Materials for membranes in FDA material

[Fritsche]

We are often asked to improve on the diaphrammaterials used in for example Alfa Laval Saunders diaphramvalves.
Have anyone got experience in replacing the EPDM rubbers with other materials.
The problem is that the EPDM cracks/hardens - and they have to replace the diaphrams every 10 - 12 weeks in the whole system.
PTFE covering the EPDM does not help.

Anyone having improved solutions to the problem ?

 

[pg11]

To develop the best solution to this problem it is neccessary to know the full details of the service conditions, operating temperature, maximum temperature reached, what flows through the valves etc. EPDM is not a particularly good diaphragm material.

 

[Fritsche]

The diaphrams are used in diaphram valves in both the food lines containing milk, and in pharmaceutical lines with raw materials for enzyme production, as well as a lot of other media, where one does not want to have media contamination due to for example using a ball valve.
The medias themselves are more a matter of chemical attack -for example does epdm not do well in milk with fat content.
The problem is more the sterilisation process with live steam at 145 degrees C - 3 Bar - maybe 2 or 3 times a day up to an hour each time.
the maximum temperature is the 145 degrees C, the operating temperature from 5 to 60 degrees C.

 

[sealguy]

You are at the upper resistance level for EPDM in steam. AFLAS would be a much better material, but I am not sure if they make an FDA grade. You could also try an inserted EPDM diaphragm. The insert will add life Vs a solid homogeneous EPDM. Is the diaphragm convoluted or flat? Let me know if you need more information.

 

[pg11]

You should consider using Silicone or even Viton , more expensive but cost effective because of reduced downtimes.
For silicone contact GE or Shin Etsu and for Viton, Dupont.
Both suppliers provide a full technical service.

Regards

Peter Goodwin

 

[rk12]

i have replaced epdm and nitrile rubber diaphragms in potable water contact pressure regulators with silicone. you may find it necc. to revise part design to allow for the difference in mechanical props between the silicone and the other elastomer.

 

[berti]

Hi Fritsche and all,

some comments.

Silicone is not best choice for equipment which is in contact with hot steam, even if there are special "steam-resistant" types. SHIN-ETSU and UNIROYAL have EPDM/Silicone-"Copolymers" worth trying.

Another recommendation: try surface fluorination of your EPDM parts. You will find this as a service.

If all this does not help - as we saw in case of hot tomatoe ketchup- only fluoro rubber (there are some more than VITON )remains as - very expensive - solution.

Hope to help
Berti