The Old Timer of Royal Oak, Mich., was a regular contributor to H&P years before we ever even heard of the internet. But most of his advice is just as useful — and interesting — today.
So rather than leave his wisdom printed on pages archived in our storage room, I pulled out issues from the late 1980s and early 1990s and have been reproducing relevant entries in this blog. Here is my 25th, and final, installment from the series. It was originally published in the February 1990 issue:
In the early days of running hydraulic equipment, the solution — or at least the first step toward the solution — to any operating problem was to increase the pressure. In our shop, the unwritten rule was to up the relief valve setting by 100 psi if the hydraulic equipment wasn’t running right.
That sounds simplistic today but back then it often worked—at least temporarily. The reason: manufacturers and users knew less about sealing, filtration, surface finished, alignment, etc., so circuits were plagued with sticking, jumping, and binding, that literally could be cured by increasing pressure. On the other hand, we also knew less about heat build-up in hydraulic systems and if heat-related warpage caused binding, more pressure could do permanent damage. In any case, higher pressure usually got equipment operating again to satisfy the production people. And when the pump eventually wore out prematurely, no one could remember who cranked up the pressure.
Over the years since then, we’ve learned to look for the cause of any extra resistive load and remove it. If anything, today we seek to run circuits at lower pressure — to cut down noise and pump wear while improving reliability and efficiency. But old habits are hard to break, particularly when you can change a relief valve setting in a few minutes, while troubleshooting a complete system can take all day or longer.
A case in point: Production asked us to design a small custom hydraulic machine, and for unexplained reasons, the designer decided to run it at 1500 psi. That meant our standard 1000-psi pump couldn’t be used so we had to arrange a one-time purchase of a high-pressure pump and relief valve. No big deal — except someone else decided the high-pressure pump should have a 4000-psi rating and bought an accompanying 3000-psi relief valve. Because bigger numbers must be better, I suppose.
We assembled the machine, hooked it up, got it running, tuned it to the production requirements, and walked away. I almost forgot about it for a few months, then took a close look at it one day when I was back in that area. You guessed it. The guys on the floor had walked the pressure setting up to 3000 psi, and actually asked me how to push it up to 4000psi so they could use full pump capacity. Old habits die hard.