Technical Library

Learn more about coolant management and how it can benefit your business.

• Part 1 - Choosing The Right Coolant
• Part 2 - Basics of Coolant Management
• Part 3 - The How and Why of Sump Cleaning
• Part 4 - Contamination Control
• Part 5 - Control of Bacteria and Fungus
• Part 6 - The Art of Coolant Recycling
• Part 7 - Coolant Start-up and Testing

Part 3 — The How and Why of Sump Cleaning

To clean or not to clean

In most shops, cleaning a sump means draining the old coolant, shoveling out the chips, and recharging with fresh coolant. To properly manage your coolant, your cleanout should include running a cleaner throughout the machine, dislodging sludge and removing biological residues. The cleaning process is an essential first step in the practice of coolant management, insuring that your coolant has a fair chance at giving maximum performance with minimal problems.

Once you have decided to chemically clean your sumps, chose a cleaner that is specially designated for this job. It is important to note that you should not use floor cleaners, bleach, or hand cleaners to clean your sump. A worthy sump cleaner should possess disinfecting properties, corrosion inhibitors and foam control. Your coolant vendor should be able to provide detailed information on their recommended cleaning approach.

There is a proper method to chemically clean a sump, however. Unfortunately, it takes a great deal of commitment to carry out all the steps involved. Virtually all coolant suppliers will recommend several steps of cleaning and rinsing to produce the best result. Review the 10 Step Sump Cleaning procedure, below.

Procedure for Coolant Sump Cleaning

1. Drain the entire coolant sump
2. Remove all swarf, chips and other solids
3. Fill the system with enough water to allow circulation through all lines, filters and tanks
4. Add the sump cleaner at the recommended concentration, usually 2%-4%.
5. Circulate the cleaner for 2-8 hours, or longer. If your system is severly contaminated, use the higher concentration and circulate the sump cleaner for as many hours as possible.
6. Manual scrubbing of some areas may be necessary. Steam cleaning of filters and tanks should be done on large systems, primarily in areas where the cleaner cannot reach.
7. When completed, drain the cleaner from the system
8. Refill the system with enough water to circulate through the system to rinse out the cleaner and other residues. If the water is exceptionally dirty, a second rinse may be necessary
9. Charge the system with the required amount of water
10. Add the recommended amount of coolant
11. Circulate the system to assure that the coolant mixes well. In precision grinding, make sure to circulate the fresh charge until it reaches normal operating temperature, so as to avoid size control problems.

So, can I skip some of the steps?

The answer is yes; you can skip some steps. However, that depends on how often you clean your sump and how contaminated the system is to begin with.

Sometimes production demands and manpower availability will force you to compromise. When this is necessary, there are alternatives. Try to incorporate as many steps as possible into the alternative methods.

Short cycle cleanouts

During Shutdown - If you have a shutdown period, add sump cleaner directly to the dirty coolant in the machine reservoir or the central sump. It is recommended that you add the cleaner at 4%–5% concentration.

Circulate the mixture for 4 hours (or longer) through all the machines and lines. Drain, rinse and recharge your machine with new coolant. In some cases, the rinse cycle can be skipped if you can drain the sump of all liquids.

During Production - Add the cleaner directly to the coolant while production continues. This is not an ideal approach to sump cleaning and should be monitored carefully to avoid undue operator exposure. Add the sump cleaner at 1%–2%, circulate for 4–8 hours, drain, rinse and recharge.

Additional Items of Note

Chemical cleaning may not achieve the desired results. With deposits of chips, swarf, mold and fungus, physical agitation of the metal surfaces may be needed to free the contaminants.

On smaller sumps, a simple cleaning brush can be used to break up deposits. For multiple machines and central sumps, a power washer with heated solutions can save a lot of time and effort.

If you have heavy biological contamination, it is highly recommended that you carry out the complete cleaning cycle. It will pay dividends.

If you cannot do a complete rinse, use a hose to rinse down surfaces as you drain the sump. Watch out for rinse water on machines however, as it can cause rust. Spray all surfaces with coolant as soon as possible to provide rust prevention.