The indication coming from the clogged filter indicator, is something very important and sometime not seriously taken in consideration. An heavy machinery producer, called us since they experienced blockage problems on proportional valves spools on a test bench, even if protected with in line filter. On a valve they even found a splinter so big to block immediately the spool.  From a first glance, it seemed nothing wrong on the system, but after a more attentive look, we noticed that the filter  clogging indicator was disconnected.