In this article we will discuss about:- 1. Basic Components of Hydraulic System in Tractor 2. Types of Hydraulic System in Tractor 3. Advantages and Disadvantages.
Basic Components of Hydraulic System in Tractors:
The basic components are:
1. Hydraulic pump
2. Hydraulic cylinder and piston
3. Hydraulic tank
4. Control valve.
Operation:
The hydraulic pump draws up oil from the oil reservoir and sends it to the control valve under high pressure. From the control valve, the oil goes to the hydraulic cylinder to operate the piston, which in turn, raises the lifting arms. The lifting arms are attached with implements. The hydraulic pump is operated by suitable gears, connected with engine.
There are two types of arrangements for storing hydraulic oil in the system:
(i) There is a common oil reservoir for hydraulic system and the transmission system in some tractors.
(ii) There is a special tank for hydraulic oil. It is separate from the transmission chamber.
1. Hydraulic Pump:
There are several types of hydraulic pump, such as gear pump, plunger pump, vane pump, and screw pump. Gear pump is widely used in tractors. Gear pump can flow a bigger amount of oil, compared to plunger pump. The oil pressure in the pump varies from 150 to 200 kg/cm2.
2. Hydraulic Cylinder:
It is a bigger size cylinder, fitted with a piston and a connecting rod. It is also called Ram cylinder. The connecting rod transmits power from the piston to the lifting arms. Piston moves in the hydraulic cylinder and causes reciprocating motion in the cylinder. The lifting arms are raised by the hydraulic pressure while raising the implement but it is lowered by its own weight.
3. Hydraulic Tank:
Hydraulic tank is used for storing hydraulic oil for the system. In some tractors, transmission chamber itself works as a hydraulic tank and same oil is used for transmission system as well as hydraulic system. In some tractors separate tank is there for hydraulic oil.
4. Control Valve:
Control valve is a type of valve, which controls the movement of hydraulic oil to have desired direction, magnitude and speed of lifting.
Thus control valve is to perform three functions:
(a) To change the direction of lifting
(b) To change the power of lifting and
(c) To change the speed of lifting
The control valve is operated by hand lever and it is of two types:
(i) Manual type and
(ii) Automatic type
Manual type valve is used mostly for small tractors. There are only three positions in this case (a) Up, (b) Down and (c) Neutral.
In automatic type, there are more than three positions. Any of the positions inside a quadrant can be chosen for operation.
Oil Filter:
It is small filter, located at a convenient position in the passage of the oil.
Types of Hydraulic System in Tractors:
There are three important methods in hydraulic control system:
i. Position Control:
In this system, constant depth of ploughing is maintained by automatic adjustment of draft of tractor. In this system the control valve can be operated directly by the driver to raise lower or hold an implement, mounted on the linkage at any chosen height.
ii. Draft Control:
In this system, the working depth of any implement can be controlled continuously without the need for a depth wheel on the implement. The hydraulic control valve reacts to changes in the loading in either the top or lower links which are due to changes in the draft or pull required by the implement. If any implement goes too deep its draft increases.
This increase is sensed through the top link or lower links. The control system then raises the implement until the draft is back to the present level and the implement is at the original depth again using the draft control system.
iii. Mixed Control:
It is a combination of position control and draft control.
Advantages and Disadvantages of Hydraulic System in Tractors:
Advantages:
a. Very compact and powerful.
b. Easy prevention of overload.
c. Continuous speed change.
d. Remote control possible.
Disadvantages:
a. Difficult pipe connection.
b. Sometimes leakage of oil.
c. High power consumption.
d. Affected by high temperature.