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.

What do you mean by hydrostatic lubrication in bearings?

In hydrostatic lubrication the bearing surfaces are separated by a lubricating film of liquid or gas forced between the surfaces by an external pressure. The pressure is generated by an external pump instead of by viscous drag as is the case with hydrodynamic lubrication.

Where is hydrodynamic bearing used?

Hydrodynamic bearings are commonly used in large turbines, generators, compressors, gearboxes and pumps in the power generation and oil, gas and chemical processing industries.

Which lubricant is used in hydrostatic bearing?

Practically, a low viscosity lubricant, such as water, is applied to hydrostatic bearings for high speed use.

What is boundary lubrication?

Boundary lubrication is defined as that in which the sliding surfaces are separated by a very thin molecular film of lubricant, so that the chemical and physical natures of the surfaces and the lubricant are of major importance.

How does a journal bearing work?

In a journal bearing, the shaft rotates inside a loose-fitting bearing shell of softer, often porous, bearing material. Lubricant, such as oil, grease or a low-friction compound like PTFE or graphite is used between the surfaces. The shell is sometimes split into two halves.

What are the types of hydrostatic journal bearing?

Hydrostatic bearings rely on an external pump….Three types of bearings include:

• Self-acting: Film exists due to relative motion. e.g. spiral groove bearings.
• Squeeze film: Film exists due to relative normal motion.
• Externally-pressurized: Film exists due to external pressurization.

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.

What is a hydrodynamic bearing?

A hydrodynamic bearing is typically a low-clearance assembly that relies on a film of oil (and occasionally air) that develops space while the spindle is rotating. The bearings transmit (float) the load on self-renewing film of lubricant.

What is fluid dynamic bearing?

A fluid-static bearing uses a pump to deliver the liquid and a fluid-dynamic bearing uses the movement of the parts themselves to draw the liquid into the bearing. Some fluid dynamic bearings may also use a supplemental pump for fluid delivery during start-up or shut-down operations to eliminate wear.

What is a fluid film bearing?

A fluid bearing is a type of bearing that has no parts that actually come in contact with each other. Instead, a thin film of fluid, sometimes under pressure, serves to bear the entire load placed on the bearing.

What is hydrostatic system?

The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow. A hydraulic drive system consists of three parts: The generator (e.g. a hydraulic pump), driven by an electric motor, a combustion engine or a windmill; valves, filters, piping etc.