There's another problem with installing a presure switch after a pump, on proportionally controlled/servo controlled hydraulic systems the pressure will not be constant after the pump (the only pressure you would expect to have constant would be pilot pressure) hence a pressure switch would be continualy switching based on the system demand. I've always found a good way to determine if a hose has split is (if the hoses are close to the powerpack) is to install a float switch in the powerpack drip tray if it's large enough that will cut the motor if the drip tray overspills (from a split hose). Albeit this will not detect a split hose anywhere else but i've always found that 90% of the time the hoses nearest to the powerpack are the one's to fail due mainly to hydraulic shock or (as we use a lot of internal gear pumps they fail regualr due to oil quality) from improper fitment i.e. rubbing hoses, badly made hoses (we make our own - says it all).
Anyways, Jimtech, Can you provide a little more info as to what capacity the tank is roughly, pressures involved and on they hydraulic control side if it's a fixed displacement pump(s) or variable displacement. Thanks
EDIT:- Just had a thought that may work, how about using flow sensors, one in the pressure line out from the powerpack and one in the tank line and monitoring the flowrates, outgoing versus return, when a movement occurs you would expect there to be flow in both lines at the same time (albeit with a slight delay) so detecting flow in the outgoing pressureline above a certain threshold with a very low flow in the tank line would probably indicate fluid is being lost.
Regards
Tom