Chemical Engineering March 2014 - 55

Solids Processing
temperature. A locally mounted
temperature indicator should be
provided at the blower discharge,
and also at the blower after-cooler
discharge if an air cooler is used.
This temperature is needed to
carry out calculations for the " asbuilt "
conveying system. If this air
temperature can affect the conveying
characteristics of solids
being conveyed, it must be monitored
closely.
Rotary-valve motor interlocks
with the blower motor. A manually
adjustable timer with a selector
switch should be provided in
the control room to provide three
functions: 1) Automatically stop the
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56 ChemiCal engineering www.Che.Com marCh 2014
rotary valve if the conveying pressure
starts to increase (indicating
start of formation of a line plug); 2)
Allow the blower motor to continue
to run for the selected time, such
as 10 to 15 minutes (in an effort
to clear the line plug); and 3) Restart
the rotary-valve motor if the
conveying pressure falls to the normal
pressure.
Diverter valves. Position lights are
provided in the control room graphic
panel to indicate if the valves are in
the " through " or " divert " position.
Receiving bins. Low- and highlevel
lights are provided in the
graphic panel for the receiving bins.
An alarm should be provided in the
control room to indicate high level
in the bins. At the high level, the rotary
valve motor should be stopped
automatically.
Bin vent filters/dust collectors.
The bin vent filters or the dust collectors
on the bin vents must be
running before the conveying system
is started. A " run " light for the
filter should be provided in the
graphic panel.
Pressure drop indicators should
be installed locally to show the pressure
drop across the filter elements.
Their locations should be easily accessible
to the operating staff. For
conveying materials that have high
dust loading, alarms for low- and
high-pressure drops should be provided
in the control room. The lowpressure
drop alarm would indicate
a ruptured filter element, and
the high pressure drop alarm
would indicate a completely clogged
filter element.
Instrumentation checklist
A summary of the instrumentation
requirements, as described above, is
provided below:
For the blower:
* Local and control room mounted
running lights for the blower
motor
* Local pressure indicator at the
blower discharge
* Local temperature indicator at
the blower discharge
* Local temperature indicator at
the blower after-cooler discharge,
for applications using a cooler
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Chemical Engineering March 2014

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