Hydraulic Cylinder Rod is Stuck and Bend Due to the Hitting of Heavy Stone | Check How it's repaired

I explain how to check the straightness of a hydraulic cylinder rod and calculate allowable run-out. This is an essential task when repairing any hydraulic cylinder, because if a bent rod gets put back in, the life of the rod seal(s) is compromised and the cost of the repair largely wasted.

I also explain that bent rods can, in many cases, be successfully straightened and re-used. Provided they can be straightened to within the allowable tolerance. One of our members who works for a cylinder repair company, sent me his counter position on this:

"In our experience, 'straightened' rods are never really straight. They almost always have an S curve in them after straightening has been attempted - because they do not re-bend in the same place they originally bent. Using these bent 'straightened' rods greatly compromises the column strength of the cylinder, and is unsafe for a heavily loaded cylinder. It also wears unevenly on the gland and rod bearing, and frequently doesn't seal well. For these reasons, we never try to straighten or reuse a bent rod. I would urge you to rethink your advice on straightening hydraulic cylinder rods."

I respect Don's viewpoint. I just happen NOT to agree with it.

Before I explain why, let's clarify what I mean when I say "bent" and "straight". I'm not talking about bent like your elbow. I'm talking about a deflection that's only detectable with a dial gauge. In this context, a rod is "bent" when it's run-out is outside allowable tolerance, and "straight" when within allowable tolerance.

Now, here's why I don't agree with Don. Many years ago, I worked for a company which repaired a lot of cylinders off mining-size hydraulic excavators - 250 tons operating weight and above. So we're talking about rod diameters of 200 millimeters (8") and up. Many of these rods were induction-hardened. And a lot of them would come to us "bent" as defined above.

At the time, the replacement cost of the smallest of these rods was around $10,000. So if we had refused to straighten these rods, we would have made a heap of money - right up until the point when our customers woke up and we lost all this work to our competitors.

Back then, we gave a 6,000 hour warranty on all our rebuilds. And the expectation of any rod we straightened to our satisfaction, was that we wouldn't see it again for at least 10,000 hours.

Notice too, I said many of these rods were induction hardened. In the interest of full disclosure, I have heard third or fourth-hand accounts of the induction-hardened layer violently shattering while straightening was been attempted. In my direct experience of straightening induction-hardened rods, I've never known this to happen. Nor have I ever heard a first or second-hand account of this happening from a reliable source.

My suspicion about this is, when it has occurred, the rod being straightened was bent like your elbow, rather than "bent" as I have defined it above. Either way, the benefit of doubt, and therefore the possibility of this happening, must be conceded. You have been warned.

#HydraulicCylinderRod #CylinderRodBent #hydraulicCylinderstuck
#pakistanitruck #USAExcavator #amazingtechnology #USAHeavymachine

These craftsman have amazing truck manufacturing and crafting skills.

[loadedlever]

We have safety glasses, shoes, hoists, chains, shops with all the equipment, highly trained and paid people, but we do one thing exactly the same as these guys. One guy does all the work and everyone watches

[point]

Best episode of Cutting Edge Engineering ever.

[prithiviraj]

A series problem is that when a rod is bent like that, it has crossed it's elastic limit at that specific zone and it can no longer withstand heavy loads intended for it. And It will get even worse. Just straightening it up won't solve the problem.

[chrissturgess]

Will be amazed if it worked .I used to work making hydraulic rams and the tolerances are around 10000th of an inch....

[ursnccx]

Хром повредили, поверхность поцарапана, масло будет течь из-под сальников. Цилиндр уже не даст расчётной мощности.
Ещё и сделали отжиг штока.
Теперь нужно делать закалку и отпуск, а они, скорее всего, даже не знают из какого сплава сделан этот шток и какой режим закалки делать.
Судя по всему этот шток гнулся и выпрямлялся уже не в первый раз, если его так сильно погнуло…
Качественный ремонт в таких условиях не сделать, если там только нет чудо-мастеров, которые обладают необходимым парком оборудования для такого ремонта (судя по тому, как доставали шток из гидроцилиндра, с мастерами и оборудованием там все не совсем хорошо).

[jaceknowaczyk]

This shows that adjusting the pressure relief valve can save you a lot of work on unnecessary damages of hydraulic equipement :)

[diegobom]

This video should be seen in all workshops around the world. What NOT to do at work.

[Bobby_Uterus]

That chrome plating is pretty important, looks like they did a number on it. Not to mention ruining any prior heat treatment by putting the part in fire. I’m sure it will still work, just not very well or for very long.

[jamessands]

Metal has memory. Once the grain flow has been disrupted, that’s forever. Incredible repair with available resources.

[SendLead]

I love the OSHA approved safety sandals

[moeelza]

People making fun of these guys probably never even changed a car tire. They have minimal resources and got the job done, you think if they can afford a new rod they wouldn't have thought of that?

[bonzai]

I don’t know where to start. Annealing the rod in the fire will destroy its strength. The chrome platting is damaged by the bend and will flake off in short order. In the straightening process they used a flat rough metal plate, nothing to say the v block on the bottom, there is more scars on that rod than you can imagine. This hydraulic cylinder is going to leak and the first hard push and the rod is going to bow due to being annealed. As far as the rod being straight, well, I’ll leave that up to you.

[FjordTrotter]

For those who comment on the reconditioning quality - you need to consider the costs involved.
The average wage for a worker there is less than $1000 USD / yr. So a full replacement cylinder is about 9-12 years wages. In developed nations, think of it as a $250, 000 job just to replace a part for the machine. How would you go about it? This is their only choice for survival - and it does work, albeit not perfectly.

[-yeme-]

Id love to see a reaction to this from Kurtis at Cutting Edge

[franksmith]

I've straightened rams before, when a new one wasn't available quickly enough and they've been run every day for years, cancelled the order for a new one. Seals will tolerate a little bit of wobble, maybe not as long as a dead straight rod but plenty good enough for these guys. Not everybody can afford to just buy a new one. I've done some very sketchy repairs to get me going, then bought the new part but kept it until the repair fails and incredibly, it never fails.

[BoogWeed]

Respect to these men working with whatever they have available.

[carybecker]

To do all this before you even take your pajamas off in the morning. My hats off to these guys!

[MartyT]

Good to see they're all wearing their safety sandals and dressing gowns

[dongraham]

This is a temporary solution at best when a machine "must" go . Hydraulic cylinder rods have to be perfectly straight else the seal will leak . The "straightening" process here did not truly straighten the shaft, only turning on a lathe, which is tricky, at the end will do that after pit repair, the chrome is severely compromised . It should be rechromed ! The strength of the shaft also has been compromised, to what degree ? The first heavy load will tell !

[pubwvj]

I had a boulder fall on a heavy stabilizer hydraulic cylinder just like that and bend the rod. I straightened it by very slowly working it over a period of hot days and keeping it max lobbed. It worked and is fine now 15 years later.