Compressor Control System and Aftercooler

[Redlunn]

Hey all,

I have been a long time lurker and searched this site extensively while working on my compressor optimization. Perhaps someone can gain some ideas for their own projects.

It started with a 3hp Puma 60 gallon compressor and an Allen Bradley Micro810 PLC looking for an application. The two items found each other and turned into an unnecessarily complicated but still effective compressor control system. A small LCD display and touch pad allow for viewing status and adjusting settings.

Some of the features:
1. Redundant contactors with feedback monitoring (PLC verifies that the contacts change state both on and off)
2. Solenoid valve condensation drain that gets triggered after run and also a secondary drain cycle after the air in tank has cooled.
3. Maximum continuous run time setting to protect compressor from running excessively if an air line breaks while unattended.
4. Green lighted start button that indicates when the compressor is enabled, even when it is not running because it is at pressure.
5. Emergency stop button that is wired to a PLC input for diagnostics and also directly kills power to the contactors.
6. Maintenance interval tracking.
7. More features pending as I think of them. Open to ideas.

The micro PLC runs about $100 usd and I'll share my program with anyone that wants it.
http://ab.rockwellautomation.com/Programmable-Controllers/Micro810






Aftercooler
I was getting excessive airline moisture so the most recent addition was an aftercooler between the pump and tank. For the cooler I picked a heavy duty oil cooler that was nearly the same size as the belt guard on the compressor. It mounted easily and plumbed with regular NPT fittings. The temperature difference was substantial.

Before Cooler Installation
After a 15 minute continuous run the temperature at the pump outlet was 320 F and 240 F at the tank inlet.

Cooler Installed
After a 15 minute continuous run the temperature at the pump outlet was 325 F and 83 F at the tank inlet.

Cooler can be found here...
https://amzn.com/B000HEADJ2




I'm open to any questions as well as constructive criticism. Thanks for looking.

 

[Cue]

Can you post more pics of the cooler lines? How are you getting the moisture out of it, just letting it go into the main tank and draining it from there?

 

[engineer2]

We got a two new industrial compressors and I did a control panel with indicator lights, hour meters, manual shutoff switches and an alternating relay. I hindsight, we should have done it all with a small PLC and added the cool features you have. It probably would have been cheaper, LOL. The other thing to add is digital communications so you can monitor and possibly control your compressor remotely.

 

[matt_i]

Hardwired I/O! Love it! (Miss it...)

Curious what the output is when the contacts fail to make or fail to break.

 

[udderlyoffroad]

Nice! Gotta love some PLC-based control…
How are you monitoring the pressure? Or is the compressor’s built-in pressure switch/unloader valve still in the system, and you’re supplying power to that via the contactors?

If it were me – I’d incorporate an auto-drain valve and a ‘shutdown’ function. I.e. one which vented the tank when I was done for the day. This would enable me to leave the compressor pressurised, say, over the weekend when I know I’d be back in the shop the next day.

Matt

 

[Redlunn]

Can you post more pics of the cooler lines? How are you getting the moisture out of it, just letting it go into the main tank and draining it from there?

I don't have any additional pictures at this time but the lines are 0.5" copper with flared ends. Manually bent and aligned using my eye that appears to be out of calibration (probably why I didn't take more pictures of it). The tank already has the PLC controlled drain valve so I'm just letting the cooler drain into the tank.

The other thing to add is digital communications so you can monitor and possibly control your compressor remotely.

Networking capability is one thing lacking from the Micro810 controller I am using. I would have to get creative if I want to control the compressor from my phone. I do have a pile of Arduino hardware looking for something to do....

Hardwired I/O! Love it! (Miss it...)

Curious what the output is when the contacts fail to make or fail to break.

When a fault is detected, both contactor outputs turn off and a message is scrolled across the top line of the LCD explaining the fault.

Nice! Gotta love some PLC-based control…
How are you monitoring the pressure? Or is the compressor’s built-in pressure switch/unloader valve still in the system, and you’re supplying power to that via the contactors?

If it were me – I’d incorporate an auto-drain valve and a ‘shutdown’ function. I.e. one which vented the tank when I was done for the day. This would enable me to leave the compressor pressurised, say, over the weekend when I know I’d be back in the shop the next day.

