Maintenance

Management of the Metal Removal Fluid Environment

Maintenance

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Keeping the metal removal fluid in the best possible condition will ensure that the fluid does its job well and will help keep the workplace more comfortable. A fluid in good condition can also reduce health risks. Here you'll find out what a regular program of maintenance should include.

What should a maintenance program include?

The MRF maintenance program should include the following steps:

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1. Make a commitment to carry out the maintenance program conscientiously.

2. Assign responsibility for control of the fluid.

3. DCR (drain, clean, and recharge) the system properly.

4. Maintain the concentration at the recommended level.

5. Keep the fluid free of chips and grit.

6. Use good quality water (80-125 PPM hardness, low in chlorides, sulfates, and nitrates).

7. Keep the fluid aerated; circulate on weekends and during shutdowns.

8. Provide good flushing action at the machines and in the trenches.

9. Practice good housekeeping in the machining and MRF management areas.

10. Fix oil leaks and remove tramp oil.

11. Keep microbial growth under control by making timely concentrate or
      biocide additions before problems develop, instead of trying to regain
      control.

12. Maintain a record of system testing and control actions. Use appropriate
      procedures to analyze the data and make system improvements.

Regardless of the size of the machine tool sump system, the machinist, supervisor, and others working in the area should be trained to observe the system and the condition of the MRF.

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What should the machinist or machine operator look for?

The machinist should do the following:

1. check the sump level at the start of the shift

2. determine if the fluid color looks normal (a color picture of fluid at different
states could be used as a comparison)

3. determine if the fluid has an abnormal or bad odor

4. check to see if there is anything (growths, masses) floating on the top of the
MRF

5. estimate the amount of tramp oil floating on the surface

6. check for excessive foaming of the fluid

7. check the cleanliness of the machines and/or trenches

8. check for and report any skin irritation or dermatitis

9. check for and report respiratory irritation or other respiratory ailments
that might be associated with exposure to the MRF.

By checking the system daily, problems can be addressed at an early stage.

What is a low sump level?

A low sump level (30% below the full mark) indicates fluid evaporation, which may mean that the fluid concentration is too strong. Large lathes have higher evaporation rates than milling machines. Make-up fluid can be added at an appropriate dilution, which boosts the concentrate and additive components that have been consumed or carried off on the parts. Water can be added if the dilute fluid is not used.

What should a fluid in good condition look like?

A fluid in good condition will be clear (if a synthetic fluid), transparent to milky (semi-synthetic), or milky white (soluble oil), with no "cream" or free oil layer. If the fluid turns gray or black, bacterial problems are present. If the fluid picks up a yellow or brown tint or its dye fades, a significant amount of tramp oil is present.

What does a bad odor indicate?

Most objectionable odors are caused by uncontrolled microbial growth. Although it may be possible to mask the odor, a better solution is to address the root cause, because the microorganisms present in the fluid can be aerosolized into the air as part of the mist. Exposure to high levels of microorganisms in the air—or to a great deal of mist—can cause adverse health effects to exposed employees.

If the fluid has a strong odor of "locker room" or sewer, it has spoiled (soured) and must be dumped. See DCR.

What if strange masses are floating on the fluid?

Floating chips, swarf, or mold growths may be present. None of these conditions is normal. The material can be removed with a skimmer or pumped off. Remove as much as possible. DCR for floating mold.

What should be done if there is oil on the surface?

With water-diluted fluids, if the sump is completely covered with oil and the machinist cannot swish the oil out of the way for more than 5-8 seconds before the sump is covered again, there is too much tramp oil present. Skimming or pumping the surface oil to remove it is recommended.

The machinist should report any of the conditions discussed above to the area supervisor, who can initiate corrective action or change-out of the fluid. The situation needs attention.

What problems might cause excessive foam?

