A wheel loader is earth moving machine, handling materials that scoops soil and loads it onto a truck. The host arm of the wheel loader can be compared to the arms and shoulders of a human being with the pin-connected portions the human joints. The joints of a human being have cartilage and hyaluronic acid that naturally lubricate the joints so that the arms and shoulders move smoothly. Unfortunately, this is not the case for machines. The machine needs an artificial supply of lubricants from outside. This is what we call greasing, which is a part of the daily inspection.
A: Grease is defined as a solid or semi-solid lubricant made by mixing a lubricant with a thickening material (or an agent that increases viscosity). In other words, grease is made up of three components – a base lubricant, thickening material for increasing viscosity, and additives that produce various characteristics. Different mixtures of these components create various kinds of grease. One of the biggest differences between oil and grease is as follows. Oil is a liquid that naturally runs off and easily escapes even through a tiny clearance, while grease sticks to the point of lubrication and stays there because of its semi-solid state even if there is some sort of clearance. This characteristic makes grease best suited for lubricating the joints of a wheel loader.
Why does it have to be grease?
A: Unlike the rotating elements of an engine that revolve at high speeds, the link joints of the soil handling device of a wheel loader repeat a semi-circular motion back and forth relatively slowly. Because of the nature of such a motion, a liquid lubricant would drop off and could not very well reach every part of the pin or stay where it has to be. On the other hand, grease sticks all around the pin and will stay there.
In addition, since the seals of the joints are exposed to muddy water, sand, and dust during operations, it is impossible to perfectly seal off the areas to be lubricated. Liquid oil would escape through an area that is not sealed sufficiently. On the other hand, semi-solid grease will not leak out.
Necessity for greasing
A: The link joints of the soil handling device of a wheel loader bear the load locally. Because of the lack of fluidity, the grease near this area will not spread around, making grease in a limited area bear the load. This accelerates the deterioration of the grease in that area.
Muddy water, sand, and dust penetrate through tiny clearances to gradually deteriorate the lubrication area from both sides. If you leave the deteriorated grease and penetrating foreign matter unattended for a long period of time, it will completely solidify to block the path of the next grease coming through. Lack of fresh grease will cause insufficient lubrication that could lead to a critical failure which may require large scale repair. To avoid this, be sure to lubricate the areas with grease periodically within the interval specified in the operation manual. Greasing is intended to feed fresh grease into the lubrication area while pushing out the deteriorated grease and foreign matter. When lubricating, be sure to inspect the machine to spot possible problems.
A: With an automatic greaser installed, you can let it take care of greasing while relieving yourself of the burden. However, there is something you have to be aware of. An automatic greaser continues to supply a very small amount of grease while the engine is running. Since the grease has to travel through long, small tubes that branch out in several directions, if any of the branch tubes gets blocked, it could cause the corresponding pin to seize. Because the machine has to deal with rocks, the possibility is high that rocks may damage the piping or tubing. Make sure that you check the machine condition carefully every day when using an automatic greaser to locate possible problematic areas such as damaged tubes, pins with the grease supply shut off, and areas that look as though they may fail. This will allow you to operate your machine without being hindered by machine trouble. Daily checks are important not only for human beings but also for machines.