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I believe the problem with just adding a
relief valve would be, the pressure shut off switch and the added relief valve
could not be on the same hydraulic circuit. To relieve the extra pressure to
stop the switch from opening would require the relief valve to open before the
switch does. In the down position this would cause the pressure switch to never
open, thus never shutting off the pump motor.
The ideal situation is that the lo
circuit is wide open when the hi circuit is pressurized and vise versa for
the hi when the lo is pressurized. Why the pump doesn't do this I'm not sure.
Maybe it's something in the design of the shuttle valve that causes it to close
after the pump stops on the hi side. Of course this problem wouldn't have any
effect on the lo side. The pressure differential is between the lo and hi is
wide. I'm sure there's a better fix then to crack open the dump valve just
before landing on a warm day..... Have to put some thought to it.
Randy Stuart
LNC2
----- Original Message -----
Sent: Tuesday, April 17, 2007 08:09
PM
Subject: [LML] Re: Gear Trouble
Posted for "Randy" <randystuart@hotmail.com>:
When opening the dump valve the pressure equalizes between the hi and
lo
sides, this releases enough pressure to allow the sensor switches to
come
alive. The hi and lo are still separated when the dump valve is
closed. The
rising temp increases the pressures on both sides. I've seen
the hi gauge read
as much as 2000 psi on a hot summer day.
Randy
Stuart
LNC2
{Randy, I thought that the relief circuit inside
the pump was designed in such
a way to eliminate this possiblity. If
that isn't the case, then the addition
of a couple pressure relief valves
set to limit the circuit pressures could
solve the problem. They are
readily available, McMaster Carr has them. Go to
http://www.mcmaster.com/nav/enter.asp?pagenum=447
and scroll down to the
middle of the page, where the heading is "Steel
Tamper-Resistant Adjustable
Relief Valves"... Just another thought to add
to the mix. <Marv> ]
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