Randy,
I’m not getting this concern. The dump line goes to the tank and ends submerged in fluid with a ¼” down tube in the reservoir. Additionally, in my opinion no fluid would ever travel upstream toward the valve. Thus, no air
would be added to the system by use of a 3 way vavle.
Larry
From: randy snarr [mailto:randylsnarr@yahoo.com]
Sent: Sunday, February 10, 2008 9:59 PM
To: lml@lancaironline.net
Subject: Re: [LML] Re: 235/320/360 gear dump valve idea
Chris,
Is there such a thing as a check valve that could be incorporated into the 3rd pressure dump line to the hyd reservoir?
That way you could open the dump valve releasing positive pressure from the high/low sides of the system but you would not be allowing air from that same line if the was no
positive pressure or negative pressure?
Could a shuttle valve help do that?
Randy Snarr
Chris Zavatson <chris_zavatson@yahoo.com> wrote:
<<From: Randy <randystuart
Then the pump pressurizes the high side and it stops, and the shuttle valve centers,...>>
This is where pumps in the fleet differ. In my two pumps the shuttle valve does not return to
center. It stays where the fluid last pushed it. The O-ring on the spool offers up much more friction than the spring on the poppet valve could ever hope to overcome. I am curious if all pump vintages have O-rings on the spool valve and/or how snug the fit might be? If the spool can be made to stay put, the problem goes away. I am simply suggesting this as something to investigate before a lot of new plumbing is added to the system.
A little over a year ago, when this issue was last discussed, I took a series of photos showing the effect of heating and cooling. What is observed is that the high side pressure goes up and
down with temperature (heat gun and ice bath) while the low side remains at zero.
My pumps are '95 and newer.
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