From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: Water_pump Curves
To: flyrotary
Date: Mon, 18 Nov 2002 06:56:46 -0500
Message-ID: <web-1880856@logan.com>
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Posted for Wschertz2@aol.com:

> I must be missing something really important here. It doesn't make sense 
to 
> 
> me
> that the highest pressures should result in zero flow, and vice-versa. 
> There
> was no mention of deliberate restrictions (valves) in the lines. Also 
> absent,
> was any intimation that power input to the drive motor was varied.
> Help me out here .... Jim S.
> 
-------------------------
Jim,
There is a valve (ball valve) on the exit side of the pump. Therefore, if I 
close the valve, and turn on the pump, it goes to its "stagnation" pressure, 
which is the highest pressure that the pump can generate. As you then start 
to open the valve, the water starts to flow, and the pressure that the pump 
can make is less, down to the point that the valve is full open and the pump 
is moving the maximum amount of water. 

These curves are typical for a centrifugal pump (which is what we have here)

I have some small corrections to make to the data, having made a careful 
measurement of the bucket and finding that it was 5.8 gallons instead of 5, 
and I think i can correct for the pressure effects in the tubing connecting 
the system to the pump.

With regards to the power input. The motor was an electric 1-HP motor from 
my table saw. It is a synchronous motor, that tries to always run at 3450 
rpm. To vary the speed of the pump, I varied the pulley diameter. the motor 
will run at 3450 rpm at no load, and continue with only small variations up 
until you exceed its ability. I don't think that I was anywhere close to 
causing major slippage. The current the motor draws varies with the load.

Bill Schertz
KIS Cruiser #4045