We all contribute whenever we can sharing knowledge and experiance. I for one get great satisfaction from helping people whenever i can and wherever they are. I know at times i am strong willed but thats what comes from being a business man. There are some on this forum that have labelled me a bully if i come over that way feel free to put me in my place.
Regards u all Gordon.

With the normal CAT hydraulics used on the older tractors, when adding valves, don't think "Tee"

All open center hydraulics have to have all valves in series......The pump output goes through the first valve and on to the second. When they are all in a block, that's taken care of for you, but when you want to add a valve, you still have to stick to that plan. When you operate a valve, the spool blocks the flow of oil and diverts some or all of the flow to the function. Only if there is a return flow from the function (double acting cylinder for example) will there be any flow to other valves after the one that's pulled. First valves in the loop have priority. Valves downstream are secondary.

If you install a T on an open center system, then the pressure oil flow can go through either valve, whichever is open, and unless you pull both spools at once, nothing will happen.

CAT did use diverter valves like on the older #44 controls fitted to the D2's to allow one valve to control two different functions. The diverter is the Tee in both pressure and return lines and locks off one set of outlets while allowing the valve to control the other two (or the other way around).

With closed center hydraulics, Tee's are the way it works, Every valve is basically on a Tee off the main pressure line and when there is no valve open, the pump has to go out of stroke and maintain system pressure. No valve has priorty unless a priority valve is installed to create this function.

Thanks for the input on the hydraulics

Hi Richard,happy new year,your tractor looks to be coming on well,what we
did when converting our D8,s to work hydraulic box,s we simply plummed in
our spool block in to the main feed line from pump to tank making sure it can
take the flow,in our case 68 galls min and keeping the tractors standard
presure of 2400psi,we can still use the blade without the need for taps or
valves,the returning oil from the scraper goes through a gallerey in the spool
block (carryover) back to tank through the ripper line so not to disrupt flow
or put pump under extra load in the main feed line,pipework to quick release
couplings is 1" flow but to get 1" flow we had to use 1 1/4 couplings,to slow
the speed on apron lift we changed the pipe from 1" to 1/2" flow, that done
the trick,hope this helps.

Hello Roly just wondered if you are doing any Beach work or have they knocked it on the head like at salthouse ?

"Gordon." wrote:

Hello Roly just wondered if you are doing any Beach work or have they knocked it on the head like at salthouse ?

Hi Gordon,i dont normaly get a call until end of jan or mid feb about the
beach,so as yet dont know whats going on,but i,m sure they will want
the dog shit bladed up and burying:D

Was in Brancaster for christmas and new year, took a drive up to salthouse.
One more good storm ad the sea will be in. Makes no sence to me. Some big rock like at sea palling would help i would have thought,
Gordon

"ccjersey" wrote:

With the normal CAT hydraulics used on the older tractors, when adding valves, don't think "Tee"

All open center hydraulics have to have all valves in series......The pump output goes through the first valve and on to the second. When they are all in a block, that's taken care of for you, but when you want to add a valve, you still have to stick to that plan. When you operate a valve, the spool blocks the flow of oil and diverts some or all of the flow to the function. Only if there is a return flow from the function (double acting cylinder for example) will there be any flow to other valves after the one that's pulled. First valves in the loop have priority. Valves downstream are secondary.

If you install a T on an open center system, then the pressure oil flow can go through either valve, whichever is open, and unless you pull both spools at once, nothing will happen.

CAT did use diverter valves like on the older #44 controls fitted to the D2's to allow one valve to control two different functions. The diverter is the Tee in both pressure and return lines and locks off one set of outlets while allowing the valve to control the other two (or the other way around).

With closed center hydraulics, Tee's are the way it works, Every valve is basically on a Tee off the main pressure line and when there is no valve open, the pump has to go out of stroke and maintain system pressure. No valve has priorty unless a priority valve is installed to create this function.

one last question on the hydraulics theme (should have asked before) but what is the max. operating pressure of these systems - a-la D4?

Hi Richard, the maximum relief valve pressure on the D4 is quite low, I'm not sure exactly what is, around 1900PSI I think,,I'm sure someoen else will be able to post. This is the reason for using extra valves in series with their own relief valve, so that you can use higher pressure for your attachments.

Pressure relief valve setting is 1725 psi +/- 25 psi.