● High and low temperature Condition
The performance and serving life of lubricants are determined by the temperature variation of the friction part. At high temperature, the phenomena of evaporation, oxidation, condensation and oil separation of lubricant greatly increase. The higher the temperature is, the shorter lubricant’s serving life is;
The higher the temperature is, the higher base oil’s viscosity should be. And vice versa;
The high temperature resistance of thickener should be considered at the same time.
In high temperature situation, it is necessary to choose compound soap base grease, polyurea grease, synthetic grease and grease containing solid lubricant;
In low temperature occasions, grease with low viscosity of base oil should be selected, such as benzyl silicone grease, fluorosilicone grease, polyphenylene ether grease, synthetic hydrocarbon grease, etc.
● Heavy Duty Condition
Heavy load will break the molecular chains of lubricant, then lubricant become black and malfunction;
The viscosity of the base oil should be determined by work load. The larger the load is, the greater the viscosity should be;
For heavy and impact work load, strong grease film and heavy load capacity are needed. So lubricants with high viscosity of base oil must be selected, and sometimes solid lubricant;
For light work load, excessive viscosity of base oil will result in thick film, which result in great friction resistance and energy loss.
● High Speed Condition
High shear force formed at high speed has a great destructive effect on lubricant performance.
Generally speaking, the higher the speed is, the lower the viscosity of the base oil is required.
For bearings, not only their speed, but also their size should be considered.
DN value takes both the speed and size of bearing into consideration.
Lubricating grease with low viscosity shall be selected for the equipment work under high speed, such as motor and fan. Generally, the viscosity shall be ≤ 100mm2 / S (40 ℃).
Equipments work under super high speed, such as machine spindle and precision instrument need lubricating grease with lower viscosity. The viscosity of base oil is 20-30mm2 / S (40 ℃), and DN value≥ 1 million.
● Washout Steam Condition
Environmental factors include dust, humidity, water, corrosive medium, nuclear radiation, etc;
Lubricants will emulsify or deteriorate under wet or watery environment. As their mechanical stability decrease, lubricants become thinner.
Water resistant (composite) calcium base grease or synthetic grease should be selected;
In the case of corrosive medium in chemical industry, lubricants resistant to corrosion shall be selected;
In the case of radiation presence, radiation resistant lubricants should be selected.
● Flour dust Condition
Invisible impurities in lubricants have great wear effect on lubricants and friction parts, especially under high speed condition.
For dusty environment, the grease with high viscosity and solid propellant should be selected.