Maintenance of Hydraulic Systems

2012-06-08   来源：润滑油情报网 网友评论 0 条

Hydraulic systems consist of a number of components:

·Reservoir and Accumulator - holds a volume of fluid, transfers heat from the system, facilitates the release of air and moisture in the fluid

·Pumps (internal/external gear pumps, vane pumps and piston pumps) - transmits mechanical energy into hydraulic energy through movement of the fluid

·Control Valves - start, stop and direct the flow of the fluid

·Actuators/Motors - convert hydraulic energy back into mechanical energy through the use of hydraulic cylinders (converts into linear motion) and hydraulic motors (converts into rotary motion)

·Hydraulic Fluid - transmission medium for energy conversion

The oil or fluid is pressurized in a gear, vane or piston pump, typically at 1,000 to 2,000 psi and at the application point it moves a cylinder or rotates a motor or power unit. The oil circulates continuously in the system.

Successful hydraulic operations require the careful selection of hydraulic fluids that meet the system’s demands. They serve multiple purposes. Apart from energy transmission, they lubricate the system components, ensure heat transfer and control contamination. There are three types of hydraulic fluids:

·Mineral-based Fluids - properties depend on the additive package (ant-corrosion, anti- oxidation, anti-wear, foam control, demulsifier) and the petroleum refining process

·Water-based Fluids - used for fire resistance, oil-in-water or water-in-oil emulsions and water-glycol blends; possess limited lubrication properties and need to be monitored closely

·Synthetic Fluids - engineered fluids with excellent lubrication characteristics for high temperature and pressure systems

Other important properties to consider when selecting hydraulic fluids are:

Viscosity - a fluid which is too high or too low in viscosity can damage system, excessively high viscosity can contribute to high fluid temperature and greater energy consumption

·Viscosity Index (VI) - a high VI fluid can maintain its viscosity over a broad range of temperatures. This is particularly important for hydraulic systems that operate outdoors

·Oxidation Stability - oxidation caused by heat can greatly reduce the life of a fluid, leaving by-products such as sludge and varnish

·Wear Resistance - ability of the fluid to form a protective film on the metal surface to prevent abrasion, scuffing and contact fatigue on components

·Resistance to Emulsification - it is important to find out how the fluid in use might be exposed to water, preventing emulsification is critical, since conventional mineral oils are easily contaminated with water