Matt

I am using the pressure switch that came with the compressor. It is wired to a PLC input but it also switches the power to the contactors directly as a failsafe for the PLC. The system does have an auto-drain valve but I may have described it poorly as a "solenoid valve condensation drain". For the 'shutdown' feature you suggested, do you mean a large valve on the output of the tank to isolate the tank from the air distribution lines? (Currently the distribution lines consisted of a single hose. Enhancements are in the planning stage).

 

[pcmeiners]

Nice setup....

Cooler definitely over size, but that is not hurting anything but the wallet, mine are oversized. Good choice of a professional full flow cooler, instead of poorly designed, low burst pressure aluminum evaporator coils which will end up with fatigue cracks. You got a good price on the Hayden, nice.

Liked the option of maximum run time shutdown. You leave for a week or two,even a weekend, pipe burst, unit runs continuously, you come back to dead unit and a possible really large electric bill. Read a couple posts where this has happened.

PLC, really cool. I used discrete relays, I should have used a controller

Notice you reduced you piping to/from cooler a lot, I would have maintained larger pipe size, no biggy.

PLC, since you have plenty of in/out channels, rig a heat sensor to knock off compressor/dump air to outside if fire detected, full tank has a lot of air to feed a fire if piping is compromised.

Agree with Enginee2, easily visible hour meter/ammeter. Ammeter is very important, you tell a lot from amp usage at particular pressures. If your good collecting data at the beginning, can give you an idea of dirty filter, bad valve, low voltage, low oil. Volt meter would be nice but overkill or perhaps a combo v/a meter, Ebay cheap. Ammeter coil pickup vs shunt (safer/less bulk/easy mounting of coil). Perhaps program an amp set point to auto shutdown compressor.

"It probably would have been cheaper, LOL." Agree, but in my case I am more sure of it
Doing a setup for a Qr325 at the moment, in the same boat, yes, likely will cost more with discrete delay relays. Did not give a PLC any thought before design or purchasing..I should have. Only advantage of discrete is it is more difficult to mess up the logic of the controls if a novice gets in the box. Next compressor get PLC

"6. Maintenance interval tracking." Nice feature !!!

PLC, head temperature sensor, might protect against low oil or other issues.


Have tons of money ?, add softstart I realize you probably spent 5x on the extras then originally planned. Just purchased a Quincy without thinking of the "extras"...until I got home...actually I knew, I kind of stuck my head in the sand until I got home.

If you will be using the unit a lot, Solberg filter double to triple the size, gives a little more air, plus it makes it less important to monitor for filter change, lower noise level.

All of my suggestion not necessary but fun, would be for me anyway.

Nice workmanship, enjoy the build.

 

[turfgnome]

I like some of the idea here, I have bought a few things to use an Arduino to control my air compressor and connect it to the alarm system so that it does not run when the door alarm is on.

 

[Redlunn]

pcmeiners: thanks for the post, lots of good info. I will consider your suggestions for future upgrades. I project like this is never really done, just waiting for the next feature.

One thing I can comment on right away...
"Cooler definitely over size"
Agreed, when running, the cooler is hot at the inlet side but it's cooled to ambient temp about 6-8" away from the inlet. The remaining 16" of cooler aren't doing much. I never really gave this much thought, just figured bigger was better, but I now realize that there are savings available here.

 

[engineer2]

easily visible hour meter/ammeter.

We added a power transducer (probably cheap on ebay, but make sure the range is correct) with a 50:5 CT (smallest I could easily find) with 2 wraps of wire. The power transducer has a couple of 4-20 mA outputs (Volts and Amps) that we may run to an analog to wifi converter.

Volt meter would be nice but overkill

Voltage is critical for us because we've had brownouts in the past that are really hard on the motors.

We also monitor air dryer outlet temperature to (hopefully) indicate problems with the air dryer.
A pressure dewpoint transmitter would be better, but they are $$$$.

Low oil level monitoring a good idea too. Our Champions have low-oil level cutoff switches, but we don't monitor them remotely. They are factory wired to kill the compressor and have a manual reset

Most of the recips are 80% duty cycle, so if that level is exceeded for a period of time, a warning should come up. The difficulty is 80% of what time period.

Some good ideas here: head temperature, run time limiter, maintenance tracker.

