Maintenance
1
2
3
4
6
5
Fig. 24:
Functional testing of the backflow preventer
►
Open the maintenance ball valves to depressurize the device.
►
Mount the needle valves (5 and 6) of the measuring device on the maintenance
ball valves and connect the measuring device.
►
Open both isolating valves (1 and 2).
►
Vent the device via the two needle valves and draw water. Then close the
needle valves again.
►
Close the isolating valves (1 and 2).
►
Slowly release the pressure via the needle valve (5).
►
Watch the tundish. The differential pressure must
exceed 140 mbar
upon
the first drop from the tundish; otherwise there is an accumulation of dirt or a
mechanical defect.
►
Open the needle valve (5) and discharge the intermediate pressure zone
until it is completely empty .
►
Close the two maintenance ball valves.
►
Remove the measuring device and fit the manometer plugs again to the test
ports .
►
Open both isolating valves.
33
