Way to weigh

3 February 2003

Will Dalrymple visits a company that opted for a useful extra feature on its new crane

Mills Manufacturing Technology is a UK distributor of lathes and machines tools imported from Asia. "We often thought it would be great to weigh the machines as they are loaded on to trucks," operations manager Nick Frampton says, but he did not know it was possible.

Now, the company has installed a new crane with an SWF Nova electric wire rope hoist with a built-in load sensor. The NovaMaster lifting gear monitoring system's central computer relies on sensors to calculate the crane's load with a margin of error of 5% (with a tare function included). Sensors on the power supply and motor measure current, voltage and motor temperature, and a strain gauge attached to the rope drum or the rope itself, depending on the model, measure the forces acting on the rope. Mills' hoist displays this information on the control pendant, but it is also possible to specify the information to be displayed on a computer via an RS 232 (standard PC peripheral) port, or on a bridge-mounted screen for an extra fee. Other optional features include safe working period (SWP) and duty cycle monitoring and dual-hoist control.

The new crane arrived at a crucial juncture in the 28-year history of Mills.

A management buy out in 1998 led to the decision to move from East Anglia to a more central location in the Midlands. "We never got people who were passing through," managing director Mike Jenkins says. The company's new warehouse, opposite its showroom in a light industrial business park, did not have a crane. A third party referral led to Granada Material Handling, sole UK distributor for SWF-branded hoists, made by KCI Konecranes. Granada Material Handling buys the hoists and associated electrical parts in kit form, and then fabricates and installs all of the structural steel.

Granada sales engineer Mark Sidwell says that the scales added about £700 ($1,000) on to the £40,000 ($60,000) price of the 16t SWL overhead gantry (which spans 18m and has an under hook height of 5.5m). This weighing system is only available in new SWF Nova hoists.

Installation of the crane was not simple. Delays in legal procedures compressed the schedule and forced Granada to plan the work without a signed order. Then there was the support structure - it transpired that neither the walls nor the floor could support the weight of the fully-loaded crane.

Concrete contractor Turnkey Installations had to bore through nearly a metre of reinforced concrete floor to dig 10 holes, each 2m deep and 1.2m in diameter, for new concrete supports for the pillars. Once the floor was ready, subcontractor Peterborough was able to get a mobile crane in to install the girders. Then the biggest job in lifting in the crane was balancing the two 3.6t girders on the crane, though the boom head was only millimetres below the peaked ceiling as it lifted them into place, says Frampton.