Lead pump controls

Does any-one know of a quick/easy way to collate 4 registers into order of highest number to lowest number.
I have 4 pumps each with their own hrs run. These hr's run figures will be stored into 4 seperate registers. I would like to make the lead pump the pump with the least hr's run and so on for the 3 other pumps. I am using an AB micrologixs 1200.
There must be an easier way than using a **** load of compares.
Cheers.

I do not know how good the instruction set is in the Micrologix as I prefer to use Omron. The Omron PLCs have a find minimum instruction that could be used. You define the area to search and the I/O memory address is returned to a channel where it can be read.
You can define quite a large area of memory to search.
Hope you have something like it.
beerchug

4 pumps, but what about 30-40...

There must be an easier way than using a **** load of compares.

Loops comes to my mind....

Is your PLC capable of doing loops?

The largest system I have done with sorting of hrs run and motor start, is a road tunnel with 32 fans. 3 levels of CO and NO starts a dynamic (from a control system) numbers of fans, sorted by hrs run.

Doing this in ladder (or list) without a sorting function or loops is NOT the way to go, or?

2 and 3 registers to compare is OK, but with increasing number of elements it gets nasty pretty quick.

And I forgot: Also Index or Indirect adressing..

Do you really need to order all four registers? Can't you accomplish what you want by just identifying which of the four pumps has the least accumulated time and should be the next to start? You can do that in a single pass through all four accumulated time values. To identify second, third and fourth place requires successive passes through the accumulated time values.