Precision eye surgery16 December 2011
Shackle load cells and hand-held indicators are playing a vital role in the refurbishment of the London Eye. Overleaf, Cranes Today looks at two innovative shackles.
Sprinting to complete the £12.5m project in time for the London Olympics, Merlin Entertainments Group is employing 20 subcontractors to renovate the London Eye, the famous Ferris wheel near Big Ben that attracts thousands of tourists every year.
The group is improving the Eye, increasing its environmental credentials, and preserving it as a landmark.
One of the subcontractors is LCM Systems, a British load cell manufacturer, providing a load cell that is being used in combination with an air hoist as the carriages are lowered.
The shackle load cell monitored by a TR150 hand-held indicator is calculating the precise weight of each of the carriages as they are lowered onto a pontoon on the River Thames. The carriages are then transported by pontoon along the river for further work.
As the hoist gradually fills with air and begins to lift each carriage, the load cell records the increasing weight being supported. When the hoist is fully supporting the carriage, an engineer can read the full combined weight of the carriage and rigging from the load cell on the hand-held indicator.
The carriages are attached to the Ferris wheel using four pins, and once the engineers confirm that a carriage can be lowered safely, workers remove the safety pins and lower it.
The London Eye’s technical operations manager, Mark Robinson, said: “Although a relatively small part of the overall operation, it is vital that the load cell is reliable and accurate. We have also found it is easy to install and operate, with the digital indicator enabling us to monitor the load from the ground.”
The SHK-B is LCM Systems’ range of shackle load cells designed for harsh or rugged environments. The company can provide it as a cabled version with Crosby shackles as standard or with Greenpin shackles as an added option.
All shackle pins are forged from high tensile carbon steel. For added safety they are also proof loaded to 150% of the normal rated load, and protected against from the stresses of harsh weather by tight sealing according to standard IP66.
The TR150 hand-held load indicator, used to take measurements for this project is also sealed against environmental conditions, and designed for versatility and ease of access, requiring that operators use only six keys.
The configuration menus, easily accessible through the front panel, are used to set tare values, display resolution, filter rate, auto power off as well as a selection of low power modes.
The indicator operates using different ranges. LCM Systems said: “The TR150 accepts an input range of up to 50mV/V and two separate ranges are available, which means that the instrument can both read and display two separate parameters. In each range all the variables can be set, including zero and filtering.”