×
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

Cracking of HNBR diaphragms

Cracking of HNBR diaphragms

Cracking of HNBR diaphragms

(OP)
We have a case of a thin rubber (HNBR ~ 1-2mm) diaphragm in a high pressure CO2 valve failing.  It had cracked completely round the flange plus part thickness crack around central support plus a few smaller concentric cracks.  It is not ozone cracking.  We suspect valve may get cold under some operational conditions (CO2 expansion)and that diaphragm could have cracked when it operated.  Any experience?  Anyone know how cold HNBR would have to get?  Thanks

RE: Cracking of HNBR diaphragms

The stiffening point of the diaphragm will be controlled by the acrylonite content of the base material, the degree of hydrogenation and the specific formulation of the HNBR but generally speaking HNBR has a Tg of about -15 to -40 deg C.  That can be lowered by the addition of low temperature plasticizers in the compound.  Of course there is always a trade off with high temperature properties with the plasticizers.

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