Dirty metalworking fluid can cause a host of problems for your operation, and can be harmful to machines as well as the machinists - unless you care for it properly.
In this article, I'll explain the main reasons to keep your coolant healthy and the best ways to do so.
There are three main influences on the health of your coolant:
1. Concentration
2. Tramp oil
3. pH levels
How does concentration affect the health of my coolant?
First up, it is imperative that you maintain the correct concentration, otherwise, it can impact both the coolant performance and the machinist's health.
Coolant can cause rashes and dermatitis.
When the concentration is too low the coolant can grow bacteria that can aggravate skin issues including simple cuts and scratches. This is because the additives that prevent harmful bacterial growth are at too low a concentration to be effective. When the concentration is too high, the overdose of chemicals can cause rashes and skin issues (but only in rare cases).
The skin abrasions often occur when the operator gets coolant splashed on their skin and then wipes it away with a dirty rag. This causes micro-scratches on the surface of the skin, resulting in irritated skin, with the tiny cuts allowing the coolant to seep into the skin and cause agitation. This is a good case for treating coolant with respect.
To make sure you keep safe:
- Wash your hands regularly with a mild, non-abrasive soap
- Use a moisturizer to create a protective skin barrier that slows the absorption of chemical additives
- Wear thin nitrile gloves
Further to this, keeping control of your concentration is key to reducing health issues and having a high-performing coolant.
You can do this by checking what concentration level is recommended by your manufacturer, then testing the concentration frequently using an optical or digital refractometer. Track the desired concentration versus the actual concentration every week and correct it as needed with an emulsion.
How does tramp oil affect how healthy my coolant is?
When you're machining, tramp oils (such as slideway oils) sit on top of the coolant, holding debris. This leads to bacteria growing between the coolant and the oil, as well as stops it from 'breathing' (getting oxygen).
In some instances the tramp oil can dissolve into the coolant, destabilising the emulsion and causing it to get thicker and stickier. Bacteria can feed easily on this emulsified tramp oil, and ruin your tank of coolant.
We also don't like the look of it! Tramp oil is dirty and looks bad sitting on top of a tank of coolant.
Does the pH impact the health of my coolant?
As a rule, water-soluble or “miscible” cutting fluids are fairly alkaline, with a pH of around 8.6 or higher. This helps to prevent corrosion of metal surfaces, keeps microorganisms in check and is a bit easier on human skin.
If your coolant has become acidic, it's not healthy.
However, to maintain this you need to monitor the pH. The pH measurement is an indicator of your cutting fluid’s “health.” You can usually tell when there is a problem with the coolant because it has gone acidic. This is preferably done with a meter, or test strips weekly. If the pH is out of range, you can run the sump low and top it up with a new emulsion. If you’re not sure how to calculate what concentration you need, you can use this calculator.
Okay, so how can I maintain the health of my coolant?
There are a number of things you should be doing to keep your coolant safe and fresh.
- Skimming
- Filtering
- Mixing correctly
1. Skimming
Using an Oil Skimmer will remove the tramp oils in the coolant while the machine continues processing parts. It's a very effective way of keeping your coolant fresh because it removes oils that foster bacterial growth.
It works by pumping a small amount of coolant from the machine tool sump into the oil skimmer. Where the tramp oils are separated the tramp oil is drained to a separate tank. De-oiled coolant is returned to the machine.
Moreover, this process has the added benefit of aerating the coolant, which reduces the risk of developing infected coolant.
2. Filtering
Coolant filtering systems are important in keeping the coolant free from metal and other by-products, to prolong the life of the coolant. However, to allow them to function properly, you'll need to make sure that you clean the filtering screens regularly to keep them free from swarf and sludge.
If you don't have a filtering unit, they're often available from specialist machinist suppliers.
3. Mixing coolant
When mixing, always add the coolant concentrate to the water.
The way you mix your coolant is also critical to ensure that it stays clean.
It is important to always add the coolant concentration to the water. If you don't do this, the coolant will not emulsify properly, and the coolant will degrade much more quickly.
Always use clean containers, so there's no risk of a pre-emptive bacterial infection.
Use the right coolant for your water hardness. The minerals in hard water can result in problems with residues, while chemically softened water can tend to cause excessive foaming. Your fluid supplier can advise you as to what coolant to use for your water hardness and will have different products to alleviate your water-quality problems.
Keep your coolant in check
Keeping your metalworking coolant in top shape is vital for a smooth operation and the well-being of your machinists.
By managing tramp oils, monitoring concentration, and checking the pH regularly, you can avoid nasty bacteria and skin issues. Simple maintenance tasks like skimming, filtering, and mixing correctly will help your coolant perform better, last longer, and stay healthy.
