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.
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.
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.
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?
