The economic benefits of recycling coolant are enormous. The larger the shop, the larger the savings.
Does it work? Absolutely. Manufacturers of metalworking fluids have vacillated between selling them and pretending they didn't exist. Let's face it. The machine shop that recycles uses less coolant, a lot less. It's easy to understand the love-hate relationship metalworking fluid suppliers have. That is a serious loss of profit for them. Three things you can expect from the metalworking fluid suppliers:
1. They never deny that recycling is a damn good idea (which would cost them all credibility).
2. They will remind you that sooner or later you will have to replace the coolant anyway, as it will eventually "break-down".
3. They don't know when or what "break-down" actually is, but it happens, they will tell you. It's a fact of life: Death, Taxes, and MWF breakdown.
Well, that helps. No one seems to have an answer or even the cause, so measurable parameters for testing for "break-down" of coolant don't exist. We're not talking about tramp oil contamination, biological contamination, foaming, or other measurable maintenance and troubleshooting issues. This is about the superstition of a natural death of metalworking fluid - dying of old age. What is that?
So when do you discard the fluid and run a fresh charge of new coolant?
There is one variable that you can track without any lab test, and it generally takes into account all other variables acting on the chemistry of the coolant. Time. If you're going to guess, start here. You can develop an individual machine history and make adjustments to the schedule. You only need two things to measure it:
1. a calendar, and
The supplier will provide the calendar. Accountability is defined as a record of the duty life and service of a volume of metalworking fluid. Accountability is difficult to come by mathematically unless you recycle portably.
Portable recycling has most of the benefits of central system(stationary) recycling without the logistical nightmare of shutting down machines and hauling dirty coolant around the shop. To take coolant to a stationary recycling center, the machine must be down while evacuating the coolant. The coolant must then be transported, usually by a tug driven by a greasy looking fellow, pulling a large messy sump sucker around your shop like a third world carnival choo-choo train. Before the coolant goes back into the machine, it will have passed a pump four times, been mixed will several other fluids from around the shop, and lost all of its accountability related to the machine of its origin (age, concentration, application, etc).
The limitation of portable recycling is that it does not completely eliminate the interval requirement of evacuating the sump. Sooner or later you need to drain the sump to remove the sludge that builds up on the bottom and throughly clean the machine. For this reason, combining portable recycling with stationary recycling makes sense. If you can avoid draining a sump at least every other regularly scheduled service event, you can probably save money. In reality, you will probably be skipping 2 to 4 drains unless you are grinding.
The best solution is further extension of the sump life may be a portable centrifuge. Alfa Laval introduced such a product in recent years. My personal experience is that this type of product should be given a very serious look by any manager of metalworking fluids contemplating recycling. If your machines have individual sumps, this type of product may reduce the frequency of a stationary recycling combination.
Recycling originated with "central" or "stationary" recycling systems. A number of them have been on the market for years. They have a couple of advantages over portable systems:
1. Many stationary units incorporate centrifuges to remove sludge for recycling.
2. Some stationary units have pasteurization capability for killing bacteria (some portable units now accomplish this with ozone).
When shopping, keep in mind the primary limitation of portable recycling - it has difficulty with sludge. If your stationary system does too, why did you buy it? Consider a system that includes a centrifuge. Also, consider a system that doesn't require the use and storage of a lot of chemicals. Who needs that?
Sizing of the system is critical. You will need to have a good handle on the total of your plant coolant capacity, as well as your current rate of disposal. You will also need a lot of money to buy this thing (if you think $30 -40 grand is a lot).
Ultrafiltration is almost what is sounds like. For the purpose of visualizing the results, imagine real tight filters taking out everything down to the selected micron size of the filter. The smaller the size, the cleaner the product. Of course, go small enough and you can drink it to keep cool while you constantly change filters or backwash the system. These systems work very reliably,with relatively little maintenance, and work best on synthetic products.
Decanting is a system that involves placing numerous silos around your shop where you let a water-soluble oil product sit until the oil emulsified in the coolant slowly floats to the top for removal. The process is slow and you never get all of the unwanted oil out. The process may be your only choice depending on the product used. Effective and ugly, be prepared to give up some real estate for these suckers.
Many companies lack the time, technology, equipment or desire to manage their own metalworking fluid. If you fall in this category, there are companies that can help you.
Generally speaking, avoid the company that has a single solution to manage everyone's coolant. You need a site specific solution developed by experienced personnel. The range of services include placement of on-site staff, to simply coming to your site to recycle fluid in a large tank. It may be costly, but it will provide a big-time savings over failing to manage and recycle your coolant.
There is a separate page under the Services section that explores the topic further and lists mobile recycling companies.