In extreme high temperatures, in addition to staff needing to pay attention to heatstroke prevention and cooling, metal working fluids also need to pay attention to maintenance and management to avoid odorization, discoloration, deterioration, etc. caused by the rapid growth and reproduction of microorganisms due to the increase in workshop temperature, which affects the performance of metal working fluids and reduces machining quality. Introduce you to the bacteria in cutting fluid There are a large number of bacteria in all metal processing fluids: Pseudomonas aeruginosa and Pseudomonas oil stains. A type of bacteria is called aerobic bacteria. In the absence of oxygen, they grow slowly or stop growing. Currently, there are over 2000 types of bacteria in our environment, but only a dozen in water-soluble cutting fluids, where they reproduce to varying degrees: Rare bacteria in metal processing fluids include Mycobacterium avian, Salmonella typhimurium, and Staphylococcus aureus. Many products contain bacteria, such as Escherichia coli, Klebsiella pneumoniae, Proteus, etc. Bacteria and fungi in metal working fluids. When oxygen enters, their reproductive speed increases. Usually, there are several aerobic bacteria in metal working fluids.
The two most troublesome types of aerophilic bacteria are Pseudomonas aeruginosa and Pseudomonas aeruginosa. Oily Pseudomonas aeruginosa likes to use mineral oil as food and thrives rapidly on machine tools with severe oil spills. Therefore, oil leakage from the machine tool should be prevented. If oil leakage cannot be prevented, the oil should be skimmed off the liquid level or removed using a centrifuge. Pseudomonas aeruginosa can feed on almost anything: minerals in water, components of coolant, lubricants, and discarded food. Among known bacteria, the above two are also the most difficult to kill. Another type of bacteria is anaerobic bacteria, also known as sulfate reducing bacteria, which grow much slower under hypoxic conditions than aerobic bacteria, splitting once an hour and producing unpleasant results. These bacteria only reproduce in the cutting fluid after being attacked by aerobic bacteria. Desulfovibrio, a type of anaerobic bacteria, can grow in almost all water-soluble liquids, resulting in a strong odor of rotten eggs. It contains hydrogen sulfide, which is the source of the "Monday morning odor" and causes corrosion on machine tools and work surfaces. In the presence of iron, the color of the liquid will turn black. These bacteria consume lubricants and rust inhibitors in metal working fluids, causing a rapid decline in their functionality. They also produce organic acids and salts, leading to corrosion. The faster they grow, the greater their impact on the fluid. Hazards caused by microbial growth Microorganisms such as bacteria and fungi in metal working fluids can cause varying degrees of harm: 1. If a biofilm is formed, it will accumulate at the filtration system as the processing fluid circulates, causing blockage of the filter medium and coolant nozzle, resulting in interruption of coolant supply, insufficient cooling and lubrication of the tool surface, and even inability to process normally. 2. Microorganisms produce various enzymes that may damage the chemical components in the cutting fluid, reduce the stability of the processing fluid, and shorten its service life, such as causing a decrease in pH value, viscosity, and rust prevention function.
3. The key components of Metal Working Fluid are damaged by microorganisms, leading to a decrease in performance. Adding fluids to ensure various performance increases daily consumption.
4. Bacteria can cause corrosion or discoloration on the surface of machined parts.
5. The proliferation of microorganisms produces uncomfortable odors or toxins, which are detrimental to the environment and worker health.
How to control the growth of bacteria in cutting fluid?
The composition of metal working fluid should be selected from bacteria that you do not like, as bacterial growth will be hindered.
Add fungicides to the concentrated solution or as needed during on-site use.
Properly mix and maintain working fluids. For example, maintaining an appropriate concentration, using water that contains no or less minerals, and so on.
Try to keep the machine clean as much as possible, reduce bacterial feed, remove iron filings and residues, reduce the hiding places of bacteria, and reduce the chances of bacterial reproduction.
The central liquid supply system is more affected by bacteria, and compared to the sum of several independent machines with the same liquid volume, it uses 3-5 times more working fluid. Therefore, the daily liquid consumption accounts for a smaller proportion of the entire tank liquid, which means that the liquid usage time is longer than that of individual machine tools. The central liquid supply system, due to the relatively low agitation of the liquid itself, makes it easy for bacteria to deposit together with other metal shavings to the bottom, which is the place with the least oxygen, providing assistance for the growth of anaerobic bacteria. The combination of these factors makes it more difficult for the central fluid supply system to control bacterial proliferation than a separate machine tool cutting slot.
This can be achieved through the selection of cutting fluid, system cleaning, and maintenance. Fungi can attach to the surface of the liquid tank, forming a continuous layer of material, causing great trouble to the infusion system of the machine tool. Just like the garbage at the bottom of the box filled with bacteria, the layer of dirt formed by fungi is difficult to remove chemically and must be removed mechanically. Fungicides and fungicides can only kill the organisms they come into contact with, and cannot penetrate the entire soil layer. The minerals in water are the nutrients that bacteria and fungi rely on for growth. Reducing minerals can also reduce the number of fungi. Synthetic coolant is easier to breed bacteria than lotion, and lotion is easier to be infected by bacteria.
