Category Archives: Hydraulics and pneumatics

Reciprocating Pump | Working of Single Acting Reciprocating Pump

SINGLE ACTING RECIPROCATING PUMP

If a reciprocating pump uses one side of the piston for pumping liquid, then it is known as a Single Acting Reciprocating Pump.

01 - SINGLE ACTING RECIPROCATING PUMP - TYPE OF RECIPROCATING PUMPS

Description

The main parts of a single acting reciprocating pump are discussed below.

1.Cylinder, Piston, Piston Rod, Connecting Rod and Crank

A single action reciprocating pump consists of a piston, which moves forwards and backwards inside a close fitting cylinder. The movement of the piston is obtained by connecting the piston rod to the crank by means of a connecting rod. The crank is rotated by an electric motor.

2.Suction Pipe and Suction Valve

Suction pipe is connected to the cylinder. Suction valve is a one way valve, i.e., non-return valve. It allows the liquid to flow in one direction only. That is, it permits the liquid from the suction pipe to the cylinder.

3.Delivery Pipe and Delivery Valve

Delivery pipe is connected to the cylinder. Delivery valve is also one non-return valve. It permits the liquid to flow in one direction only. That is, it allows the liquid from the cylinder to the delivery pipe.

Working Principle

In a single-action reciprocating pump, liquid acts on one side of the piston only. A single-acting reciprocating pump which has one suction pipe and one delivery pipe; It is usually placed above the liquid level in the sump.

01 - SINGLE ACTING RECIPROCATING PUMP - TYPE OF RECIPROCATING PUMP

1.Suction Stroke

When the crank rotates from IDC to ODC the piston moves towards right in the cylinder. This is called suction stroke.

Now, the volume covered by the piston within the cylinder increases. On the free surface of water in the sump, atmospheric pressure acts. Thus there is a pressure different at the two ends of the suction pipe which connects the sump and the cylinder. This pressure difference between the free surface and inside of the cylinder causes the flow of water from the sump into the cylinder through the suction valve, which is kept open.

During this stroke, the non-return valve at the delivery side will be closed by the atmospheric pressure existing in the delivery pipe. At the end of this stroke, the cylinder will be full of water, the piston reaches the right end, which is called outer dead centre since, the water is continuously sucked into the cylinder, this stroke is called suction stroke. At the end of this stroke, since the pressure in the cylinder is atmospheric, the suction valve is closed.

2.Return stroke or Delivery Stroke

When the crank rotates the piston from its extreme right position starts moving towards left in the cylinder. This is known as Return or Delivery Stroke.

The movement of piston towards left increases the pressure of the liquid inside the cylinder to a pressure more than atmospheric pressure. Therefore, the Suction valve closes the delivery valve opens. The liquid inside the cylinder is forced into the delivery pipe through the delivery valve. Consequently, the liquid is raised to the required height. The liquid is discharged at every alternate stroke.

Types of Accumulator | Weight, Spring, Gas Loaded Accumulator

Types of accumulator

Weight loaded accumulator

It consists of a piston which is loaded with a dead weight and moving within a cylinder this tends to exert pressure on the hydraulic fluid. Potential energy to compress the fluid is generated by the dead weight present on the piston. Concrete block, iron or steel is generally used as dead weight. The piston is made to move in the accumulator in precision fit in order to reduce the leakage. One side of the accumulator is connected to the fluid source and other to the machine.

01 - weight loaded accumulator - type of accumulator

Working

The ram is at the lower most position at the beginning of a cycle. The fluid is admitted continuously inside the cylinder during the idling period where the drive is provided by the machine. This makes the ram to reach the top most position, thus the piston or the plunger gains its potential energy. During the working stroke the accumulator is discharged to drive the machine.

Spring loaded accumulator

This type of accumulators is similar to that of the dead weight loaded type of accumulator. Spring loaded consists of spring in place of the dead.it is preloaded with the help of compression spring. It consists of a cylindrical body, a movable plunger and a compression spring.

01 - spring loaded accumulator - types of accumulator

Working

In the beginning the spring is in a compressed stage which makes the hydraulic fluid to flow inside the cylinder of the accumulator. Load of the spring is responsible for the pressure inside the cylinder.as the spring gets compressed the pressure inside the accumulator gets increased. When the fluid gets discharged out of the cylinder the spring gets expanded.in this method also the pressure exerted on the fluid is not constant as that of weight loaded type

Gas loaded type accumulator

This type of accumulator is also called as hydro pneumatic accumulator. This accumulator is widely used in many types of industries. This is classified into two types. They are,

Non-separator type accumulator

It consists of fully enclosed shell containing pneumatic-loaded actuator, gas charging port in the op and oil port at the bottom. The gas is occupied on the top and the hydraulic fluid is present at the bottom since there is no membrane to separate the gas and the hydraulic fluid it is called as non-separator type accumulator.

01 - non seperator type accumulator - gas loaded accumulator

Working

In this type of accumulator pressurization is achieved by the entry of pressurized gas into the cylinder. When the pressure of the machine increases the oil port opens and the oil enters the cylinder and the volume of the gas is reduced. This reduction in volume of the gas increases the pressure. This pressure gap or potential energy is used to drive the accumulator.

Separator type accumulator

the construction of the outer parts are similar to that of the non-separator type except that it consists of an additional piston separator or seal.

01 - seperator type accumulator - gas loaded accumulator

Working

The piston serves as the barrier between the gas and the hydraulic fluid. The working is similar to that of the non-separator type of accumulator. The gas gets compressed when the charged oil pushes the piston against it. The reduction in volume of the gas increases the pressure. This pressure gap or potential energy is used to force the oil out of cylinder when it is required in the circuit.