We raised the floor by filling it
We raised the floor by filling it with concrete fill
And what is cavitation, usually a badly misused term to explain why a pump is not operating as expected. Many well qualified engineers don't really understand cavitation so any comments from a field operative is always suspect in my mind plus comments like "cavitation is happening because of vortexing" certainly doesn't engender any confidence in what is actually going on with these pumps. Also, far too many unknows at this point to make any real judgements, the flows and heads haven't even been established yet. You have to eliminate the obvious and be there when "cavitation" occurs. First of all I assume people believe cavitation is occuring because of the the "classic cavitation noise":1. You should be there to witness the "cavitation" and record the water level. Have the station staff record water levels when cavitation occurs2. During the "cavitation period" check to see if the pump suction is plugged with rags. 3. Throttle the pump discharge. If you still get the "cavitation" noise your problem is not cavitation. It is air entrained in the water. Cavitation and air in the water produce the same cavitation noise but the solution to fixing either problem is very different from each othercaviat
You can never ask a stupid question when it comes to site trouble shooting, some of the things I have come across over the years are just unbelievable - for instance - one of the best; "the pump doesn't go round when we started it" "I see, tell me, did you check the pump motor alignment after installation" knowing what the problem was already and baiting the site-engineer - guessing the answer would be yes. "yes""do you know that we shipped the pump / motor spacer coupling a few days after the pump /motor unit was dispatched"Long silence, followed by "I'll get back to you". I heard later from an other source, the coupling was retrieved from the store, fitted and aligned and the Self-priming pump ran Ok. If the suction inlet(s) is (are) too close to the bottom of the well, the abrupt acceleration of the flow can induce sub-surface vortex formation that can persist after either pump stops. Since you seem uncertain about the dimensions for the clearance between the end of the suction lines and the floor of the well, you can get a fairly accurate measurement by fabricating a long "L" shaped rod that can be dropped into the well adjacent to the pump. You can use the distance from a fixed reference point to the bottom of the well and then raise the rod to touch the bottom of the suction pipe with the top of the protruding portion of the rod. This should permit clarifying the height of the suction inlet from the bottom of the well with an accuracy within less than 1/4" and possibly much better. You know the configuration of your site, so you should be able to design such a measuring tool fairly readily and relatively inexpensively. (You may need to cut one or more reasonably small access holes in the floor or grating adjacent to the pump.)
2011-09-22
