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How to Choose A Pump That Suits Your Needs

Dec 16, 2022 | Technical Literature | 0 comments

How to choose a pump that suits your needs, first of all, in order to meet your needs, you need to determine the type of medium to be transmitted to avoid corrosion, thereby avoiding premature wear of the pump. Therefore, it is very necessary to know the chemical composition, viscosity and possible solid content of the pumped medium. A thorough knowledge of all physical properties of the fluid being processed enables the selection of the ideal technology for your application and selection of materials compatible with the pumped media.

Before selecting a pump body, it is necessary to refer to the chemical compatibility table.Then you need to check the properties related to the transmission medium, especially:

Required flow: typically in m3/h (cubic meters per hour) or GPM (gallons per minute), this flow will necessarily affect the size and dimensions of the pump;
Suction head: (the height between the inlet of the suction pipe and the pump): In general, the suction height should not exceed 10 meters. Beyond that, a submersible pump needs to be considered.
Discharge head: (height between pump and discharge pipe outlet).
The length of the discharge circuit.
Head loss associated with obstructions on the pumping circuit: (valves, elbows, etc.).
The presence or absence of a drain tank may change the head.
Choose the pump body according to the temperature.

From these different values, the NPSHa (Net Positive Suction Head) of the device can be calculated. Allows you to choose the right pump and avoid the risk of cavitation. You also need to control the efficiency; the efficiency must be optimal at about 30% of the desired nominal flow.


What kind of media do I need to pump?

The medium to be conveyed is very important when selecting a pump, as the characteristics of the pump depend on its viscosity (i.e. the resistance of the fluid to uniform flow), the suction temperature and the presence or absence of solid matter in the medium. In order to select a pump for operation under these conditions, you need to determine whether the media to be transported is chemically neutral or aggressive.
In general, the more viscous the media, the more difficult it will be to flow through the pumping system, but be aware that the viscosity of the media will vary with operating conditions. According to the viscosity level of the fluid, it can be divided into 4 categories. In the first category, fluids such as water, oil or alcohol move in the same way regardless of speed or degree of agitation. For these types of applications, you don’t have too many restrictions in choosing a pump. In the second category, certain foods, such as butter or cream, increase in viscosity with stirring; therefore, standard centrifugal pumps are not suitable for fluid flow in this case. The third category includes media that are to exceed a threshold before flowing. Once this point is reached, the viscosity will decrease with stirring. Adhesives, paints, and greases fall into the fourth category and are viscous at rest, but will become less viscous if kept under constant agitation.
In general, for low viscosity fluids (types 1 and 2), centrifugal pumps are the most suitable, because the pumping action generates high shear rates of the fluid, and as the viscosity increases, it needs to be considered that the fluid will Additional resistance applied by shear rate. Positive displacement pumps, on the other hand, are the best choice for viscous fluids (classes III and IV) because they operate at lower speeds and transfer less shear energy to the fluid than centrifugal pumps.

What are the different types of pumps?
Different types of pumps, including:

1.Centrifugal pump (suction of fluid through an impeller or propeller); is the most common model.
2.Diaphragm pumps (fluid is sucked in by the vibration of the diaphragm).
3.Piston pumps (fluid is sucked in and expelled by the reciprocating motion of one or more pistons).
4.Peristaltic pump (pushes fluid into tubes compressed by rotating rollers).
5.Gear pumps (fluid is sucked in and discharged by the rotation of the rotor and pinion or the counter-rotation of the two pinions).

There are also dedicated pumps for specific applications, which combine various operating principles described above, such as:

1.Quantitative or metering pumps for precise injection of fluids.
2.Lift pumps are used, for example, to discharge waste water.
3.Drum pumps are used to transfer fluid in a drum or canister.
4.Lubrication pumps, as the name suggests, are used to manage the lubrication of the system.
5.Submersible pumps suck fluid directly into the pump and are therefore not limited by suction height.



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