Graphite oilless bearing on large crane
Oilless bearings are composed of metal substrates and solid lubricants embedded in the friction surface in proportion to a certain area. In the process of friction, the metal base material supports the load, and the solid lubricant embedded in the friction surface forms a layer of solid lubrication medium layer to achieve the lubrication effect.
Large Cranes Solution
Oilless Lubrication | Large Cranes Bushing & Pin
Since large cranes often operate under conditions of heavy load, high temperature and dusty conditions, and high operating frequency, it is not easy for lubricating grease to be stored on the sliding friction surface, which makes the bearings work in harsh environments. The most outstanding performance is the matching part of the upper pin shaft of the gantry plate hook and the shaft sleeve. Although an oil hole is drilled in the center of the pin shaft, it can be regularly greased by the centralized lubrication pump on the gantry frame, but it is often subjected to high-temperature baking by molten steel. The grease is dried and even carbonized and caked, making refilling difficult. This part has a small action swing and a large bearing-specific pressure. It is difficult to form a uniform oil film on the bushing, resulting in dry friction between the bushing and the pin, and the hook cannot swing normally. In the past, it was relied on artificially to regularly apply oil on the surface of the bushing. , because the hook is often under high temperature, heavy load, and dusty conditions, the oil film is quickly squeezed away or dried. At the same time, there is still a lot of steel slag remaining on the surface of the lining, which causes the surface of the lining to be rough or cracked. Therefore, the VIIPLUS graphite oilless bearing, a mixture of graphite lubricating material and polymer organic material, has a good practical effect.
Requirements for solid lubricants
1. Oilless bearing can continuously provide lubrication to the friction surface.
2. The formed solid lubricant medium layer has a low friction coefficient. During the friction process, the blended material has the properties of releasing (or escaping) and reducing friction. It has a certain adsorption effect on the surface oil film.
3. Graphite plugged bronze bushing has certain heat resistance, corrosion resistance, and good compatibility with foreign objects.
4. Brass oilless bearing should have a thermal expansion coefficient not lower than that of the metal base material. When the temperature of the friction surface rises, due to its high thermal expansion coefficient, the friction surface will protrude, so that it can contact the counterpart and continuously provide lubrication.
Self Lubricating Bronze Bushing Mosaic technology
How to make a self-lubricating bronze bushing? First, the various materials of the solid lubricant are mixed and stirred in a certain proportion and pressed into a cylindrical shape. Scribe and drill holes in the bushing metal base so that the embedded solid lubricant accounts for 25 to 35% of the total friction surface area. The formed solid lubricant is then embedded directly and combined with a binder to bond to the substrate by natural curing. Finally, the graphite bronze bushing is finished.
Self-lubricating bearings can be used more than a few times the normal copper sleeve period, used in the parts that are not easy to replace or grease is difficult to lubricate the occasion. Such as robot joint bearings, bearings used in aerospace vehicles, in vacuum conditions or high temperature, low temperature, and other extreme environments that need to be used for a long time is not easy to replace the bearing.
Tin Bronze Bushing VS Graphite Plugged Bronze Bushing
1. The load-carrying capacity of tin bronze bearings increases with the increase of speed, while the opposite is true for graphite plugged bronze bearings. When the critical speed is exceeded, higher load-carrying capacity can be obtained by using tin bronze bearings. Therefore, graphite inlaid bearings can work well for the bushings of the shaft sleeve of the plate hook part with low speed and heavy load.
2. When the PV value of the tin bronze bearing exceeds a certain limit during operation, the temperature rises sharply, and it is easy to produce glue. The temperature rise of graphite inlaid bearing is lower than that of tin bronze under high PV value, so it can operate normally under high PV value, which also shows that the inlaid bearing has high-temperature resistance.
3. Graphite plugged bronze bearing is different from tin bronze. When wear debris and residues accumulate on the bearing surface, under certain pressure and temperature, these residues will mix with the grease applied on the surface and stick to the surface of the solid lubricant, so that the friction surface of the lining is not directly connected to the surface of the solid lubricant. The friction of the paired parts reduces the wear on the surface of the lining.