Keofitt W9, User Manual, Page: 42 / 50

KEOFITT W9 USER MANUAL V.4 PAGE 42
14. FAILURE MODES
If the membrane is not replaced with a new one at regular intervals (depending on the application), it
may eventually break, usually around the tip and more seldom along the side.
14.1 Broken membrane tip:
This failure usually causes product to leak from the process side and more or less product will flow out
through the lower port, also when the valve is in closed position. As such the valve port acts as a leakage
hole (weep hole).
14.2 Broken membrane side:
A longitudinal slit in the membrane is a rare incident and will only occur if the membrane has been kept
in operation far beyond its expected service life.
Should it happen, product will during sampling enter the cavity between the internal surface of the
membrane and the rod operating the membrane. As there is no significant pressure in the valve chamber
during sampling product will only flow slowly through the slit and will eventually leak between the head
union nut (pos. 7) and the turn knob (pos. 6). However, this is likely to take many rounds of samplings
due to the short sampling time and the very low pressure on the external side of the membrane.
The valve is not foreseen with a leakage hole in the valve head as the risk of building-up of dirt inside the
valve head from such a hole does not outweigh the manageable consequences of a broken membrane
side.
The effect of such a failure will be an accumulation of a small quantity of product, which cannot be
removed during the ordinary post-sampling cleaning or steaming. The consequence of this is a risk of
contaminating samples taken after the failure occurred. However, the risk of contaminating the process
side is considered to be negligible.
14.3 Cleaning the valve after a failure:
In case of any of the above failures the valve needs to be completely taken apart a cleaned properly using
a non-abrasive cleaning agent by performing the following sequence of operations (the choice of clean-
ing agent is for the user to decide as it depends on the product in the process line):
1. Unscrew the valve head from the valve body as explained in chapter 13.3
2. Disassemble the valve head as explained in chapter 13.6
3. Clean all individual components from the disassembled valve head
4. Clean the valve body
5. Assemble the valve head as explained in chapter 13.6 and fit a new membrane
6. Fit the valve head to the valve body as explained in chapter 13.3