SHIPBUILDING: Succes for SCHAAF in Export
KAWASAKI rationalizes with Hydraulic Nuts

Every marine engine must undergo an extensive test procedure. For this purpose, the flange of the driven shaft with the flange of the water brake (hydraulic dynamometer) to run all types of load.

Up to now for producing this connection, 12 body-fit bolts were inserted into the bores of the flanges and equipped with mechanical nuts M 100x6 on both ends. The nuts were tightens with torquing wrenches. It is well known that these nuts must be tightened with great care, crosswise and in several steps. This used to take half of a working day.

For the new solution, the former hexagon nuts were replaced by round nuts since they have non longer to transmit a turning moment and to produce the tensioning force, but they, now, must only be turned to their correct position. On one end, hydraulic nuts (though without thread, but with plain bore) are placed under the round nuts; they are fixed to the flange of the water brake. The Hydraulic Nuts are equipped with springs for retracting the piston and a stroke limiting valve, to make operating errors practically impossible. All Hydraulic Nuts are linked by bent tubes and are pressurized by an air driven pump.

When the engine is installed besides the water brake, the bolts are stuck through the two flanges and the round nuts are screwed on at the side of the engine. The hydraulic pump is connected to the supply fitting (fast-lock system) and the pressure is generated up to the determined value. Thge pressure is monitred on both ends of the ring with Hydraulic Nuts for best accuracy.

This entire procedure guarantees most accurate pre-tensioning and uniform distribution. The total operation time is 20 minutes.

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