silo 3 - U.S. Department of Energy

10.3 HVAC SYSTEM CONTROL PHILOSOPHY
Process Control Plan for the Silo 3 Project
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Document No. 40430-PL-OOO3, Rev. 1
Jacobs Project Number 35H19605
September 5, 2003
50 69 I
The Supply and Exhaust Air Systems utilize controls typical of industrial installations. Each
of the three air-handling units (consisting of intake filters, fans, electric heaters, and
refrigeration-based air conditioning components) has local controls provided by the
manufacturer. The exhaust filtration system consists of two filter units and two exhaust
fans, with a crossover to allow either filter to be used with either fan. The major HVAC
system components are interfaced with the main PLC control system, allowing monitoring
and control of HVAC functions via the main HMI in the Operations SupportKhange Room
Trailer. The HMI display configuration includes a suitable display area for HVAC control
requirements.
The system is operated from the HMI by aligning the dampers and then selecting and
starting one of the two exhaust fans and two of the three air-handling units. One of the
three air-handling units serves as a backup. The pressure differential between the
Packaging Area and outside ambient is maintained using a variable-flow vacuum- relief
damper. A PLC-based proportional-integral-derivative (PID) control loop modulates this
damper. The PID loop uses input from a differential pressure transmitter, which senses
both the Packaging-Area pressure and ambient pressure. The PID loop is enabled and
provided with operating and alarm setpoints from the HMI. Additional inputs are provided
from door position sensors to tailor the response of the PID algorithm during off-normal
operating conditions.
The interior temperature is controlled by a PLC-based PID control loop utilizing input from a
temperature sensor in the Packaging Area and setpoints from the HMI.
The following upset conditions are alarmed at the HMI:
0
0
Failure of an air-conditioning unit
Failure of a fan
Failure to maintain either temperature or differential pressure
0 Detection of a fire
The HVAC system control logic is interlocked with the fire detection and air quality
monitoring systems to force the system to the most suitable operating mode during upset
conditions. Operators are able to control or reset the HVAC system from the operations
support trailer without entering the Process Building.
10.4' HVAC SYSTEM INTERLOCKS
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Detailed listings of interlocks for the Supply Air System, the Exhaust Air System, and the
Miscellaneous HVAC Systems are provided in Tables lo-=,
respectively.
10-2B, and 10-2C,
10.5 HVAC SYSTEM SETPOINTS
Detailed listings of setpoints for the Supply Air System and the Exhaust Air System are
provided in Tables 10-3A and 10-3B, respectively. There are no setpoints in the
Miscellaneous HVAC Systems.
10-5
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