Inspection and Maintenance
7-4
750-96 (revised 2010)
Model CB Packaged Boiler Manual
to check and clean float ball, internal moving parts, and the bowl housing. Also check the cross-connecting piping
to make certain that it is clean and free of obstruction.
7.4 — Water Gauge Glass
A broken or discolored glass should be replaced at once. Periodic replacement should be a part of the mainte-
nance program. Always use new gaskets when replacing a glass. Use a proper size rubber packing. Do not use
“loose packing” which could be forced below the glass and possibly plug the valve opening.
Close the valves when replacing the glass. Slip a packing nut, a packing washer, and packing ring onto each end
of the glass. Insert one end of the glass into the upper gauge valve body far enough to allow the lower end to be
dropped into the lower body. Slide the packing nuts onto each valve and tighten.
If the glass is replaced while the boiler is in service, open the blowdown and slowly bring the glass to operating
temperature by cracking the gauge valves slightly. After the glass is warmed up, close the blowdown valve and
open the gauge valves completely.
Check the try-cocks and gauge cocks for freedom of operation and clean as required. It is imperative that the
gauge cocks are mounted in exact alignment. If they are not, the glass will be strained and may fail prematurely.
7.5 — Electrical Controls
Most of the operating controls require very little maintenance beyond occasional inspection. Examine the tight-
ness of electrical connections. Keep the controls clean. Remove any dust that accumulates in the interior of the
control using a low pressure air hose and taking care not to damage the mechanism.
Examine any mercury tube switch for damage or cracks: this condition, indicated by a dark scum over the nor-
mally bright surface of the mercury, may lead to erratic switching action. Make certain that controls of this nature
are correctly leveled using the leveling indicator, if provided. The piping leading to those controls actuated by pres-
sure should be cleaned, if necessary. Covers should be left on controls at all times.
Dust and dirt can cause excessive wear and overheating of motor starter and relay contacts, and maintenance of
these is a requirement. Starter contacts are plated with silver and are not harmed by discoloration and slight pit-
ting. Do not use files or abrasive materials such as sandpaper on the contact points since it only wastes the metal-
lic silver with which the points are covered. Use a burnishing tool or a hard surface paper to clean and polish
contacts. Replacement of the contacts is necessary only if the silver has worn thin.
Thermal relay units (overloads) are of the melting-alloy type and when tripped, the alloy must be given time to re-
solidify before the relay can be reset. If overloads trip out repeatedly when the motor current is norm all, replace
them with new overloads. If this condition continues after replacement, it will be necessary to determine the cause
of excessive current draw.
The power supply to the boiler must be protected with dual element fuses (fusetrons) or circuit breakers. Similar
fuses should be used in branch circuits and standard one-shot fuses are not recommended. Information given on
the Fuse Sizes Chart (Figure 7-2) is included for guidance to fuse requirements.
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