What are hydrostatic bearings?
Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and the pressurization is done by a pump. Hydrodynamic bearings rely on the high speed of the journal (the part of the shaft resting on the fluid) to pressurize the fluid in a wedge between the faces.
What are the advantages of hydrostatic bearings?
Hydrostatic bearings have the advantage of very low friction at low speeds and allow a work table to be positioned with extremely high accuracy. There is also the advantage of very high damping and stiffness in the normal direction to the feed motion. The further advantage is the absence of wear.
What is the difference between hydrodynamic and hydrostatic bearing?
Hydrostatic bearings are externally pressurized with a lubricant and do not rely on rotating of the shaft to develop a fluid film. Conversely, hydrodynamic bearings rely on the speed of the shaft to pressurize the fluid in the bearing and lift the shaft off the bearing.
Where hydrostatic bearings are used?
Hydrostatic bearings can be designed for use in linear or rotary motion with radial loads, depending on the application. This makes them ideal to support elements in process fluid pumps. The design of the bearing can be very complex and requires precision pressure and gap control to operate properly.
Which lubricant is used in hydrostatic bearing?
Practically, a low viscosity lubricant, such as water, is applied to hydrostatic bearings for high speed use.
How does a hydrostatic bearing generate load carrying capacity?
Hydrostatic bearings derive their load capacity not from shear flow driven effects (hydrodynamic wedge and surface sliding) but rather from the combination of pressure versus flow resistance effects through a feed restrictor and in the film lands.
When would you use a hydrodynamic bearing?
Hydrodynamic bearings are commonly used in large turbines, generators, compressors, gearboxes and pumps in the power generation and oil, gas and chemical processing industries.
What is a zero film bearing?
A sliding bearing in which the working surfaces are completely separated from each other by lubricant is called zero film bearing.
What is the difference between fluid lubrication and boundary lubrication?
In the boundary lubrication region, the coefficient of friction is much larger than that observed in the fluid lubrication region. The use of lubricating oil with a lower viscosity is an effective means of reducing the friction force in this region.