Before that, you should figure out your pump application, which is used for sanitary applications such as food, dairy, beverage, pharmaceutical industry or industrial oil, gas or agricultural application.
Please be sure to determine the viscosity of your fluid. You need a viscosimeter to measure the viscosity of the fluid
Firstly, We can simply choose pump by fluid viscosity, please check the below picture for your reference.
Regarding the positive displacement lobe pump or twin screw pump, we need to know your media viscosity, different viscosity the pump motor should work at a suitable speed.
The second is depending on your flow needs, please send me your flow requirement.
We will recommend you best suitable model to meet your requirement.