Why Does the Load Measurement Vary with Crane Movement?

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SUMMARY

The load measurement discrepancies during crane movement are attributed to dynamic factors affecting the load cell readings. In this case, the load cell at pulley 5 shows a reading of 32.5 tons when stationary but fluctuates between 30 tons during lifting and 36.2 tons during lowering. The system includes two winches on motor M1, moving pulleys 3 and 4, and a fixed pulley 5, with a steel cable of 30mm diameter and a lifting speed of 1m/min. These variations complicate the adjustment of the safety relay to 110% of the nominal load.

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Marinel
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The problem bellow is a real problem and I would like to get some ideas in order to overcome it.

As you can see in the attached doc, we have two winches ( drum 1 and 2 ) on the same shaft of motor M1, two moving pulleys ( 3 and 4 ) and a fixed pulley (5).
The load is 130 Tons, and we can measure that with a load cell at pulley 5 ( 32,5 Tons) after the lifting of the load.
But during the time as the load is rising we measure only 30 tons! Note that we have a cable of steel with 30mm diam. and the rising speed is about 1m/min.

When we lower the load, the load cell measures 36,2 Tons. and as soon it stops we get again 32m5 Tons.

When the load gets the floor than we read 0 Tons (of course!)

Can someone explain this? This is a real case and my problem is to adjust the safety relay to 110% of nominal load, which is impossible with this beahviour of the system!
 
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