December 2008 Edition

COOLANT

Play it Cool

Environmental concerns are not the only reasons for maintaining clean coolant. It is also essential for running an efficient and profitable shop.

Interest in maintaining the cleanliness of coolant in machine tool sumps was once primarily from in-shop environmental concerns: obnoxious odor, smoke, or operator contact dermatitis – problems attributable to tramp oil in the coolant. Now, while environmental issues remain important, most shops recognize that maintaining clean coolant is essential for running an efficient and profitable shop.

The cost advantages of proper coolant maintenance are emphasized by the rise in coolant purchase costs, paralleling the increase in oil prices, and the increasing cost of spent coolant disposal. An efficient pump/skimmer can increase the life of the coolant from two months to a year, a reduction of five coolant changeouts per year per sump.

Running the Numbers

For one machine with an 80 gal sump, the cash saving of five coolant changeouts per year are significant: $400 per year for 20 gal of coolant at $20 per gal; $800 per year for 400 gal of spent coolant disposal at $2 per gal; $400 per year for four man-hours per changeout, or 20 man-hours per year at $20 per man-hour. This results in a potential coolant-related cash savings of $1,600 per year.

By reducing the changeouts from six-per-year to one-per-year, the saving in machine downtime is 20 machine hours per year. The saving in reducing unscheduled downtime could be as much as $1,400 per year for 20 machine hours at $70 per machine hour.

Running clean coolant improves tool life. Savings are shop-specific, but a conservative estimate would be a 10 percent saving in tooling cost, which means an annual tooling cost per machine of $1,000, for a possible saving of $10,000 per year.

The total quantifiable saving could be as much as $4,000 per machine per year with an investment of about $1,000 per machine for a pump/skimmer – a three month payout. For a 20 machine shop, for example, the cash savings could be as much as $80,000 per year.

Money isn’t Everything

The non-quantifiable savings are more significant. Shops now have cradle-to-grave responsibility for disposal of liquid waste. Reducing the coolant waste by 83 percent reduces potential liability for improper disposal of waste. Also, with a pump/skimmer unit that filters chips as well as removes tramp oil, the possibility of shutting down a machine by plugging the pump inlet screen or the coolant delivery lines are reduced.

The result of incorporation of a pump/skimmer is the machine can run untended without coolant-related unscheduled shutdowns. For "lights-out" operation, using automatic feeding devices and specialized software, maintaining clean coolant is low-cost insurance for the shop’s investment.

While shops may want to reconsider coolant maintenance due to potential out-of-pocket savings, careful analysis shows that running with clean coolant is an essential to Lean Manufacturing: machine tools have more efficient operation with clean coolant than with dirty.

Coolant Problems Lead to Unscheduled Downtime

Stanfordville Machine, Stanfordville, NY, a supplier of precision parts to the semiconductor, medical, aerospace, and electronics industries, runs a shop with 24 machines. Management invests in new machines to ensure just-in-time deliveries and maintain the latest in machine technology.

Peter Johnsen, manufacturing manager, found objectives for long-term investments in tools and tooling were compromised by a lack of maintenance of the coolant in his machine sumps. Buildup of tramp oil and other impurities in the coolant required frequent pump-outs of the sumps, resulting in excessive coolant and waste disposal costs and unacceptable, unscheduled machine downtime.

Johnsen evaluated tramp oil removal products on the market. He pursued some standard approaches, including belt skimmers, with no success. A belt or disc skimmer operates in a small area of the sump, leaving most of the sump covered with oil, removing a large quantity of coolant along with the tramp oil. He next tried a pumping separator with an electric pump. The electric pump proved unreliable, and the overall construction of the separator was not rugged enough for the Stanfordville application.

He then contacted Keller Products, Acton, MA, which makes coolant cleaning systems for sumps of less than 1,000 gal. The pump/separators are designed for 1/2" air-operated diaphragm pumps and permanent oil separating elements. The salesman recommended the TKO line of pump/separators, designed to service individual sumps.

The Right Solution to a Difficult Problem

A TKO skimmer pumps oily coolant from a floating inlet on the surface of the sump, through a pre-filter to remove floating chips, into a separator tank containing the permanent separator element. The separated tramp oil is held in the tank until drained. The cleaned coolant recycles to the sump at high rate of flow. The recirculation rate cycles the sump, ensuring that there are no stagnant areas in which oil and solids can accumulate. The TKO-6 can be mounted to the side of the machine tool without hardware, using the CLO-1 magnetic support frame. This feature keeps the floor clear.

Johnsen ordered two TKO-6 units with magnetic frames and evaluated them for one month. They met his expectations. Stanfordville machines aluminum, which generates a large quantity of floating fines that are pulled into the separator along with the tramp oil.

Although the TKO separators are equipped with a cartridge-type pre-filter as standard, Johnsen requested that Keller supply the unit with a high-capacity bag filter for operating convenience. With the bag filter and the 1/2" air operated pump, the system was more economical than the pump separator the firm evaluated.

"I cut my waste generation from 10 drums per month to two drums per month," Johnsen said. "We increased production by minimizing downtime, which helps us meet our customer deadlines. By removing the tramp oil, there is less foam. Filtering out the aluminum means we’re less likely to plug coolant lines in the machines.

"The Keller units paid for themselves in a few months," he said. Keller Products

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What do you think?
Will the information in this article increase efficiency or save time, money, or effort? Let us know by e-mail from our website at www.ModernApplicationsNews.com or e-mail the editor at pnofel@nelsonpub.com.