Large Hydraulic Piston - Environmental Protection 1

[joemock]

I am designing a system that utilizes two large dual-ram hydraulic units for deployment of a satellite antenna. Our customer is concerned about pitting of the stainless steel and sand/grit sticking to the surface; ultimately the concern is that both conditions could lead to possible leakage at the seals.

Does anyone have experience with protecting these units (i.e. motorcycle style boots, teflon/gortex sock). The protection needn't be permanently installed, since the area of the piston that is a concern is only exposed during antenna deployment. The piston may be in the deployed (extended) position for a several weeks.

My concern with the boot approach is that it will eventually trap moisture, I am leaning towards a sock that is installed as part of the deployment; something that acts more like a rain coat.

All comments/input is appreciated.

 

[btrueblood]

Why would the stainless steel become pitted - is this a marine environment? Wiper seals should take care of any grit/sand that blows onto the surface. Most construction equipment runs without any covers over the rams, and in pretty dirty/dusty/wet environments including marine, and I've never seen one with pitting corrosion on the rods. Not even sure if the rods are stainless? Every extension cycle of the ram coats the exposed rod with a film of oil, and every retraction "wipes" the grit off the ram at the wiper (which is seperate from the pressure seal, typically).

The Gore-tex sock sounds good, but from experience (wearing a parka on a ski lift that dripped greasy snowmelt on it) Goretex becomes non-waterproof when it gets dirty/oily. Since you may drip hydraulic fluid onto the sock, I think it may be a no-go from that standpoint. But maybe a PVC-coated fabric. Why not a vented/drained boot?

 

[joemock]

Thanks for the input.

Yes the pistons are stainless but they have seen quite a bit of salt spray. I haven't researched the type of stainless so I can't comment on their resistance to corrosion; I doubt it's an exoctic type (i.e. duplex stainless). The bottom line is it's that the client has seen pitting and wants some added protection.

I found a product called 'Seal Saver', that is more or less what I had in mind. They have several materials nylon, kevlar, and aluminized silica cloth (looks like they ruled out gortex also). Most of their applications were on heavy equipment. Their claim is that it can extend the life of the hydraulic unit 3X. Basically it allows the wipers/scrapers to do less duty during each cycle.

Regarding the heavy equipment, I agree with your comment. However, units on heavy equipment are cycled frequently when in use and the pistons are rarely left in the extended position for weeks at of time while parked on a beach.

This site had some good info on corrosion resistance of stainless steel

http://www.azom.com/details.asp?articleID=1177#_Pitting_Resistance_Equivalent

 

[sreid]

These Gortite "boots" are probably what you are looking for.

http://www.gortite.com/bellows.htm