Pumps are devices that are used to move fluids (liquids and gases) from one point to another using mechanical action. Pumps find applications in agriculture, the oil and gas industry, and various other industries where the transport of fluids is required. The working principle involves the creation of a pressure difference at two points and the generation of a suction force to move the fluid.
Radial Piston Pumps are a type of positive displacement pump. They work by enclosing a fixed volume repeatedly in an area leading to the movement of fluid through the entire circuit mechanically. They can work in high-pressure conditions and provide the same flow rate at those conditions. They are commonly used in industrial applications such as in hydraulic systems and machine tools. Using radial piston pumps, a smooth flow of fluid in a varying range of pressures and speeds can be ensured. These pumps are also durable, energy efficient, and compact when compared to other types of pumps. A rotor with several pistons that are arranged radially around the central axis of the pump is the major moving part of a radial piston pump. This rotor is housed in a stationary cylinder that has inlets and outlet ports. The rotor is made to rotate inside this cylindrical chamber. As the rotor rotates, the pistons undergo a reciprocating motion, coming out of and going into the cylinders. This creates a hydraulic pressure that is responsible for the transport of the fluid.
Components of a Radial Piston Pump
1) Rotor: It is the major moving part of the radial piston pump, usually made of high-strength materials like steel or aluminium alloy. It holds the multiple piston arrangement and is responsible for the creation of reciprocating motion by rotating as a whole part. The surface is also coated or treated to reduce wear and tear.
2) Fixed Cylinder Block: It acts as the stationary component in the pump that holds the multiple cylinder arrangement. The pistons from the rotor are paired with the cylinders in the cylinder block. The design is in such a way that it withstands high pressures and forces produced in the pump.
3) Inlet and Outlet Ports: The flow of hydraulic fluid into and out of the pump is facilitated using inlet and outlet ports. They typically come as a part of the cylinder block and are usually connected to other hydraulic components.
4) Shaft: The shaft is the component that is used in connecting the rotor to the drive motor or engine in order to impart the rotational motion from the motor to the rotor. The design of the shaft is often influenced by specific requirements. Each design may offer efficient operation according to one’s needs.
5) Valve Plate: The component installed between the rotor and the cylinder block to regulate the flow of fluid in and out of the cylinder with the help of multiple valves. The shape, size, and number of valve ports can be varied as per the requirement. These variations can take an important role in controlling the flow of the fluid.
6) Bearings: They are components designed to reduce friction in the pump and to support the rotating parts of the pump. They are usually made of steel or ceramics or similar materials that are capable of withstanding high stresses. According to the performance requirements of the pump, different types of bearings can be installed in the pump.
7) Housing: The outer casing of the pump that contains all the internal components of the pump is called the housing. It also provides a point for mounting the pump. It is also responsible for protecting the internal components of the pump from damage or contamination.
The Working of a Radial Piston Pump
The Radial Piston Pump works on the principle of hydraulic pressure difference. This difference in hydraulic pressure is created using the help of a multiple-piston-cylinder arrangement. The rotor contains pistons that are arranged radially around the central drive shaft. These pistons are individually paired with their own cylinders that are present on the stationary cylinder block. As the rotor rotates, the centrifugal force acts, and the pistons are forced outwards. There is the presence of an angled swash plate just outside the cylinder which controls the flow of the fluid into the cylinder. The pistons first make contact with the angled swash plate. The angle of the swash plates is what determines the stroke of the piston and its further inward and outward motion. The valve plate is the part of the pump that holds the swash plate. Screws and bolts are typically used to hold the swash plate onto the valve plate.
As the pistons move outward, they create a large volume in the cylinder and hence an area with reduced pressure, this reduced pressure area acts as a vacuum that draws the fluid through the inlet ports into the cylinder. And when the pistons move inwards, the volume of the cylinder is reduced and the fluid is compressed. This creates an increase in the pressure and hence forces out the fluid from the cylinder to the outlet ports. And since the shaft is in continuous rotation, the pistons repeat the reciprocating motion leading to a steady and continuous flow of fluid in the pump. The angle of the swash plate can be adjusted so as to increase or decrease the amount of fluid that enters the cylinder. This is done for the smooth and continuous working of the pump i.e. the angle is adjusted accordingly if the requirement of fluid is more or less than what is already being pumped.
Advantages of Radial Piston Pumps
i) High Efficiency: Radial Piston Pumps can deliver large output with high volumetric efficiency.
ii) Variable Flow: Radial Piston Pumps are useful in cases where pressurized fluid is required at a variable flow rate.
iii) Durability: These pumps have a very rugged and rigid design increasing their endurance level.
iv) High Pressure: They are capable of producing high-pressure output and are hence widely used in injection mold machines.
v) Low noise and Vibration: Compared to other types of pumps, radial piston pumps have low noise and vibration. This eventually increases the life of the machine.
Disadvantages of Radial Piston Pumps
i) Maintenance: Radial Piston Pumps have a variety of moving parts. This makes them difficult to maintain.
ii) Compatibility: Radial Pumps are not advisable for fluids with high viscosity range. It is also not compatible with many chemical fluids too.
iii) Noise at high-speed levels: Though the machine is stable at low speeds, it generates higher noise and vibration at higher speeds. This reduces the efficiency of the machine.
iv) Cooling: Radial Piston Pumps require an efficient cooling mechanism to keep the temperature within the operating limit.
Industrial Applications of Radial Piston Pumps
i) Aerospace Industry: For their durability and capacity to deliver high-pressure output, they are used in landing gear and other hydraulic systems of the aerospace industry.
ii) Mining Industry: Mining equipment often requires heavy-duty hydraulic systems to power equipment such as excavators and bulldozers. Radial piston pumps may be used in these systems to provide the necessary pressure and flow rates to operate. iii) Injection Molding Machines: They are used in Injection molding machines to deliver molten fluid at high pressure and sufficient flow rate.