Beyond maintaining production levels, most metalworking shops constantly struggle to improve bottom-line revenue. With tight margins, quick production turnarounds and rising material costs, equipment management and cost-saving measures are top priorities.
Operations that successfully manage these financial pressures often share two priorities: proactive maintenance strategies and careful coolant management practices.
With year-end maintenance during holiday shutdowns around the corner, we sat down with PRAB Project Manager Sam Proos to discuss the essentials of proper fluid management and equipment maintenance to help shops lower costs, optimize processes, and run more efficiently.
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Q: Contamination management can help cut costs. With tramp oil, fines and bacteria contaminating coolant differently, how does each one show up on the shop floor, and how can a plant recognize it early? What challenges do plants face if this is unaddressed?
Sam Proos: With tramp oil, typically in the sumps, you see a layer of oil buildup on top of the tanks. Or if the oil makes its way back through the process to the tool, you can sometimes see smoke as it hits the tool; it burns rather than cooling it down. It can also decrease the useful tool life if it’s prevalent in that coolant.
With fines, it’s the same for tool life, just more wear on the tool. And as fines build up in the holding tank or the sump, it decreases the amount of space for the coolant to sit. So you can see an increase in coolant temperature.
With bacteria, if there’s a growth of bacteria in the coolant, it can cause some skin irritation or dermatitis in the workers who are interacting with this coolant on a daily basis.
The big ones with fines and tramp oil are that they can increase the cost of your machining process. You will likely replace tools more often than not, and run the risk of employees coming down with skin irritation or other reactions to the coolant. And that increases costs for a full swap out if you get that bacterial growth, rather than normal maintenance.
Q: What clues tell you that coolant is running too rich or too lean, whether on the tools, the parts or the operators? How can plants hold coolant concentration in range without increasing the maintenance workload?
SP: If it’s lean—too much water in the coolant—you can see some of the time the coolant can’t hold a tolerance in the machining process. You’ll also see decreased tool life because, without as much concentrate, you won’t get as much cooling or lifespan extension from the coolant.
If the coolant is too rich, or at a high percentage, you’ll see increased foaming. That can cause overflow and spillage onto the floor. We manage that with a couple of coolant makeup systems on some of our equipment. One is an automated system with a refractometer that measures and automatically doses based on what percentage you need, or one with a set percentage. So you can dose to your set percentage and avoid exceeding it with manual mixing.
Q: Once a coolant recycling system is running, what does ownership look like for the maintenance team every week? Which tasks are most often skipped, and what happens when they are?
SP: Our Guardian system is a little bit more centralized point for the coolant. It doesn’t have a system where you pump back into it.
Often, it requires the customer to drain their sumps with a sump sucker, bring it over to the machine and load it into the Guardian. So sometimes that can be skipped if they don’t maintain the procedure of bringing it over and making sure that it runs to the Guardian to be cleaned.
Then I would say, maybe not weekly, but long-term maintenance is just making sure that the filters are changed out at the correct pressures. We have some disposable bag filters and cartridge filters on the system. And then similarly, we have a paper bed filter as well that just removes fines for the customer and just making sure that paper is loaded in there and doesn’t run out over time.
Q: As plants plan holiday maintenance, which tasks on conveyors, chip processing, coolant recycling and industrial water recycling and reuse deserve the limited downtime window? Which ones are most often overlooked?
SP: Speaking to the fluid and wastewater side of things, where a lot of our systems are, we recommend an annual maintenance tank cleanout where you do a drain and wash down the inside of the tank to make sure there’s been no solids or fines buildup over time in the bottom of that tank and just making sure you get a fresh start there.
Similarly, we have coalescing media for oil separation. On some of our wastewater systems, we have semi-permanent media that can be taken out and rinsed down, and that should be done as a preventative solution to make sure you’re getting adequate oil separation.
Then probably the last thing I would say is just checking all the pumps and gaskets to make sure all the seals are intact and make sure everything’s running smoothly.
Q: How does the maintenance approach differ between heavy-duty equipment like conveyors and process-sensitive systems like coolant recycling and industrial water recycling? Is there anywhere run-to-failure still makes sense?
SP: I would say it’s equally important just because a lot of our systems are involved in processes that, if you run to failure, it’s going to cost more money to shut down for an immediate fix rather than preventative maintenance.
