a.
Blower Failure
b.
Blower High Temperature
c.
Bag Filter Failure
d.
Bag Filter High Differential
e.
Bag Filter Off
f.
Plugged Hopper
g.
Conveying Complete
h.
Clinker Crusher Abnormal Shutdown (1 required for each boiler)
i.
Low Conveying Air
j.
High Conveying Vacuum
2.12.21.4
Vacuum Transmitter
To measure conveying system vacuum. Range shall be zero to 101 kPa 30
inches mercury with 4 to 20 mA dc linear transmitter output.
Display
vacuum on the operator interface console specified under VAMS Section 15901N
CONTROLS AND INSTRUMENTATION BOILER PLANT.
2.12.22
Controls Operation
2.12.22.1
Automatic
Normally operated in the automatic mode. Automatically sequence through
automatic intakes except the clinker crusher for each boiler after the
system is started. When a unit is not in operation, selecting the "bypass
mode" shall cause intakes on that unit to be skipped. For Manual
operation, "index" is used to select the desired intake. As the conveying
system shuts down automatically, the main conveyor line shall be purged for
approximately one minute to remove ash remaining in it.
2.12.22.2
Switching
Sequence system under the control of vacuum switches and timers. Maximum
vacuum will be when system is conveying material. When a hopper is empty,
vacuum will drop and a "no load" vacuum switch shall cause the system to
shift to the next intake. Prevent premature sequencing due to momentary
low vacuum with a timer. When a plugged hopper occurs, vacuum will be
between "no load" and normal value. Provide a timer to allow packed or
arched material to break loose before alarming the condition.
2.12.22.3
Valves
Provide solenoid air valves for each air operated device, timers,
contactors, relays and devices and equipment required for system control,
measuring and operation. Identify each device with an engraved plastic
identification plate [in accordance with a system graphic display] provided
by the ash handling system supplier.
SECTION 15502N
Page 142
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