Minimum flow rate of the pump, minimum continuous flow of the pump
In order to ensure the correct use and normal operation of the pump, the pump manufacturer will indicate the minimum continuous running flow of the pump on the sample to remind or guide the user to the correct selection or use. According to the API standard, the minimum continuous flow is divided into a minimum continuous steady flow and a minimum continuous heat limited flow.
(1) Minimum continuous steady flow. The API-related standard specifies that the minimum continuous steady flow rate is the minimum flow rate at which the pump can operate normally without exceeding the vibration limits specified by the standard. For example, under the condition of small flow, the self-priming pump will increase the noise and vibration. The API is to ensure the service life of the pump and avoid the adverse effects on the pump due to improper operation.
The minimum continuous steady flow rate can be obtained by experimentation, and in general, the pump supplier will indicate it.
(2) Minimum continuous heat limit flow. The API specifies that the minimum continuous heat limit flow is the minimum continuous flow rate at which the pump can maintain operation without being affected by the temperature rise of the pumped liquid.
The minimum continuous heat limit flow can be calculated by:
Where, Pe - rated point shaft power. kW;
P—— pumping medium density, kg/m3;
At'- - Allowable temperature rise of the pumped medium, °C,
C- pumping medium specific heat, kj / (kg ° C);
Ho-off the dead lift, m.
The minimum continuous flow rate takes the maximum of the minimum continuous steady flow rate and the minimum continuous heat limit flow rate. During the selection or use of the small flow pump, the minimum flow required by the process must be greater than the minimum continuous flow of the pump, otherwise the pump vibration will be caused. , noise, cavitation, so that the pump parts are destroyed. If the minimum continuous flow of the pump does not meet the minimum process requirements, a bypass return or return system can be installed on the pump line to ensure a minimum continuous flow of the pump.
