We noticed you're blocking ads.

Keep supporting great journalism by turning off your ad blocker.

Questions about why you are seeing this? Contact us

Font Size

- Aa +

Sat 20 Mar 2010 04:00 AM

Font Size

- Aa +

Pile drilling machines

Torque, not ground weight is the key consideration when purchasing this equipment.

Pile drilling machines
These machines work a hard life although it would be a very reckless operator who uses one near full capacity.
Pile drilling machines
A large piling rig prepares to bore a hole. Technical changes to foundations have seen a switch to heavier equipment.

Torque, not ground weight is the key consideration when purchasing this equipment.

They are big, awkward to shift, and make the earth shake, however most plant managers know very little about pile drilling machines, as their function is managed by specialist contractors. In the GCC, there are several firms working in order to sink the enormous bores needed for high-rise projects.

While the rigs share much in common with the common excavator, there is an important distinction in the way they are rated, as Mark Newton, operations manager, Dutch Foundation explained; “All piling rigs are rated according to the amount of torque power of the rotor, not machine weight”. For example, one of the firm’s machines, a top-of-the range Bauer BG36H produces 36Nm of torque. However these distinctions can occasionally be misleading. “That’s how they are rated, but actually the gearbox on the (slightly larger Bauer) BG40 is the same.” The winches on this larger model are stronger, and that is a decisive factor, according to Newton “More often than not on the large diameter drilling it is the winch that limits the capacity of the machine, not the gearbox.

“The gearbox runs on two speeds. When you are doing normal pile drilling you would only run at 50 per cent, so you’d only be running at 15 tonne, top. There would never be a case where you would need thirty tonnes of torque to drill in to the ground” he explained, adding that full torque would only be used when the machine is installing temporary casings. “You would never use the full torque, especially on the BG machines when you are only drilling. It would rip the Kelly bars (a set of concentric, telescoping bars that transmit torque and downward force to the attached to the auger screw) apart.”

“The Kelly bar, the bar that is attached to the tool is designed to carry 50 percent of the torque for drilling. The maximum capacity of the machine is to turn a temporary casing, not to turn the Kelly bar.” He added “Of course, they don’t sell machines on that basis.”

Chinese

Not every machine that Dutch Foundation runs is a Bauer. Some of the equipment in the firm’s 30-strong fleet hails from China, and is branded Sany. These machines are cheaper to purchace when compared to its nearest rival.

This is too much of a saving any plant operator to ignore. However, the budget equipment has some drawbacks, which for the main part relate to the quality of steel, meaning some adaptations are needed before the machines can be put in the sandpit. “Basically [the modifications are] material strengthening exercises. Most of the machines, which lay their masts backwards the heavy machines - being the Bauer BG40 and the BG36C - lay the mast forward and split them.” Newton explained.
“On the Chinese machines, because the material quality is not as good, we have strengthened completely that trapezoidal arrangement, because we were finding that just a few ups and downs were fracturing it.” Newton said, adding that Dutch Foundations made a number of small modifications such as installing an additional pulley wheel, which impressed the Chinese factory when they visited site. “When Sany came out to see our site, they took our modifications back to the factory and now the later generation machines have incorporated these mods - so we have been a guinea pig in a way” he explained.

Worthy

Despite having to perform these modifications, Newton is convinced that the far-eastern rigs offer value for money. Indicating the large test pile he said: “This is a 1.5 metre diameter pile, 40 meters deep in rock. I wouldn’t put a Chinese machine on it, but on the majority of jobs, I mean shoring jobs, with piles of maybe 20-22 meters the Sany is more than adequate.” He added “I would say that the later generations are a match for the [various European] machines.”

Newton explained that new technology and economies of scale are dictating a shift from drilling many small piles, to fewer, larger bores, which is why his firm, as well as others in the region have been splashing out on the high-end heavyweight machines such as the giant Bauer that is hammering away next to us. “We bought this one for specific reason at the heavy duty end” he said. “Now, the market is tending to go that way and it is a natural progression. The way the market is going it will require more of the heavier duty machines in future.” All of the rigs in the fleet would have been intended for cooler climes, so they have needed the cooling systems to be beefed up for the hot UAE summers.

“Generally, we modify the cooling system because these machines are built for a European climate. We increase the size of the radiators and the oil coolers and we put twin fans on them, which is an improvement on the original single fan. That will be for the majority of our machines for the summer working.”

Operators

Of course, any machine can only be as good as the person driving it. Newton said; “Operator inexperience can do a lot of damage. That’s another advantage of the Chinese machines. They are very simple to operate.” He added that you fix machines like this with spanners, but the more expensive machines, with a large amount of electronics could only be repaired with the use of laptops. All machines in the busy foundations industry are rarely allowed any downtime, and this takes a toll on the wear and depreciation cycles. “They would normally depreciate to a residual value of about 20 per cent over six years.” said Newton. “They do work hard here and they require a huge amount of maintenance.

“The nature of the sites is that with sand everywhere it is very abrasive. Generally from the undercarriages, the tracks, the motors and the drive gears. All get worn and when you’ve got a 1.5 million investment, you want to look after it” concluded Newton.

Arabian Business: why we're going behind a paywall