6, air compressors,how such a process is compiled

6, air compressors, pressure control input, the pressure range of 7 to 9, the pressure is less than 7:00, followed by inputs 1 # .2 # .3 # .4 # .5 # .6 #. The pressure is greater than 9:00, followed by unloading 1 # .2 # .3 # .4 # .5 # .6 #. how such a process is compiled?rslogix5000,5561

Hello ypf_108,

If I were going to do it...

I would break the input down further, if your 7 and 9 input is a analog input.
if input </= 7 then compressor 1 is on
if input is </= 6.75 then compressor 2 is on
if input is </= 6.5 then compressor 3 is on
etc....

then just the reverse for the unload

Or use the limits function to specify the pressure ranges for each load / unload.
LH

I need to add that,

I need to add that, based on the pressure of automation and control air compressor unload units into a few, I hope to write some applications, thank you

for each compressor make a block with a start and stop sequence:
#1 start when below 7.1 stop above 8.1
#2 start when below 7.2 stop above 8.2
etc.
this way they do not start all at once
another way is a stepper control:
if pressure below 8 start a compressor next in line.
if pressure above 8.1 stop a compressor
wait for a minute and check again.
etc.

Consider using a PID function to generate a value for the amount of compressor needed, then use that value to decide how many compressors to operate. Then use a rotating sequence to spread the operating hours.

Every time you need to add a compressor, add the next one in line. Every time you need to drop a compressor, drop the last one in line.

Wally
What are you going to measure to use as control variable? Generally compressors are brought on line to maintain system pressure. I suppose you could use system flow corrected maybe for pressure as a control variable but I am having difficulty seeing how it would work better than just sensing plant pressure with a single pressure switch. Can you explain further please?

I tend to mix up process and control variable so forgive me using wrong term.

Dan Bentler

Oh. 6 sets of air compressors is to give coal mine to provide energy. Is to pipeline gas tank pressure sensor control of the return value of the input air compressor units, and if we stress that small, pressure fan Number of units will, in turn set the order of loading the contrary, will be followed by unloading. I want to know how a specific program it. I am using a ControlLogix 5561

Input to PID is a pressure transmitter.
PID has a set point and will generate an analog value out based on the deviation from the set point and the PID parameters. You could come close to this just by cycling them on based on a band - pressure less than 7, turn on another compressor, pressure more than 9, turn off a compressor. PID will provide tighter control. Of course, once on, most compressors load and unload based on a pressure sensor so you have to account for that. 6 compressors idling isn't efficient. This is something that the major compressor manufactures, of course, will do FOR you. We are re-inventing the wheel but probably at lower cost than the OEM wheel.