XLC 420
15
1) Checking the diaphragm
In order to verify if the diaphragm has suffered any damage simply proceed as follows:
a) slowly close the upstream and downstream gate valves;
b) close all the ball valves of the circuit;
c) completely open the air vent valve from the position indicator, if the latter is not present
the fitting of the isolation valve on the chamber;
d) open the upstream gate valve slowly but not completely little by little so that the pressure enters
the main valve body.
The water that flows will raise the mobile block and the membrane therefore, the air vent will
discharge the remaining water trapped inside the main valve bonnet.
When all the water of the main chamber has been expelled (this operation could take a few
minutes and is related to the DN of the valve as well as the opening percentage of the upstream
gate valve) if the membrane is not damaged, the flow will come to an end and you can be sure the
cause of the problem has to be found somewhere else.
On the contrary if the flow keeps going the diaphragm is surely damaged or the nut fixing the
membrane to the shaft is not tightened enough, therefore intervene accordingly, simply by
replacing the diaphragm or setting the nut tight.
Warning
: remember to close the upstream gate and decrease all the remaining pressure inside
the valve before removing the bonnet.
Movement of the mobile block
In order to verify the proper movement of the mobile block to proceed as follows: isolate the main
chamber closing the two isolation ball valves
on the upstream and downstream side of the valve’s
body, and open the drain port located on top of the position indicator. In this way you will relief the
pressure out of the valve’s bonnet.
Attention
: with this operation we will basically open the valve completely, therefore no regulation
will be performed. Make sure to avoid dangerous consequences of the pressure system onto which
the valve is acting.
When the main valve is
completely opened mark the glass of the indicator to the
corresponding position.
Now close leave the isolation ball valve downstream and open the correspondent upstream, also
close the air release valve on the position indicator. The main valve will close.
Verify that the valve closes following the movement downwards of the indication rod (a slowing
down in the final phase is normal and caused by the bending and adjustment of the diaphragm).
When the valve is closed, mark the glass of the indicator to the corresponding position and verify
that the movement of the rod is like the one indicated below, if different, then means that there is
something preventing the proper movement of the mobile group and please contact us
immediately.
DN in mm
50 65 80 100 125 150 200 250 300/400
Stroke in mm
15 18 21 27
27
43
56
70
84