So there’s not one glaring issue that needs to be prioritized over the other, but it’s just a regular practice or habit to get into to make sure things keep running smoothly.
For the coolant wastewater cycle, a lot of it involves haul-away, and if the system is down, it’s going to be an added cost for the customer.
It’s always easier to schedule a one- or two-day planned shutdown rather than a week-long shutdown when something comes up.
Q: What early warning signs should maintenance techs watch, listen and feel for before a conveyor, crusher, wringer or recycling system fails?
SP: If you’re seeing some oil buildup, more than normal, it could be a sign that maybe you’re not getting enough flow. Or if you see higher pressures than expected on some systems, that can mean some things aren’t running as smoothly as they should.
We use a lot of pumps on our systems. So, if you ever hear a sound coming from a pump and you’re still getting flow, it could mean a seal or something else needs to be replaced before it fully fails.
Q: When this equipment goes down unexpectedly, what are the usual root causes? How often does the problem trace back to maintenance versus how the equipment is being loaded or operated?
SP: For pumps, a lot of the common failures are solids, like if something unexpected got into the tank or got into the pump. Or, if they have a seal and are allowed to run dry for a period of time, that can damage the seal and reduce flow.
Then, as long as the fluid is maintained—the similar fluid that was expected for the application—typically on the oil removal and the paper bed, there’s not any direct root causes for something like that. But I would say the pumps are the main thing to look at.
Q: How do you evaluate whether aging equipment should be repaired, rebuilt or replaced? What do you look at first when a plant asks you about a 20-year-old conveyor, chip processing or recycling system?
SP: A lot of times, when we look at something that needs to be replaced, it’s because we’ve had a system in place for 20 or 30 years.
We’ve had a couple this year where the tank has just been rusted through, and then you’re seeing leaking, or the baffles inside the tank are causing pass-through from clean to dirty. That would be a sign that the system there needs to be replaced.
As far as the items alongside it, like pumps, seals and filters, those can always be replaced on a good tank if you just need to repair the flow or replace the seals causing the leaks.
If the tank’s starting to rust through, you can always replace the chain if it’s a dragout-style filtration system or replace the pumps on there, but if the tank’s starting to wear, it’s time to get a new one.
Q: For water reuse and recycling programs, a plant may have several water projects on the table, such as treating incoming water, reusing process water, meeting wastewater discharge limits or working toward Zero Liquid Discharge. How do you identify which to do first, and what is the best way to decide?
SP: I would say the main thing to look at, for which area you want to tackle first, is what’s driving the cost. Sometimes cities contact customers, driving the discharge charge limits. So sometimes that’s driving it, where if there’s a cost savings in maintaining the discharge limits to make the city happy, that drives whether you need to do the wastewater discharge process versus pre-filtration. A lot of the wastewater expenses we deal with are haul costs. So, I would say that’s the main thing to look at there.
Q: What does a plant need to know about its wastewater (composition, flow rate, discharge or reuse goals) before a system can be designed? How do free fluid testing and Demo Before You Buy help close that gap?
SP: A lot of the information we do on the application side of things is that they’ll contact us with the quantity of fluid that they’re using or the quantity of fluid they need processed, and then they’ll send us a sample to have evaluated to see what contaminants are in it.
We’ll do a couple of tests here for what size those are, and some other testing at our facility. We have the ability to test on some of the ultrafiltration equipment here, in addition to some of the vacuum evaporation systems, and that helps identify which avenue to take with the quantity of flow you’re running and the different contaminants that you need to remove from your stream.
We can help identify if there’s something present that won’t be as efficient or won’t work with the ultrafiltration systems, and then we can direct them toward vacuum evaporation, or vice versa, where something’s not going to work with evaporation but can be removed by UF.
Q: What does it take for a plant to reach Zero Liquid Discharge, and at what point does it make sense to commit to that goal rather than stopping at discharge compliance?
SP: I would say start with the reuse and the discharge charge limits and attack those first to lower those costs.
Then, if you’re still looking to do Zero Liquid Discharge, you might need to do some separation there, where you have the collection of the waste stream from the filtration process you’re doing on the initial filtration, for the reduction of the waste stream and the reduction of haul-away costs. Then, you can treat the second waste stream to achieve Zero Liquid Discharge.
