Accessories

IV. ACCESSORIES

ACCESSORIES

In addition to pumps, actuators, and valves, there are other ancillary devices are required to complete a hydraulic system. The important ancillary equipment and their functions are presented in Table 6.5.

Table 6.5. Ancillary equipment used in the hydraulic system

1. Fluid Reservoir: 

• Reservoirs basically are used to provide a storage facility for the hydraulic fluid used by the system.

• In addition, the reservoirs also serve to separate entrained air, remove contaminants, and dissipate heat from the hydraulic fluid.

2. Pressure Switches: 

• The pressure switches are used to sense a change in pressure automatically, and opens or closes an electrical switch when a predetermined pressure is reached.

• They have usually two pressure settings, namely high and low pressure. For example, in a circuit it may be required to stop a pump to maintain a given pressure. In this circuit, the low-pressure setting will start the pump and the high-pressure setting will stop the pump.

• Fig.6.36 shows the graphic symbols used for pressure switches.

• Fig.6.36(a) shows a normally open pressure switch, which is abbreviated PS-NO. Fig.6.36(b) depicts a pressure switch which is normally closed.

3. Filters and Strainers: 

• Filters and strainers are devices for trapping/ removing contaminants.

• Since the long-term operation of a hydraulic system depends on the cleanness of the hydraulic fluid used, therefore filters are necessarily used to prevent any contaminants from entering the system.

• Strainers are nothing but coarse filters.

4. Heat Exchangers (or Hydraulic Coolers): 

• Heat exchangers, also known as hydraulic coolers, are devices used to dissipate the heat generated in a hydraulic system.

• We know that heat is generated in all hydraulic systems. The main sources of heat include, the pump, motor, pressure relief valves, and flow control valves. Much of this heat is transferred to the hydraulic fluid, causing a rise in fluid temperature. Since all hydraulic fluids exhibit a limited temperature range over which the viscosity and lubricating characteristics are optimum, the heat must be dissipated to ensure satisfactory operation. This function is accomplished by the heat exchangers,

5. Accumulators: 

An accumulator, also known as pressure accumulator, is a device which can store hydraulic (pressure) energy.

• Accumulators can be used for pressure compensation, pulse damping, leakage compensation, emergency power, auxiliary pressure, and several other applications.

6. Intensifiers: 

• An intensifier, also known as pressure booster, is a device used to compress the hydraulic fluid by a pressure greater than the system pressure generated by the primary pump.

• The intensifier convert a large-volume, low-pressure hydraulic fluid supply to a proportionately small-volume, high-pressure output.

7. Pressure gauges : 

• Pressure gauges are used to measure the fluid pressure at various points in the system.

• Pressure measurement is considered as an important means of troubleshooting faulting operating hydraulic circuits. Pressure measurement can provide a good indication of leakage problems and faulty components such as pumps, motor, valves, and actuators. So pressure gauges are essential in any hydraulic system.

8. Temperature Switches: 

• A temperature switch is an instrument that automatically senses a change in temperature and opens or closes an electrical switching element when a predetermined temperature point is reached.

9. Shock Absorbers : 

• A shock absorber is a device that brings a moving load to a gentle rest through the use of metred hydraulic fluid.

• The shock absorber accomplishes the 'smooth' deceleration by metering hydraulic fluid through orifices, converting work and kinetic energy into heat which is dissipated.

10. Hydraulic Piping: 

• The function of hydraulic piping is to contain and conduct the hydraulic fluid from one port of the system to another.

• The design of the fluid conductors is just as important as the design of other components of a hydraulic system.