Gulf Construction Online - Tough debut for Tamrock rig in UAE

Northern Emirates

Tough debut for Tamrock rig in UAE

01 November 2003

Following the successful operation of the first Tamrock Ranger 700-2 surface drill rig in the UAE, leading drill and blast contractor Technical Drilling & Blasting has taken delivery of a second rig.

The first surface drill rig - fitted with Sandvik Rock Tools drilling bits - is working in a variety of quarries where the rock has been described as the 'toughest in the world'.

The rock - high-density gabbro with a density often in excess of 3 tonnes per cu m and a crushing value of 10 - is in high demand for asphalt and concrete production and rock armour for breakwaters.

Technical Drilling and Blasting Company specialises in drill and blast contracts for a number of major quarries throughout Fujairah and also undertakes some civil engineering projects including pipelines across the region. Originally founded in Oman, a subsidiary company was formed in the UAE in 1998, with branch offices in Dubai and Fujairah.

Since the formation of its UAE operation, the contractor has also been using two purpose-ordered Tamrock CHA 660 surface rigs with great success. Says deputy manager, Tom Ross: 'Both rigs have each provided more than 10,000 hours operation. Last year alone each rig recorded more than 4,500 hours.'

Ranger 700-2 rig
The first Ranger 700-2 rig was ordered by Technical through local distributor Dynatrade as it began winning additional contracts with new quarries.

'We wanted a rig to up production and increase the degree of accuracy for our production drilling,' says Ross.
The model features a rear-mounted power pack, which effectively counter-balances feed and boom assemblies, thereby providing an inherently more stable drilling platform. A hydraulically-operated winch complete with cable tightness automatics ensures maximum operator safety.

The turntable-mounted articulated boom and rock drilling assembly offers 120-degree arc movement and a massive 17 sq m drilling area coverage. 'The configuration provides improved drill location range even at the most acute angles,' says Ross.

With a major emphasis on operator comfort and safety, the cabin features laminated windows and both roll over/falling object structure protection to the appropriate ISO standard.

Excellent all-round visibility of the drilling area together with air conditioning, filtered air intake and soundproofing to 80 dB (A), provides the operator with an excellent working environment, he says.
A single multi-function joystick proportionally controls drilling rationale and a number of standard operations are automatically implemented, allowing the operator to focus on the work in hand.

Operations
Technical Drilling and Blasting recently retained its contract with Gulf quarry for a further three and a half years. Located in the foothills of the Hajar mountains, southeast of Fujairah City, the quarry provides more than 900,000 cu m of blasted rock per year.

The quarry, owned by RMC, has at least 200 years of reserve and it is almost a case of moving from one mountain to the next, Ross says. It has at least two years life in its present operation with currently seven working benches - each 15 to 20 m high and maximum bench widths of 80 m as it nears the top of the current peak.

Typically, the rig will spend two to three weeks on-site before moving to other quarries on a regular rota, or as required, working 'round-the-clock'.
Up to 100 holes per blast are drilled by the Tamrock rig at an incline of 5 to 10 degrees, depending on the rock and in a standard square pattern to depths of between 15 and 20 m. Sandvik T51 Retrac drill bits with spherical buttons are fitted to the Tamrock rigs to produce 89 mm holes.

The drilling times are determined by the type of quarry and rock. At Gulf quarry, for example, holes can take 20 to 60 minutes to drill. Drilling at the nearby Fujeirah Building Industries quarry can take up to two hours for each hole. The ground conditions at Gulf quarry are, says Ross, 'a real mess.' The rock is a mix of igneous rock, generally classified as gabbro but is additionally very fragmented.

'This fragmentation can cause the drill rods to frequently stick, causing loss of alignment,' he says.
To overcome this the Ranger 700-2 is fitted with an anti-jamming device, automatic flushing and a power extractor.
'The anti-jamming device is very good,' continues Ross. 'It reduces sticking and when it does occur, the power extractor is used.'

During drilling operations, the contractor is achieving 400 to 500 drilling-metres life out of each Sandvik T51 drill bit at Gulf quarry. For the much harder ground conditions at the FBI quarry, this production rate is reduced to just 100 to 150 m, due entirely to the density and high silica content of the gabbro rock.

Throughout blasting operations, the specialist contractor is using a mix of power gel and anfo, which is restricted to 5 tonnes per blast by the local police. Nevertheless, with the company's expertise and specialist knowledge, it is able to achieve more than 15,000 cu m per blast, he says.