Storing hydraulic cylinders - Part 2
In a previous newsletter article, I discussed the procedure I use when preparing hydraulic cylinders for storage. If you missed it, it's available here.
In response to this article, one of our members sent in this question:
Hmmm. I intentionally didn't mention it because I didn't want to do anything to perpetuate the myth. Because based on my experience, that's exactly what it is. Two cases I was indirectly involved in come to mind. In both cases the cylinders in question were off 400 ton mining-size hydraulic excavators. We are talking here about cylinders that weigh between two and three tons. The piston rod typically weighs well over a ton by itself.
So you have a situation where big, expensive, high-pressure cylinders are suffering premature seal failures. In both cases, the machine operators sought the advice of "seal experts". The recommendation of these supposed experts was to store the cylinders vertically.
Let's consider the reality of this nonsense:
A truck arrives to transport the cylinder to a remote mine-site. The route consists of 1,000 miles of rough, unsealed road. Given you have gone to the trouble of storing the cylinder vertically in the warehouse, surely you must insist that it is transported in the same orientation? I mean, if it can't be stored horizontally in a shed, then surely the pounding it is going to get if it's laid down on the back of a truck will turn the seals into mush, right? The truck driver thinks you're crazy but he doubles his rate and obliges anyway.
The cylinder arrives at the mine-site in the mandated vertical position. Trouble is it's a stick cylinder so it's orientation on the machine is horizontal. If the bearing bands on the piston and in the gland can't adequately support the piston rod and prevent it from distorting the seals when the cylinder is sitting in a shed or bouncing around on the back of a truck, how on earth will it cope with the thrust developed when it goes into service on a 400 ton excavator?
Common sense would tend to suggest that if the bearing bands have sufficient area and are correctly tolerenced to adequately support load-induced thrust without distorting the seals, then surely they will cope with the static weight of the piston-rod in storage and any dynamic loading that may occur during transport?
Whether you agree with this assessment or not, you know troubleshooting is a process of elimination. So when seal failures continue to occur even after the cylinders have been stored vertically ... well it's safe to say that's not the root cause of the problem. And that was the outcome in the two situations I mentioned above. No surprise to me.
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