Metalworking Fluids

RECYCLING EQUIPMENT COMPATIBILTY

With the ever increasing needs for higher cutting performance, longer coolant life, cleaner components, improving operator acceptance and machine cleanliness it has become almost imperative to utilise hi technology equipment to keep coolants in optimum condition. Lubriserv have a comprehensive range of equipment covering reclamation of cutting fluids from swarf, tramp oil separation, filtration or high speed centrifuging for particle removal. Once using these technologies it is important to remember the effect this can have on the coolants themselves. Whilst giving you significant benefits in terms of costs, performance, cleanliness etc by recycling or extending a waterbased coolant life will increase the water hardness and, as this makes up over 90% of the volume is a very important area of control. As the coolant life is extended and subsequent top ups are added to compensate for evaporation, the dissolved salts in the water increase as they do not evaporate like the water. This type of effect can be seen when using a kettle at home – if you have hard water you will quickly see a build up of scale or ‘hardwater salts’ in the kettle. This also occurs in a coolant after weeks/months or years of top up to a point when the coolant can split, separating out from the water phase and floating on the surface as a greyish oil like layer which is commonly mistaken for tramp oil. Other indications are increased coolant concentrate usage as the product in use splits out the additives a higher concentration of neat metalworking is required to maintain the working concentration of the coolant.

If you suspect that you may have this problem call Lubriserv for advice. Lubriserv have a great deal of experience in this area and have a range of metalworking coolants which are fully compatible with hard water types and are a great addition when using coolant recycling equipment. Total hardness indicates the presence of dissolved minerals and their salts in water. Predominant ions are calcium and magnesium. Other ions contributing to hardness include iron, zinc, aluminum, potassium and silicon. Total hardness is reported in parts per million (ppm) of calcium carbonate (CaCO3). It can also be reported in units called grains. One grain of hardness is equivalent to 17 ppm of calcium carbonate. Water hardness is typically defined using the following scale:

WATER COMPATIBILITY

Hardness can readily affect metalworking fluid performance.

Soft water may degrade the performance of all fluids by promoting the formation of foam. This condition is especially likely when using synthetics in grinding operations and semi-synthetics and soluble oils in both machining and grinding applications. Foam can drastically impair fluid performance by contributing to poor wetting and coverage properties, which diminish lubricating, cooling and proper film coverage for in-process corrosion protection. Foam can also hamper fluid detergency, making it more difficult to handle and filter swarf. When dense foam forms, it can lessen the filtering capabilities of a system by interfering with indexing mechanisms and by creating poor filter beds. Foam can also suspend tramp oils, preventing skimmers and other mechanical devices from removing them effectively. Tramp oils can act as a matrix, becoming finely suspended on a dense bed of foam. This development further intensifies a dense foam layer. Excessive foam can also lead to housekeeping issues by causing system barges and return lines, such as floor troughs, to overflow. Foam can also cause pump cavitation, creating excessive wear and premature mechanical failure.

As hardness increases, it can adversely affect the stability of semi-synthetic and soluble oil emulsions. The formation of hard water soaps from calcium and magnesium ions and anionic components (typically fatty acid-based emulsifiers) can radically alter emulsion particle size. This development will rapidly lead to scum formation and lose emulsions in which cream and free oil are present. Both semi-synthetics and soluble oils are harmed by calcium soaps. High magnesium levels especially hamper semi-synthetics. Hardness can build up in water stored for use as well in metalworking fluid systems as a result of evaporation. Many systems can loose from 5 to 25 percent of their water on a daily basis, depending upon system size, openness to plant environment, time of year, geographical location, plant conditions (air temperature and circulation patterns) and metalworking fluid temperature as the water circulates. Adding hard water to make up for loss resulting from evaporation will cause levels of hardness in the system to rise rapidly. As a result, emulsion instability in semi-synthetic and soluble oils will lead to corrosion problems, susceptibility to emulsification of tramp oils and microbiological attack, poor tool life, inferior surface finish, foam, and filtering problems.

Optimal hardness levels must be maintained by using the appropriate blend of water types for proper metalworking fluid performance. If you have any concerns give Lubriserv a call.