Applied Research of Australia (AROA) has managed to release its new range without increasing costs from its previous series.

LIKE STEEL bolts have ultra high torque strengths in excess of 320Nm that resist damage by powerful installation equipment and are just as easy to install as steel bolts.

This new product range comes in ultimate tensile strength from 15 tonnes to 38 tonnes and includes a high density version that sink in washeries preventing coal contamination.

The high bolt torque strengths resulted in new nut products with high cap breakout strengths of 40–50ft/lbs preventing the common problem of early cap failure and resultant encapsulation failure.

“We believe that these new products are at the cutting edge of this technology and the best products of this type in the world,” the company said.

AROA is a privately owned company based in Adelaide, South Australia. It was originally established in 1968 as an Australian Government licensed organisation to research and develop various products for very diverse types of industries.

AROA manufactures out of Adelaide under strict supervision and quality control a range of products used in strata reinforcement for civil and coal mining projects.

In 1994 AROA developed a cutable rockbolt reinforcement for the underground coal mining industry. Rock bolts or dowels are used as reinforcement to prevent collapse of the roof and rib walls of the development tunnel.

Rock bolts are installed by inserting a two-part resin capsule in a pre-drilled hole, inserting the bolt which is spun to break open the capsule and mixing the resins together. After resin hardening a nut is turned to apply load to the coal strata.

AROA developed, patented and has manufactured since 1994 the first fully moulded “cutable” rock bolts used to reinforce the rib walls in the tunnels in underground coal mines. This bolt was developed to be used in hand-held drilling and installation equipment also developed by AROA.

Cutable bolts made of glass reinforced plastic (FRP) are used instead of steel bolts on the “to be later mined” side of the tunnel to prevent damage to the mining and conveying machinery and are easily broken up by the shearing equipment.

In 1994 the AROA bolt was different from previous types in that it was fully moulded in one single operation with a fully formed threaded end for nut termination and shank deformations to assist in resin mixing and load transfer.

At the time other bolts used pre-made fibreglass rods which were brought in, cut to length and then had threads or enlarged terminations moulded onto the rod. Although the shank rod was of high strength these “hybrid” cutable bolts were much weaker in critical areas than the single piece AROA product, the company said. Hybrid products have no shank projections or deformations and therefore no means of mixing the encapsulating resin resulting in numerous rib failures.

The weaknesses of the hybrid bolts has led to a negative perception by some miners that think all cutable bolts are difficult to install and expensive due to the necessity to re-bolt sections of the rib walls that have partially failed.

Although the AROA bolt was superior to the hybrid types, it was still much weaker in torque strength than steel bolts allowing it to be damaged during installation by high powered installation machinery.

In 2005 there was a shift by some mines to switch to steel bolts, so AROA decided to re-invent the cutable bolt. In 2006 AROA released the “Eliminator”, a bolt designed to eliminate the most common form of rib failure known as “gloving”, whereby the capsule casing can migrate up the shank of the bolt preventing resin mixing and load transfer.

The eliminator bolt has extra large mixing vanes at the bolt tip creating a very large 25mm “spin diameter” in the hole as it is spun and pushed home. This effect forces the penetrated capsule casing to the back of the hole. At the same time the resins are extracted from the casing and thoroughly mixed by the vanes.

The shank tip is tapered to reduce resin back pressure and assist the mixed resin to travel up the bolt shank and complete the encapsulation. It also has a very high nut thread strength up to 10.5 tonnes.

The eliminator torque strength was still too low and AROA decided to develop it to equal the performance and ease of installation of a steel bolt. In 2007 AROA developed the LIKE STEEL cutable bolts.

To see the range of LIKE STEEL bolts and discuss their benefits, visit AROA at booth B1057 or visit www.aroa.com.au to learn more.