We are also looking at timer functions to turn the compressors off at night. I told the plant people it wouldn't be needed if they fix all their air leaks and shut off unneeded equipment.

 

[pcmeiners]

Miss being a building Engineer, I loved it, fun work.

"Voltage is critical for us because we've had brownouts "
My friend has a 15hp 3ph compressor at his warehouse, he has lost 3 motors in about 3 years so your right, it is pretty critical . I tried to explain they have controllers to protect motors...in one ear and kept on going.

"easily visible hour meter/ammeter. "
Couple years back, picked up a couple ammeters with coils on Ebay, about $17; coils are tiny so they do not take up real estate.

http://www.ebay.com/sch/i.html?_odk...0A+Digital+Ammeter++Coil+Transformer&_sacat=0


"We also monitor air dryer outlet temperature"
Excellent idea

"Low oil level monitoring a good idea too."
Same here with pressure lub. Rigging a Nason switch, contacts opening or closing on lowing pressure. Only issue, I need to get a time delay relay, to take it out of circuit for a few seconds on startup. The OEM part is hundreds, this will cost $50, and works the same, I will need to manually start to reset it. NASON Pressure Switch CJ-2C-16G / WL115

" maintenance tracker"
we need a cheap one which would pester maintenance with emails or tweets.

"run time limiter"
Excellent idea, simple with a multimode timer. Perhaps a 1 or 2 hour continuous "make" relay contacts, breaking/ locking after that time, pressure switch or manual switch resetting the "make" contact time period.

"I told the plant people it wouldn't be needed if they fix all their air leaks and shut off unneeded equipment."
Unless you fix the leaks, order the timer, those leaks might get fixed in a couple decades.

"and connect it to the alarm system so that it does not run when the door alarm is on"
Another good idea.

"Cooler definitely over size"
Not a criticism, better to over engineer, then not have it work properly/break down early.

Last but not least, a gripe...the electric enclosures I use to get on Ebay for $15 plus $10 shipping are now $70 plus $20

 

[86turbodsl]

This is really cool use for a PLC and i will incorporate some of your features in my build! Thank you!

 

[bfr57]

Redlunn,
Great setup! Did you move your tank check valve? From the way I see my system, the check valve will have to be removed from the top of the tank and installed in series on the line from the pump to aftercooler. Is that how you did it?

 

[Redlunn]

Redlunn,
Great setup! Did you move your tank check valve? From the way I see my system, the check valve will have to be removed from the top of the tank and installed in series on the line from the pump to aftercooler. Is that how you did it?

Thanks. I did not move the check valve, it is still right at the tank. When pressure is reached the unloader valve exhausts the air between the cylinder head and the check valve, which includes the aftercooler. There is noticeably more air being exhausted due to the increased volume of the aftercooler and lines but otherwise no issues with this configuration.

 

[ssdave]

Is there any concern about the pressure rating of the oil cooler used for the intercooler? I've tried researching these, and most are pressure tested at 150 pounds. My compressor is set to run at 175. It looks even worse if you use an AC evaporator or transmission cooler. At least the Haydon coil referenced above is tested to at least 150 (I couldn't find a spec for this one, but some of the ligher duty ones said tested to 150).

 

[pcmeiners]

300 psi....
http://www.transmissioncoolers.us/category/allison-transmission-cooler.html

 

[Cue]

Is there any concern about the pressure rating of the oil cooler used for the intercooler? I've tried researching these, and most are pressure tested at 150 pounds. My compressor is set to run at 175. It looks even worse if you use an AC evaporator or transmission cooler. At least the Haydon coil referenced above is tested to at least 150 (I couldn't find a spec for this one, but some of the ligher duty ones said tested to 150).

The Hayden listed above is rated at 250psi, I bought the same one for mine and contacted the manufacturer before buying it. Its been working great on mine for about a month now, my compressor is set to 160psi.

 

[sberry]

It looks great, nice work. There is even a back up system. Not only can a guy turn off the ball valve but he can disconnect the hose too.

 

[pcmeiners]

To bring up this thread....
If for nothing else, wiring the discrete components ( relays, timers) on my compressor control was a royal pain, plus it required more real estate, and required a good bit of thought to get around limitations of the relays' logic . Definitely will use a PLC unit when I build my next control.