Fundamentals of centrifugal pumps
- Posted by: Daniel Irigo
- Category: Rotating Equipment
Pumping devices have been used to move liquids since ancient times. The first of them were waterwheels, reciprocating or screw pumps.
The appearance of the centrifugal pump dates back to 1600, reaching our days after successive modifications and improvements. Basically, a centrifugal pump is a kinetic machine that converts the mechanical energy received from the drive into hydraulic power, using the centrifugal effect.
Centrifugal pumps are the most widely used equipment in modern industry after the electric motor. Coupled with different types of drives, they allow liquids to be transported, pressurized, or lifted.
The hydraulic and mechanical design of modern centrifugal pumps allows them to be used in a wide range of operating conditions but is always limited by the manufacturer for each application.
The selection of suitable materials is decisive for the manufacture of a centrifugal pump and for it to withstand the required service conditions. Higher grade or more expensive materials do not always ensure the extension of the service life of certain pump parts or sealing devices.
Identifying the basic components and understanding the function of each is important for the operator, and crucial for maintenance personnel who must always strive to extend the time between failures.
The manufacturer’s documentation supplied with the pump should include the pump sectional drawing and the Bill of Materials, which lists all components with their drawing and material numbers. These documents should be used when ordering spare parts, always referencing the Serial Number of the pumping equipment.
Considering that the operating energy cost is the most relevant within the life cycle of a pump, it is imperative to know the most efficient way to use this equipment, since it impacts directly on production costs.
To achieve a successful operation of the centrifugal pump, it is necessary to previously know the flow rate and differential head required by the hydraulic system where it will be installed. In other words, the selection process starts from the demand required by the future user. Based on this data, the pump that satisfies both parameters with greater efficiency is selected, also considering the metallurgy, assembly, accessories, etc. required for the service.
A common mistake is to oversize pumps, installing them in systems that require significantly less flow or head. This leads to inefficient future operations in mechanical and energy terms.
In addition to proper pump selection, the pump must be manufactured, tested, and installed as per the manufacturer’s requirements. Commissioning according to good practices is very important, as well as operation and maintenance throughout the life of the equipment.
Modern centrifugal pumps are normally installed with measuring instruments for suction and discharge pressure, casing and bearing temperature and vibration, etc., which allow continuous monitoring and also collect data to support maintenance actions.
To minimize maintenance costs, special attention should be paid to the sealing system and bearings, since they are usually the components that demand the largest budget and workforce.
It is imperative to understand the internal forces developed in the pumping process that impact the useful life of the pump components, especially the bearings, as well as the importance of proper lubrication.
Sealing systems demand more maintenance attention in most centrifugal pump applications, so it is fundamental to be familiar with the factors that impact their proper operation.
For all of the above, there is a need for personnel who select, install or operate pumping equipment to be fully aware of the fundamentals of centrifugal pumps.
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