Cutting fluids

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Contents 1 Overview 2 Environmental Impact 3 Best Practices 4 Alternatives to Cutting Fluids 5 Health and Safety 6 Suggested Products/Services 7 References

Overview

Cutting fluid or machining oil are used in metal processing applications. They are used in order to improve machine performance, product quality, and equipment life by cooling the lubricating the cutting tool. Metal processing applications that rely on cutting fluids include lathes, grinding machines, machining centers and many other types of machine tools and manufacturing equipment. Cutting fluids are made up various substances including oils, oil-water emulsions, pastes, gels, and mists. Industrial metal processing tools create a significant amount of friction and heat during use and require cutting fluids in order to reduce the wear and tear of the machine and transfer the heat being generated. The most effective cutting fluids keep the tool at a stable temperature, removes particulates, limits microbial growth, lubricates the working edge to maximize life of the tool and reduce tip welding, prevent rust formation or corrosion on the tool, and ensure safety for people handling it while not being hazardous to the environment.

Environmental Impact

The global market of cutting fluids is around 600 million gallons prior to dilution. In the United States alone, the market is 175 million gallons. The environmental and cost issues concerned with the use, recovery, and cleaning of cutting fluids are of substantial importance. With the recently devised and introduced ISO14000 environmental series legislation, companies are looking for methods to reduce their consumption of metalworking fluids. Companies are attempting to adopt more cost effective methods of recycling cutting fluids or removing them from the processes completely.

Companies are creating new fluid management practices that are utilizing more efficient methods of using cutting fluids. New machine technology, recycling methods and ultrafiltration techniques before disposal are helping to extend the life of cutting fluids and minimize their impact on the environment. Cutting fluids also pose a human health risk for those working in manufacturing environments. The National Institute for Occupational Safety and Health (NIOSH) published a recommended standard in January 1998 that has increased the level of concern about the safety of metalworking fluid formulations. Companies are seeking to use innovative cutting fluid formulations that meet health and safety recommendations as well as increase efficiency.

Best Practices

A Comprehensive Cutting Oil Management Manual is available through the Iowa Waste Reduction Center.

Fluid Management Administration

PERSONNEL AND TRAINING-A successful fluid management program requires a great deal of cooperation among designated personnel. Suppliers of cutting equipment and fluids uphold good communication with management and employees in order to maintain fluid quality and extend the life of cutting fluids. Management must have a good understanding of the chemistry of cutting fluid and monitor fluid performance, cost data, and disposal procedures. Management also creates training programs and educates employees about the importance of fluid management and how to successful implement fluid management guidelines. An organized structure of responsibility for cutting fluid usage and disposal that involves employees in the decision making is important as well.

OPERATING PROCEDURES AND TRACKING SYSTEM-Management must design a written standard operating procedure (SOP) for fluid usage/data collection and successfully followed by personnel. Following proper operating procedures while tracking cutting fluid usage and quality measurements allows personnel to identify a baseline for which fluids should be maintaining. Creating an informational database helps determine facility efficiency over time by comparing usage with amount being disposed and/or recycled.

Monitoring and Maintenance

RECORDING USAGE AND QUALITY INSPECTION-First and foremost, fluids should be mixed according to the manufacturers directions. Using untreated water with acceptable mineral content during initial mixing is recommended. However, in order to maintain fluid concentration after initial use, it is ideal to add pre-mixed fluids to the system after water loss from evaporation has occurred. During application, recording the fluid usage and quality factors in a detailed log helps maintain an organized system of information in order to identify trends that will help identify ways of improving metalworking techniques. The metalworking fluid manager establishes what factors need to be documented and tracked. These factors may include fluid pH, concentration levels, biological growth, water quality, foaming tendency, biocide use, particulates present, tramp oils, rust, rancidity, and color. Each facility determines what factors are necessary to monitor for their specific fluid program. Monitoring cutting fluid quality is essential to extending its life and anticipating problems. Periodic measurements and inspections are necessary for maintaining optimal fluid quality and performance. Appropriate adjustments must be made if quality measurements are not optimal. Recording fluid quality measurements in a detailed log allows management personnel to identify what adjustments need to be made and prevent further problems from occurring.

