Pumps are mainly used to transport fluids or mixed fluids, including liquids, gases, gas-liquid mixtures, solid-liquid mixtures, and mechanical equipment for gas-liquid three-phase mixtures.
1. Classification of pumps
There are many types of pumps, and there are mainly three classification methods.
1.1 According to the "Classification Standards for Construction Projects" GB/T50841-2013, pump equipment installation engineering categories are classified as centrifugal pumps, vortex pumps, electric reciprocating pumps, plunger pumps, steam reciprocating pumps, metering pumps, screw pumps, gear oil pumps, vacuum pumps, shielded pumps, simple mobile submersible pumps, etc. Among them, centrifugal pumps have high efficiency, simple structure, and the widest range of applications.
1.2 Classification based on the working principle and structural form of the pump
Positive displacement pump. By the movement of the working components, the working volume periodically increases and decreases to suck and discharge materials, and by the compression of the working components, the pressure of the materials can be directly increased. According to the different motion modes of moving parts, reciprocating pumps and rotary pumps are divided into two categories. Reciprocating pumps include piston pumps, plunger pumps, diaphragm pumps, etc; Rotary pumps include gear pumps, screw pumps, and vane pumps.
Wheeled pump. A impeller pump relies on the impeller to drive the liquid to rotate at high speed and transmit mechanical energy to the material being transported. According to the different characteristics of the impeller and flow channel structure of the pump, impeller pumps are divided into centrifugal pumps, axial flow pumps, mixed flow pumps, and vortex pumps.
1.3 Other classifications
According to the position of the pump shaft, it can be divided into vertical pumps and horizontal pumps.
According to the number of suction ports, it can be divided into single suction pumps and double suction pumps.
According to the prime mover of the driving pump, it can be divided into: electric pump, turbine pump, diesel engine pump, pneumatic diaphragm pump, etc.
2. Pump performance
2.1. Performance parameters of the pump: mainly including flow rate and head, as well as shaft power, speed, efficiency, and necessary cavitation allowance.
Flow rate refers to the amount of liquid output through the pump outlet per unit time, usually using volumetric flow rate.
Head is the increase in energy per unit weight of liquid transported from the pump inlet to the outlet. For positive displacement pumps, the energy increment is mainly reflected in the increase in pressure energy, which is usually represented by pressure increment instead of head. For example, a 30 story high-rise building should have a fire pump lift of at least 130m.
The efficiency of a pump is not an independent performance parameter, it can be calculated from other performance parameters such as flow rate, head, and shaft power using formulas.
2.2 Relationship between various performance parameters of the pump
Curve characteristics. There is a certain interdependence and variation relationship between the various performance parameters of the pump, which is represented by characteristic curves. Each pump has a specific special curve provided by the pump manufacturer.
The working range (performance range) of the pump. The recommended performance range for the pump is usually indicated on the characteristic curve provided by the factory.
The relationship between the working range and characteristic curve of the pump. When selecting and using a pump, the working point of the pump should be within the working range. When the same pump transports liquids with different viscosities, its characteristic curve will also change.
For example, for power pumps, as the viscosity of the liquid increases, the head and efficiency decrease, and the shaft power increases. Therefore, in industry, liquids with high viscosity are sometimes heated to reduce viscosity and improve conveying efficiency.
The relationship between water pump and motor is actually very simple. The operation of water pump cannot be separated from the motor, except for pneumatic diaphragm pump, which uses compressed gas as the power source. The main component of a water pump is the impeller, which is connected to the motor and pump shaft through a coupling. The pump shaft is connected to the impeller, and then the motor drives the rotation of the impeller, so that the water pump can start working normally. Therefore, the relationship between the water pump and the motor is very close, and the head and flow can be adjusted by the motor.
The relationship between water pump and motor
The rotor of the pump is connected to the pump shaft with a coupling, and the pump speed is equivalent to the motor speed; The selection of motors is generally three-phase asynchronous motors, and different connections can change the speed of the water pump; The pump shaft is connected to the motor shaft through a gearbox, and the pump speed is equal to the motor speed multiplied by the gearbox reduction ratio; The star and Y-shaped connections of three-phase motors can directly intervene in the head and flow rate of the water pump; The higher the power of the motor, the greater the head of the water pump.