M.S.E. – Baripada
Dept. of Automobile Engineering
4th Semester, Summer - 2022
HYDRAULIC CONTROL SYSTEM
Prepared by :
Er. Sourin Mohanty
CONTENT
ABSTRACT
Hydraulic control system of butterfly valves are presently valve-controlled and pump-controlled. Valve-controlled hydraulic systems have serious power loss and generate much heat during throttling. Pump- controlled hydraulic systems have no overflow or throttling losses but are limited in the speed adjustment of the variable-displacement pump, generate much noise, pollute the environment, and have motor power that does not match load requirement, resulting in low efficiency under light loads and wearing of the variable-displacement pump. the system is compact, produces a large output force, provide stable transmission.
INTRODUCTION
application of force is a common requirement in the industries.
These operations are performed mainly by using electrical machines or diesel, petrol and steam engines as a prime mover.
The enclosed fluids (liquids and gases) can also be used as prime movers to provide controlled motion and force to the objects or substances.
The specially designed enclosed fluid systems can provide both linear as well as rotary motion.
The controlled movement
of parts or a controlled
WORKING PRINCIPLE
The Hydraulic System works on the principle of Pascal’s law.
Pascal’s law states that “The pressure in an enclosed fluid is uniform in all the directions”’. The force given by fluid is given by the multiplication of pressure and area of cross- section.
As the pressure is same in all the direction, the smaller piston feels a smaller force and a large piston feels a large force.
Fig. working principle
SCHEMATIC DIAGRAM OF HYDRAULIC SYSTEM
Fig. schematic diagram of hydraulic system
COMPONENTS OF HYDRAULIC SYSTEM
Prime Mover
Pump
Control Valves
Actuators(Hydraulic motors, pistons)
Fluid
Filters
Protective Devices
Control Devices
PRIME MOVERS
Prime mover is a device which develops the mechanical power.
This power in a hydraulic system is basically used to drive the pump.
Prime mover includes IC Engine, Turbines, etc.
Fig. prime mover
HYDRAULIC PUMP
Pump is a device which converts mechanical energy to fluid energy.
The hydraulic pump takes hydraulic fluid (mostly some oil) from the storage tank and delivers it to the rest of the hydraulic circuit.
The hydraulic pumps are characterized by its flow rate capacity, power consumption, drive speed, pressure delivered at the outlet and efficiency of the pump.
EX. Vane pump, piston pump, Gear pump, Centrifugal pump,
Fig. vane pump
Fig. gear pump
Fig. centrifugal pump
Fig. piston pump
CONTROL VALVES
The control of the mechanical outputs (motion and force) is one of the most important functions in a hydraulic system.
The proper selection of control selection ensures the desired output and safe function of the system.
In order to control the hydraulic outputs, different types of control valves are required.
There are basically three types of valves employed in hydraulic systems:
1. DIRECTIONAL CONTROL VALVES
Fig. Directional control valves
2. FLOW CONTROL VALVES
Fig. Plug valve
Fig. Butterfly valve
Fig. Gate valve
3. PRESSURE CONTROL VALVE
The pressure control valves are used to protect the hydraulic components from excessive pressure.
It is normally a closed type and it when the pressure exceeds a maximum value by diverting pump flow back to the tank.
Pressure control valves
are the functional part of the system.
Fig. pressure control valve
HYDRAULIC ACTUATORS
Hydraulic Actuators employ hydraulic pressure to drive an output member.
These are used where high speed and large forces are required.
The fluid used in hydraulic actuator is highly
incompressible.
They convert fluid power into mechanical power.
Depending on motion they can be classified as:
1. Linear actuators: linear motion as output(cylinder and piston) .
2. Rotary actuator: rotary motion as output(motor).
1. HYDRAULIC CYLINDERS
Fig. Single Acting Cylinder
Fig. Double Acting Cylinder
2. HYDRAULIC MOTORS
Motors work exactly on the reverse principle of pumps.
Output Shaft
pressure and is converted
In motors fluid is forced into the motor from pump outlets at high
to
mechanical energy.
This fluid pressure creates the motion of the motor shaft.
EX. Vane motors, gear motors.
Fig. Hydraulic motor
HYDRAULIC FLUID
Hydraulic fluid must be essentially non-compressible to be able to transmit power instantaneously from one part of the system to another.
The most common liquid used in hydraulic systems is petroleum oil because it is only very slightly compressible.
Properties of hydraulic fluids: Non compressible
Low toxicity Low volatility
Fire resistance Good lubricator Corrosion control
FILTERS
The hydraulic fluid is kept clean in the system with the help of filters and strainers.
It removes minute particles from the fluid, which can cause blocking of the orifices of servo-valves or cause jamming of spools.
EX. Suction filters, pressure side filters, return side filters, offline filters.
Fig. Filter
APPLICATIONS OF HYDRAULIC SYSTEMS
Industrial: Plastic processing machineries, steel making and primary metal extraction applications, automated production lines, etc.
Mobile hydraulics: Tractors, irrigation system, earthmoving equipment, material handling equipment etc.
Automobiles: It is used in the systems like breaks, shock absorbers, steering system, lift and cleaning etc.
Marine applications: It mostly covers ocean going vessels, fishing boats and navel equipment.
Aerospace equipment: There are equipment and systems used for rudder control, landing gear, breaks etc.
ADVANTAGES & DISADVANTAGES OF HYDRAULIC SYSTEM