Low Carbon Steel Bushing Compatability with Brine

[johnchrc]

I have a question about the compatibility of low carbon steel in light chlorides with exposure times of 3-4 hours.

A 5/16" ID caster(17-4 H900) rides on a BUSHING made from low carbon steel w/bronze substrate & PTFE overlay. The BUSHING wall is only 1/32". It fits on a 1/4" OD 17-4 H900 shaft.

The casters guide a tool inside a pipe that is submerged in a light chloride based brine environment - typically seawater or CACL2. It stays exposed for 3-4 hours. When the tool is retrieved, the bushings are gone. Could corrosion be the problem?

 

[unclesyd]

I could be but with a little more information a more definitive answer could be forth coming.
You have the right combinations for rapid corrosion but also wear could very easily contribute.

What is the Temperature of the brines?.

What is the RPM of the shaft?

Are there any marks on the 17-4 shaft in the busing area?

 

[EdStainless]

What is the risk if it does corrode?
There will be some rust and some swelling.
Will this kill the device?

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[johnchrc]

RPM = 800
Temp = 250F
Yes, the shaft wears significantly when the bushing is gone. The Caster wears on the OD but not the ID.

EdStainless,
The casters will wear one side of the shaft and will ride too low. The extension legs that hold the caster will rub against the casing instead of the caster. The legs are expensive to replace. The shaft also has to be replaced.

 

[metman]

Probably I am not visualizing it correctly but it would seem like you could eliminate the low carbon steel by using a thicker wall Bronze bushing -- all Bronze -- with PTFE overlay.

 

[rnd2]

I think Unclesyd is right about the wear. Corrosion is going be a factor with carbon steel but not over only three hours. What you have not mentioned is how much radial pressure the bearing is taking.
250 deg F salty water is a severe environment for a sleeve bearing. Many conventional bearing materials will sadly disappoint.
I caution against bronze as a bearing material for this application. It will provide only a short life and PTFE is a complete waste of time.
I believe my company may be able to assist. The website is

http://www.maritex.com

 

[rnd2]

Oooops try

http://www.maritexbearings.com.

Sorry about that.