750-96 (revised 2010)
Model CB Packaged Boiler Manual
7-3
7.3 — Water Level Controls and Waterside of Pressure Vessel
Always be sure of the boiler water level. The water column should be blown down routinely. Check samples of the
boiler water and condensate in accordance with procedures recommended by your water consultant. Refer to Sec-
tions 2.8 And 2.9 in Chapter 2 for blowdown instructions and internal inspection procedures.
Since low water cut-off devices are generally set by the original manufacturer, no attempt should be made to
adjust these controls to alter the point of low water cut-off or point of pump cut-in or cut-out. If a low water device
should become erratic in operation, or if its setting changes from previously established levels, check for reasons
and correct, repair or replace as required.
FIGURE 7-1. Low Water Plate
Figure 7-1 is a replica of the low water cut-off plate attached to a steam boiler. These instructions should be fol-
lowed on a definite schedule. These controls normally function for long periods of time which may lead to laxity in
testing on the assumption that normal operation will continue indefinitely.
Water cut-off device(s) should be removed from the bowl at least once a month to check and clean the float ball,
the internal moving parts, and the bowl or water column.
Remove the pipe plugs from the tees or crosses and make certain the cross-connecting piping is clean and free of
obstructions. Controls must be mounted in a plumb position for proper performance. Determine that piping is ver-
tically aligned after shipment and installation and throughout life of the equipment.
A scheduled blowdown of the water controls on a steam boiler should be maintained.
It is impractical to blowdown the low water cut-off devices on a hot water boiler since the entire water content of
the system would become involved. Many hot water systems are fully closed and any loss of water will require
make-up and additional feedwater treatment that might not otherwise be necessary. Since the boiler and system
arrangement usually makes it impractical to perform daily and monthly maintenance of the low water cut-off
devices, it is essential to remove the operating mechanism from the bowl annually or more frequently, if possible,
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