Let us talk about HPU design, shall we? If you design hydraulic power units, you should definitely read this. In this short article, I want to show you a way of making your designs a lot better.
If you followed my story, you know that I started as an illegal alien from Eastern Europe who fled to Portugal at the end of the last century and eventually found himself working in the field of industrial oil hydraulics with zero technical education and prior experience. It's a long story... But the best part of it is the fact that when I, eventually, progressed to the stage where I began doing designs of my own, I already had a very extensive hands-on shop and field experience under my belt, ranging from cleaning (thousands of) parts and servicing (countless) HPUs to troubleshooting multi-million dollar hydraulic installations.
Some people may look at it and say - "Well, working on a "proper technical" malfunction in clean overalls with a laptop in your lap is something one can be proud of, but how can you be brandishing all of that pats cleaning and tank scrubbing experience? Like it has any "real" value?"
Oddly enough it has. In fact, I believe that a mechanical engineer, who does design work in the field of oil hydraulics, can become an immeasurably better professional, if he invests in some hands-on shop action, and especially if he does at least a round of routine maintenance on every HPU of his design. Let me explain what I mean.
The devil is in the details. Properly sizing and choosing hydraulic components for a hydraulic build is only one side of this coin. Obviously, you need substantial knowledge for that, and my intent is never to take away from the value of formal education, but after you've worked on as many hydraulic installations as I have, you see that many (the word I actually want to use here is "most", but "many" seems to be more "politically correct") hydraulic systems are designed and built around the operation and the simplicity of construction, and not around the maintenance, and this happens due to the simple fact that the people responsible for their design and production have no "real" maintenance experience.
HPUs get built, they work, they do what they were designed for, and they even seem to be (sort of) serviceable, but believe me - there's a lot you need to learn "first hand" as a designer if you want to create a hydraulic unit that is capable of "painless maintenance". And the only way to get this knowledge is to do the maintenance yourself. In the field. Many, many times. You can find a lot of guides on how to size a pressure filter, but you won't find a guide on how to install it so that the mechanic who will replace the filtering element a year from now does it without cursing.
You may choose an open frame HPU design because it is easier to build, but when you arrive at the client's place six months from the commission date to find the main pump under a couple of inches of dust - if you are just a designer, you may think - "Hmm... Am I glad I am not the one who's gonna service this piece for crap!", but if you are the one who's going to work on the pump, most likely you'll want to strangle your younger self, and I guarantee you the next time you do a similar build the components will be enclosed.
You may think that using a simple steel tank is a money saver, but after you've re-painted a rusted tank - and then discovered a month later that all of the new paint is peeling off, and is causing even more trouble than the rust - you'll switch to a stainless steel tank design in a snap.
The service parts list is another thing designers never think of. When you designed an HPU and supplied an "official" parts list with it - you think that you're completely "covered", but you are not, I guarantee you that. A proper "service list" should include not only the common "replaceables"(like filter elements and breathers) but also stuff like seal kits, or, which is even better - the dimensions of the o-rings and backup rings for pressure filters, return filters, inspection covers, and other gaskets/o'rings and whatnots. But you will only learn to give value to this when you arrive at a remote location to service an HPU and see that the o-ring and the backup ring on the pressure filter got busted when you removed it and all you brought along is a new filter element. Bummer!..
The catalog says a four-inch clearance below the filter cup is sufficient. Yeah, right - that is - if the element doesn't get stuck and you don't have to pry it out with a couple of screwdrivers... But the catalog, man, the CATALOG!!! Yeah, right, the catalog... Just let me finish the damned service and I'll tell you exactly where you can shove the catalog!
This list is endless. Like I said- the devil is in the details. And there are so many! So, if you want to become the best designer - don't shun the hands-on service, for you are missing out on the chance to learn something useful!
Here's a bonus pic from this week for you:
Check out the placement of the two pressure filters. I guarantee you that the person who built this unit has never replaced a pressure filter in his life! I had to go one floor below, and pry the HPU around so that I could insert a socket key through the floor grating to unscrew the filter cups (after I remover tons of crap piled over them)!
Such a wonderful example of industrial engineering at its best, don't you agree?