Keofitt W9, User Manual, Page: 14 / 50

KEOFITT W9 USER MANUAL V.4 PAGE 14
3.7 Membranes
All valve heads may be delivered with any of the 4 materials: Silicone, EPDM, PTFE and FFKM.
The only exception is the MicroPort Valve head, for which membranes are only available in Silicone and
EPDM.
They all have different properties and different resistance to various chemical substances, as seen in the
table below.
Resistance to - EPDM Silicone PTFE (Teflon) FFKM
- weather and Ozone
- hydrolysis (water and
steam)
- to acids and bases
- mineral oil and gas X
X
=not suitable =less suitable =Suitable =Very Good =Excellent
Put in words the properties can also be described like this:
• The Silicone membrane has the advantage that it in general can withstand high
temperatures, but it cannot tolerate moisture condensation resulting from steam
sterilisation
• The EPDM membrane is better able to cope with the condensation in the steam and at
the same time it can be used with a majority of CIP fluids and disinfectants in normal
concentrations
• The PTFE membrane resists all CIP fluids and disinfectants except highly oxidising acids in
high concentrations
• The FFKM covers the highest temperature range and has excellent chemical resistance to
virtually any chemical compound
Membranes in rubber materials like EPDM, Silicone and FFKM are fully interchangeable (except for the
MicroPort version). This means that you may change from for instance Silicone to EPDM, if required.
However, valve heads with PTFE membranes are designed differently from the others. As PTFE is a stiff
material with no elastic properties, it cannot be stretched. Therefore, it is made with a bellow to allow for
the valve movement.
If you would want to upgrade from Silicone/EPDM to PTFE, it is necessary to contact your local Keofitt
dealer or Keofitt directly.
NOTE! The membrane functions as a dynamic seal in the valve seat as well as a hygienic static
sealing against the valve head.