Hello, I have a Mustang 940E skid steer, I have adapted it to fit a Kelley B-15 backhoe with a 3-point hitch adapter and some fabrication. I tried to power it off of the aux hydraulics and all was working well until the filter exploded (gasket let go). When I adapted it to the skid steer, I wanted to put a filter in the return line just to ensure no "junk" got in my mustang's main fluid. I used a 3/4" NPT filter kit from surplus center (15 PSI bypass) for the return path. The backhoe is open center so fluid is constantly flowing from the inlet to the outlet. I was using the hoe today and when I applied some pressure to the cyls of the hoe, the filter in the return line let go. letting fluid go everywhere... So did I exceed the 100 PSI maximum rating of the filter; I would have assumed that the return line would be day lighted back to the tank with no pressure; but it appears that there is pressure in the return. The return I was using is the return from the aux feed. The aux control lever was in the full forward direction (detent). So is the "return" line pressurized, does the return line build pressure? So is the return line back to the tank pressurized? Thanks in advance!
I'm not sure about mustang but I would guess you put the filter between the return from the hoe to the skid steer qrc you will be generating back pressure as you say it's open centre valve block and I would try running a free flow line back to tank you may have a anticavition valve on the return on the machine though but at least you could try it to see if it works .But best think would be to put a 'T' piece in the return before your filter and and sick a gauge on and see what you got going back through your aux line and then you can work out filter required or just pipe clean line back to tank.
No the tank is not pressurized. There is no specific "return" on your machine (and most SSLs for that matter) . You have two hookups, either of which can be pressure or return depending on which way you run the control. Fluid is sent out one and returns back to valve block from the other one. Just like the rams for the loader as well. Same control valve block. Pressure is sent to that block from charge pump and fluid leaves the block through the return line, through the cooler, through return filter and it the tank. Just get rid of the filter you added. There is no need for it. For starters you aren't going to get any contamination from a backhoe attachment. Contamination comes from motors that fail. Should there ever be any contamination it all has to go through the factory return filter before the tank anyways. The tank also has a suction strainer before the charge pump. The charge pressure that goes to the piston pumps for the drives has to go through the charge filter first as well so they are also protected even further. To answer your question somewhat, no it is not a straight shot back to the tank. That would be a case drain, some machines have them, some tools with motors require them. You can always add one easily if needed.
Most likely you got the lines reversed and had the filter in the pressure line, but in any case yes there's back pressure on those aux lines. When running attachments like hammers and mowers with motors some manufacturers have an optional "Free return" line that's added for low pressure flow back to tank. I agree with durallymax, lose the filter in the backhoe lines, if you're adamant about having one use a medium pressure filter (500 psi rating) and install a check valve at the quick coupler for the line coming off the filter to prevent inadvertently reversing flow.
Yes, The 940 has a pressurized tank, 15 psi