Age hardening: the phenomenon that the consistency of lubricating grease increases with storage time. Appearance: the characteristics of lubricating grease seen only by visual inspection, usually including overall appearance, texture, color and luster.Main Functions of Lubricants
Main Functions of Lubricants
Overall appearance: smooth, rough, granular, oily, etc.
Texture: creamy, elastic, brushed.
Color: red, blue, yellow, white, etc., with restricted adjectives such as “light”, “medium”, “deep”, etc.
Gloss: shiny, dull, etc breaing.
Consistency: consistency refers to the degree to which plastic substances resist deformation under the action of external forces.Main Functions of Lubricants
Cone penetration: cone penetration is a measure of grease consistency. The greater the cone penetration, the softer the grease.
Consistency grade: nlgi (American grease Association) is divided into nine grades, from 000 to 6.Main Functions of Lubricants
Mechanical stability: the ability of lubricating grease to resist the change of consistency when subjected to mechanical shear. The smaller the change of consistency, the better the mechanical stability.Main Functions of Lubricants
Thixotropy: when the grease is sheared, the consistency decreases, and when the shearing is stopped, the consistency increases again.
Water resistance: the ability of lubricating grease to resist washing out from the bearing, the ability to resist the structural damage of grease due to water absorption, and the ability to prevent metal surface corrosion in the presence of water.Main Functions of Lubricants
Colloidal stability: the ability of lubricating grease to resist oil separation.Main Functions of Lubricants
Similar viscosity: generally, the viscosity of lubricating grease decreases with the increase of shear speed, so the grease viscosity is called similar viscosity or apparent viscosity.
1. Control friction: add lubricant between friction surfaces to form lubricating film and reduce direct metal contact between friction surfaces, so as to reduce friction coefficient, friction resistance and power consumption.Main Functions of Lubricants
2. Reduce wear: the lubricating film with certain strength between the friction surfaces can support the load and avoid or reduce the direct contact of the metal surface, so as to reduce the adhesive wear of various degrees such as plastic deformation, melting welding, cutting and re bonding of the contact surface.Main Functions of Lubricants
3. Cooling: the lubricant can reduce the friction coefficient and reduce the generation of friction heat.
4. Sealing and isolation: lubricant, especially grease, covers the friction surface or other metal surface, which can isolate the contact between water, moisture and other harmful media and metal, so as to reduce corrosion and wear, prevent rust and protect the metal surface.
5. Reduce vibration: the lubricant can convert the mechanical energy of impact vibration into hydraulic energy, which can slow down the impact and absorb noise.
If the amount of grease is too large, the friction torque will increase, the temperature will increase, and the grease consumption will increase; If the amount of grease is too small, reliable lubrication cannot be obtained and dry friction occurs. Generally speaking, the appropriate amount of grease is 1 / 3 ~ 1 / 2 of the total void volume in the bearing. Grease should be applied to the edge of the bearing according to the situation.
Avoid the cross use of grease containers and tools, otherwise it will have adverse effects on grease, such as drop point drop, cone penetration increase and mechanical stability decrease.
As the variety and quality of lubricating grease are constantly improving and changing, when the old equipment changes to new lubricating grease, it should be tested first and can be officially used after trial; When replacing with new grease, first remove the waste grease and clean the components. When adding lubricating grease, the waste lubricating grease shall be squeezed out until new lubricating grease is seen at the grease discharge port.
Lubricating grease can reduce mechanical friction, prevent metal aging and prevent air leakage, oil leakage and water leakage, so as to ensure the normal operation of mechanical equipment. When selecting lubricating oil, the following factors should be considered:
Temperature: the temperature has a great influence on the grease. If the environment and mechanical operation temperature are high, the grease with high temperature resistance shall be selected.
Speed: the temperature rise of high-speed parts is high and fast, which is easy to dilute and lose the lubricating grease. The lubricating grease with high consistency should be selected.
Load: since the cone penetration of grease is related to the load that can be borne during use, the grease with small cone penetration (high consistency) should be selected for heavy load; If it bears both heavy load and impact load, the grease containing extreme pressure additives shall be selected, such as the grease containing molybdenum disulfide.Main Functions of Lubricants
Requirements for special parts: selected according to different mechanical working environment. Grease with strong water resistance shall be selected in humid environment;
In the dusty environment, use thick lubricating grease containing graphite; In acid containing environment, warp base grease is selected; If there are special requirements for sealing, barium based grease shall be selected.
Lubricating with grease is an effective measure to improve the antifriction and anti-wear performance of moving parts of construction machinery. Due to the particularity of the service environment of construction machinery, its service life is greatly affected and the service performance of the whole machine is seriously affected. Therefore, only by recognizing the failure mechanism of lubricating grease can it be used correctly.