SYSTEM MAINTENANCE-An important element of extending the life of cutting fluids includes general maintenance of metalworking equipment. Dirt, oil, and other particulates remain in the system if not routinely cleaned and creates buildup and bacterial growth. General cleaning and routine preventative maintenance procedures include particulate removal, tramp oils control, general contaminants removal and an annual machine cleaning and disinfection. Preventative procedures help to extend the life of cutting fluids by reducing the frequency of fluid recycling.

Recycling and Disposal

RECYCLING METHODS-Once fluid quality has reached a point where it can no longer be maintained at an optimal level, it needs to be recycled for contaminant separation or disposal. The most important part of the recycling process is determining when to recycle. Once cutting fluids have degraded to a certain point, they are unable to be recycled. That is why it is essential to monitor cutting fluid quality. There are many different types of recycling equipment available to remove contaminants from fluids. The most common recycling equipment used are skimmers and coalescers (removes tramp oils), settling tanks, magnetic separators, hydrocyclones, centrifuges (removes particulates), filtration equipment and flotation process (removes smaller particulates).

RECYCLING INDICATORS

A) The pH is less than 8.0

B) Fluid concentration is less than 2%

C) Appearance is dark gray to black

D) Odor is strong rancid or sour

RECYCLING SELECTION AND SCHEDULE-How often cutting fluid needs to be recycled depends on fluid type, water quality, fluid contamination, machine usage and filtration, fluid control, and fluid age. The largest factor for determining a recycling schedule is the frequency of use. Generally, recycling can be done only a few times before it needs to be disposed. However, depending on the productivity level of the facility, cutting fluid may last only a few weeks or up to a few months long. Some manufacturers require that a recycling procedure is conducting at least once a month.

DISPOSAL-Even with recycling, cutting fluid will eventually require proper disposal. Before disposal, metalworking facilities must have the ability to determine whether the fluids are hazardous or nonhazardous. Waste is considered hazardous is it meets one of three criteria:

A) Exhibits one or more characteristics of a hazardous waste (ignitability, corrosivity, reactivity, and toxicity).

B) Has been identified and listed as hazardous waste by the Environmental Protection Agency.

C) Contains a mixture of hazardous waste and nonhazardous waste.

Used cutting fluid that is determined to be hazardous must be disposed by an EPA-permitted hazardous waste management company. It is essential that the waste management company disposes of the hazardous waste in accordance with applicable federal and state regulations. Nonhazardous waste may be treated on site prior to disposal but is required to be disposed of at either a local treatment plant or local municipal sanitary sewer system with permission from wastewater authorities. Options for treatment and disposal of nonhazardous cutting fluid include chemical treatment, ultrafiltration systems, evaporators, centrifugation, contract hauling and disposal as wastewater under local guidelines. Metal cuttings removed from cutting fluid is exempt from hazardous waste and are economically and environmentally safe to recycle. Cutting fluid disposal is not considered hazardous waste by the EPA if it is recycled or burned for energy recovery. However, some states consider used oil as hazardous and thus generators must comply with all state and federal disposal regulations.

Alternatives to Cutting Fluids

Dry Machining

New technology in metalworking equipment has made it possible to produce the same results without the use of cutting fluids. The new type of equipment is designed to eliminate the need for cutting fluid without losing the benefits associated with using cutting fluids. The new equipment has an added coating that insulates it from heat and friction. Dry cutting eliminates waste, maintains cleaner cuttings, and metal cuttings can be added directly to other scrap metal. Dry cutting also creates a cleaner and safer environment for workers. The potential drawbacks are initial start up costs to purchase equipment as well as a higher potential for machine rusting. However, if long term costs of cutting fluid recycling and disposal are considered, dry cutting may be a competitive or even superior option.

Minimum Quantity Lubricant (MQL)

MQL or semi-dry machining is very similar to dry machining. MQL requires a very small quantity of lubricant delivered precisely to the cutting surface. Nearly all of the lubricant used in the cutting process is either deposited on the equipment or vaporized from heat. Thus, there is no cutting fluid waste generated but only very small quantities that may require an extra cleaning procedure and proper ventilation. Fluid selection is important for MQL because it must be a superior fluid such as vegetable oil or synthetic oil. The cost of these superior fluids are higher but eliminate the need for costly fluid recycling and disposal services. MQL may be an ideal option because of the elimination of fluid waste while maintaining the benefits of using oil, but the specific fluid delivery method for individual facilities requires an in depth understanding of the technical aspects of MQL that could make it unfeasible to use this method.

