London’s newest lifting bridge relies on draw wire sensors
07 February 2016
Draw wire sensors from Variohm Eurosensor are helping Hunger Hydraulics to monitor the position of long-travel telescopic hydraulic cylinders deployed on a lifting bridge application in East London.
Hunger Hydraulic UK recently supplied four 4.25 metre stroke telescopic hydraulic cylinders to main contractor John Sisk, to lift a new 80-metre pedestrian and cycle access bridge linking Canning Town station to a new island development on the Leamouth Peninsula, east of Canary Wharf in London’s Docklands.
The Leamouth Peninsula will eventually host 'London City Island' a new neighbourhood on the 12 acre site, surrounded by water and connected only by the new bridge. In addition to high-density residential housing and residents' facilities, London City Island will be home to the English National Ballet.
The 160 tonne bridge, which was successfully commissioned in July last year, is raised vertically to allow boats to navigate the river. As an integral part of its hydraulic control and synchronisation system, it includes four Celesco SR1 series draw wire linear position sensors that were specified and supplied by Celesco’s UK distributor, Variohm EuroSensor.
As conventional hydraulic linear position sensor types could not be considered due to the telescopic style long travel cylinders used for this application, Hunger’s designers opted for draw wire or cable sensor technology and chose the competitively priced Celesco SR1 for its rugged build quality and reputation for extended durability in tough outdoor construction, agricultural and industrial equipment applications.
For redundancy purposes, two sensors are mounted and work in parallel each side of the bridge. To ensure complete protection, the sensor pairs are encased in a pivoting steel housing which includes telescopically extended cylindrical sections that fully enclose the cable.
For this application, the SR1M model draw wire sensor provides a user-scalable 4-20mA proportional signal to the control system. The sensor is supplied factory calibrated to the full stroke range but, thanks to its internal programmable digital circuitry, the output signal can be easily re-scaled to match the actual application stroke length with an easy-to-use push-button zero and span adjustment.
Other models in the SR1 series include voltage divider, 0-5Vdc, 0-10Vdc and incremental encoder versions with standard stroke lengths of 3,175 and 4,445mm. The plastic-hybrid precision potentiometer returns a rated life of 250,000 cycles with positional accuracy specified at 0.5 percent full-scale, with repeatability to 0.1 percent full-scale.
Along with many draw wire sensors from Celesco Inc., the SR1 is designed for outdoor use and features an IP67 environmental rating, tough polycarbonate housing and a nylon coated stainless steel cable. The sensor can be universally mounted with cable exit positions orientated in ‘up’, ‘down’, ‘rear’ and ‘forward’ directions with no critical alignment being required. Electrical connection is via an M12 connector with mating cable-sets available as required.
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