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Electrode Boiler
Sampling system and surface blowdown
The piping schematic will show the specific details of these
lines. The most common configuration of the sample line is a
gate valve at the vessel, a sample cooler, and sometimes a flow
control metering valve to a fitting holding the conductivity cell.
From the conductivity cell, the water is piped back to the
boiler. The sample flow should be at the minimum that will
give an accurate measurement.
The conductivity cell takes a reading of the conductivity of the
boiler water and feeds the signal to the conductivity controller.
The conductivity controller automatically oversees the
conductivity of the boiler water, keeping it within the limits
acceptable for proper operation (see 4.3 - Boiler Control
Circuits).
The surface blowdown line usually contains a gate valve,
solenoid valve, and a flow control metering valve. It operates
when the conductivity of the water is too high, drawing off
some of the water from the vessel so that fresh makeup may
be added to dilute the conductivity. It is a blowdown line and
must be piped to drain in a safe area such as a b1owdown
tank.
Figure 6 - Sample cooler
Safety Valves
Safety valves are standard with this boiler The valve
discharge must be piped and vented to the atmosphere
outside the boiler room at a location that is safe for persons
in the area. These valves must be piped in such a manner
that they will not hinder access to any of the boiler controls.
Use a gravity drain for condensate near the safety valves,
and at any low points below the valve seats. Small
condensate drain valves may be used if they are left open
during operation and are piped to drain in a safe location.
Steam outlet
The steam outlet size is determined by the boiler 's capacity
and operating pressure. The piping schematic will give the
Figure 7 - Safety valves & steam outlet
actual size. Usually, there will be a gate valve directly
outside the boiler, and a back pressure regulating valve with
its controller.
Chemical feed pump
The chemical feed pump is not part of the standard boiler package, but can be added as part of a
completely automatic conductivity control system. The pump is actuated by a signal from the
conductivity control circuit if a low conductivity condition is sensed in the boiler water. It pumps
chemical into the boiler to bring the conductivity to the correct level for operation. The pump starter
may be located in the medium voltage compartment.
750-272
7
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