Centrifugal and positive displacement pumps are powerful tools that can move fluid through complex industrial and municipal systems. But it’s essential to choose the right equipment for your facility’s needs. Next, we'll talk about the differences between these two pumps.
Centrifugal pumps are widely used in water conservancy, the chemical industry, HVAC and other industries, and more and more attention has been paid to the selection of working conditions and the analysis of energy consumption. The so-called working point refers to the actual water output, head, shaft power, efficiency and suction vacuum height of the pump device at a certain moment, which indicates the working capacity of the pump. Usually, the flow rate and pressure head of the centrifugal pump may be inconsistent with the pipeline system, or due to changes in production tasks and process requirements, it is necessary to adjust the flow rate of the pump, which is essential to change the operating point of the centrifugal pump. In addition to the correct selection of the centrifugal pump in the engineering design stage, the selection of the working point of the centrifugal pump in actual use will also directly affect the energy consumption and cost of the user. Therefore, how to reasonably change the operating point of the centrifugal pump is particularly important.
Centrifugal pump is a kind of liquid conveying equipment widely used in various fields. Its working principle is to convert the kinetic energy into the pressure energy of the liquid by utilizing the centrifugal force. Centrifugal pumps have many advantages that make them the first choice for many applications. The following are the reasons for choosing a centrifugal pump.
Centrifugal pump refers to the centrifugal force produced when the impeller rotates to transport the liquid pump. Centrifugal pump is the use of impeller rotation and make the water centrifugal movement to work. We should not only know what is centrifugal pump, but also pay attention to the main points when choosing products. In this article, Inverter.com will show you the steps to choose a centrifugal pump.
Centrifugal pump is a pump that relies on the centrifugal force generated when the impeller rotates to transport liquid. Before the pump is started, the pump casing and suction pipe must be filled with water, and then the motor is started, which makes the pump shaft drive the impeller and water to do high-speed rotational movement, and the water will undergo centrifugal movement and be thrown to the outer edge of the impeller, and flow into the pressure pipe circuit of the pump through the flow channel of the worm-shaped pump casing. Let's introduce the types of centrifugal pumps.
Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. Its basic components are a high-speed rotating impeller and a fixed snail-shaped pump casing. Usually centrifugal pumps have impellers with several backward curved blades fastened to the pump shaft and driven by the motor to rotate at high speed along with the pump shaft. There are two ports on the pump casing, the inlet leading to the center of the impeller is connected to the suction line. The tangential side of the pump casing is the outlet, which is connected to the discharge pipeline.
In the case of a pump filled with liquid, the impeller rotates to produce centrifugal force, and the liquid in the impeller groove is thrown to the periphery under the action of centrifugal force and flows into the pump casing to form a vacuum in the center of the impeller. The liquid will flow from the suction pool to the impeller under the action of atmospheric pressure. This way the liquid is constantly being sucked and beaten out. In the impeller to obtain the energy of the liquid out of the impeller has large kinetic energy, these liquids in the spiral pump casing is collected, and in the back of the diffusion, the tube will be kinetic energy into pressure energy.
Centrifugal pump is a pump that relies on the centrifugal force generated when the impeller rotates to transport liquid. What causes the centrifugal pump to fail to deliver water? Here are the failure analyses.
1. Some users do not fill enough water before the pump is started. Sometimes it seems that the water filled has overflowed from the vent hole, but the pump shaft is not rotated and the air is completely discharged, causing a little air to remain in the inlet pipe or pump body.
Centrifugal pump is a pumping machine that uses the centrifugal movement of water to work. Its basic components are a high-speed rotating impeller and a fixed snail-shaped pump casing. Generally, centrifugal pumps have several (usually 4-12) impellers with backward curved blades fastened to the pump shaft, and the impeller is driven by the motor to rotate at a high speed along with the pump shaft.
The working conditions of centrifugal pumps are generally harsh. Affected by environmental conditions, mechanical vibration and other factors in the working process, its technical status will undergo different changes. The maintenance of the water pump is to tighten and adjust the place that should be tightened and adjusted before the normal technical state of the unit itself is damaged. In addition, it is necessary to change the lubricating oil promptly to maintain normal lubrication conditions; frequently observe various instrument monitoring devices. If any problem is found, the fault should be eliminated in time, so that the unit is always working in good technical condition. Only in this way can the service life of the water pump unit be prolonged and the unit can work with high quality and high efficiency.
In order to buy the correct pump, you need to know what flow rate and total head you will need.
Generally speaking, when the pump output pressure increases, the pump head increases, and when the pump output flow increases, the head will decrease. That is why some few pumps manufacturers use the pressure term instead of head to characterize the pump specs, but the head is still more useful and clearer term to assist you in the pump job evaluation.
In a certain application, if you need to pump a liquid for 40 ft, this means that you need to select a centrifugal pump with at least 40ft total head plus the friction losses, so it is better to select a bit little higher head to substitute for the friction to get required flow.
Pump head will not be affected by pumped liquid type as long as the liquid viscosity is low like water, so the head achieved by the pump will be almost the same.
The horizontal centrifugal pump is required to install the basement. In normal conditions, it is the single-stage end suction port/double-suction pipeline downwards inlet and upwards outlet/horizontal inlet and outlet. The inlet pipe diameter is larger than the outlet pipe diameter. The power can be very high. Its efficiency is higher than the vertical pump, and it has a smaller shock on the pipeline. As to the big pump, it is usually recommended to adopt the horizontal type.
The cleaning and maintenance of centrifugal pump parts includes mechanical external cleaning and part cleaning. Part cleaning can be divided into pre-identification cleaning, pre-assembly cleaning and painting or bonding parts cleaning.
What is centrifugal pump cavitation?
When the local pressure of the liquid in the pump drops to the critical pressure, bubbles will be produced in the liquid. Cavitation is the whole process of bubble aggregation, movement, division and elimination. The critical pressure is generally close to the vaporization pressure.
The self-priming of the self-priming pump refers to the starting of the pump under the condition that the suction pipe does not need to be filled with water (but there must be enough water in the pump body). It has the function of automatically removing the gas in the suction pipe and entering normal work after a short period of operation. The self-priming pump must be filled with enough water before the first start, and then start again from the water left in the pump body to normal operation.
The principle that a centrifugal pump can transport liquid is that a high-speed rotating impeller exerts a centrifugal force to the liquid. That's why it is called a centrifugal pump. Before start-up, it is firstly required to fill the pump casing and suction line from the funnel with liquid. When the impeller rotates rapidly, the liquid in the impeller rotates as well under the driving force of the impeller blade, so that the liquid obtains centrifugal force and moves outward from the center of the impeller along the vane flow passage. Afterwards, it is tossed out of the end of the blade, and thrown into the volute or diffusion pipe of the pumping shell(or guide wheel). When the liquid flows to the diffusion tube, the flow speed slows down because the sectional area of the liquid flow expands gradually, and a part of the kinetic energy is converted into a static energy head, the pressure is raised, and eventually pushed out of the discharge tube. At the same time, a partial vacuum is generated at the center of the impeller because the liquid is thrown away, so that the liquid in the sump is continuously sucked into the pump from the source of the suction pipe under the action of the liquid surface pressure. The impeller keeps on rotating, and the liquid is continuously sent from the suction tank to the high level tank or pressure vessel.
