The selection of centrifugal pump mainly involves the transfering liquid, head, flow rate, ambient temperature and other data. The suitable centrifugal pump not only works smoothly, but also has a long service life and can save the user the greatest cost.
Basic data of pump selection:
1. Characteristics of medium: medium name, specific gravity, viscosity, corrosivity, toxicity, etc.
2. The particle diameter and content of the solids contained in the medium.
3. Medium temperature: (°C)
4. Required flow rate The general industrial pump can ignore the leakage in the pipeline system in the process flow, but must consider the impact on the flow when the process changes. Agricultural pumps that use open channels should also consider leakage and evaporation.
5. Pressure: suction tank pressure, drain pressure, pressure drop in the piping system (head loss).
6. Pipeline system data (pipe diameter, length, type and number of pipe attachments, geometric elevation of sink to pressure tank, etc.).
The device characteristic curve should also be made if necessary. When designing and arranging pipes, pay attention to the following items:
1. Reasonably select the pipe diameter, the pipe diameter is large, the flow velocity is small, the resistance loss is small, but the price is high, and the pipe diameter is small, which will lead to a sharp increase in resistance loss. Large, the head of the selected pump is increased, the power of the belt is increased, and the cost and operating cost are increased. Therefore, it should be considered from a technical and economic perspective.
2. The discharge pipe and its pipe joints should take into account the maximum pressure that can be withstood.
3, the pipeline layout should be arranged as straight pipe as much as possible, minimize the attachments in the pipeline and minimize the length of the pipeline. When turning, the bending radius of the elbow should be 3 to 5 times the diameter of the pipeline, and the angle should be as large as 90. °.
4. The discharge side of the pump must be equipped with a valve (ball valve or shut-off valve, etc.) and a check valve. The valve is used to adjust the operating point of the pump. The check valve prevents the pump from reversing when the liquid is reversed, and prevents the pump from hitting the water hammer. (When the liquid is reversed, a huge reverse pressure will be generated to damage the pump.)
Determination of the flow rate and head:
1. If the minimum, normal, and maximum flow rates have been given in the production process, the maximum flow rate should be considered.
2. If only normal flow is given in the production process, consideration should be given to leaving a certain margin. For the large flow low lift pump with ns>100, the flow balance is 5%, for the small flow high lift pump with ns<50, the flow balance is 10%, the pump with 50≤ns≤100, the flow balance is also 5 %, for pumps of poor quality and poor operating conditions, the flow margin should be 10%.
3. If the basic data only gives weight flow, it should be converted into volume flow.
