By James J. Joseph, Joseph Marketing

The technique for cleaning coolants by using off-line coolant recovery filtration installations was presented in International Filtration News last fall(air filtration& liquid filtration). This particular procedure removes dirty coolant from the machine’s sump at scheduled milestones and transports the fluid to a remote off-line filtration system for cleaning. There the off-line filtration system cleans the liquid and holds it in a reservoir so a cleaned batch can be pulled and transported back to the machine. Separate transporters are used so clean liquid is replaced as soon as the sump is emptied and cleaned. Remote coolant recovery systems with mobile transporters work fine for many facilities. However, there are situations where it is impractical to set up a remote facility within a plant.

This article discusses the use of portable filters when it is not practical to install a remote recovery system. A portable coolant cleaning filter has the mobility to move to the machine and clean the coolant while it is by the machine’s side. This is referred to as sump-side or tank-side filtration.

PORTABLE FILTERS
Portable or mobile filters are designed in compact modules with the necessary components so it can be positioned next to the machine when the working area around the machine is limited. With the use of hoses, the portable unit pulls the dirty coolant from the sump and sends it through the cleaning device and returns it back to the sump. Some units have a reservoir to contain the cleaned coolant while others turnover the volume in the sump. Depending upon the design, some units work with a single pass flow while others use a multi-pass concept. When timed properly the sumps are cleaned relatively quickly without the need to totally empty them. A mobile unit can be scheduled to move among the machines and clean their sumps on a routine basis. Down time is minimal since this is a form of on-line maintenance.

EVALUATE THE NEED
The technique to save the fluid must be economically justified where the value of coolant saved is more than the cost of purchasing and operating a portable cleaning device. Many times the money saved by not dumping almost covers the investment and the need for extra funds is kept at a minimum.

The first step is to see if the money saved by not disposing the dirty coolant can be used as a budget for the portable program. The saved fluid would be continually reused so the volume of disposed coolants would be much lower. Calculations of the costs of dumping are relatively easy. Since the majority of the costs are for disposing and replenishment, tabulating their costs should yield a general idea of the money involved. There will be advantages in tool life, machine maintenance, and lower scrap but these items can only be estimated at the beginning. Their contribution to savings could be significant and will be measurable by studying trends after the portable unit has been operating for a while.

The irony is that the concept does not need large volumes of fluid or large numbers of machines to show justification. Portable equipment comes in many sizes and designs, which could satisfy a facility with just a few machines or a much larger plant with many, stand alone machine tools. When determining the budget for possible equipment to implement this option, the procedure is to convert the volumes of coolant lost into potential dollars saved, and then see what kind of equipment could be used to achieve an acceptable economic justification.

The following points are offered as a general guide to evaluate the economics of reducing the dump frequency. The calculations can be simple to get a general idea without an elaborate study. For example, a typical metalworking operation uses a coolant on standalone machine tools with a 150-gallon sump and no filtration. Any number of machines can be factored in the calculations even when the waterbase coolants and metals are different as long as the differences do not obviate the use of the same filter. The coolant may be dumped every 4 weeks because problems begin to occur with production or machine maintenance. The expenditure for legitimate disposal could be about $1.00 per gallon. Replenishing the lost fluid with new coolant at a typical $8.00 per gallon of concentrate and a 4 percent mixture could be about $.32 per lost gallon. Labor savings will not be a factor since time will be spent to operate the portable filter.

The tabulation of potential costs for this example could be:

Number of Machines	Cost per mo.	Cost per year
5	$990.00	$11,880.00
10	$1,980.00	$23,760.00
15	$2,970.00	$35,640.00
20	$3,960.00	$47,520.00
25	$4,950.00	$59,400.00

For this discussion one can estimate that 10 percent of the costs will still occur because of some dumping, spillage and other losses. Therefore, 90 percent of the annual cost becomes the budget for portable equipment investment. If a company can accept a two year payback, then it can invest up to:

Number of machines	Two Year Payback
5	$19,250.00
10	$28,500.00
15	$57,750.00
20	$76,980.00
25	$96,250.00

When there is no readily apparent economic justification because cleaning costs appear to be higher than the dumping costs than dumping can be justified as long as it is legal and permission will continue. If the measurable costs for cleaning are equal, there are other savings, which may be realized after the procedure is in place and factored in at a later date. A few major areas for further savings could be:

1. Since the machine had no cleaning system other than what may have settled in the sump, it was working with a progressively dirty liquid until the fluid was so bad it had to be dumped. The portable filter cleaning cycle will allow the operation to work with cleaner coolant longer than it was before. Portable filtration cleaning frequency should be more often than the dumping frequency so the coolant will be at a “constant” clean level. Even when there is more labor because of the increase in frequency to clean, the time required for a portable filter to clean a sump, which is not too dirty, is less than the time to clean the sump when the coolant is really dirty.

2. Tool life will increase. Depending on the tools it may not be significant but still a plus. There are many operations where tool life increased drastically because the metal cutting operation did not have to contend with debris affecting the rake angle and minimizes “built-up edge” phenomenon.

3. Quality increases while scrap and reworking are reduced.

Cleaning Devices
There is significant advantage in this endeavor because of the choices in the options of equipment at various prices. Portable units are designed with different types of cleaning devices. The modules are specifically designed for easy maneuverability, compact for tight spaces and efficient cleaning. Although the term “portable filter” is generally used, centrifuges and tramp oil separators are also effective portable clarifiers. The roster of designs include:

• Centrifuges; high speed disc stack or bowl
• Bag filter modules; pressure fed or vacuum suction
• Cartridge filter modules; multiple or single elements
• Gravity filter with rolled media or sheets
• Pressure filter with rolled media or sheets
• Tramp Oil Coalescers
• Flat bed vacuum filter with rolled media

Figures 1, 2 and 3 show three versions from one of many suppliers.

Price Range
The prices for new units complete range from $8,000 to $120,000. Bag and cartridge filters are at the low end while disc stack high-speed centrifuges are at the high end. Bowl centrifuges and roll media filters are usually within the range of $25,000 to $60,000.

There are a number of reconditioned used filters and centrifuges, which can be purchased for less money. Also, leasing arrangements are available with typical prices from $2,000 to $6,000 per month depending upon the equipment and leasing terms.

Follow Through
Once the range of economics and a general selection of options are established, the concept should be reviewed by all involved and by outside resources if more know-how on filtration devices is needed.

Here are just a few of the fundamental questions, which should be asked for follow through.

1. What is the practical timing for using portable filters for the machines?
2. Will there be chemical dosing required for maintaining needed additives?
3. What type of filter will satisfy the needs of both performance and economical operation?
4. What operator talent will be needed to handle the portable filter?

James J. Joseph is a consultant who has also written the book “Coolant Filtration 2nd Edition, Additional Technologies.”

For more information contact:
Joseph Marketing, 120 Richmond Hill Court, Williamsburg, Virginia, 23185 United States
Tel/Fax: 1-757-565-1549
Email: josephmarketing@verizon.net