Help in developing this ladder logic!

[hisaurabh]

Hi,
Help me building this logic in AB’s ladder logic format. I have ControlLogix PLC.
In field, I have three pumps connected in series. Say Pump-A, Pump-B, and Pump-C.
Every time “START” bit goes TRUE, two of the pumps should start but not the third one.
In below combination:
START = Start (Pump-A and Pump-B)
START = Start (Pump-B and Pump-C)
START = Start (Pump-C and Pump-A)
And then again… same cycle repeats.
Please note that I have only one “START” bit … I mean, had there been three different “START” signals I could have placed them to start in above combination. Every such START command will stay TRUE for 4 hours and then will remain FALSE for one hour. Then again START command for 4 hours…and so on. BUT EVERYTIME THIS START COMMAND COMES; PUMPS SHOULD START IN ABOVE COMBINATION ONLY.
This logic is because I do not want same pair of pumps to run all the time and get heated.
Please help in developing this ladder logic.
Thanks in advance,
Saurabh

 

[dginbuffalo]

Here's one way to accomplish.

 

[GTUnit]

What you are looking for is "Pump Sequencer Logic"
Googling the above search term will give you some good info.
Here is another thread with the same and a sample program:

http://www.plctalk.net/qanda/showthread.php?t=41143

You should also have switchover to a good pump if a running pump fails.

 

[hisaurabh]

Here's one way to accomplish.

Thanks a lot man! I got that.

 

[hisaurabh]

What you are looking for is "Pump Sequencer Logic"
Googling the above search term will give you some good info.
Here is another thread with the same and a sample program:

http://www.plctalk.net/qanda/showthread.php?t=41143

You should also have switchover to a good pump if a running pump fails.

Thanks! I did do a search for that.. there are many such interesting logics available! A lot to learn from...