On Tue, 19 Jul 2011 02:21:32 -0700, Andy Dingley wrote:

On Jul 18, 8:07Â*am, harry wrote:

There is a problem with all boiler feed water pumps and that is
cavitation.

Utter ********. Cavitation is a problem of _low_ pressure in pumps,
sufficient to form bubbles (i.e. "cavities"). The one thing we know
about a boiler feedwater pump of any form is that it has to work at
around boiler pressure. Whilst the Giffard injector stops working with
hot water, heat isn't a big problem for pumps.

Um.. Cavitation occurs when water boils against a surface, and the collapsing
bubbles can lead to pitting and damage to that surface. The cause is localised
boiling as a result of low pressures in those regions.
In marine propellors, of course, it occurs at ambient temperatures and
very low pressures, but there's no reason at all why it couldn't occur
in a pump if the feed temperature were hot enough and the small drop
in pressure produced at some point in the pump were large enough for
the water to begin to boil.

--
From the Model M of Andy Breen, speaking only for himself