Today's blog has its origin in a recent dispute between two renowned hydraulic bloggers - Brendan Casey and Rory McLaren, both of whom I follow on LinkedIn and have a lot of respect for, even though I am not personally acquainted with either. I am sure that if you are curious about industrial hydraulics to the point of finding and going through this page, you know who these men are and what they do. But in case you don't - do check them out, they deserve your attention because they have been providing tons of useful information relevant to this field for years.
On a side note, a long time ago, at the beginning of my own blogging endeavor, when I didn't know anything about copyrighting (still don't), I used Mr. McLaren's presentation file in my article about the type of injury that scares me the most as a hydraulic technician, and he contacted me with a demand to remove the file I wasn't the author of, however when I asked him to allow me to keep the presentation (giving him full credit, of course) because this kind of information was, quite literally, of vital importance to readers of my blog - he allowed it immediately, agreeing that safety of folks working with pressurized hydraulic fluids was more important than a copyright claim.
So, about a month ago, Mr. Casey made a post about the troubleshooting method advocated by Mr. McLaren, which revolves around using a lever-operated hydraulic pump as a portable pressure source, which can be used for detecting/evaluating leakage of components and, obviously, other things a pressure source can be used for. The MicroLeak test kit, promoted by Mr. Mclaren, appears to be composed of a compact hand pump and a set of fittings/connectors, and you can evaluate how it looks here (I will say what I have to say about this kit in a minute).
In a nutshell - Mr. Casey called this technique a "hand pump troubleshooting doohickery" and stated that in most MicroLeak use cases, presented by Mr. McLaren, alternative diagnostic procedures could be applied that wouldn't require a hand pump, thus making the application of "principles before method" a superior and safer approach to troubleshooting. And then a series of "debunking" posts from both of these gentlemen followed on LinkedIn... I think you can still find them there, but I am not sure for how long the platform keeps this stuff, so I am not putting any links here. You can always check the activity sections on their LinkedIn pages yourself, in case you're interested in the (rather interesting, IMO) technical details of the debated examples.
Now, there's no denying that both of these gentlemen have years of experience with all kinds of hydraulic systems and that they both are successful businessmen and even, dare I say, influencers in this field - so I am not going to discuss any of the concrete troubleshooting examples that they argued about - simply because I know that both of them know that in real life the question "What is the best troubleshooting technique in this particular case?" always, but always, starts with "It depends..."
When you tell me: "It is easy to diagnose this if you close this adjusting screw..." - I imagine a screw that looks like this:
Touch it and it's gone. Now what? When you say - "...let us imagine there are measuring test points in the cylinder lines..." - I want to ask you: "What planet are you from?" When I see someone point to a drawing and say something along the lines of "Now you need to determine which of the two components has internal leakage..." - I ask but what if both of the components have leakage... But that's me - I always imagine and expect the worst stuff.
There's an intelligence test when you are given a sock and a bunch of quarters and you need to come up with ideas about what you could do with these objects (other than putting one on your foot, using the other for buying soda, and combining the two into a blackjack) - the more use cases you can come up the more intelligent you are. From the way Mr. Casey makes his point in his numerous articles on hydraulics, I would say that he strikes me as a very intelligent man, so I do not believe for a second that he does not see the benefit in having a portable pressure source around on a service call - even if he seems to disagree with the suggestion of using it as the main tool for pinpointing components with internal leakage.
But what about me? Well... First - I believe that the best diagnostic tool that you have is the one that sits between your ears, second - I also believe that there's no such thing as "too many tools", and ever since I saw the video on MicroLeak testing (about ten years ago) - I have been entertaining the idea of making a similar kit for my practice to see how it would fare. We have two test benches in the shop, and I also built a small AC-powered HPU as my portable test bench a long time ago. I can't say I've been using it much - but it definitely had its moments. But even with all that gear, the idea of the hand pump tester has always been at the back of my mind, and when I stumbled into the argument I just described, I said to myself: "That's it! I want to try it and I want to try it now! Then I'll be able to say whether I like it or not!" And that's, basically, what I will be showing you today.
