Re: 970 joystick controler

Mel,
I totally understand where you are coming from, as per engineering stand point. With an auxilary valve without PB and no return to sump line on it;- installed between the pump and the Case service valve which has the relief built into it an unlikely senario would have to happen to ruin the pump. First in the senario, one of the Case valves which return to neutral at end of stroke, would have to be manually overidden by holding the lever, or a malfunctioning detent. (could be posible). Then relief pressure from the Case service valve would backfeed the aux valve on the back side and render it's relief valve inoperatble. Then the operator would have to activate a spool on the aux valve and bottom out it's function, and at that point there would not be an operating relief valve in the entire circuit,and would cause probable pump damage. As you say with a properly plumbed aux valve with a secondary return to sump line on it, the Case service valve could not apply back pressure to the back of the aux relief valve. As I said in the previous discussion, highly unlikely, but a posible senario. Your way would be company engineering policy. As described in previous posts the series hookup without secondary return to sump works, BUT.
Loren

Loren, You are correct but as big a point as that is, also without a case drain the whole valve assembly is at high pressure including the spool seals whenever the downstream system is used, a situation that is never meant to exist, the drain line keeps the pressure from building in that part of the circuit including the backside of the main and secondary reliefs, and as you correctly pointed out pressure backing up against the backside of the relief cartridge renders it inoperable. A properly designed circuit would use a Power beyond and a drain line. I have said all I'm going to into the matter, everyone on here is my friend as far as I know and my desire is to maintain that.

Mel

I have a Gresen loader valve with a pressure release plumbed in the pump line on my 970 and it has been there for over 25 years. I use it for #3 and #4 remotes. I understand what it would take to have a problem and keep that in mind. I have never had a lick of trouble with it, and would do it all over again today. Just my observations. No comments taken personally. DK