Pumps are widely used in industrial production and daily life, but how to choose the right pump can be a headache. The following practical examples will help you easily master the selection method of pumps.
1. Key points of pump selection
(1) Clarifying selection conditions
Before selecting a pump, it is essential to determine the key parameters. The flow rate Q is of utmost importance; the rated flow should not be less than the maximum flow of the equipment or should be 1.1 to 1.15 times the normal flow. For example, in a food processing plant, the liquid conveying flow during normal production is 50m³/h, and the peak flow can reach up to 60m³/h. Therefore, when selecting a pump, the rated flow should be at least 60m³/h.
Head H should not be ignored either. The rated head is generally 1.05-1.1 times the required head of the device. For example, in a water supply system, the water needs to be lifted to a height of 20m. Considering factors such as pipeline resistance, the rated head of the pump should be between 20×1.05 = 21m and 20×1.1 = 22m.
In addition, import and export pressure, temperature T, device cavitation margin NPSHa, operating state (continuous or intermittent) and site conditions (indoor or outdoor, environmental temperature and humidity, dangerous area level, etc.) are all factors that must be considered when selecting.
(2) Consider the performance of the medium
The characteristics of the medium significantly influence the performance and structure of a pump. If the medium is corrosive, such as in electroplating plants where solutions containing sulfuric acid are transported, a corrosion-resistant pump, like a fluoroplastic alloy centrifugal pump, should be chosen. If the medium is highly abrasive, such as in mines where slurries containing sand and gravel are transported, a wear-resistant pump should be selected, with the pump body and impeller made from wear-resistant materials.
The viscosity of the medium is also very critical. When the viscosity is greater than 650-1000mm²/s, the general centrifugal pump is not suitable, and rotor pump, screw pump and other pumps suitable for high viscosity media should be selected.
(3) Select the pump type
Different types of pumps are suitable for different scenarios. Centrifugal pumps, with their simple structure and easy flow regulation, are the most widely used; metering pumps are the preferred choice when precise measurement is required; for high-head, low-flow applications, reciprocating pumps are more suitable; and self-priming pumps are more convenient for frequent start-ups.
Second, selection example
(1) Select according to the medium
Tap water: ordinary clean tap water, without special properties, can be selected with a clear water pump, such as IS type clear water centrifugal pump, which can meet the daily water supply needs.
Sulfuric acid: sulfuric acid is highly corrosive, so it should be used with corrosion-resistant pump, such as fluoroplastic alloy centrifugal pump, whose overcurrent parts are made of fluoroplastic alloy, which can effectively resist the corrosion of sulfuric acid.
Medicine: Pharmaceutical factories transport highly pure, highly toxic or valuable medicine solutions. In order to prevent leakage, shielding pumps should be selected. For example, when transporting insulin solutions, shielding pumps can completely seal the medium in the pump body.
(2) Select according to installation conditions
Sufficient indoor space: the center of gravity of the horizontal pump is low, and it is convenient for installation and maintenance. It is suitable for installation in large indoor environments, such as equipment in factory workshops.
Sewage tank: Sewage treatment plant can draw sewage from the sewage tank. A vertical submersible sewage pump can be selected and directly installed in the sewage tank to avoid motor corrosion caused by sewage soaking.
Fire water supply for high-rise buildings: For the convenience of connecting with pipelines and saving space, pipeline pump is a good choice, which can be directly installed on the fire water pipe.
(3) Select according to flow
Small-scale irrigation: small-scale farming