'O' RING(NITRILE RUBBER) PROBLEM IN COLD FITTING?

[cranekiran]

Dear all,

I tried shrink fitting a shaft by first cooling it in dry ice ( minimum temp.= -70 degree centigrade).The shaft shrunk as per our expectations but the 'o'ring (nitrile rubber)which has to be mounted in a groove provided in the shaft lost it's elasticity the moment it was mounted.

Now,my freinds tell me that -70 deg.c. is too low a temp. that can be resisted by the 'o'ring.My problem is that there is no option left for me other than cold fitting the shaft and the 'o' ring is the integral part of the shaft.

Is there any other rubber material that can withstand this temp.I would be really gratefull for any response.

thanking in advance!

 

[keithw]

Hi.... I see that this is an old thread but I will make a couple comments anyway. Not all buna's / Vitons etc are equal. There are low-temp buna compounds that are capable of retaining some elasticity until -67 Deg.C. Are you using the LT version? Is it possible for you to not chill the shaft beyond -65 and still install it? Of course,if you do not damage the Oring during installation, it will return to normal mechanical characteristics upon warming up. Silicon compounds also have the same temperature limits but different mechanical properties.

 

[cranekiran]

Hi,

Good to know that there are people who still appriciate old threads.I had thought people like you have become extinct.

Thanks for the reply,But for your knowledge we have changed the design of the arrangement now so that a simple locking mechanism can be introduced.

Still,I am very thankfull for your kind & thoughtfull response.