Slow trip north for a record load

EASY DOES IT: The three-truck convoy carrying Top Energy's new transformer to Pamapuria took special care crossing the one-lane bridge at Rangiahua. PICTURES/SUPPLIED

What has 142 wheels, pumps out 1590 horsepower, weighs 190 tonnes and needs three drivers to keep it on the road? The biggest thing ever seen on Northland roads.

The convoy that made its way from Auckland to the Top Energy substation at Pamapuria, eight kilometres south of Kaitaia, to bring a new transformer, part of a multimillion-dollar rebuild of the lines company's network in the Far North, consisted of three 'prime movers' (trucks), two of them pulling and the other pushing a 112-wheel trailer.

At 85 tonnes the transformer is thought to be the heaviest load transported on Northland roads.

The trailer was pulled by a Mack CL600 and a Scammell S64; pushing from behind was a Scania 530. Each truck was capable of 530 horsepower, and all up the beast weighed 190 tonnes.

The convoy travelled from Ports of Auckland to Mangamuka on Monday, making good pace on straight sections of highway but dropping to walking pace, and using the full width of State Highway 1 on the sharpest bends. Challenges on day one included the one-lane bridge at Rangiahua, where there were just centimetres to spare between the trailer and the guard rails on either side.

Tranzcarr heavy haulage Mike van Ravenstein said the Manukau-based company had transported far heavier cargo, but the transformer was "getting up there" in terms of the biggest thing that could be moved in Northland.

The real challenge was getting it over the Mangamuka Gorge. The trailer was too long for the Mangamukas' twisting terrain, so the transformer had to be jacked up at Mangamuka Bridge on Tuesday morning so it could be reduced in length by four axles. That took much of the day, the journey resuming at 4.30pm and ending at Pamapuria a little over two hours later.

The transformer was unloaded using a gantry crane system.

Mr van Ravenstein said three months of planning had gone into the job. He had carried out a thorough route survey, but found the Mangamukas provided the only possible route.

"It's been a bit of a headache but it's all coming together," he said.

Top Energy spokesman Peter Heath said the heaviest load previously shifted on Northland roads was believed to be a 79-tonne component of Kaitaia's triboard mill. And while the Mangamuka Gorge was not New Zealand's steepest road, it was one of the most challenging for heavy transport.

Kaitaia's existing transformer was bought second-hand in 1979, and had developed a significant fault last year, he added. Its replacement would be operational by the end of next month, and was expected to last 80 years. It would convert the 110kV supply entering Kaitaia to 33kV, then feed the substations at Okahu Road (Kaitaia), Pukenui and Taipa, and Juken NZ's mills in Kaitaia.

Mr Heath said it was more efficient than the existing unit, and could be easily scaled up if Kaitaia's power demand increased in future.

Ancillary equipment, such as radiators, are to be transported north separately.

It was built by Alstom Grid, in Jakarta, Indonesia. A new transformer for the Ngawha power station was made in the same factory, and arrived in Auckland aboard on the same ship on Friday and is due for delivery some time over the next couple of weeks.