosen the probe slowly. If
any steam or water begins to vent, stop
immediately and ensure that the column is
isolated from the system and pressure has
been relieved.
4
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