SYNCHRONISED HOIST HAS MORE SUCCESS THAN CANUTE

The JDN synchronised hoist system has played an important part in the environmental engineering operation at two sites. One being the Tail Sluice at Kings Lynn in Norfolk, and the other located several miles further inland at Denver. A previous hoist used for the work was manually operated with a chain mechanism. The lifting/lowering operation was both slow and required at least a two-man team to co-ordinate the work. When investigating a replacement for the original manual craneage mechanism, an electric hoist was considered. However, the need to negotiate a 90 metre transfer by track from one side of a sluice to the other, with attendant trailing power cables made this an impractical option.

The air operated synchronised hoist supplied was a GH model rated at six tonnes lift and supplied by the MFH company of Leicester. This unit features twin hoists with a common drive shaft operated by a single pendant control unit. The twin hook lifting is ideal for long loads, and the fully synchronised drive ensures that accurate positioning and placement of the dam boards can be achieved under one-man control. Air operation for the lift/lower mechanism, control system, as well as traverse movements on the overhead rail ensures that the equipment is safe for use in outdoor conditions, particularly in areas where conditions of standing water prevail.

The operating speeds (all variable) for the hoists are: lifting with load 0 to 1.1m/min : lowering with load 0 to 3.8m/min, while the traverse/travel speed is 0 to 12m/min. The control unit is a variable speed four button pendant, with maximum air consumption for the whole mechanism being 4.7m3/min. The total weight is 320kg, and a four-coat marine paint finish (230 micron thickness) was provided.