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Metalworking Fluids Control and Collection Necessary for Shop Floor Safety

Time: 2019-10-11 Source : PRATIC CNC

The metalworking fluids (MWFs) commonly applied during machining processes generate airborne mists that must be carefully controlled. Otherwise, the mists pose a variety of health risks to workers and create a dirty and unsafe work environment. It is important to understand the hazards associated with oil mists, as well as exposure limits set by the Occupational Safety and Health Administration (OSHA) and other entities. This article will review these issues and describe the role of proper mist collection in keeping machine tools and the surrounding shop area clean.

Regulations and Guidelines

The emissions generated by machining processes are formed because of a combination of mechanical and thermal effects and fall into three general categories:

1. Coolant-mist liquid aerosols, which are formed via condensation as a result of cooling or mechanical processes.

2. Coolant vapors, i.e., gaseous-phase substances that result from heating liquid coolant.

3. Coolant fumes, the finest solid particles in the air, which are generally formed during combustion processes.

Three different entities have established and published exposure limits that apply to MWFs: OSHA, National Institute for Occupational Safety and Health, and American Conference of Governmental Hygienists (Table below).

There are two general categories of MWFs used in machining processes:

1. Emulsion coolants: Water-soluble and water-mixed coolants are cooling-lubricant concentrates that are diluted with water, to their usage concentration, prior to use. The oil or lubricant proportion is typically about 5 to 11 percent. They offer effective heat dissipation and are used primarily for cooling.

2. Pure, or “straight oil” coolants: Non-water-soluble coolants are not mixed with water and are used according to the composition provided by the manufacturer. Straight oils are generally used for their excellent lubricating propertiesunlike water-mixed emulsion compounds, which provide some lubrication but primarily cool.

Mist Collectors

A variety of equipment captures mists generated when these coolants and lubricants are applied. Most commonly used are multiple-stage, fiberglass V-bag mist collectors. These units feature a first-stage Chevron metal filter, a second-stage aluminum mesh filter and a third-stage fiberglass V-bag with a 95 percent ASHRAE (formerly American Society of Heating, Refrigerating and Air-Conditioning Engineers) efficiency rating. The efficiency rating is a bit misleading in that it has nothing to do with oil removal. The ASHRAE rating system is used to measure efficiency in removing dry particulates. Most units also offer an optional fourth-stage HEPA final filter for added protection and cleanliness. A HEPA filter is usually designed to remove 99.97 percent of airborne particles measuring 0.3µm or greater in diameter.

Also prevalent are centrifugal-type mist collectors that use a rotating drum to spin the oil. Typically, a pad inside the unit functions as a final filter, but most contaminants are removed by the rotating action of the drum.

General Work Practices

You can tell when you walk into a machine shop whether or not good work practices are being observed. When they are not, you can literally smell, feel and taste the oil in the air. There are many factors involved in keeping machine shops as safe and clean as possible:

1. Always employ best-practice mist collection. As noted, it is often preferable to use a collector designed specifically for either oil-mist or emulsion-coolant-mist removal, as opposed to a “general-purpose” collector. This is particularly important for machines used for heavy-duty applications and long production runs.

2. Require the supplier to provide a written guarantee on filter life and emissions performance. Also, look for equipment that has been dye-tested and certified as leakproof by the manufacturer.

3. Inspect equipment regularly to make sure it’s working as designed. Sometimes, emissions will be fine at startup, but that may change after the collector has been in operation for a significant amount of time.

4. Frequently collect air samples to make sure you are well within the required personal exposure limits. Monitors that measure emissions and show milligrams per cubic meter being emitted are suitable for testing within the facility. If you suspect a problem or need independent verification of emission levels within the facility, it is best to hire a company that specializes in air-quality testing.

5. If you see oil on the floor, be sure not only to clean it up but also to find the source and take corrective measures to stop further leakage.

6. Monitor trends in the differential pressure across the filters and make sure pressure is within the manufacturer’s recommended operating range. Pressure monitoring should be done daily. There are a number of monitoring devices available that will measure differential pressure, as well as other critical functions, and trigger alarms at designated set points.

7. Train and educate employees on the health risks associated with overexposure, on good work practices and on the importance of good housekeeping.

8. Require handwashing several times a day if workers do not wear gloves. Do not allow workers to wear fluid-soaked clothes.

9. Prohibit food, beverages and any other personal items in any work area that may become contaminated.

As a high-technology enterprise, PRATIC has been fuousing on manufacturing cnc machining centers for more than 10 years, and PRATIC has been paying much attention to mist collection for shop floor and take all measures to protect the safety of all her workers. There is no employee suffer from diseases caused by MWFs in PRATIC and PRATIC also arranges annual medical health check for all her employees. PRATIC people are happy to work here and determied to make PRATIC a world famous Brand in CNC machine filed.

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