Burnham MEGASTEAM MST288 - Manual (Page 49)

49
SECTION Ix: MAINTENANCE AND SERVICE INSTRUCTIONS
A. MAINTENANCE OF LOw wATER CUT-
OFF DEVICES
WARNING
Probe and float type low water cut-off devices
require annual inspection and maintenance.
1. PROBE TYPE LOW WATER CUT-OFF
Although these devices are solid state in their
operation, the probe is exposed to possible
contamination in the boiler water and subject to
fouling.
It is important to physically remove the probe from
the boiler tapping annually and inspect that probe
for accumulation of scale or sediment.
Follow these steps to inspect, clean and/or replace
the probe:
a. Turn off electric service to the boiler.
b. Drain boiler water to a level below the tapping
for the probe.
c. Disconnect wiring connections between the low
water cut-off control and the probe.
d. Remove the low water cut-off control from the
probe.
DANGER
Assure that the boiler is at zero pressure before
removing the LWCO probe. Do not rely on the
pressure gauge to indicate that the boiler is at
zero pressure. Open the safety valve to relieve
all internal pressure prior to proceeding. Safety
valve discharge piping must be piped such that
the potential for burns is eliminated.
e. Unscrew the probe from the boiler tapping.
f. Inspect that portion of the probe that is exposed
to the boiler water for a scale or sediment
buildup.
g. Light deposits may be removed by wiping the
probe with a damp cloth. Wiping the probe with
a cloth soaked in vinegar will remove more
tenacious lime deposits. The most stubborn
deposits may be removed from the probe by
using a diluted amount, 3 parts of water to 1 part
of phosphoric acid (H
2
PO
4
).
CAUTION
Exercise caution when handling phosphoric acid
and follow the instruction label on its container.
h. Clean the pipe threads of the probe to remove
old, hardened pipe dope and other foreign matter.
i. Apply a moderate amount of good quality pipe
dope to the pipe threads on the probe, leaving the
two end threads bare. Do not use PTFE (Teflon)
tape.
j. Screw the probe into the boiler tapping.
k. Mount the low water cut-off control on the
probe.
l. Reconnect the control to probe wiring.
m. Fill the boiler to its normal waterline.
n. Add boiler water treatment compound as needed
(refer to Paragraph B.).
o. Restore electric service to the boiler.
p. Fire burner to bring the water in the boiler to a
boil to drive off free oxygen.
q. WARNING — BEFORE RETURNING
BOILER TO SERVICE: Follow the low water
cut-off check out procedure in Section VIII,
Paragraph I, No. 4.
2. FLOAT TYPE LOW WATER CUT-OFF
During the heating season, if an external low water
cut-off is on the boiler, the blow off valve should
be opened once a month (use greater frequency
where conditions warrant), to flush out the sediment
chamber so the device will be free to function
properly.
Low water cut-offs and water feeders should
be dismantled annually by qualified personnel,
to the extent necessary to insure freedom from
obstructions and proper functioning of the
working parts. Inspect connecting lines to boiler
for accumulation of mud, scale, etc., and clean as
required. Examine all visible wiring for brittle or
worn insulation and make sure electrical contacts
are clean and that they function properly. Give
special attention to solder joints on bellows and float
when this type of control is used. Check float for
evidence of collapse and check mercury bulb (where
applicable) for mercury separation or discoloration.
Do not attempt to repair mechanisms in the field.
Complete replacement mechanisms, including
necessary gaskets and installation instructions are
available from the manufacturer.
B. BOILER AND SYSTEM CLEANING
INSTRUCTIONS FOR TROUBLE FREE
OPERATION
1. STEAM BOILERS
a. Oil, greases & sediments which accumulate in a
new boiler and piping must be removed in order
to prevent an unsteady water line and carry over
of the water into the supply main above boiler.