1. According to the layout, terrain conditions, water conditions and operating conditions, horizontal and vertical types (tubular submersible, liquid, non clogging, self-priming, gear pump, etc.) are selected.

2. Water pump, hot water pump or gear pump, oil pump or chemical pump, corrosion resistant pump or impurity pump shall be determined according to the nature of liquid medium.

The explosion-proof motor shall be installed in the explosive area of the gear pump according to the explosive area.

3. According to the flow, determine the gear pump double suction or single suction gear pump; According to the lift, menu or gear pump of multi-stage gear pump gear pump, the efficiency ratio of high-speed or low-speed gear pump (air conditioning pump) and multi-stage gear pump gear pump is single-stage. For example, single-stage and multi-stage gear pump gear pump can also be selected. First, single-stage gear pump is selected.

4. Determine the type of gear pump. After determining which series of gear pumps are selected, the specific model can be determined on the type spectrum or series characteristic curve based on the maximum flow (when there is no maximum flow, 1.1 times of the normal traffic flow is usually taken as the maximum), taking the two main performance parameters of the head after amplification of 5% - 10% margin. Type. The operation is as follows:

For the characteristic curve of gear pump, the required flow value is found on the abscissa and on the ordinate, respectively from two upward and right lines or horizontal lines. The intersection point of the two lines falls on the curve, which is the choice of gear pump. However, this ideal situation is rare, and generally meets the following two conditions:

The first type: the intersection point is above the characteristic curve, which means that the flow meets the requirements, but the head is not enough. At this time, if the head difference is not much, or the difference is about 5%, it can still be selected. If the head difference is large, select the gear pump with larger head. Or try to reduce the pipeline resistance loss.

The second type: the intersection point is below the characteristic curve, within the sector trapezoid range of the characteristic curve of the gear pump, the model is preliminarily determined, and then whether to cut the impeller diameter is determined according to the difference in head,

If the head difference is very small, do not cut. If the head difference is very large, cut the impeller diameter according to the required Q, H and cutting formula. If the intersection point does not fall within the range of fan-shaped trapezoid, select the gear pump with smaller head. When selecting gear pump, it is sometimes necessary to consider the production process requirements and select Q-H characteristic curves with different shapes.

5. After the model of the gear pump is determined, for the gear pump with water gear pump or the physical and chemical medium of the transmission medium that is similar to water, it is necessary to go to the relevant product catalog or sample, and correct it according to the performance table or performance curve of the model to see whether the normal working point falls in the priority working area of the gear pump.

6. For liquid gear pump with transmission viscosity greater than 20mm2/s (or density greater than 1000kg/m3), the characteristic curve of gear pump tested with water must be converted into the performance curve of the viscosity (or density), especially the suction performance and input power shall be carefully calculated or compared.

7. Determine the number of gear pumps and the standby rate: generally, only one gear pump is used for normal operation, because one large gear pump is equivalent to two small gear pumps working in parallel (the head and flow are the same), and the efficiency of the large gear pump is higher than that of the small gear pump, so from the perspective of energy conservation, one large gear pump is preferred to two small gear pumps, but in the following cases, two gear pumps can be considered to be combined: the flow is large, One gear pump cannot reach this flow.