Metalworking fluids and lubricants

Monitoring and controlling contamination of metalworking fluids by microorganisms

Microbial contamination of metalworking fluids in industry

Metalworking fluids are used for three main goals in metallurgical industry:

1. lubricating the machining operations,
2. coolingthe cutting surface,
3. making easier the removal of cut material.

Aqueous metalworking fluids are liquids made up of oil and water. This combination is favorable for development of microorganisms. Indeed, source of microorganisms may be water, oil, parts and materials or contamination by workers.

Presence of:

1. organic matter, which is a biodegradable resource for microorganisms,
2. water, which is a favorable environment for microorganisms,
3. combined with high fluid temperature

are favorable for a quick microbial growth.

Which dangers may cause a microbial proliferation in metalworking fluids?

A non-controlled proliferation of microorganisms have the following impacts:

1. Microbiologically Influenced Corrosion (MIC) of machines and machined parts and moreover equipment defects.
2. Infections risk for workers, through aerosol emissions, leading to skin rashes or respiratory problems. Pathogenic microorganisms can cause more serious health problems.

1. Machines, filters and necks clogging.
2. Metalworking fluids degradation leading to a limit of emulsion stability.
3. Decrease of machining performance.
4. Odors appearance.

According to IRSST, concentration of microorganisms in metalworking fluids can reach 1 000 000 000 CFU/mL. This number underestimates the total amount of microorganisms because not all the species grow up on culture media. These microorganisms are bacteria (mainly Pseudomonas and Legionella but also Salmonella and Staphylococcus), molds (mainly Fusarium) and yeasts (mainly Candida).

Which infection risks for workers?

Studies show number of microorganisms in air, through aerosolization of metalworking fluids, is proportional to the concentration of microorganisms in fluids. Some occupational diseases among operators have been diagnosed (hypersensitivity pneumopathies, asthma, bronchitis, Pontiac fevers) where contamination of metalworking fluids has been detected. Generally, a very high total concentration of bacteria increases infections risk for workers.

So, metalworking fluids are microbiological risk sources for workers contamination. It is necessary to protect them. Get a sterile cutting fluid is illusory because microorganisms are always present but the first step is to control this source of microorganisms

How to measure quickly the concentration of microorganisms in metalworking fluids?

The most commonly used method for microbial measurement in metalworking fluids is culture, but is not adapted to problems encountered on the field. Heterotrophic plate count requires several days to results. Culture tests only measure culturable organisms (depending on the type of media being used). As a consequence, CFU/mL counts are generally only 0.1-1% of the total microorganism count in a sample while ATP testing accounts for all cells (culturable and non culturable). So, reactivity required for microbial risk control is not possible with laboratory analysis methods.

Using kits of 2nd generation ATP-metry, measuring total flora in samples in only few minutes is now possible. Quench-Gone™ Organic Modified test kit (QGO-M™) enables quantification of microorganisms through intracellular ATP quantification. Intracellular ATP is an indicator of active biomass. Every living cell contains ATP - aerobic or anaerobic bacteria, yeasts, molds, etc.

This technic brings reactivity required in industry. Indeed, to fight against microbial risk, the two main techniques used today are the addition of biocide and fungicide in metalworking fluids and the disinfection of circuits, machines and tanks.

So, how to check quickly operations efficiency?

Controlling and monitoring metalworking fluids with QGO-M test kit

Using QGO-M kit, disinfections check by a control, before and after operations, is now possible. Using ATP-metry technology, use of disinfectant can be adapted and optimized. Thus, sustainable savings are executable.

Furthermore, using QGO-M kit, efficiency of biocides and fungicide added to metalworking fluids can be controlled directly and in only few minutes. Decrease of microorganisms concentration needs a reasonable use of biocides in metalworking fluids. QGO-M test kit allows adapting the use concentration of disinfectants and controlling total flora during biocides substitutions.

Using QGO-M test kit, it is now possible to quantify in only few minutes and on-field all living microorganisms (yeasts, molds and bacteria) in any metalworking fluid. QGO-M test kit offers a possibility to measure the true total living flora present in the sample. An appropriate treatment can be quickly implemented.

Using QGO-M test kit, it is possible to define the origin of microorganisms growth and set up adapted solutions.

Origin of microbial drift may be:

1. bad quality of water,
2. non-efficient cleaning and disinfection of circuits and equipments,
3. biofilm into the circuit,
4. contamination by different oil,
5. too low renewal of products,
6. use of non adapted biocides.

To conclude, QGO-M kit allows analyzing and controlling total flora contaminating metalworking fluids.