To Reduce waste coolant generation and worker exposure to health risks, EG&G Rocky Flats Inc. has adopted a machining coolant management program which has been dramatically successful. As a result, worker safety has increased, waste coolant disposal has been virtually eliminated, and it has scored estimated savings of tens of thousands of dollars.

EG&G Rocky Flats is a former manufacturer of nuclear weapons components for the U.S. Department of Energy.

The waste reduction program involves keeping the fluid balanced, filtered and low in biological activity. A key feature is its innovative testing.

Prior to the program's adoption, bacteria growth at EG&G Rocky Flats was "poisoning" waste coolant, causing disposal and health concerns. Workers exposed to "spoiled" metalworking fluid can incur eye, nose and throat irritations, dermatitis and respiratory problems. Moreover, the coolant's performance was being degraded and it was producing objectionable odors.

EG&G RF had been trying to control the situation by adding biocides to the fluid. Biocides killed the bacteria, but they emitted harmful gases that amplified the worker health concerns. When the biocides could no longer reverse the bad smells, the metalworking plant changed the fluid. By this time the coolant was performing poorly anyway

Used coolant was at first disposed through the plant's waste drains. When the waste began to foul its evaporative system, EG&G RF had to have the coolant hauled away at a cost of $14 a gallon.

In early 1992, EG&G RF embarked on a project to eliminate its coolant waste. It began using a synthetic coolant and a testing process. Tests measured biological activity, concentration and pH. Treatment through filtration and addition of coolant/water mixtures kept the fluid in balance.

For its resistance to biological growth, it chose a synthetic coolant, Dascool 521, from D.A. Stuart Co., Willowbrook, Ill. So effective was this coolant's resistance that two years later the original product was still in use in the same machine. Previously, bacteria began spoiling the coolant within a few days. Even with liberal biocide use it had to be replaced quarterly.

Testing

To maintain a balanced metalworking system without adding biocides, BioTech International Inc., Sugar Land, Texas, developed a three-step program: Testing, Treatment and Filtration. The tests examine biological activity, pH and coolant concentration. Fluid treatment is only prescribed on the basis of these tests.

Real time measurement of biological activity is done with BioTech's "HMB System." This consists of a patented instrument and disposable test kits. The process provides a quantitative chemical method for determining microbial activity of a sample within 15 minutes. Other methods could take two to three days. The test requires minimal training.

Administration of this test is important because the monitored organisms can multiply in minutes. Speedy readings mean the spoiling fluid can then be treated before the bacteria have a chance to grow significantly.

The second factor tested is pH. As bacteria multiply acids are released. This lowers the pH. Some microbes grow faster in a more acidic environment. Bacteria also feed on pH buffers and on the coolant's lubricity and corrosion package. This "food" along with a dropping pH, promotes rapid microbial growth. The fluid can decay so much that it can quickly resemble dirty, stinky dishwater. This can be prevented by monitoring and prescribing treatment accordingly.

Ah unbalanced fluid, with too much water or coolant, can promote wear and biological growth. Water-coolant concentrations are measured to maintain proper ratios. Prior to use of this program, water was added to a mixture that was losing coolant. It was thought that the heat of grinding and cutting was evaporating water and raising the coolant concentration. Instead, coolant was leaving the mixture. Adding water only diluted a weakening fluid.

With Dascool 521 the water, not the coolant, dissipates. By measuring concentration and pH, accurate additions of coolant-water mixture can be made to maintain the proper ratio. This testing takes under a minute to perform.

With this testing system and the new fluid, EG&G RF has experienced no cases of worker irritation or illness. The company has converted the whole plant to Dascool 521.

For the first 15 months of Dascool 521's use, filtration and coolant/water additions were the only treatment methods. After this time, biological activity began to show. Instead of adding biocides, which kill the growth but can cause worker salety concerns, EG&G RF found a coolant additive, Mark II Stabilizer, that enhances lubricity and anti-corrosion characteristics while also preventing rancidity.

Besides removing suspended contaminants, the filtration system, made specifically for metalworking, extracts some of the dissolved solids and biological bodies. Each filter device operates continuously and its portability allows it to service up to 30 machines. Capable of filtering to one micron, but adjustable to the pore size needed, each device can service a 55 gallon sump in under an hour.

Cost

Cost of this system was $7,015. This included: the portable enzymatic instrument used to monitor biological activity ($1,995); one HMB Test Kit($100); filtration device ($4,500); hand held refractometer ($280); portable pH meter ($60); and Mark II Stabilizer $80). Purchase price for the new coolant is essentially the same as the old coolant.

Based on four coolant changes necessary every year, but avoided with the new system, savings would be $67,000 for each 1,000 gallons of coolant in use, mostly due to reduced waste handling. The rest would be from reduced coolant and biocide avoidance. In addition, there would be reduced labor costs, less downtime and maintenance time. Extended tool life or improvement of machining quality is not taken into account.