Grappling with skull busting
A-Ward Attachments excels at providing innovative solutions for particular, and even peculiar, applications but nothing has proved so challenging, or innovative, as designing a grapple for SteelServ. BY ALAN TITCHALL
SteelServ, part of the Multiserv Group, has an operation at the Glenbrook Steel Mill south of Auckland recovering old 12 tonne iron or steel castings (called skulls) from around the site that were disregarded in the past because of imperfections.
As the price of scrap iron soars, steel mills around the world have been retrieving these skulls and breaking them up into more manageable one tonne pieces for recycling in steelmaking furnaces.
It is standard practice to smash the skulls with a 16 tonne steel ball, dropped from the end of a crane boom through a deep field magnet, until the ore pieces are roughly the right size. The fracturing also breaks off the outer layer of high silica slag covering the skulls.
SteelServ started its skull recovery and bashing operation in May of this year with a 22-hour, two-shift operation that would see work completed by the end of this year. The skulls are lined up in a three-sided pit lined with containers filled with sand to shield the rest of the mill site from shrapnel flying off the cracked skulls. Huge holes ripped in the side of these containers by shards bear testament to the power and energy behind the smashing action.
To speed things up, SteelServ experimented with using a 75 tonne excavator with a grapple hook attachment that could pick up a 12 tonne steel ball and drop it from a height of 15 metres.
“The standard method of skull cracking requires two pieces of machinery, a crane with a 22 metre boom and a loader to feed the steel balls,” says SteelServ manager Keith Grala.
“We decided to trial a one machine approach using an excavator and a grappler to pick up and drop the balls. Without the second machine and operator, we improved cycle times and production. However, we soon found out the wear and tear on the grapple was very severe. The irregularities of the skull places uneven loadings on the tines of the grapple, which created all sort of maintenance problems.”
This is where attachment specialist A-Ward entered the scene. The job was a challenging one, says the company’s Australasian salesman, Chris Wilson.
“The finger ends of the first grapples were literally chewed to bits by the coarse skulls or broken into pieces,” he says. “The loading on this attachment equipment was unusual to say the least. It is picking up over 1800 tonnes of scrap iron every week, which tears away at the strongest metal overlays – it’s like the effect of coral on skin.”
A-Ward designed and made a special, four-finger, non-rotating grapple, with a high tensile frame. It has abrasion plate cladding and domite wear strips from Real Steel, says Wilson.
“The 20mm rams were custom-made, as were the hydraulics and pins. It is all heavy duty stuff.”
It also had to be put together in record time – just six weeks. Over the production period the grapple design has proven a moving feast of adaptations, modifications, and fine-tuning, he says. Each time the grapple was hauled in for repairs and changes, the skull bashing operation reverted back to using the crane and magnet, so time was of the essence.
“We got the mechanical strength of the grabber right and managed to narrow it down to the hydraulics, which were vulnerable to taking rough knocks and leaking. A release value should solve that.”
With the skull smashing operation drawing to a close this month, you have to wonder, has it been worth all the stress and energy to A-Ward?
Wilson says the exercise and experience goes way beyond the Glenbrook Steel Mill project.
“This has been pioneering work with a specialised grappler for this particular application. If it can replace the traditional use of the crane, then we have a huge market overseas with steel mills around the world.”
Keith Grala couldn’t agree more.
“The demand and price of steel has made scrap steel very lucrative,” he adds.
Contractor Vol.31 No.11 December 07-January 2008
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