TECHLER INDUSTRY spol. s r.o.: How oil skimmers extend the service life of metalworking fluids

Why are tramp oils on the surface of the emulsion a problem? 

Tramp oils cause several problems in metalworking fluid. They degrade the metalworking fluid and significantly shorten its service life. They promote the growth of microorganisms (bacteria) in the fluid. Bacteria can survive in the fluid even without access to oxygen. Therefore, fluid with a large layer of oil on its surface may produce a strong odour when the machine tool is started, even after just a few days. 

A layer of tramp oil on the surface of the metalworking emulsion.

As bacteria multiply, corrosion may occur on workpieces and machine tool components. Bacteria can also cause unpleasant skin problems for machine tool operators. Heavily contaminated fluid must be replaced and the machine thoroughly cleaned.  

Contaminated metalworking fluid with a layer of tramp oil and metal chips.

Other problems caused by the presence of tramp oils in the emulsion include reduced cooling performance of the metalworking fluid, possible foam and smoke formation, and greasy deposits on workpieces, as well as contamination of the machine tool and its surroundings by these oils. Tramp oils thus increase metalworking fluid costs, mainly because the fluids need to be replaced more frequently. This is precisely why it is advisable to use an oil separator, or skimmer, which helps continuously remove oil from the surface and extend the service life of the metalworking fluid.

What equipment do we have available for you? 

There are several types of oil separators. The most common include belt skimmers, disc skimmers and so-called surface oil skimmers.

The TECHLER INDUSTRY range includes several types of oil separators that will help you solve your tramp oil problem. For example, a belt skimmer with a belt width of 60 mm, a skimmer with a belt width of 80 mm or a surface skimmer.

A cleaned machine tool tank after using a belt oil skimmer.

We will be happy to provide equipment from our range for testing directly at your facility. Servicing, spare parts and the supply of belts as required are, of course, also available.

What do you need to know and do to ensure your belt skimmer operates as efficiently as possible?

Belt length
First of all, we need to establish which belt length is most suitable. We will be happy to help you calculate it, but we will need a few details.

• the proposed mounting location – most commonly the top of the tank, but it can also be the side wall,
• the total height of the tank,
• the depth from the mounting location to the "normal" fluid level.

For every skimmer belt, a few extra centimetres must be allowed for the "turns" around the rollers, and the immersion of the belt itself must also be taken into account. Of course, the tensioning roller in the tank must not touch the bottom of the tank – otherwise the belt would not be tensioned.

Belt material
We use various types of material for metalworking fluids. Belts can be smooth or have a rougher surface. A more resistant belt is suitable, for example, for use in tanks in industrial parts washers, where more aggressive chemicals may be present.

Skimmer mounting location
It is very important to position the belt skimmer in the part of the tank where the most oil accumulates on the surface. The skimmer then has something to work with and can clean your tank relatively quickly. However, make sure that there is no high flow rate or surface turbulence at the mounting location, which could "disperse" the oil or cause the belt to sway. Oil removal would then not be very effective.

The surface skimmer operates on the bypass principle.

If this is not possible during normal operation, you can use a simple timer to schedule the skimmer to start when the machine is not in production or during a break. Simply put, when the surface is calm.

Inspection and maintenance
Like any piece of equipment, a belt skimmer deserves (at least a little) attention.

• checking for belt damage – most commonly a tear caused mechanically or by sharp edges,
• checking skimming efficiency – the belt may become worn after some time, so oil no longer adheres to it as well,
• checking and cleaning the collection trough – to prevent any solid contaminants from falling back into the tank,
• checking and cleaning the collection container – to prevent separated oil from spilling around the workshop.

Moving the skimmer between several machines
Yes, it is often the case that not every machine has its own skimmer. If it is not possible to provide a dedicated skimmer, it is advisable to at least provide a belt for each machine. Not only in terms of belt length, but also in terms of potential contamination.

A belt skimmer collects tramp oil and contaminants from the surface of the metalworking fluid.	A belt oil skimmer discharges tramp oil into a collection container.

In practice, this means that if bacteria are present in one machine, you may transfer them to another machine. Therefore, before using the skimmer in another machine, we would definitely recommend a new belt as well as cleaning the equipment, especially the tensioning roller, which is immersed in the fluid.

There is also fluid beneath the oil in our collection container
Yes, this can also happen, especially if there is no longer much oil in the tank and the belt also picks up some of the fluid. The important thing is that there should not be much of it in the container – here, a different type of belt or a skimmer with variable speed control could offer a solution.

The separation container of a surface skimmer.

In this case, we recommend disposing of the fluid together with the oil. If you wanted to pour it back into the machine, there is a possibility that this fluid could be contaminated with bacteria. After all, it is standing still with a layer of oil on top.

We hope this article has helped you gain an overview of belt skimmers and their effective use with machine tools.