We have some options. With vacuum evaporation, sometimes it’s set up where you do a large reduction of the waste stream, have your clean distillate production there, and then the waste from that unit is sent to another, more heavy-duty filtration unit that can further reduce the liquid discharge.
Q: Shifting to water reuse and recycling system maintenance, how does the approach differ between membrane systems like ultrafiltration (UF) and reverse osmosis (RO), vacuum evaporators and pH adjustment systems? What does each one need most from a maintenance team?
SP: Start with the ultrafiltration system. A lot of our UF systems are automated, so when it drops below a certain flow rate, it runs a chemical clean to help achieve that desired clean flow rate out of the system.
It’s important to monitor the recovery of that fluoride after the cleaning is performed to make sure you’re at pre-process levels, so that over time you’re not seeing degradation of the membranes.
For UF, because of the recirculation in that system, you’re heavily concentrating the waste in the process tank. So that system needs to be pumped out once per month, and then you can start over with a full batch of new process fluid.
With RO systems, a lot of the work we do is on pre-treatment—when the customer wants to remove minerals or salts from their water prior to using it for things such as coolant makeup. This ensures they have a clean source of water. A lot of times, we include water softening systems and chemical dosing systems to remove any chlorine for the type of reverse osmosis membranes we use. So I would say normal maintenance there is making sure the water softeners are running properly, charged with salt, and making sure you have enough chemical to help neutralize chlorine, as that can damage the RO membranes because of how fine the filtration is.
And for the vacuum evaporator, we have a data sheet that we provide to customers. That’s just regular logging of all the performance indicators with the compressor and the vacuum pressure found in that system to indicate a trend over time.
If something does come up, it helps to troubleshoot and diagnose the issue and also gives the customer a heads-up on whether they’re seeing fluctuations in any of the data and something’s not going right. A regular cleanout procedure on the vacuum evaporator is good as well, to make sure there’s no buildup.
Q: What does a realistic preventive maintenance schedule look like for water treatment systems? What belongs on the daily, weekly and quarterly lists?
SP: For our evaporators, we provide a regular recommended cleaning schedule for how often you need to clean out the heat exchanger to make sure there’s no buildup. We also provide instructions on that cleaning cycle and, in addition, you can do a chemical clean.
Then, with that data logging and the UF, the preventive maintenance is where we include some disposable filters on those units. Just making sure those are changed out at the right time and making sure the concentrate tank is pumped down regularly. If that gets overconcentrated, you can see buildup in the membranes happening more frequently, and you end up doing more cleanings using more chemical additives.
Q: What causes membranes to foul, and how can a plant spot fouling early and keep cleaning cycles from becoming a burden on the maintenance team?
SP: Start with identifying when they need to be swapped out.
I mentioned it earlier with the recovery of the pre-process clean flow rate through the membranes. If you keep running cleans and don’t see that flow rate recover over time, it can signal that the membranes are starting to foul and not provide enough flow.
Or you can see if one of the membranes ruptures; you could see a large increase in flow because everything going into the membrane is passing through instead of being filtered out. If there’s ever going to be a prolonged shutdown, don’t let them sit in dirty fluid for long. That can cause them to foul.
Or, we monitor the inlet and outlet pressures for about a 20 PSI differential, like 40 to 20 PSI. A 40 on the inlet, 20 on the outlet. If those valves are ever adjusted and cause a large pressure increase when the outlet is blocked, the membranes can rupture as well. So ensure the discharge flow can also leave the system.
Q: Which wear parts and spares should a plant keep on the shelf for its water treatment systems (membranes, probes, and pump seals), and how should it decide what to stock versus order as needed?
SP: The two things we recommend are filters and pump rebuild kits. That way, if any seals or anything goes bad, you have a kit on hand to do replacements on site and get you back up and running.
We also recommend keeping disposable filters on hand for holiday shutdowns or for swapping filters out over time. So, bag filters, cartridge filters and rolls of paper media.
A lot of the valves and sensors we have in stock have a pretty short lead time. So we include them on some lists so that they have the part. Customers don’t necessarily need to keep them in stock, as we can get them out pretty quickly.
Thank you for your time and insights, Sam!
For any questions or to learn more about custom coolant recycling systems or water treatment equipment designed to optimize your process, visit prab.com.
