How to Keep Machine Coolant Clean for Longer

Machine coolant wears out. Tramp oil, bacteria, metal fines and the wrong mix all shorten its life. Most of these can be controlled with good habits. Start by keeping dirt out of the coolant.

Remove tramp oil

Tramp oil is oil that leaks into the coolant from the machine. It comes from slideways, gearboxes and hydraulic systems. It floats on top of the coolant in the sump.

A layer of tramp oil keeps air away from the coolant. Bacteria grow under it, and the coolant starts to smell. Tramp oil also marks the parts and reduces cooling.

Remove it with a disc or belt skimmer, or with a coalescing separator. Fix the leaks that let it in.

Filter out metal fines

Fine metal from cutting and grinding stays in the coolant and goes round the machine again and again. It scratches parts, wears tools and pumps, and turns into sludge in the sump.

Choose a filter to suit the metal you cut:

• A magnetic filter holds iron and steel particles, including very fine ones. It does not catch aluminium, brass or other non-ferrous metals.
• A barrier filter, such as a bag, paper or cartridge filter, holds any particle larger than its pores. Some fine barrier filters also take out part of the additives in the coolant.

On mixed work, use both. Put the magnetic filter first. It takes out the iron, so the barrier filter after it fills more slowly and lasts longer. Magnetic filters compared with other filters explains the difference in detail.

Clean the magnetic rods before they are heavily loaded.

Check the concentration

Coolant is a concentrate mixed with water. The mix must be right.

• Too weak, and the coolant lubricates less, protects less against rust and lets bacteria grow.
• Too strong, and it can irritate the operator's skin. It also wastes concentrate.

Check the concentration once a week with a refractometer. Adjust the mix to the level the coolant maker gives.

Top up the right way

Coolant evaporates, and the water goes first. Top up with coolant that is already mixed to the right strength. Plain water from the tap lowers the concentration and helps bacteria grow.

Water with a lot of minerals leaves deposits in the machine. Reverse osmosis or deionised water avoids this.

When mixing, always add the concentrate to the water. Never mix two different coolants. They can react with each other and make the coolant unstable.

Keep the sump clean

Swarf, chips and sludge settle in the sump. Bacteria grow in them, and sludge can block the pump.

• Remove chips and swarf from the sump regularly.
• When you change the coolant, empty the sump fully and clean out all the sludge.
• Flush the system with a system cleaner before the new fill.

Keep the coolant moving

Coolant that stands still in an idle machine goes bad faster. Bacteria grow when there is no flow and no air. Run the pump for a while each day, or use aeration, when a machine stands for a long time.

Stop coolant from smelling

A bad smell means bacteria are growing. To stop it:

1. Remove the tramp oil.
2. Filter out the metal fines.
3. Keep the concentration correct.
4. Keep the coolant moving when the machine is idle.

How often should coolant be changed?

With good habits, one fill of coolant can last many months. Without them, it may need changing after a few weeks. The life also depends on the machine, the metal being cut and how many hours the machine runs.

Watch for these signs that it is time to change:

• a bad smell
• foaming
• a thick layer of tramp oil
• sludge that returns soon after cleaning

Store coolant concentrate safely

• Keep containers sealed.
• Keep them out of direct sun, frost and great heat.
• Label every container clearly.
• Use clean mixing equipment that is kept only for coolant.
• Keep the store clean and away from other chemicals.

The SMAG range

Santosh Magnetic Works builds the magnetic coolant filter to order in Mumbai. It takes fine iron out of coolants, oils and wash liquids, and it is cleaned by lifting the rods out and wiping them. See the filtration range or contact us with your machine and flow rate.