The foam may be caused by one or more of several possible problems:

soft water, with some products

high metal removal fluid concentration

contamination by cleaners

imbalance in the fluid surfactants

an undersized system

excessive flow rates

fluid not at rest long enough to allow air to escape

Foam with large, quickly breaking bubbles is probably caused by an excess of anionic surfactants. Tight, dense, stable foam results from an excess of nonionic surfactants. The foaming characteristics of a fluid may change in use as tramp oil selectively extracts the oil-soluble portions of the surfactant package, so that a fluid that did not foam when it was fresh may become foamy with age, in the absence of any contamination.

Foam may also have a physical origin. Systems need to be designed so that the fluid can rest long enough in the pit to allow solids to settle and air to escape. A trend in the design of modern central systems is to undersize a system, which results in magnifying any foaming tendency a fluid may have. Reducing flow rates, flush pressures, and nozzle flows can help to reduce foam.

What do dirty machines and trenches indicate?

They indicate one or more of the following:

the emulsion is becoming unstable

the cleaners in the fluid have been depleted

contaminants are being deposited from the fluid

filter failure

poor housekeeping

What would skin irritation indicate?

It could be a sign of one of the following in the fluid:

too high a concentration

high alkalinity

metal contamination

an unstable emulsion

contamination from workpiece coatings

But skin irritation might also be due to other things not related to the MRF, such as

changes in the weather

poor personal hygiene

poor work habits

the use of harsh hand soaps

wearing contaminated clothing

prolonged exposure to fluid

What does it mean if respiratory irritation is reported?

Exposure to high mist levels can lead to complaints of irritation and tightness in the chest. Animal tests and practical experience indicate that all fluids are potentially irritating, suggesting that the remedy should involve improving conditions rather than replacing one fluid with another.

Irritation problems may be associated with the following:

improper delivery of fluid to the cutting zone

improper use of additives

high coolant concentration

a heavy concentration of machines in a small area

inadequate or poorly designed enclosures and mist collectors

poor general ventilation of the shop

insufficient fresh air make-up rates

high mist concentrations, even in the absence of machining operations, may be associated with areas where coolant flumes make sharp turns

How should fluid concentrate additions be made?

Fluid concentrates should always be added to water, not the other way around. Adding concentrates in areas of rapid flow or high turbulence will speed emulsification or dissolution.

How can microbes be controlled?

Because it is not possible to keep microorganisms from being introduced into a sump, control depends on keeping them from multiplying.

There are three ways to achieve control:

keep your system clean

use fluids that cannot be used as food (non-biodegradable fluids)

use biocides to keep growth under control.

A non-biodegradable fluid may be desirable while in use, but when its useful life is done and it faces disposal, it may fall into the category of regulated waste, to which various restrictions apply. But a biodegradable fluid will have a short sump life unless effective biocide levels are maintained and the biocides are managed properly. Since biocides are designed to be toxic to microorganisms, they must be used appropriately if they are not to pose human health hazards.

Microbes can harm a fluid in two ways:

by consuming the chemicals that provide lubricating ability, cleanliness and rust protection

by producing acidic metabolic products that reduce pH

Other metabolic products can have strong, objectionable odors. Dead bacterial cells, present in the air as endotoxins, may be a source of respiratory irritation for exposed employees.

Many organisms, especially molds, will form slime colonies, will grow on the surface of the machine, filter, etc., and will be concentrated in a small area, rather than being evenly distributed throughout the fluid.

When collecting samples for microbial analysis, it is critical to look for stagnant areas in troughs or even under machines.

If odors are present and no microbial counts are found, always question the sample and believe the nose.

How is the metal removal fluid kept clean?

Filtration systems and oil skimmers remove suspended dirt and tramp oils from metal removal fluid systems. These important systems require periodic maintenance to operate effectively. Periodic checks are necessary to assure they are functioning as designed.

The fluid treatment system may be sophisticated or simple, depending on the amount and type of contaminants from the metal removal process. Typical systems may include:

skimmers or centrifuges to remove solids, free-floating oil, and loosely emulsified oil

filtration units to remove particulate (especially in grinding systems)

chip conveyors or drag out systems for the continual removal of chips or swarf

automated or manual metering stations for the addition of coolant concentrate and additives

Prepared by AWARE Services