LsFarm wrote:Ian, that hammering is one of the damaging effects of bubbles in the system. If there were not bubbles in the water going into the pump causing the hammering, then there are low pressure points on the impeller or impeller housing that with just the right temp, flow and impeller RPM cause bubbles to form and cause the hammering. The impellers have to be very heavy duty to stand up to this.
In aircraft pumps, once cavitation has occured the part is usually replaced, the cavitation or hammering eventually causes pitting or cracking of the impeller.
I know, we just remaned some 13" 60 HP Goulds pumps on my Ultrafilters. You would not believe the pits in the 316 S/S impellers. It looked like someone worked it over with a prick punch on a jackhammer. And these pumps did not make any noise, so you can imagine the damage that is going on if they are banging loud enough to hear.
Water treatment is critical in steam boilers as the loses in the system are much higher than a hot water boiler. The large amounts of additional makeup water always brings in fresh Oxygen and dissolved solids along with salts and sediment. This is why steam boilers must be blown down daily and drained and cleaned yearly. The sediment will build up and eventually destroy the steel because of the heat. Home boilers use extremely small amounts of makeup water so the treatment is not a real big issue. It probably should be, but most people just don't bother.