Hi all, I have a 2003 hitachi ex 135 and I am looking to add an auxiliary circuit to it as it hasn’t already been done. It is to work a saw or mulcher. I have been told a priority flow valve off the outlet of the two pumps is best as it will allow slew and track function while working the saw/mulcher but I haven’t figured out on how to plumb this up yet and what else needs to be added along with the valve on the pressure side to run the saw. Any help would be appreciated. Thank you.
Welcome to HEF Mark . I assume this a Fiat Hitachi machine ? Are the flow specs very similiar for the saw and the mulcher ? Can you elaborate on this “ what else needs to be added along with the valve on the pressure side to run the saw. “ Can you post a picture of the hydraulic pump and the pump information tag.
Hi Dave, Yes it’s a fiat hitachi, the flow spec would be very similar but a mulcher will be the more likely purchase. As for the what else needs to be added I wasn’t sure whether a relief valve or means of avoiding cavitation of the mulcher motor when oil flow is stopped would be necessary I have attached the photo of the pump and tag. Thanks.
If the plumbing on the mulcher does not include a make up valve, then a simple check valve between pressure and return could be used as a make up. The hydraulic pump looks similar as to what would be on a Hitachi EX120-5 or a Deere 120. The pump compartment floor is nice and deep to install a dual priority valve and plumbing. Need to come up with a mini pilot system with shuttle valves to stroke up the 2 pumps when using priority oil only.
I’m assuming a dual priority valve is necessary due to two pressure feeds,one from each pump? Will that be just two priority valves plumbed together or can you get it as one unit ? I have some thinking to do to come up with the mini pilot lines but I’m guessing when the priority function is being used the pumps will be at full swash ?
In the day I have used two single priorities but found the one dual priority valve worked out the best for ease of installation. I have no idea on pricing but worth investigating. . “I’m guessing when the priority function is being used the pumps will be at full swash ? “ Not likely , What are the operating specs for the mulcher ?
Ok thanks I’ll look into that valve. I haven’t got a mulcher yet but they would be running at a minimum of 150lpm/40gpm from what I’m reading on spec sheets of different brands. Some also have variable displacement motors so lmp/gpm can be varied during operation.
I see the Fiat Hitachi EX135 hydraulic pump specs are 2 X 95 lpm. The “mini pilot system” will contain at minimum a solenoid pilot valve ,adjustable pilot pressure reducing valve, 1 tee and 2 shuttle valves. A flow meter or a mechanical tach will be required for the setup. The solenoid valve would be triggered at same time as the priority valve(s). Adjust the pressure reducing valve to stroke both pumps to maximum flow. Set the priority valve(s) to example 150 lpm @1000 psi or mulcher maximum free running speed. Then slowly re adjust the pressure reducing valve until the lpm or free running speed just begins to drop off. This will help find a balance between mulcher performance and the pumps not being over stroked when using the mulcher function only. There are some very experienced mulcher owners here on the forum if you need any input on purchasing the right unit.
yes that all makes sense thanks. Is the two shuttle valves joined into the pilot lines going to each pump to upstroke the pump in normal operations, and then when the priority valve is switched this will allow the priority valve to control the pumps?
The purpose of the two shuttle valves is to allow the control signal to each pump to originate from two different sources. When using the mulcher function only, the pilot signal from the pressure reducing valve to each pump maintains the same flow from each pump.
Thanks very much for your help Dave I have a good idea of what I have to do now