I like to relate interesting troubleshooting episodes because it's a way of documenting and sharing exclusive knowledge, and if other techs can use it in their practice - I am happy. This industry can use as much practical knowledge as it can get. But some malfunctions, while being unique in the sense that they are something you don't see every day, aren't "complicated enough" to warrant a separate article. They are more like something you would bring up in a friendly conversation as one of those "you'll never believe what happened the other day" tales only techs can appreciate.
So, I decided to collect a few of such "failures" in a single post. They are, kind of, stupid, but knowing that something like that can happen is another way to expand our hydraulic horizon, don't you agree?
Stupid Malfunction 1 - "Pinched Hose":
Happened to a friend of mine, who had to diagnose a core drilling rig that displayed a very strange intermittent behavior. In the end, the malfunction boiled down to one of the pilot hoses that ran between the rig and the control panel and got accidentally routed under the rig's frame. The hose got pinched, and as the drilling head was moving up and down, the frame was closing the hose off completely! Talk about a bunch of coincidences!
Stupid Malfunction 2 - "Misunderstood Flushing":
A perfectly functioning Rexroth A6VM055 hydraulic motor was replaced with a new one on the account of its loop flushing valve. The tech mistakenly attributed the large case flow to internal leakage - and a couple of months' worth of salary got spent on a component that wasn't needed. Not at the moment anyway. In the end - the pump was the culprit.
Stupid Malfunction 3 - "Not Knowing How a Pump Control Works":
A perfectly functioning A4VG71 pump with an automotive control got a major overhaul two times in a row because of the lever-operated DA valve, that had the lever fixed in the "off " position whenever the pump was re-mounted on the machine. What a shame. The owner spent tons of money on the handler and didn't want to believe his eyes when I "fixed" the transmission by turning a lever nobody knew was there.
Stupid Malfunction 4 - "The Plugs are for Transportation Purposes Only":
I actually mentioned this "malfunction" in my article about Obvious Not Obvious Hydraulics. In short - a hydraulic equipment user acquired a new gear pump, and since nobody told him that he needed to remove the plastic caps from the pump before the installation, it was mounted with the plastic caps in place, and obviously wouldn't work. Believe it or not - I, personally, witnessed such a mistake several times!
Stupid Malfunction 5 - "Fitting that's too Long":
A Rexroth A10VO pump had a control malfunction, and the control module was replaced before the "malfunction" was discovered. The load sensing control valve had a 7/16'' ORB port situated directly on top of the control spring, which is a pretty standard LS port placement for many controls. The "installer" didn't manage to find a proper fitting, so he used a standard 7/16" JIC fitting which happened to have the same thread, but since he didn't cut it down, the protruding JIC "nose" jammed the regulator springs.
Stupid Malfunction 6 - "Check Valves and Ferrules are there for a Reason!":
Not exactly a hydraulic system, but the principles apply. A maintenance shop installed an extensive progressive lubrication system on a large machine (SKF SSV-based if you need to know, about 40 lube points). But instead of using proper fittings on the metering manifolds (fittings that have special ferrules and check valves), they used common M10 fittings, and only in the end discovered that there was "something strange" in the way the lubrication system behaved... The point is - do educate yourself on that something you're working on before you start the work!
Stupid Malfunction 7 - "When Fauna Attacks":
Not an uncommon thing to happen in the rural area where we operate. People often store their replacement hoses in barns hanging on the walls. There's this local wasp, that likes building its houses out of clay, and especially favors small round orifices for some reason. If it finds an open hose end - it builds a very strong clay plug inside, and when the insect is gone - the plug can be completely unnoticeable, and, as you can imagine - a hydraulic hose with a clay plug inside it can lead to all sorts of "mysterious failures". Definitely a thing city folks never hear about!
Maybe I'll add to this list in the future...