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REV. STV20110519
Figure 13: Replacement of pressure plate type 1 for type 2
For valves
12
(1/2”) to
76
(3”), with PTFE diaphragm, no pressure plate is required in the valve
stem. The PTFE diaphragm is provided with a threaded stud that will screw direct to the valve
stem.
In the event of replacing a silicone or EPDM diaphragm for a PTFE diaphragm on an existing
installation, the pressure plate type 1 or 2 must be removed from the stem. The pressure plates
are glued to the stem. Caution should be taken that all residual glue is carefully removed from
the threads in the stem, so that the PTFE diaphragm can screw all the way into the stem. Failure
to do so may result in diaphragm damage. A tap can be run on the stem threads to ensure
removal of all residual glue.
NOTE:
When replacing silicone or EPDM diaphragms for PTFE diaphragms on valves that
have been in operation for some years, ensure that the valve is tested for leaking prior to put
back into service. Small scratches, misaligments, etc that may be present in the valve housing
may not affect the sealing capability of silicone or EPDM, but may affect PTFE.
For valves
51
(2”) and
76
(3”), the diaphragm is provided with a threaded insert that screws
directly into the valve stem.
