CleaverBrooks CBEX-DE, Эксплуатация и обслуживание

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Introduction
1-12
750-392
CBEX -DE
1.2.10 — Temperature Controls (hot water boilers)
High Limit Temperature Control : Breaks a circuit to stop burner operation on a rise of temperature at a selected
setting. It is adjusted to stop the burner at a preselected temperature above the operating control setting. The
high limit temperature control normally is equipped with a manual reset.
Operating Limit Temperature Control : Breaks a circuit to stop burner operation on a rise of boiler temperature at
a selected setting. It is adjusted to stop or start the burner at a preselected operating temperature.
1.2.11 — Water Level Controls
The Low Water Cutoff (LWCO) shuts down the burner if water level goes
below the safe operating point. The LWCO is also responsible for starting
and stopping the feedwater pump to maintain the proper boiler water
level. The Cleaver-Brooks Level Master is the standard LWCO on CBEX-
DE boilers.
1.
Low Water Cutoff and Pump Control : Float-operated control responds to the water
level in the boiler. It performs two distinct functions:
•
Stops firing of the burner if water level lowers below the safe operating point. Energizes
the low-water light in the control panel; also causes low-water alarm bell (optional
equipment) to ring. Code requirements of some models require a manual reset type of
low water cutoff.
•
Starts and stops the feedwater pump (if used) to maintain water at the proper operat-
ing level.
2.
Water Gauge Glass Drain Valve : Provided to flush the gauge glass.
3.
Vent Valve : Allows the boiler to be vented during filling and facilitates routine boiler
inspection as required by ASME Code.
4.
Water Column Drain Valve : Provided so that the LWCO and its piping can be flushed
regularly to assist in maintaining cross-connecting piping and in keeping the float bowl
clean and free of sediment. A similar drain valve is furnished with the auxiliary low water
cutoff.
5.
The Auxiliary Low Water Cutoff (ALWCO) stops burner operation in the event boiler
water drops below the primary low water cutoff point. May require manual reset in order
to restart the boiler after a low water condition.
FIGURE 1-16. Low Water Cutoff, Aux. Low Water Cutoff
Level Master safety features include float detection, routines for water column
blowdown and ALWCO testing, and an independent watchdog system for
shutdown in the event of microprocessor failure. An internal clock provides
time-stamped event logging for all blowdown cycles and alarm occurrences.
The Level Master keypad/display unit is mounted in the control panel next to
the Hawk HMI. A bar graph provides a continuous reading of water level,
while a two row backlit LCD display shows controller messages. The sensor
component is mounted in the water column and can be easily removed for
inspection or cleaning.
Expanded programming features can be accessed via RS-232 computer con-
nection.
For further information see the Level Master manual provided separately.
1
3
2
4
LWCO
ALWCO
5
FIGURE 1-17. Level Master
display