Frequently Asked Questions

Both water and concentrate should be at ambient temperature and hopefully over 55 degree Fahrenheit. Instability can occur when water and coolant temperature are both below 55 degrees Fahrenheit or when there is a major difference in temperature between the two fluids. Coolant concentrate should be added to the water while continually stirring as normally water will be the large of the liquids from a volume perspective. You are “diluting the coolant into the water.” 

There are several reasons foam can occur. First and foremost, certain chemistries in industrial fluids are prone to foam and certain chemistries inhibit foam. If you are high pressure machining, you must make sure to choose a coolant that is designed with raw materials that will not foam in excessive pressure applications. With respect to chemistry, any coolant run at too high of a concentration or residual cleaner left in a system can be causes for foam production. Entrained air is a major issue for foam creation. Hoses might have pinholes, seals may not be fully seated, or fittings can be slightly loose. Additionally, machine configuration can contribute to foam. Any place in the system where air is introduced to the fluid is a potential cause for foam creation. If the sumps is too small or not filled to an appropriate fluid level, natural occurring air bubbles may not have enough time to dissipate leading to the creation of foam. This also leads to pump cavitation which only worsens the foam situation while harming the pump. Dirty/blinded filters create foam by creating a pressure differential which leads to the creation of foam much like the foam that occurs at the bottom of a waterfall. 

This smell is caused by microbial attack of the coolant by bacteria, yeast, and fungi. There are a number of different mechanisms that drive this “food chain of events” nonetheless a general rule is air and circulation of coolant help to inhibit this growth. Upon coolant sitting unagitated over the weekend, anaerobic microbials can start to grow and release sulfur containing chemicals which lead to “Monday Morning” odors.

The main reason for rusting with water miscible fluids is a concentration that is too low and below the critical concentration level (CCL). All industrial fluids have a CCL for the various properties of the fluid. If the CCL for corrosion protection is breached, there will not be enough corrosion inhibition properties to protect metal surfaces. This especially occur if there are dissimilar metals involved and the miscible fluid allows galvanic reactions to occur. Additionally, selective depletion of corrosion inhibition raw materials can occur. If excessive surface area resides in the sump (in the form of chips), corrosion inhibition chemicals in the fluids can coat these surfaces and be depleted from the fluid. In time, the selective depletion of these additives can be such that the concentration of the overall fluid is good but there are no longer enough corrosion inhibition properties in the fluid. Lastly, mineral/salt content can increase in a formula such that it helps to keep water located at the metal surface rather than evaporating. In time, this can lead to rusting. 

Emulsifiers are chemical compounds which allow the stable distribution of oil droplets in water. There are three main groups which can be classified by their polarity: Anionic emulsifiers are normally potassium sodium soaps, amine compounds or sulphonates. Cationic emulsifiers are often quaternary ammonium compounds (not often found in machining fluids). Nonionic emulsifiers are often ethoxylated compounds or esters. 

Water soluble coolants have four times the cooling capability to that of neat oils and are used when cooling is the major demand. Neat oils have the advantage of higher lubrication power. 

Multi-functional oils are fluids that are used for cutting and machining while also being the main lubricant for the machine tool equipment itself. These fluids have very specific properties as they must possess a compromise between cutting tool performance while not being too aggressive for hydraulic, spindle, and slideway lubrication. 

Here are the five factors:

1. The water quality
2. Tramp oil
3. Microbiological attack (bacteria, yeast, and fungi)
4. Chemical reaction with the machined material
5. The temperature being too high or too low
   
   

• Reduced biostability due to low concentration
• Tramp oil on the surface of the emulsion and poor aeration promote the growth of anaerobic bacteria. 
• Instable emulsions (see item 1) have low bio resistance.
• The mixing water has microbial contamination.
• The machines and systems have not been cleaned before the refill.

Although there are dozens of tests that can be run to evaluate the health and condition of your coolant in a machine, there are a few that should definitely be conducted. At a bare minimum, the coolant concentration could be monitored on a regular basis. Using a refractometer, it is a must to know that your coolant is within the desired target range. The next most important test to run is pH. This test can be run with a pH meter or even pH strips for a very quick reading. If your concentration and pH are within the desired target range, there is probably more than a 90% chance that your coolant is in good working order. The next test is more of a visual observation that revolves around the observance of tramp oil and contamination in the coolant. Although not a test, it should be noted if excessive tramp oil is residing in the sump fluid and if it is the oil should be removed in a timely and consistent manner. 

There is not an exact answer for this question. However, there is a general consensus on how to answer the question. Soluble oil machining coolants are products which contain basically mineral oil, emulsifier, and a few different additives (defoamer, rust inhibitor). They normally possess no water and when added to water make a turbid emulsion. A synthetic coolant contains no mineral oil and actually no hydrophilic raw materials such that an emulsion is created. These products are almost always translucent or transparent when added to water. They are often based on neutralized acids or esterified polymeric compounds. A semi-synthetic coolant is a combination of a soluble oil and a synthetic chemistry. Semi-synthetic products contain oil, and thus and emulsion, but are fortified with neutralized acids (synthetic portion) to provide additional properties. General rule – soluble oils lubricate better and cool less than synthetic chemistries which cool better and lubricate less. Semi-synthetic technologies are often thought of the best of both worlds containing both properties.

The term hard water can have a relativeness associated to it based on the circumstances that you are considering. When it comes to metalworking fluids and plant conditions, water with less than 100 ppm calcium carbonate is considered soft. Water with a calcium carbonate reading greater than 200 ppm is considered hard. The ideal water hardness for metalworking fluids is in the range between 100 and 150 ppm calcium carbonate. Water that is too soft can lead to excessive foam while hard water (over 200 ppm) can destabilize emulsions in metalworking fluids. Due to many of the high quality raw materials used in metalworking fluids today, it is common for coolants to be stable in systems with water hardness in excess of 500 ppm calcium carbonate. Certain ValCOOL products have extreme water hardness stability remaining stable in excess of 1,000 ppm calcium carbonate.

Tramp oil is a catch all term for all types of oil that make their way into the sump of a machining tool. The likely types of oil contributing to the makeup of tramp oil are the following: hydraulic oil, slideway oil, spindle oil, gear lubricants, and sometimes corrosion inhibitors or quench oils that reside on the work piece. The presence of tramp oil in a coolant can lead to numerous problems. Tramp oil in a system can destabilize emulsion forming coolants as tramp oil begins to become stabilized inside the coolant. This often affects the coolant’s ability to effectively rinse off of walls, parts, and windows causing maintenance issues. Additionally, the presence of tramp oil can lead to an increase in microbial growth and ultimately rancidity of coolant. Tramp oil can become a food source of microbes kicking of a cycle of exponential growth. Excessive tramp oil cuts off oxygen from the surface of the coolant thereby helping to create an anaerobic environment which many microbes find ideal. Tramp oils often contain zinc, phosphate, sulfur, and other chemicals which can lead to skin issues or nasal passage issues when they come in contact with worker.

Both digital refractometers and optical refractometer are tools that are commonly found measuring coolant concentration in machine shops. Both instruments are highly accurate. One benefit of an optical refractometer is the ability to “visually” see loose oil in the coolant. A digital refractometer gives you a number which tells you the Brix% concentration. It gives you one number with no additional information. An optical refractometer will give you the same number, but the line providing the concentration value can vary. If there is no tramp oil or loose oil in the system, the line will be very sharp. If there is tramp oil or loose oil residing in the coolant the line providing the Brix% concentration will be fuzzy and blurry. The more tramp oil in the system, the more blurry the Brix% concentration line will be. The cleaner the coolant the more sharp the Brix% concentration line.