In the area of metalworking the terms mineral oils, petroleum oils, base oils are often used interchangeably. The presence of oils in a metalworking system can be a benefit or a hindrance depending on the source and where it occurs.Petroleum oil containing fluids/coolants provide needed lubrication/ antiwear properties for both tooling and work piece production.
They provide good rust protection and are considered one of the most trouble free types of metalworking fluids. Their limitations include higher cost, disposal, smoke and fire hazards and limited tool life. Other sources of petroleum oils found in metalworking systems can be attributed to leaking machine tool lubrication systems. When this occurs, the oils generated are called tramp oils.
Unfortunately, tramp oils that are generated as a result of petroleum oil based hydraulic oil and gear oils can pose maintenance, environmental and performance issues for the manufacturer.In recent years, the waste disposal of metalworking fluids has been an issue which often affects the choice of metalworking fluid additives and types of fluids used.
In some cases, customer have requested mineral oil free systems, but in doing so have limited their ability to provided adequate lubrication to the tooling, as well as limit their ability to produce acceptable products.
Facts vs myths regarding the use of mineral oils found in metalworking fluids-
Myth 1 - Mineral oil contents of metalworking fluids will contribute to increase VOC's in my effluent.
The term "VOC" refers to "volatile organic compounds". These are organic compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the atmosphere.Common sources of VOC's include solvents, petroleum fuels and distillates such as gasoline's, kerosene's etc. Also, formaldehydes and primary amines that are emitted from certain biocide and corrosion inhibitor chemistries; these can also contribute to VOC's.
Fact 1 - Mineral oils used in Chemetall Oakite's metalworking coolants are high flash, petroleum oils that do not contribute to major increases in VOC's if used appropriately.
VOC's attributed to oil based metalworking fluids must be determined by EPA prescribed test method. This method is designed to detect any organic compound with high vapor pressure. Such components are found in industrial solvents, petroleum fuel components, components of some grades of lubricating oils (hydraulic, gear, or compressor oils) along with components from biocides and rust inhibitors.
The VOC loading that could be observed with petroleum oil based metalworking fluids will be negligible when compared to VOC's which can occur through tramp oils. Tramp oils can contain not only residual lube oils from machine leakage, but also RP's, greases, additional process oils related to parts delivered to operation.
Myth 2 - Mineral oils are more difficult to dispose of than water soluble synthetics.
Some manufacturers may claim that since synthetic metalworking fluids are water soluble and contain no mineral oils, that their waste treatability is better over mineral oil products. Disposal costs for any types of metalworking fluids-mineral oil based or water based- can be costly depending on the chemistry and the municipal water requirements.
If the facility cannot waste treat products on site, and must have products hauled away for disposal, a surcharge may be applied based on free mineral oil content. Much of this is based on regional and municipal requirements.
Synthetic metalworking fluids are true solutions and that make the ability to strip additives from the water phase of these products very difficult. In most cases, highly specific and costly polymer agents will need to be added to the effluent in order to remove the organic additives.
Fact 2 -Micro emulsions such as GARDOCOOL C 9157 and GARDOCOOL C 9158, as well as semi synthetics such as GARDOCOOL C 9127 can be easily waste treated by a simple acid split mechanism. Similar to conventional soluble oils. Since the majority of the additives are oil soluble, they can be readily split out in an acidic environment. Oil containing MW fluids can be waste treated by conventional methods.
