In his system using a pump 3 phases from afar draw water. The problem occurs when not water or bursts (some damage) through pipelines. Suppose that the station will run 30 minutes. Then the pump runs 30 minutes without water. For this reason, I use the pressure sensor and the pump to shut down before damage can occur.
Thus: master must turns into a certain time to be in the line pressure (or flow), otherwise the program is terminated (in my case ospy send email arrives, it is a disorder) pressure is an online monitoring