Alright guys I have noticed a lot of people starting to get interested in hydraulics and the word starts popping up more and more. In some cases it worries me and others it raises interest, however in all I must stress safety.
I have been working with hydraulics a while now between working on tractors and building/rebuilding cylinders I have seen a fair share of accidents and complete failures.
Lesson one is always build a full system I don't care if you just want a cheap wood splitter you need a filter and a relief valve and a tank with the same capacity as you flow at the minimum. So if your running 5gpm you want at least a 5 gallon tank to allow a minute of rest for your oil.
One way around the large tanks is a oil cooler, these are plumbed on the return end of your system so that you are cooling the oil before it reaches your tank thus keeping the overall temp down.
Lesson two is staying within ratings, adding more flow to a hydraulic motor may make it spool faster or adding pressure may make it pull harder but you can also burn up bearings or blow off the cap or relief valve. Most of your motors are designed to limit flow to their maximum but pressures are limited externally along the line with regulators or the mentioned relief valves.
Lesson three is avoiding mix match junkyard parts such as old motors, pumps, and valves. I highly suggest getting cylinders from junkyards however, just have them inspected and most importantly pressure tested for leaks and damaged seals.
Lesson four SAFETY is first second third eighth beginning middle last first again! Check fittings, hoses, valves, controls, and the moving parts regularly in most cases these things are running between 2500 and 3500psi that's enough pressure to fire a steel plug through your garage your buddies garage and their moms house a mile down the road. I used to test cylinders at 4500psi I have seen bad threads in cavity blocks lead to catastrophic failure leaving a 2" hole in a cement wall. On the other end of the spectrum is the slow "pissing leak" a small stream at high pressure. People don't realize what that pressure is doing so they poke at the stream with the I'm going to plug the dam mentality and get either a lethal injection of hydraulic oil or they get bits and pieces cut off. This is water jet fundimentals at there basics.
So in closing, if you want to run hydraulics talk to professional designers, I hate saying the next part but it's for most people's own good, if you can't afford to do it right or feel you can skip certain essential parts please for your safety and the safety of others don't do it! If you can't trust a piece of equipment with your life especially one that may be lifting or holding a load you need to go back to the drawing board.
I'm sure other people will have other ideas and I'll catch flak but these are my opinions and experiences I thought may be helpful.