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Weight and CoG Control Before Lifting -> Reducing costs and increasing lifting safety.

By: Leonardo Roncetti

Usually, cost reduction and increased safety are conflicting objectives. However, in heavy-lift, both can be achieved through prior weighing of the load, or more specifically, weight and CoG control.

PRECAUTIONS

🔸 For steel structures, we have already seen cases of a 15% increase in the calculated weight (or design weight).

🔸 For process equipment (pressure vessels, silos, storage tanks), mainly those assembled on field, we have seen increases of 10 to 20% in the calculated weight.

🔸 When there is no design, the variation can be from 100% to 150% (+) of the actual weight, as in demolition, decommissioning, rescue, salvage, etc.

🔸 The crane’s computer (LMI) should not be used to determine the load weight.

🔸 Incorrect determination of the load weight is a major cause of crane accidents.

Auxiliary crane tension load cell (80 t), by Eilon Engineering.

Main crane tension load cell (55 t), by Eilon Engineering.

WEIGHT CONTROL

TechCon Engineering performed the weight and CoG controle of a 81 tonnes pressure vessel.

🔸 Should be carried out according to ISO 19901-5.

🔸 Done in the design, manufacturing, and assembly phases.

🔸 Use of load cells rather than hydraulic cylinders.

🔸 Cranes can be used to activate the load cells (photos), not to measure the magnitude of loads.

🔸 Results recorded and the weight and center of gravity of the load calculated and a certificate of weight and Center of Gravity is issued.

Pressure vessel ready to be lifted and weighed
Pressure vessel ready to be weighed, 81 tonnes, using 2 load cells, one on each crane hook.
Leitura do valor da célula de carga para pesagem antes do içamento final
Reading of gross weight values of the load.

BENEFITS

🔸 Precise determination of weight and center of gravity.

🔸 Reduction of weight contingency factor.

🔸 Savings in crane foundation and slings and accessories.

🔸 Does not depend on the crane computer calibration to ensure lifting safety.

LOAD CELLS

🔸 Eilon Engineering tension load cells. Access Eilon web site.

Pesagem de vaso de pressão antes do içamento, baseado em plano de rigging

Reading final values of forces in each load cell.

PHOTOS:

🔸 Weighing carried out by TechCon Engineering and Consulting in the same lifting operation to unload the pressure vessel from the top of trailer.

Learn more: Why does the main crane’s load cell have a lower capacity than the auxiliary crane’s?