Compressed air is supplied from the main along pipeline 1 through needle flow-control valve 2, which establishes the working pressure measured by manometer 3. Flow-control valve 2 is adjustable in order to compensate for drops in pressure due to increased air consumption. Entrance nozzle, or restrictor, 5 is taken to correspond to the diameter of the hole to be checked in work 4. The pressure measured by manometer 6 varies in accordance with the actual size of the hole in work 4. The scale of manometer 6 can be graduated into units that show the deviation of the hole size from the basic value.
$3703$SHP,M$