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Technical Manual MT 188-E
DISASSEMBLY
1) Make sure that the blocking device is in closed position.
2) Disconnect the connection pipe between the downstream pressure connection
point and the control head of the slam-shut valve pressure switch.
3) Loosen the tightening screws pos. 36 (fig. 13) and separate the device from the
flange (pos. 8).
4) Lay the slam-shut device on one side.
5) Unscrew and remove the reinforced gasket pos. 1 (fig. 13) from the blocking
fitting pos. 2.
6) Remove the spring from pos. 48 and the spring support pos. 18.
7) Remove the elastic ring pos. 28 and the bushing pos. 10.
8) Loosen the tightening screws pos. 10 and remove the hollow flange pos. 3 (Fig.
12).
9) Remove the valve seat pos. 4 (Fig. 12).
10) Remove the tightening screws pos. 35 from the pressure switch (Fig. 13).
REASSEMBLY
To re-assemble the slam-shut valve, follow the procedure described for
disassembly in reverse order.
Before reassembling the tightness elements (O-rings, membranes, etc.), it is
necessary to check their integrity and, if necessary, replace them.
Once again, pay utmost care while handling the valve seat pos. 4 (Fig. 12) in order
not to damage the sealing edges.
7.0 FINAL OPERATIONS
7.1
CHECK OF TIGHTNESS AND
CALIBRATIONS
1) Open very slowly the on/off valve positioned upstream of the slam-
shut valve and, using a foamy solution or the alike, check the
following:
• tightness of the valve external surfaces;
• internal tightness of the slam-shut valve (downstream pressure
shall not increase).
2) Open the manual bypass and pressurize the network part
downstream of the valve. Completely open the valve till it blocks.
Close the manual bypass.
3) Verify the calibrations as described under point 4.3.
7.2
COMMISSIONING
1) Open very slowly the downstream on/off valve;
2) Verify that the downstream pressure is stable and shows the
forecast value;
3) Make sure that the plant is under safety conditions.
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