Coincidentally, I just received these three closed-center directional valves (Walvoil DLS7) with a complaint that suggested excessive port leakage - so they were the perfect test subjects for this test.
Obviously, I didn't want to build a full-blown hand-pump test rig - what I wanted was a proof-of-concept prototype I could build fast, just to see if I liked working with it or not. It took me not one, but three attempts before I came up with something I could use. Let me show you the failed attempts, real quick. First - I stole the pump from the Pressure Maker I (can be seen here), secured it in a vice, and added a couple of accessories for measuring/venting pressure. It looked very nice:
But it didn't work that well because it was a 25 cc model, and even though the manufacturer stated the max rated pressure of 350 bar, the best I managed to pump it up to was about 180-ish bar - any higher a value would require a two-meter long lever and me ripping the vice off of the bench.
My second idea was to use the next best thing (please bear in mind that I was building a fast proof of concept) - the hand pump of our press (which conveniently had two speeds, the slow one being about 12 cc/stroke):
I actually worked, and I was able to test the pump against a plugged test hose and even reached about 300 bar (the max pressure of the press is 400 bar) - but then something either broke or got stuck (still "under investigation") and I "lost" the low-speed/high-pressure stage, which once again meant that the pump would require a muscle input I didn't have for the pressure I was aiming at.
Then, as a last resort, I went to my "someday/maybe" scrap pile, in which I store stuff that's "too good to through away, " and I managed to dig out an old and rusted 12 cc hand pump that had been there for some years. When a hand pump reaches this state - you don't repair it, at least not for a client - because the repair costs them about the same as a new pump does, but throwing away a pump that only required a thorough clean up and a new rod to work again didn't feel right - so I kept it around. I'm glad I did:
I made a new rod and cleaned the parts:
And after putting it back together with new seals I got a free pump that I could manageably pump up to 250-300 bar with a 900 mm long lever, without feeling like I was trying to break my dead-lifting record:
Now it was finally time for the test. The hydraulic system the valves originated from was simple - an open loop DCV directly driving a single articulated frame steering cylinder of a mobile core drilling rig. The valves were supposed to be closed-center, with the inlet relief valve set to 150 bar and the anti-shocks set to 190 bar. The operators were complaining that the steering cylinders of the two drilling rigs that they received recently would not hold their position when the lever was at neutral, so the valves were replaced and the problem was gone - and we were asked to see if anything could be done to the faulty valves to fix them. One of the three valves was actually brand-new - it was sent to us "for good measure" - to verify the settings. So, I decided to start with this one just to see how easy (or not) it would be to check the settings of the anti-shock valves and the main relief valve with the newly reborn hand pump:
There's one thing that I can tell you about this experience - you have got to try it for yourself to see how it works! I even dare say how good it works! But it is hard to explain with words. First of all - it definitively took some getting used to - the flex of the lever, the elasticity of the test hose - your hand, literally being the pump, feels it all. You can actually feel the small spike of the cracking pressure and the lower pressure (resistance) after the valve opens, and even the pressure override, also reflected by the gauge, as you increase/decrease the lever speed. Note that a 12-cc hand pump still requires significant muscular input at 200 bar - but, in my opinion, this is exactly what makes the experience so... "feely" (This is the best term I can come up with). But I can definitely promise you that my wife, for example, would never be able to pull this off - especially given the fact that this pump is double action - it pumps both when the lever goes down and up.
I can imagine that you can come up with a bunch of reasons to call this a bad test - all I can say is that you have got to try it for yourself. Literally - get yourself a hand pump, a couple of direct-acting relief valves, or anything else "pressurize-able and adjustable" - and give it a shot before making up your mind. I can also promise you that if there were a leak - I would definitely be able to tell it was there.
But there's more - so let us continue. After verifying the anti-shock valves (and being pleasantly surprised by the "action of my contraption") I turned to the inlet section and the main relief valve. The first thing I could see when I pumped oil into the P port was the pressure of the inlet compensator spring and the fact that it was new. You could immediately tell that it was about 10 bar, and when I stopped "pumping action," - the pressure stayed there, which meant the inlet compensator spool was pretty tight. A good piece of information - don't you agree?
