Water Treatment oxidizing Grease?

[jpyeck]

I posted this in the Valve Engineering forum, but thought there might be insight from this forum as well. Any ideas?

I have some ball valves in my system that have started to exhibit higher torque requirements to actuate. I took a couple apart to see what was going on, and noticed that the stem and O-rings seemed rather "dry". The grease appeared to lose all it's lubricating qualities, although it was obvious that it was still there.

The manufacturer says the valves are made with a synthetic grease (Kluebersynth VR 69-252) and EPDM O-rings. We used a sodium nitrite based corrosion inhibitor on the system. Our medium is ethylene glycol/water (50/50).

Is it possible one of these chemicals is reacting with the grease to cause this "drying out"? Any suggestions for other types of grease?

 

[unclesyd]

I would check out the O-rings first to see if you have any swelling, it will only take a couple % swelling to affect the operating torque on the valve.

Though somewhat expensive 'Krytox' (Dupont) will work and give youe time to look at other materials.

http://www.dupont.com/lubricants/en/index.html

 

[EdStainless]

The grease may not be suitable for your temperature range. You may be either too hot or too cold for the grease to work well.
But I am with Syd on this, check the o-rings.

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

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

 

[jpyeck]

Thanks for the replies. I also looked at the O-rings and if anything there appears to be some compression set. I don't think they caused the torque increase.

We are running close to the high end of the temp range of the grease (200°F -> rated @ 212°F). Could this cause such accelerated failure? These valves have only been in place about 1 year.

 

[unclesyd]

You are getting close on temperature.

One thing to remember is the temperature limit for greases and O-rings changes with the medium being sealed and with your system may be above an acceptable use temperature of one or the other. If you have compression set that can also increase the drag imposed by the O-ring to a point where it would be problem if the lubricant isn't working.

The Krytox can very easily take your temperatures.