The ground shook as 28,000 kg of lifting force was applied to a corner pole in Tweed Heads, NSW, raising it from the ground. For EnergyAustralia senior crane borer operator, Garry Coppin it felt like an earthquake as he watched the pole and two breast logs, each approximately 1200 mm long, ripped out.
“In my whole 30 years of using a crane borer I have never been able to remove a pole with breast logs and always had to cut them off below ground level,” Mr Coppin said.
Mr Coppin and teams from EnergyAustralia and Country Energy were field testing the first PoleX machine from Redmond Gary Australia. Country Energy had already attempted to remove this pole using two pole jacks plus a 40 tonne crane and a crane borer. They estimated they had more than 30 tonne pull on the pole and couldn’t get it out.
“There were plenty of chain marks and other scars on the pole when we arrived at the site,” Mr Coppin said.
Mr Coppin organised to save some poles that Country Energy had attempted to remove without success and had them cut off to a height of approximately three metres for the test. After a few attempts it was evident that the gripper design wasn’t adequate and so a chainsaw was used to cut flats on the side of the pole. After this was done, the grippers successfully attached to the pole and the pole was removed.
According to Redmond Gary Australia, the PoleX was created in order to address the industry wide problem of safely removing poles. In mid-2008 a research and development project was started to explore several alternatives for equipment that could address the problem of safely removing poles. A four man team of engineers was allocated the task of coming up with a suitable practical solution. The design team had several meetings with major electricity authorities to discuss their work practices and to try and come up with a safe solution to the problem of removing poles. These problems include unsafe work practices, personnel injury resulting from using current methodology, damage to crane borers and downtime for repairs of the machinery.
After 12 months of full time work, a prototype design was finalised. This design concept was sent out to major electricity authorities in New South Wales and Queensland for comment based on their industry experience. A number of suggestions were made and many of these were considered and implemented into the final design.
“Over the years, many firms have tried a number of different methods to remove poles,” Redmond Gary managing director, Andrew Danks said.
“Most crane borers are equipped with pole jacks. These are hydraulic cylinders which are mounted against the pole and fixed to the pole with the aid of chains. These devices are powered by the truck hydraulics and have limited success when it comes to removing poles. Most of these devices have to be assembled from several components. These components include base plates, hydraulic cylinders and heavy chain assemblies. Often, many of these items weigh well in excess of the permissible lifting weight for personnel and as a result, using the equipment is avoided where possible.
“Instead of using pole jacks, many operators will use a crane borer to shake the pole, loosening it in the ground before attempting to lift it. This method has been used for many years resulting in substantial damage to equipment causing costly repairs and equipment downtime.”
More modern machines are provided with load monitors, according to Mr Danks. These load monitors often prevent machines from lifting poles as they often require more power than the rated lifting capacity of the crane borer. In addition to this, modern demands of workplace health and safety have restricted work practices resulting in many authorities having to ban the practice of lifting poles out using the crane borer when the lifting force exceeds the capacity of the crane borer. In addition to this, any crane operator has to know the weight of the load before attempting to lift it.
“When a pole is in the ground, there is substantial friction force to remove the pole from its hole. This force is unknown and therefore the load is unknown and the crane cannot be used in this application. As there is no real data available on how much load is necessary to pull poles out of the ground, some assumptions had to be made to set the machine design criteria,” Mr Danks said.
The PoleX has been designed to have a safe working load of 50,000 kg (lifting capacity). There were other constraints based on the physical size of the machine and mechanical strength so the standard machine has pole diameter capacity of 250-530 mm. A larger machine can be manufactured for a pole up to 700 mm but this version would have limited smaller diameter capacity. After extensive research of common pole diameters in the Queensland and New South Wales areas, it was determined that a machine with capacity 250-530 mm would cater for almost all of the poles.
After the first field trial was completed, the pole grippers were re-designed and the PoleX was retested. The second test was carried out at Cabarita and at the time, there was quite a large crew from Country Energy on the site together with EnergyAustralia fleet manager, Wayne Atkins, and a number of other representatives from EnergyAustralia. The two poles were removed with relative ease.