Having a strut rebuilt for a customer's 740 haul truck. I don't have nitrogen on the truck but I do have are argon. From my research it seems that that would be OK if not I do have access to nitrogen servicing cart that we use at the airport for aircraft struts. Jason
I would stick with nitrogen given the chance. It's too much of a risk with the strut pressurized to whatever psi.
I've heard things about nitrogen being better suited to handling heat exchange and such.
It is common to find CAT struts with Gas Burns inside, this is with Nitrogen so I would keep clear of any other gas as the effect could be damaging, good tip is to fill your strut with the set amount of oil before fitting strut to dumper, then gas up and check both sides of dumper for ride hight on level surface. tctractors
I've seen that too, and had always put it down to the fact that the strut was full of air (i.e. oxygen) when assembled "dry" during the rebuild. How we used to do our struts was different to the way Tony does it, but that was on struts on larger kit. We had a nitrogen kit that had two inlets to it, one for oil and the other for gas. We'd install the struts on the machine dry, then we would first hook up the nitrogen kit to the steering system test port and use that system to pump oil into the strut. If the manual called for 1" of oil height before gassing we'd pump it up to 2", then go for a coffee (or lunch). When we came back we would slowly drain out what would initially be an oil/air mixture from the strut. Usually before the strut got down to the specified 1" height we'd be getting 100% oil from it. Then to gas them we'd jack up the truck until the struts were fully extended and gas each one using the onboard strut pressure sensors to measure pressure, they're much more accurate than any gauge. The thing about gassing struts with the weight of the machine on them is that friction comes into play, if the strut is fully extended you're gassing a fixed volume above the piston. Once that was done drop the truck off the jacks and whatever ride height it had that's what went in the records for checking ride height in the future. We found this to be the most accurate method of charging and especially if the truck had an on-board weighing system it produced results which were generally only a couple of % away from a scale reading.
Here's a photo of the connections on the nitrogen kit. The connection to the left of the single shutoff valve is for nitrogen, the quick coupler connection facing upwards from the tee between the shutoff valves is for hooking up a test line to supply oil to the cylinders.
I got it done. Welding shop let me borrow a cylinder of nitrogen. Hardest part was getting the fluid in there as I didn't realize it would take that much pressure in the hand pump I had would not make the pressure so I ended up using my Porta power filling it that way which took forever.
That's where our kit comes in (see photo above), you can use the hydraulics on the truck itself to charge the cylinder with oil.
The manual called for 10w tdto and an additive. I might need to rig up a kit in my spare time.
I'd use either 10W TDTO or 10W HYDO in Cat struts, despite what the manual says. IMO the viscosity is more important than the presence or absence of the TO-4 additives. The 1U-9891 anti-chatter additive we would simply dump into the cylinder in while overhauling the strut.
I realize this is a extremely old thread but anyway. I just bought a cat nitrogen kit from a guy cleaning out his dads shop. It’s set up just like yours but with a 3500psi gauge where your oil test port is. Can I add a test port to it and not interfere with the system rea
IMO you can add as many extra parts as you like to the Christmas Tree provided you use correctly-specified hydraulic fittings to make the changes. You can't use regular pipe fittings for obvious reasons with the pressure involved. Attached is the instruction manual that gives the Cat Part Numbers for all the fittings.