On Jul 20, 10:55*pm, Andy Dingley wrote:
On Jul 20, 12:33*pm, Jeremy Double wrote:

On 19/07/2011 23:43, Andy Dingley wrote:

Where is there a drop in pressure (required) where either (one of
which is also required) such a pressure drop approaches below
atmospheric pressures, or else the temperature is approaching the
steam temperature of the boiler?

There is a drop in pressure where the liquid accelerates on entering the
pump. *

Of course there is. If we're talking about a centrifugal pump, then it
might even get to the stage of cavitation.

I am however unaware of any *of Trevithick's engines, or even of any
steam locomotive, using such a pump.

Steam locomotives often used axle driven or steam driven reciprocating
pumps, the latter were poplar in America. All liable to cavitation.
But as they used cold water, not a problem.

Found this BTW.
http://www.model-engineer.co.uk/foru...s.asp?th=38918