Not enterig into the NPSH debate, but there are mixed phase pumps availible that have compressor vane type primary stages that concentrate the gas back to a liquid that is then pumped by an ordinary closed shrouded impeller final stage.
I have experienced a similar problem with a filter press in a mining appliaction. The press was run 12 hours a day continuously. The problems arose on the next shift startup. The pumps were posotive displacement (Wilden). Our suggestion was to try to get the fine settled particles back into...
