1、 Working principle and performance characteristics of self-priming pump
Self priming pump is a self-priming centrifugal pump, which has the advantages of compact structure, convenient operation, stable operation, easy maintenance, high efficiency, long service life and strong self-priming ability. The pipeline does not need to be installed with bottom valve. Before operation, it is only necessary to ensure that the pump body is stored with quantitative liquid extraction. Different materials can be used for different liquids.
2、 Performance comparison of several commonly used Self-priming pumps
The self-priming of the self-priming pump refers to starting the self priming pump when the suction pipe does not need to be filled with water (but there must be enough water in the pump body), which has the function of automatically removing the gas in the suction pipe and entering into normal operation after a short period of operation. The self-priming pump must be filled with enough water before the initial start-up, and then the water left in the pump body will start again to normal operation.
According to the structure and working principle, the self-priming pump can be divided into the following categories: gas-liquid mixing type (internal mixing type, external mixing type); water ring type self-priming pump; jet type (water jet, gas jet).
The performance comparison of several Self-priming pumps is as follows:
The internal mixing self-priming pump has the advantages of high efficiency, low manufacturing cost, long self-priming time, less than 10 meters of self-priming height and long service life.
The efficiency of the external mixing self-priming pump is low, the manufacturing cost is medium, the self-priming time is short, the self-priming height is less than 10 meters, and the service life is long.
The water ring self-priming pump has the advantages of high efficiency, high manufacturing cost, short self-priming time, self-priming height less than 10 meters and short service life.
The jet self-priming pump has the advantages of low pump efficiency, high manufacturing cost, short self-priming time, high self-priming height of more than 10 meters and long service life.
3、 Difference between self suction centrifugal pump and centrifugal pump
According to the structure and working principle, the self-priming pump can be divided into the following categories: gas-liquid wet type (internal mixing type, external mixing type); water ring type; jet type (water jet, gas jet). The performance comparison of several commonly used Self-priming pumps is shown in the table
4、 Specification for arrangement and installation of suction pipeline of self priming pump
Since the liquid level of the suction pipe of the self-priming pump is lower than that of the pump, the water can be pumped up only after the pipe is pumped into a negative pressure state. Therefore, the installation of the suction pipe of the self-priming pump should be in accordance with the following installation specifications:
(1) In order to prevent air leakage in the suction pipe of self-priming pump, the suction pipe must be completely sealed and no air can be sucked in. The suction pipe of self-priming pump is usually made of steel pipe, and the joint is connected by welding or flange.
(2) When the water in the suction pipe contains dissolved gas, it will escape due to the decrease of the pressure in the pipe. If there is gas accumulation in the suction pipe somewhere, it will form an air bag, which will affect the water carrying capacity of the pipeline. When serious, it will damage the real house to absorb water. In order to make the water pump discharge the gas in the suction pipe in time, the suction pipe shall have a continuous ascending slope along the water flow direction, and I ≥ 0.005. The gas in the pipe shall be discharged from the top of the pump shell at the inlet of the water pump.
(3) The installation and laying of the suction pipe of the self-priming pump should avoid the formation of air bags in the pipe. Several correct and incorrect installation methods of the suction pipe are introduced below.