Pump control

Hello everyone, as always, great information here!!! I have never written logic for a pump control system. I am going to use (4) Saftronics GP-10's AC drives, to run 4 boiler feed pumps. I plan to use the 4-20mA signal from a pressure transducer on each pump to control the speed of the drives. I would however like to incorporate a PLC with this so I can get a lead/lag function, instead of all 4 pumps running simultaneously. Any creative ideas? I will probably be using a Micologix 1500 PLC, or maybe a SL/C 503 so I can get it on the Ethernet.

Thanks for any input

Greg

Hi Greg,

As far as i am aware the only slc which is ethernet compatible is the slc 5/05.

Yes, typo, thanks So does anyone have any good ladder logic examples?

If I am not mistaken the 5/05 is the only one with built in Ethernet but most can be connected to net with a NET-ENI, at least those with RS232 ports?
http://www.ab.com/networks/ethernet.html

You may actually want to look at the last traffic light post and investigate Prof Bill's cascading timer scenario, I take it you not only want to stage the pumps to turn on but rotate the order that they sequence..ie 1234 then 2341 then 3412 etc or something along those lines?

lead lag

I'm primarily concerned on how to write the lead/lag function

Thanks

Greg

Greg, you might want to reconsider the Saftronic drives. Some AC drives including those from ABB include pump software in the macros. It's all done internally and no PLC is required unless you are doing other things with it.

I don't want to be to blatant about brand promotion so, if you want more information, just email me and I'll take care of it for you.

Great

e-mail me at [email protected], and I'll get in contact with you.

Greg

Demo Communication Programs

GregPLC said:

Yes, typo, thanks So does anyone have any good ladder logic examples?

Click to expand...

Example SLC5/05 Ethernet Demo

Other Ethernet and Profibus Examples

With the lead lag setup, do you want to flip flop the pumps each time on is requested to start?
If so, contact me and I can help. beerchug

Greg if I had a pump program that fit your scenario I would offer it. I dont know your specific application so cant offer much advice on it. In many cases drives can handle encoder feedback and speed within themselves, in some cases a master/primary drive is used to set the speed for the other drives. Sequencing the drives can in many cases be done within the drives..ie starting them in a preset order.

From your post I gathered that you didnt want to just sequence them but also wanted to rotate the order they were sequenced, maybe I misunderstood that.

If ABB or any other brand VFD/DC drive can do that (sequence and rotate) within their own software I would like to know it and ask that the information be posted here.

For any application there are numerous paths to follow, I offered the use of cascading times. With AB in many cases the SQO command can be used along with commands like BSL etc.

Many state "BE THE COMPUTER/PLC". My imagination is not that good but any time I see a post like this I attempt to think "HOW" this could be done.

I dont know the drives but will assume they can handle the speed values within their own software and encoder feedback, if you want you can decide on using a PID motion control. I will just suppose a scenario that enables the drives in a sequence and rotates the drive to sequence in order that the first to start last time enabled will be last to start next time enabled. This make sense and what you are seeking? If so I will attempt using RSLogix500 to create the ladder. If it can be simpler please let us know.

The shift commands can be used for sequencing if there are many pumps to sequence. Particularly easy if the PLC has a proper shift register and not just a shift bit right or shift bit left command. Takes time to set up and test the hard way.
If only 2 pumps to be sequenced, I have a latch circuit that works very well and an override circuit if the sequenced pump is unavailable.
Let me know if you want it. I can print it to a PDF file. I also have a sequencing setup for an Omron shift register. Also load control for a reversible Omron shift register.
Regards
beerchug

Auto lead-lag of pumps using SLC 5-03 or similar

Hi Greg,

I've used an SLC 5-03 to provide lead-lag control on multiple pumps for a large a/c chiller before, I can check to see if the ladder logic is still around. It should be directly portable to the 5-05 without too much hassle.
I do have a couple of questions.
1) do you simply want to change which pump is the lead pump when the system shuts down? e.g. 1234321, 23414321, 3412143, 4123214
2) the system I recall would automatically move on to the next sequence if the lead pump was unavailable due to fault inputs to the plc - is this what you need? (in that application not all pumps were required for full operation, one was effectively a "hot-spare" which could be switched in or out as needed by maintainance)
3) Are you reliant on the 4 individual pressure sensors by each pump or is there a sensor which provides overall system pressure?

Tim

Thanks for the help

Tim, Yes, pump rotation is important....example every 12 hours the lead pump will be a different pump.....There are 4 pumps with 20hp motors...this is on a boiler feedwater system, all I am trying to do is maintain about 250psi. There are currently 4 pressure transducers in a header, which is working with the old system, I can use all 4 or I can use just one, doesn't matter. Under what I would call a normal consumption, two pumps run, and an occassional 3rd pump will come on to maintain pressure. The pump control system that is in there right now is a "canned" system, and has had a very high failure rate, so they are being returned. I would just like to use regular VFD's, with a PLC. I don't want to run the pumps synchronously, I want lead/lag.....so when the pressure falls below setpoint, one pump will come on until it is at 60Hz, then if that can't maintain pressure, #2 pump will come on, and then #3 etc....and I also want that #1 pump to rotate through the pumps, so the SAME pump isn't always running....I really appreciate the help.....I hope this clarifies my needs a bit.

Thank you so much,
Greg

to GregPLC and rsdoran

For applications 50hp and smaller, ABB's standard ACS400 has a PFC Macro that does PID control, multi-pump sequential speed control, and rotation of lead pump. It looks to me like an optional relay output module may be required for applications using more than 2 pumps.

ABB's standard ACS400 Instruction Manual has detailed info on this macro in the Appendix Section.

For applications over 50hp, it looks like an ACS800 with optional Pump/Fan software is needed.

In the US, your local ABB Drive rep should be familiar with these options. If you need help finding them, contact me and I will get you their phone numbers. Actually, it should be available from the ABB website as well.

In fairness, I do believe there are other manufacturers that offer this feature in their drives, too.

Hi. A New Zealand company (PDL) has macros for their drives that will accomplish this task. They have been recently bought out by the schneider group so their products should be available world wide. Regards Alan Case