Insane Hydraulics
Bold and audacious blog about fluid power
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I am throwing this post in the air to see what happens because I am not entirely sure that the things that I am saying are correct. Consider it to be a field report of sorts - Setting the Neutral of a Rexroth A4VSG500EO2 Closed-Loop Pump.
This week I had to "attack" a set of four (enormous) badly centered closed-loop pumps, which made me go back to my "Finding Zero" series, where I discuss techniques for adjusting the correct null position of different types of closed-loop pumps. Me being me - I had to re-do everything, and therefore, I, present the three-article series once again - Part 1, Part 2, and Part 3.
Troubleshooting a Rexroth M4-15 Load-Sensing Valve
Another very embarrassing mistake of mine in Counter-Balance Valve Relief Function With A Closed-Center DCV.
This short blog is more than a simple "back-engineering" session. Aside from documenting a Rexroth motion control manifold that I've been repairing a lot lately (always with the same "malfunction"), this is also a story about a good example of a bad example and a hydraulic diagram of an interesting over-center valve arrangement that can be used on equal area rotary actuators - Rexroth R978035707 Motion Control Manifold.
A couple of takeaways I wanted to share after bumping into Parker's Parflex division hose catalog - A Few Words on The Volumetric Expansion of Hydraulic Hoses.
Principle of Operation of the Axial-Piston Hydraulic Transformer
A long time ago I built an interactive graph that plots the pressures of a cylinder equipped with a pilot-to-open check valve and subjected to external load and trapped pressure. Today I found and corrected a small bug in the code (pressure scaling issues that skewed the lines' slope a tiny bit), and I enhanced the graph with an extra slider for the check valve cracking pressure. I also realized that I never wrote a post about what the graph is all about - so, today I stand corrected: Wrapping My Head Around the Pilot-to-Open Check Valve Mounted on a Double-Acting Hydraulic Cylinder.
In today's blog, I want to continue with the last weeek's topic, and talk about something that was a mystery to me when I started in hydraulics - How to Determine the Maximum Working Pressure of a Hydraulic Cylinder Tube.
Quite often I need to ballpark a pressure rating for a steel tube (be it a simple pipe or a honed cylinder tube). There are two generally accepted formulae for that, the most commonly used one being the Barlow's, and then the Lame's. I'll put up a more detailed post on that matter next week, but for now, I wrote a small calculator app to make my life easier - it uses both of the formulae at the same time, and now I don't need to use one formula, and then wonder what would the result be if I used the other one, then look it up, and then re-do the calculation, and then (once again) see that the Barlow's gives out a more conservative result, and therefore is safer to use... Well, now all I need to do is punch in the numbers and awe at the "quick thinking" of the modern browsers! - Maximum Pressure Calculator for Steel Pipes and Cylinder Tubes
Best (Free!) Software for Drawing Hydraulic Diagrams.
How Making Diagrams Can Help You Learn Hydraulics
Why Would Anyone Put a Check Valve in a Leg of a Bidirectional Closed Loop?
I realized that my article from last week is incomplete because I only tested the adequately sized elbow fittings, and even though I mentioned the importance of the correct sizing, I never backed my words with hard data. So, I (somehow) found time this week to run more pressure drop tests of "slightly undersized" and "grossly undersized" elbow fittings, and then I ended up re-writing the article completely. Today I present to you the new version of my post on Pressure Drop of Elbow Fittings. (Don't forget to hit that refresh button, if you already clicked the link last week).
Reporting on my experiments with Pressure Drop of an Elbow Fitting.
It is very intuitive to think that over-speeding would be impossible in a hydraulic system, where the minimum displacement of the hydraulic motor is set so that even when it's hit with the maximum available flow, its speed doesn't go over its max rated rpm. But this is not true. See why in When the Load "Fights Back".
Two Seemingly Insignificant Symptoms That May be Indicating an Imminent Failure of a Hydraulic Pump
Two Years With a FLIR Smartphone.
I want to show you something really cool today - a relic from my past, that is supposed to be a Pressure Gauge That Measures Pressure Through Walls!
I was preparing a very different article for this weekend, but "fate intervened", and I had to drop everything and attend to an urgent service call on Friday afternoon, which threw a wrench into my content-creating plans. But the assistance call went well. In fact, it went so well that I want to write about it because it touched on a point that is very dear to me. I apologize for being sentimental in advance - Check Your Pressure Sensors Regularly (And Some Sentimental Thoughts).
Today I am going back to a very controversial article of mine. I've even been thinking about taking it down for good because it definitely has the potential of drawing some (a lot?) hate towards my persona because I describe techniques that are undoubtfully unsafe, to say the least, which is nuts because the field of industrial hydraulics already suffers from the complete lack of any type of proper safety training. Well... After giving it some thought, I decided to leave it. It's important, in my opinion, and hopefully, some readers will see (or eventually see) why. Feel absolutely free to use this article as a reference for "how things should not be done", if you want - I'll totally understand. So, once again (updated and re-edited) - Human Hands as Troubleshooting Instruments?
This is directed to hydraulic equipment owners who may venture to overhaul their repairable gear pumps themselves. And I decided to devote a separate post in my mistakes collection to this subject because I just saw another of our clients do a correct overhaul and then send his new pump to scrap simply because he omitted a simple yet very important procedure... So, let's talk about this Repairable Gear Pump Mistake.
I realized that a very important article of mine, in which I promote the "study it before you repair it" attitude to the service of components that a technician is not familiar with (a practice, that is often regarded as a punishable waste of time by the shop management), and use a White Drive orbital motor with its unique "Valve-in-Rotor" design as an example, was lacking the example pictures, which is a major flaw. It's one of my better posts, so I dropped everything to fix it. It's all good now. Here's what you'll learn:
And a lot more. I strongly suggest you read it only if you have spare time because it's definitely one of those posts that you don't want to rush - An Exercise With a White Hydraulics Motor
A hands-on session today for you. A short video, that shows How to Remove the Pulsations Orifice of the Rexroth A10VO(18...100) DFR/DFR1 Controller (when compressed air "is not enough").