OK you process techs and EE peeps... I am investigating building a custom pump system. It would need 2 gear pumps driven by motors (AC?) controlled by VFD's which are controlled by a PLC. The out put of the pumps would go thru flow meters that feed flow info to a PLC. The PLC would control this whole mess. The object is for the flow meters to tell the PLC what the ratio of the 2 materials is and then adjust 1 of the VFD's to hit a certain target. I have the pump info I need. I have not done much work with PLC or VFD and that was years ago. Can anyone recommend a good resource for this? Motors look to be fractional hp ~.25-.5hp. I am investigating some flow meters, so I need info on what drive motor/VFD you would use for this. Unless we find someone who is a AB wizard we plan to use Opto 22 for the PLC. Any other suggestions? If this project takes flight we could need several of these so something that is clean, reproducible and supportable is necessary. Thanks
Rockwell 525 VFD Depending on media, either mag flowmeter or mass (Coriolis). What program is the PLC running for communication?
For PLC one of the biggest issues is ensuring you have someone to program it. We use all Siemens in 30+ plants but AB is good stuff too, lots of options out there. Does it have to be a PLC? Is it part of another system? There are other ways to control these things besides a PLC. Heck you could use an arduino to control it.
It will be a stand alone system. But the ability to add modules for ethernet capability to communicate would be nice. Also we will need a touch screen for operator interface. There controller will have to do some calculations for the ratio/flow/pressure etc and if necessary trigger alarms or shutdown. If something other than a PLC can do that I'm all ears.
Based on flow amounts and very high viscosity we will probably use wheel type flow meters. Not sure on communication. Looks like there are a lot of these that run on ethernet pr digital comms vs the old way of using voltage or amperage to tell the vfd what to do. That's why I'm asking you guys what works best in the new stuff
For something kind of small and self contained the AB MicroLogix might even be overkill. We use some of these little Horner PLCs on some ancillary equipment and they handle a few discrete and analog ins/outs without any fuss. The Horner PLC software was free to download last time I checked vs. a few g's for Rockwell stuff. https://hornerautomation.com/product/x2/ Also, a lot of $ difference if its in a hazardous area or if you need certain certifications like SIL.
Running 2 gear pumps, metering a thickened adhesive, resin is 100 parts the activator is 2 parts. We need to keep the ratio very close, so use flowmeters and feedback to trim the vfd's so the ratio stays close. The pumps I want to use should be the correct ratio (ie one pump is 15cc per revolution the other is .3cc/revolution). So the flow meter/feedback should only trim these very slightly at a decent sample rate, say 10-30 Hz. Another question is should we use encoders on the motor for real time speed, or is there a different way? I expect the motors to run around 20-60 rpm.
Use a peristaltic pump that can be tied back to the control panel and HMI. You can eliminate the flow meter and still have controlled metering/dosing. Watson Marlow is what we’ve used in the past.
Ive never seen a peristaltic that can pump ~300,000 cps (basically paste). The gear pumps I want are being used in an automated dispense machine pumping the material now. So I know they'll work just fine. Its figuring out all the other controls....
Rockwell is not cheap. This looks like a great fit for AutomationDirect. Productivity Series. Software is free and decent. Sent from my SM-G960U using Tapatalk
Would running an air over/hydraulic style system and use the PLC to control metering valves be a feasible plan? It would eliminate 2 VFDs, and the motor/pump from the equation. Something similar to a Nordsen Hot Melt glue pot as reference.
Not really. They have an air powered piston pump system now using 1 flow meter and maybe a pressure sensor and pump stroke sensor to calculate ratio. It works good about 95% of the time. The parts they are gluing cant be right 95% of the time. These are done by hand. The auto line using gear pumps and dual flow meters is about 99.9999999% correct every time. So we basically want to replicate this system but make it usable with a manual mix gun. This company has several of these installations, and this product is used nation wide and there really is no good, reliable way to dispense it. Up till now we have only sold/serviced/rebuilt pumps and systems, along with the adhesives and such, so we havent had to build something like this from scratch. The boss thinks there is enough potential to explore it. Right now im trying to figure out how we would want to do it, get the major components priced and see if the customer wants to go forward. All the info/suggestions above help. As i dig a little more im sure Ill have more questions.
You don't need a PLC just for 4-5 loops. Cpl 4-20 i/p's for your flows, one for the speed, and a 4-20 out for your vfd's. Just get a stand alone controller that already has an hmi on it. Then set up your ratio control in it. Something like this but cheaper for your budget. https://new.abb.com/products/measur...-field-mountable-universal-process-controller
+ 1 on the referral to Automation Direct for everything you're looking to do. Best customer service you'll find anywhere in industry, and no one can come close to their prices. Quality stuff. You can even get your Wera tools there! Do the research yourself.
