How Do I Maintain My Coolant Over Summer?

If your workshop closes over the summer, then you’re likely faced with a problem.

How do I maintain my coolant properly while the machines aren’t in use?

It’s a common question, and can be a tricky situation, with coolant tending to become stagnant, bacteria infested, and over-concentrated.

However, fear not, because in this article we’ve listed out the correct shutdown and start-up process to ensure your CNC coolant stays healthy over the holidays.

Let’s get into it.

The Shutdown Process

Check your concentration

First up, make sure that the concentration of your coolant is at least 5%. It’s okay if it’s a bit higher, but anything below that and you’ll need to increase the concentration, using an emulsion. Do not add water directly to the tank to dilute it.

If you’re not sure what ratio of coolant to water you need to get the right concentration for your top-up, click here for our coolant concentration calculator.

And if you’re not sure how to check what the concentration of your tank is, click here.

Recirculate the coolant

Once you’ve got your concentration correct, all you need to do is make sure the coolant is recirculated for 30 minutes every day in every machine. This ensures that the coolant stays oxygenated, minimising the risk of anaerobic bacteria attacking the coolant and causing a stench.

However, if it’s not possible for the coolant to be circulated every day, you need to make sure it is in a good condition to prevent it from going off.

Remove tramp oil

First and foremost, check that there is no tramp oil. If there is tramp oil present, remove as much as you can. Tramp oil will slowly dissolve into the coolant, causing to it to get thicker and stickier over time. Bacteria can feed easily on this emulsified tramp oil and then can attack the coolants’ oils as well, resulting in stinky and low-performing fluid.

Use maintenance biocide

If you have a maintenance tank-side biocide for preventative purposes (one that is continuous-action), then it’s probably a good idea to add it. This should slow down bacterial growth – however, we can’t guarantee this will totally prevent it.

Note that bacteria thrives in warm conditions, so high temperatures can significantly exacerbate growth. This is why it’s highly recommended to recirculate your coolant over the holiday period.

The Restarting Process

The pre-check

Before you restart your machine, you need to make sure that the coolant is still in good condition.

Here a few things you should be checking:

1. Does it look good?
2. Does it smell okay?
3. Is the concentration correct?
4. Is the pH within range?

Visual

There are several visual indicators that coolant has got issues. If it has lumps in it, or little island-like growths on it, it likely has bacterial growth. If there’s also tramp oil present, it’s likely the cause.

Another indicator that it’s gone off is the coolant has separated into two layers, one water, and one oil. It will look like olive oil on top of water.

And if the anti-foam has failed or worn out, the coolant will have white clumps with the texture of chewing gum.

Smell

If your coolant is smelly (e.g. has a ‘rotten-egg’ stench) then it’s not healthy. You’ll need to completely clean out your tank to get rid of the smell, and the bacteria that caused it.

Concentration

If the concentration isn’t correct, you’ll need to top it up. If it is significantly higher than how you left it, it’s likely due to evaporation. Make sure you do a top-up to get it back where it needs to be before you start using it again – concentration is critical to healthy coolant.

pH

You can usually tell when there is a problem with the coolant because it has gone acidic. Most coolants are alkaline, which helps to prevent corrosion of metal surfaces, keeps microorganisms in check and is a bit easier on human skin. Testing the pH is preferably done with a meter, or test strips. If the pH is out of range, you can run the sump low and top it up with a new emulsion.

Restarting

Once you’ve got all of the parameters where they need to be, you can go ahead and restart the machines.

Do a test run. If everything is going well, your restart is complete, and you’re good to go!

However, if you’re having issues, you probably need some further help. Give us a shout on 5551 4555 and one of our technical team will help you out further.

Disclaimer: All metal working fluids should be disposed of in accordance with national and local legislative requirements. An approved waste disposal contractor should be hired.