Liquid Nitrogen Technology

Another option is using liquid nitrogen as a cooling and lubricating agent. Liquid nitrogen is cheap and can perform the same duties of traditional cutting fluid by maintaining a constant low temperature and flow rate. Liquid nitrogen may actually be a better alternative because its low temperature enhances the finish quality and tool life. Liquid nitrogen is a cheaper alternative for facilities because it is an abundant gas present in the air and cuttings chips have no residual oil on them. Liquid nitrogen is also safer than oils because it evaporates harmlessly into the air. The only dangers that it possesses is the extremely low temperatures that can potentially cause frostbite as well as non-combustible explosions due to pressure increases from warming. However, nitrogen is a safe and environmentally friendly alternative if handled correctly. Newly developed cutting technology by companies such as Creare Engineering uses liquid nitrogen technology in order to create cutting tool cooling equipment that eliminates the need for conventional oil coolants. Another alternative is coupling nitrogen with carbon dioxide, which has been found to eliminate environmental problems associated with the traditional petroleum-based flooded lubricant systems. An example of this product is Chilaire by CoolClean Technologies, Inc.

Health and Safety

Fluid Exposure

Reducing fluid exposure is the most effective way of reducing health risks associated with cutting fluid. There are a number of different methods of reducing worker exposure to cutting fluids. Choosing an appropriate cutting fluid is the first step towards reducing health risks. Facilities should have a good understanding of the Material Safety Data Sheet (MSDS)(Click link for example) provided by the cutting fluid manufacturer. These provide detailed information about fluid toxicity, flammability, and disposal. Facilities can use this information in order to determine the appropriate required safety equipment as well as potential hazards. Other important steps that facilities can take in order to reduce health risks involve the metalworking environment. Facilities can use a combination of methods including source or dilution ventilation, low-misting and low-pressure fluid delivery systems, splash guards and ensuring proper maintenance of equipment. The Occupational Health and Safety Administration (OSHA) has specific and in depth information on recommended exposure limits for cutting fluids. The National Institute for Occupational Safety and Health (NIOSH) also provides criteria for recommended standards on exposure to cutting fluids. Adverse health effects from exposure to cutting fluids are related to contact with skin and inhalation from breathing mists and aerosols.

Protective Equipment

Using protective equipment is an added method of reducing health risks. OSHA's Personal Protective Equipment Standards requires that employers evaluate the need for protective equipment. Employers must provide recommended protective equipment as well as training programs that focus on the potential dangers of exposure and proper use of protective equipment. Training should also include how to survey the workstations for potential hazards and when to consult appropriate operator manuals. Gloves, aprons, sleeves, and caps are recommended to protect workers from skin contact and respirators are available to reduce the fluid particles from being inhaled. In addition to using personal protective equipment, it is recommeneded that facilities monitor worker exposure by implementing an effective management program. Management programs not only track costs and environmental compliance information, but also help record the hazards and health risks to workers. An effective management program can have a positive impact on employee health and safety as well.

• A cutting fluid health and hazard evaluation report is available through the National Institute for Occupation Safety and Health (NIOSH).

Suggested Products/Services

Metalworking Lubricants and Fluids. Environmental Lubricants Manufacturing, Inc. Retrieved August 31, 2009.

Machining and Cutting. UNIST Micro-Fluidization Systems. Retrieved August 31, 2009.

References

Cutting Fluid Management. Iowa Waste Reduction Center. Retrieved May 8, 2009.

Metalworking Fluids. Occupational Health and Safety Administration. Retrieved May 8, 2009.

Personal Protective Equipment. Occupational Health and Safety Administration. Retrieved May 8, 2009.

Occupational Exposure to Metalworking Fluids Recommended Criteria. National Institute for Safety and Health. Retrieved June 18, 2009.

Cutting Fluid Health Hazard Evaluation Report. National Institute for Safety and Health. Retrieved June 18, 2009.