×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Grease at Low temperatures

Grease at Low temperatures

Grease at Low temperatures

(OP)
I have experienced the use of a -20deg lithium based grease at low temperatures (about -15deg)and there was evidence of solidification and crytals present. The grease is used to lubriacate seawater seals and led to the seals passing. Does anyone know if the grease expands or contracts at lower temperatures?

The grease properties are as follows:

Drop point 180degC
Base Oil Viscosity  150cSt @ 40degC
Penetration 265-295 (N.L.G.No.2)

RE: Grease at Low temperatures

You need to know what the viscosity is at -15 or -20.  Viscosity changes significantly with temperature.

RE: Grease at Low temperatures

Yeah DaveJC, the properties of grease change with temperature.  In cold weather engineering, "cold" meaning -45C and worse at higher Canadian latitudes, valve applications, these changing properties cause considerable problems for grease seat injection systems.

My valve designs specifically call for a teflon free grease base, lithium is not as bad but is also thermally influenced.  I have found that Esso Equilub 80 to be probably the least responsive to temperature, so that it would be my recommendation for seat injection(s).  Perhaps this will work for you.

One practice that the industry uses in our winters, is to dehydrate the valves with methanol.  Field technicians typically pour significant amounts into the valve cavity.  It has been our experience that this is the number one cause of elastomer swelling, methanol is absorbed by the base rubber matrix thus elevating compression.  Once this happens, the valves typically hang up.  I don't think that there is ANY solution to removing either grease or water in the form of ice from internal components.  Some say a nitrogen purge works well, I really don't know since personally I have never used it.

You may want to try blowing out the grease lines with air, basically 78% nitrogen.  I would definitely be interested with your experience in this regard.

Hope this helps.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

RE: Grease at Low temperatures

(OP)
Hi Guys

Thanks for the help, the grease is only used when fitting the seals, although it fills the cavities of the seals.  There is no constant grease charging system.
I was interested to know if the grease expands, would this contribute to the seals leaking.
We replaced the grease with lower temperature grease (-40degC) but I am trying to establish the root cause of leakage.
The temperature has now risen and is no longer sub-zero

Thanks

RE: Grease at Low temperatures

Sounds like a good question.

I would go to the manufacturer for this
information.  Let us know the reply.

RE: Grease at Low temperatures

Hi DaveJC,

Have a look at the forum list, and maybe post your question in one of the other forums.

Tofflemire

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources