Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/934530
40 | January - February 2018 | www . machinerylubrication.com Don't they outperform the others? I am confused w hy more m a c h i n- ists don't use them." Much of the reason for this may be due to old practices and mind- sets. If your mineral oil worked for you yesterday, why would you want to change to a vegetable-based oil today and take a chance that the new product won't perform as well? People often fall into a routine, and unless something upsets that routine, the current practices tend to stay the same. It's usually not until an event like a discharge, government agency involvement or new personnel entering the facility that old practices are questioned and new ideas are considered. Many machinists may not even be aware of the other products on the market. In today's economy, it seems as if no one wears just one hat on the job anymore. e pressing issues at hand must be addressed, so the thought of looking for new "Why aren't more machine shops using natural biode- gradable oils? Is it the cost, availability or marketing? "Do you have any suggestions for problems with the solubility of oxidation products in turbine oil at low temperatures? Recently, my clients have had a problem with the solubilit y of oxidized produc t s i n t u rbi ne and hydraulic oils. At operating temperatures (60-80 degrees C), they are dissolved, but in stop- page (i.e., temperatures below 25 degrees C), they become insoluble and begin to deposit on working surfaces. is is a problem with the hydraulic piston pumps, and it does not matter the type of turbine (gas/steam/etc. or manufacturer) or the working hours." Based on your comments, you may be dealing with varnish forma- tion, which is a frequent problem in high-temperature and high-pressure systems such as steam turbines or high-performance hydraulic systems. Varnish is the accumulation of oil oxidation and degradation compounds on machine surfaces or components. It can be the result of several possible root causes, including high temperatures, electrostatic discharges, lubricant degradation and microdieseling. Varnish can produce a number of problems related to machine operation, such as valve stiction, lubricant flow restriction, clogged filters, etc. Varnish begins as dissolved impurities. When these impurities accumulate and reach the satu- ration point, they migrate to the surfaces of the lubrication system. If these deposits remain on the surfaces, they cure (harden) with time, causing failure of the lube system and lubricated components. Oxidation resistance and solu- bility are two important lubricant properties to consider. Oxidation resistance refers to how molecules resist the chemical reaction with the oxygen in the air. Oxidation degrades oil and is one of the main reasons to change it. e greater the oxidation resistance, the longer the oil life. Solubilit y is the propert y that allows a lubricant to hold polar substances like varnish in suspension without damage to the machine. Oil solubility increases at higher temperatures. Group III oils also have lower solubility than Group II and Group I oils. ere have been many instances of machines experiencing varnish deposits due to lower solubility of the oil after switching from a Group I oil to a Group II or III oil. If you are facing varnish deposits, two actions are recom- mended to control it. First, identify the root causes. is will require a systematic study of the possible factors supported by oil anal- ysis. Next, remove the existing varnish in the machine. is can be achieved by adding solvent or detergent additives to the oil, using a synthetic product with high natural solvency or installing varnish removal systems. In cases of hardened varnish, the solution will be mechanical and may simply involve changing the components. ASK THE EXPERTS