hydraulic cylinder pitting

[tomjelly]

6" diameter hydraulic cylinder with wide 1" flange leather cup seal has rust pitted bore, too deep to hone out. Any way to fill these small pits? The huge surface of its leather cup seal I would imagine would make it more tolerant of some surface imperfections than a modern polymer U seal, but if there is a way to improve the surface I'd like to. I can treat with evaporust, spray in epoxy or something and hone the epoxy off leaving filled pits, but I don't know if anything would stand up to the (aw32) oil...

 

[john.k]

Ive seen pitting in cylinders filled with solder .....However ,if the tube wall is thick enough ,rebore it .......leather seals will still seal ,and you may need to increase the dia of the piston by brazing or welding............a whole lot cheaper than retubing

 

[Milland]

You could look into electroless nickel plating kits, then carefully clean the pits (may need to grind to fresh metal), then build up the area using a clay dam to localize the deposition. Or if you have access, clean and TIG weld. Then grind and hone. Whatever you do, cleaning will be critical to success.

Plating Kits - Nickel Plating Kits - Electroless Nickel Plating Kits - Page 1 - Caswell Inc

caswellplating.com

 

[john.k]

I used to do hydraulic repairs where a cylinder barrel was deeply scored by some metal embedding into the piston...........also did hardchrome rod repairs by welding the scores with stainless ........common damage was a hardchrome ram shorting power lines .....leaves a nasty track of copper weld and pitting ........some operators would simply pull down the powerlines to avoid problems.

 

[dana gear]

A quick and dirty repair, clean/flush all pits with brake cleaner to remove any trace of hyd oil.
Fill pits with JB weld or equivalent, let dry and hone. works amazingly well.

 

[BT Fabrication]

cant just get another new cylinder?

 

[tomjelly]

Not economically feasible to replace. I wonder if hot dip galvanizing the whole thing, then bring back to size would work...If I knew I could hone that galvanizing off back to the good original bore surface leaving the pits filled rather than boring that might be very cost effective. The cylinder is only about 13" deep. Some of the pits are small but deep, I don't know if electroless plating would work for that, JB weld might be the only practical answer.

 

[Milland]

Not economically feasible to replace. I wonder if hot dip galvanizing the whole thing, then bring back to size would work...If I knew I could hone that galvanizing off back to the good original bore surface leaving the pits filled rather than boring that might be very cost effective. The cylinder is only about 13" deep. Some of the pits are small but deep, I don't know if electroless plating would work for that, JB weld might be the only practical answer.

How much more life do you need from this cylinder? if it's a long time, 6" x 13" should be able to be TIG'd with a stubby holder (hand in the hole) a mirror on a post, and a longer filler wire bend as needed for outside holding. Heck, maybe just stub SMAW rods?

If it's light duty and not that big a deal, sure, clean well and use a metal-filled epoxy. There's probably blends out there made for this use.

Belzona 1151 (Smoothing Metal) For rebuilding pitting

2-part epoxy based composite material for rebuilding pitting in metals damaged by erosion and corrosion

www.belzona.com

Epoxy Metal Repair | EMP Inc.

www.empinc.com

 

[Garwood]

That would be easy to Weld repair, bore and hone with the right tools.

 

[tomjelly]

Looking like epoxy will be the way to go with this. It gets used only once in a while, is single acting, has internal drain of any fluid that might bypass the seal back to the reservoir so even if there was some seal bypass it wouldn't matter, and doesn't need to hold a static load. Because of this I'm more concerned with the seal wearing against any pits, which I think the epoxy would work well for as long as it stays stuck. I'll try it and if it doesn't work I can always take it apart again. Milland those products look perfect for this application & sound like they will stay in place.

 

[atex57]

Looking like epoxy will be the way to go with this. It gets used only once in a while, is single acting, has internal drain of any fluid that might bypass the seal back to the reservoir so even if there was some seal bypass it wouldn't matter, and doesn't need to hold a static load. Because of this I'm more concerned with the seal wearing against any pits, which I think the epoxy would work well for as long as it stays stuck. I'll try it and if it doesn't work I can always take it apart again. Milland those products look perfect for this application & sound like they will stay in place.

If the cylinder does not need to hold a static load then make a new piston and install piston rings. Hercules Hydraulics has a bunch of sizes. BTDT.

Ed.

 

[john.k]

If the tube is only 13" long,Id go to my "friendly" local hydraulic shop and ask if they have an offcut of 6" cylinder tube .....For a model steam engine project or some equally imaginative reason.......good chance they will give it to you.

 

[BT Fabrication]

a 6" cylinder around here by about 1 ft long is only $200. Many came on dump trailers to lift the box and are cheap. Either that or replace the whole tube, once it starts to pit, not much will help it and prevent it from destroying the whole cylinder.

 

[Milland]

OP's already indicated it's a really low-duty application, given that he's likely better of with epoxy and a bit of elbow grease than rewelding in a cylinder section.

 

[tomjelly]

plus this part has a huge flange on one end and a lot of other stuff welded on the other end. Too much to redo

 

[AlbertC]

6" diameter hydraulic cylinder with wide 1" flange leather cup seal has rust pitted bore, too deep to hone out. Any way to fill these small pits? The huge surface of its leather cup seal I would imagine would make it more tolerant of some surface imperfections than a modern polymer U seal, but if there is a way to improve the surface I'd like to. I can treat with evaporust, spray in epoxy or something and hone the epoxy off leaving filled pits, but I don't know if anything would stand up to the (aw32) oil...

Stainless steel cylinders will not rust, but it will stick just as the other cylinders will do. Oil and water are the best lubes for these, but oil is more resistant to corrosion. These will probably be okay with rust pits. All of the oil is trapped in the cylinder so it won't corrode the outside. It is the external surface that is the problem if oil and water gets outside of the cylinder, but the pits will not allow this to happen. You will probably have to use some sort of thread sealer to seal the ends. If you use the stainless steel cylinder, you will have to use tape on thread sealer to make sure it doesn't leak.

 

[tomjelly]

As it turned out I bought a lisle hone (similar to sunnen, with the gear racks) and was able to almost fully hone out all of the pits except for just a few that almost looked more like inclusions in the steel tubing than rust pits. In any case I wiped in some epoxy, ran the hone again after a few days curing time, worked my way up to 500 grit, put the cylinder back in service and its working fine. The gear rack hone works very well as you can adjust the pressure accurately.

 

[metalmagpie]

Thanks for the report.