1. Double suction pump
The impeller of the double suction pump is composed of two back-to-back impellers, and the water leaving the impeller converges into a volute. With an improved structure, the double suction pump is widely used in engineering due to its high head and large flow rate.
The double suction pump has two suction chambers. Many people think that one is for the water inlet and the other is for the outlet. In reality, the pump's suction and inlet are perpendicular to the bottom of the shaft, mainly due to the direction of the impeller.
The advantage of the double suction pump is that it is less prone to cavitation due to the reduction in inlet flow, under the same speed and flow rate.
2. Single suction pump
The single suction pump draws in horizontally and axially and discharges upwards and radially. It has a suspended structure. During maintenance it is not necessary to dismantle the inlet and outlet pipes, as the rotor components can be removed for maintenance. The pump is connected to the motor through a common or extended elastic coupling, and the pump shaft seal is sealed with soft gasket. The bearing is an oil-lubricated single row radial ball bearing. When viewed from the motor end, the pump rotates clockwise.
Working principle
When a single suction pump is started, the shaft drives the impeller to rotate at high speed, causing the liquid that has been pre-filled between the blades to rotate. Under the influence of centrifugal force, the liquid moves radially from the center of the impeller to the periphery. As the liquid flows through the impeller, it gains energy and its static pressure energy increases, resulting in an increase in flow rate.
When the liquid leaves the impeller and enters the pump casing, it slows down due to the gradual expansion of the flow channel, converting part of its kinetic energy into static pressure energy before finally flowing into the discharge piping in the tangential direction. The volute pump housing not only serves as a component that collects the liquid coming out of the impeller, but also as an energy conversion device.
As liquid is thrown outward from the center of the impeller, an area of low pressure is formed in the center. The total difference in potential energy between the liquid level of the storage tank and the center of the impeller causes the liquid to be drawn into the center of the impeller. Continuous operation of the impeller results in the continuous inlet and discharge of liquid. The mechanical energy acquired by the liquid in the centrifugal pump is finally demonstrated as an improvement in the static pressure energy.
3. Double Suction Pump vs Single Suction Pump:
- Different input
Single suction pump refers to an impeller that is filled with water at only one end, while double suction pump refers to an impeller that is filled with water at both ends, i.e. with two inlets.
- Different Flow
The double suction pump is more suitable for transporting large flows and requires stable operation. When the pump flow requirement is very high, a single suction pump should have a large inlet and outlet diameter and a speed that is not too high, and should be stable at around 1450 RPM.
If a double suction pump is used, the size and weight of the pump can be reduced, the rotational speed can be increased, and the volumetric efficiency can be improved.
- Cavitation resistance
The anti-cavitation ability of a double suction pump is stronger than that of a single suction pump. The symmetrical action of the impeller at both ends of the pump creates a more stable hydraulic balance than a single axial suction pump. Furthermore, the medium flow rate is low, making the impeller less prone to cavitation.
- Different price
Double suction pumps are more expensive, priced slightly higher than single suction pumps. Single suction pumps are cheaper and have a wider range of uses, but double suction pumps are better in many ways. Specific requirements should be based on the user's actual operating conditions.