Then I commanded the valve with a piece of string and verified the setting of the main relief and once again - it was pretty easy to see:
Obviously, you have to take into account the fact that a hand pump allows you to check only the cracking pressure, and under constant flow, the pressure will be higher than whatever value you are reading now, but I liked how it felt, I really did.
Then it was time to test the "leaky sections". As you already know, I like testing stuff with compressed air before doing it with oil (even when a test is a fast hand pump test) so I had already confirmed that both of the faulty valves had significant port leakage, but I still want to show you something very interesting about them.
The leakage I was detecting was very big - so big in fact, that the first thing I did was double-check the spool reference just to make sure that it was indeed a closed-center spool - and it was, but the spools looked new and I could not see any damage or wear inside the cavities. Now I want to show you another test scenario in which a hand pump, in my opinion, definitely outshines its "motorized brethren" - I am talking about a pressure test on a partially disassembled component, like this work-section here:
First of all - I am safe because my pump is my hand, so I am the one in control of the pressure/flow, and I will not create a dangerous situation a powered test bench with its infinite oil supply so easily could. Then - as I pump the oil into the work port - I see it pouring out of the lower T-hole and the LS-hole - but not from the T-hole of the anti-shock valve (always the first suspect of port leakage) - so I can, once again, instantly tell that the problem is not caused by the leaking anti-shock/anti-cavitation valve. Then there's another thing I can do safely now - you can see that I removed the lever box and the spring cover - I did it so that I could shift the spool by hand. As soon as I move the spool by a mm or so - the work port becomes totally closed, and I can actually see this with the hand pump and also confirm that it's airtight now, which means that the spool/cavity wear is not the issue, but most likely the configuration (or damage) of the body is. What I found really neat was the fact that I did all these pressure tests "in the comfort of my bench", without the noise of our test stand, and I did it really fast.
In case you wonder - the leakage problem was caused by the configuration of the bodies. Here you can see that the ring separating the work port from the T gallery is much thinner on the "leaking" valve (the client couldn't tell where these valves came from - all they knew was the rigs came back like that after an overhaul and judging by the fact the valves were assembled with full threaded rods rather than proper tie rods I suspect somebody "Frankensteined" this valve from parts they had around):
I couldn't find the body with thinner rings in the Walvoil catalog, so I am not sure about its origin - maybe it comes from an OEM model - the thinner rings are perfectly symmetrical on both sides, so it does not look like wear. But it's not a problem - I'll get new work sections, and we'll get the valves going in no time.
I can tell you that I, personally, liked the experience, and without giving it much thought I can totally see multiple things a tech could do with such a pump:
In my opinion, to turn this prototype into a proper tool it would require the following:
In all - I think this is a good tool to have around, but it can only do you any good if you know how to use it. I liked the experience enough to plan to spend some time in the shop upgrading the prototype, and I'll make sure to show this project off when I have it finished.
Now I want to say a few words about the MicroLeak test kit. The page says it's spec'd to 3000 psi max. I suppose It's OK for finding leaking components but it's often not enough for adjusting valves. I would say that 4000-5000 psi would be so much better - and I don't know why it is so limited pressure-wise. Maybe it has a similar large displacement but a short lever for the sake of being compact and portable? Seems like something they could improve on.
Judging by how the kit is priced - I believe that it's aimed at our clients rather than us (by us I mean shops and companies that deal and repair hydraulic stuff). I can see how easily a hydraulic business can create a similar kit tailored for their specific needs from parts they can source from their suppliers at wholesale prices (or even make in-house) for a fraction of the listed price, and I can also see how our larger clients would pay the full price for such a kit just to avoid the hassle of making it themselves. The way I see it - Mr McLaren created a product that solves a problem - and since he, apparently, has been able to sell it - I can only give him props for that.
And finally - such a pump, of course, can cause damage just as easily as it can help with diagnostics, so in my mind, this is a "professionals only" kind of tool. You already know how I feel about selling hydraulic stuff to random people, so yes - once again - professionals only!