Part 3 – Coping with Large Demands for Compressed Air
Your current program should be suitable for maintaining the desired pressure range as long as
the plant air consumption remains relatively modest. As the plant air consumption approaches
100% capacity however, it becomes obvious that we will need to have both compressors running
in order to satisfy this increased loading.the plant air consumption remains relatively modest. As the plant air consumption approaches
100% capacity however, it becomes obvious that we will need to have both compressors running
Modify your program so that the second pressure switch PE2 will detect when the storage tank
pressure drops below our current minimum setting of 110PSI. This situation will occur if a single
compressor is unable to keep up to the load and the tank pressure continues to drop. If and when
the pressure drops to 109PSI, the idle compressor should be started, and both compressors will
then continue to run until the tank is up to full pressure.pressure drops below our current minimum setting of 110PSI. This situation will occur if a single
compressor is unable to keep up to the load and the tank pressure continues to drop. If and when
the pressure drops to 109PSI, the idle compressor should be started, and both compressors will
It is likely that your modifications will also result in both compressors being run when the system
is first started and the tank pressure is initially being brought to within range of the pressure
switches. This action will reduce the time it takes to bring the plant air system up to pressure, and
is therefore considered desirable. Please ensure that your system does actually operate in this
fashion.
Once you have created your program, download it to the PLC and thoroughly test out its
operation at both 50% and 100% rates of flow. When at 50% loading, the compressors should
alternate with each taking a turn. At 100% loading, both compressors should engage once it is
detected that the pressure is continuing to drop.
Your program should now be able to handle both light and heavy demands for air quite
effectively. While this current solution likely performs as well as most systems employing relay
logic, with just a bit more effort you should still be able to even improve upon this. Before
continuing to the next part, run your system with the flow rate adjusted to 78%, 80%, and then
82%, and carefully note the result. You should now have a good idea of where improvements
please help me out i got this so far i can get the two dual compressors to alternate but i cant get the one dual compressor to go full then drain then both start up...
