For many plant and shop managers, it isn’t surprising to have a coolant inventory that’s as diverse as a medicine cabinet. Shops run many different operations that involve machinery performing a myriad of different operations that may involve different materials, processes and circumstances. These varying circumstances often lead to having various formulations and types of coolants on hand as a result.
Having dozens of coolants on-site, however, can lead to cross-contamination and waste stream inconsistencies. Instead, shops are turning to coolant suppliers to help streamline their fluids, reducing their various fluids down to a minimum number to effectively complete the job at hand, or at least a more limited selection for the processes in their plant. In order to determine the most effective solution for increasing machine and fluid life, you’ll need to consider all the cooling and lubrication needs of all processes in your plant, as well as the lubrication pros and cons of each coolant type.
To help you learn more about which coolants are best suited for different applications, here’s a breakdown of the 3 main coolant types:
The 3 Main Types of Coolant
1) Soluble Oil
Soluble oils are classified as coolants that contain petroleum oil and are mixed with water to create the metalworking fluid. These fluids may contain anywhere from a low level (10%) to greater than 50% of petroleum oil. These fluids are best suited for heavy-duty operations, especially those that remove a large amount of material or are slower-moving processes (e.g., broaching, external threading, etc.).
Likewise, these fluids are known for their good cooling properties (as compared to neat oils), as the water increases heat capacity and dissipates heat well. These fluids are blended with anti-wear and EP additives to aide the petroleum oil in lubrication at the point of cut. That being said, it’s crucial to have the correct type of water in your fluid, or you could be at risk for increased bacterial growth and rancidity. Using hard water can cause deposits in the sump or split emulsions, whereas soft water might cause foaming. Soluble oils are generally less expensive than the other two types of coolants, but their lifespan is also generally shorter.
Semi-synthetic fluids are classified as coolants that are formulated with up to 40% petroleum oil, and are mixed with water, salt, amines, and more. These fluids are best suited for moderate to heavy-duty operations, as they provide a cross-section benefit of soluble oils and synthetic technologies together in one product—allowing for higher cutting speeds and feed rates due to better cooling and wetting properties than soluble oils. Likewise, semi-synthetic oils also provide better machinability, seal compatibility, rust protection, and pain compatibility than synthetics, as well as cleaner-running environment than soluble oils. Similar to soluble oils, however, water hardness also affects the stability of the emulsion.
Unlike soluble and semi-synthetic fluids, synthetic fluids are classified by having no petroleum oil in their formulation whatsoever. While synthetics are still mixed with water—along with different amines, synthetic esters, EPs, and anti-wear additives—they’re traditionally more of a solution (think saltwater). Newer technologies can also hold these fluids together by a micro emulsion. This means once the additives are blended in, they should stay in-solution, and won’t “fall out.” These fluids traditionally are best suited for low- to medium-duty operations like surface grinding, light-duty milling, lathes, and hobbing. However, the newer micro-emulsion technology developed in the last 5 years allows for better performing additives to be added to synthetic fluid, which help make it more suitable for some heavy-duty applications as well. As a result, these fluids are also the most expensive, but they offer good microbial control, and virtually no rancidity.
Comparing Coolant Types
To help highlight the individual benefits of each coolant type more closely, use this coolant comparison chart for a side-by-side comparison of each type:
Coolant Type Comparison
© 2016 U.S. Lubricants
At US Lubricants, we know how complicated it is to get the perfectly formulated lubricant for your machines, let alone needing multiple fluids for different operations and applications. By streamlining your coolant inventory to only include one or a limited number of fluids, you can significantly reduce your inventory needs, as well as eliminate the confusion and mistakes that come from having a handful of different lubricants on hand.
For more information about how U.S. Lubricants can help you formulate the ideal coolant for your machines and applications, contact Tony Springer at TSpringer@uslube.com, or by phone at (800) 490-4900 ext. 8823.