Mini cranes in a tight spot
By Euan Youdale22 July 2009
Edmonton in Alberta, Canada has been the centre of an oil boom. "We were past busy, beyond frenzy, we just called it stupid busy," Don Lucas says.
The city and province were building infrastructure, ring routes, overpasses, bridges and light rail transit. PCL, the largest construction company in Alberta, was building new LRT stations and lines. One piece of that puzzle was the installation of four escalators.
Encore worked with the Kone elevator company. "Our part was to bring the escalators to site, offload the units, slide them into position and lift one end up to a second storey landing where it rested on steel beams and lower the other end into a concrete pocket in the floor," Lucas explains.
It sounds simple enough but the practical details made it a complex job and access was limited. The escalators were not huge. There was a pair of two piece stairs that had to be put together. Together they were 59 feet (18 m) long and 22,000 pounds (10 tonnes). The smaller pair, each in one piece, were 51 feet (15.5 m) long and 19,000 pounds (8.6 tonnes).
The recessed pit for the escalator foot was usually surrounded by open beams and columns but with a large articulating knuckle boom crane it was accessible. It had one of Encore's custom dead sticks, a five- to nine-foot extendable finger of T-1 steel, ideal for poking under overhead beams and lifting escalators.
Encore used a 75 ton [68 tonne] Fassi 1500 knuckle boom crane on a tandem tridem Kenworth chassis. "To put the technical jargon into real-speak, ‘it's a truly giant crane on a huge truck.' Ten thousand pound [4.5 tonne] lifts are child's play to this girl," Lucas explains.
"To understand the tale of the escalator and the mini cranes, you first have to listen to the story of our first installation," says Lucas. The escalator would rest between two high block walls where the only way to get in was from the ends. At the lower end, the opening had a beam across it about 18 feet (5.5 m) high and another beam at 8 feet (2.4 m).
"We could drive in and set up sideways with the crane directly in line with the final lift, and our crane sitting firmly on the concrete pedestrian platform. That was the other thing; the pocket we were shooting for was over 50 feet away. 11,000 pounds at 50 feet, that's a heavy lift for a truck mounted crane, but still doable," says Lucas.
For the other end Encore put the head of its crane in through a window aperture. The second floor was twenty-five feet (7.6 m) high but, from the steel opening where the escalator would rest, to the 20 x 10 foot (6 x 3 m) window entrance point in the wall it was 22 feet (6.7 m).
Operator Gary lifted both sections of the escalator off the trailers and set them on large rolling platforms, using the boom to push both into position. Both cranes were moved into position. "Once Gary carefully unfolded the boom, pulled the dead end and squeezed it through the opening between the beams, he pushed out the hydraulics and, grabbing both pieces of the big stair at once, lifted them, squeezing the two pieces together."
Precise alignment was needed for them to fit.
Kone called a pre-lift meeting where co-ordination was discussed then lifting started. "Joe winched up slow. That's the way we wanted it, everything in slow motion. Joe lifts, Gary follows, watching his hook; eyeing the escalator as it rose and compensating for that movement with subtle reach and lift adjustments."
Within five minutes the load was level with the second floor. "Joe boomed in, bringing the load back on to the steel. Gary had followed us up, pushing his end forward as we gained height and lengthened his radius, now he let down into the pocket." That was the first one done.
Two weeks later Encore did another, a week later a third and then, in early November, still in balmy weather, the final escalator was lifted in. As it was lowered it became clear that it was too short. The concrete pit was in the wrong place. Weeks became months waiting for the elevator company's call to reinstall.
Change of scene
By that time things had changed. The roof was on and the second floor was covered. "We thought about cutting a hole in the roof, or just taking off a couple of panels, but the thick smell of fresh tar stopped us cold." Neither PCL nor the city would go for that.
An alternative was erecting a temporary girder and raising the load on a chain hoist but that would be a week or two of hard work. Then came the idea to use a pair of mini crawler cranes. "Using two 2.9 ton cranes to do what a 50 ton had done couldn't work, or could it," lucas says. They could be positioned close to the edge of the hole with outriggers either side of it.
After much work, including setting up the cranes in a mock up of the site, to establish if it work or not, a solution was found. The most important measure was the radius. "We had to reach out beyond the edge about a foot and a half to the lift lugs in the upper structure of the escalator and add in another six inches for clearance."
There was one more problem, "One we didn't need and one we never suspected until we peered over the lip of the beams surrounding our drop of doom." Directly below, sticking out from the rising columns was a six-inch pipe, of unknown utility, protruding out another foot and a half.
Check it all out
Charts were checked. "We knew no-one had pulled off a lift like this but, if anyone could, we were the boys to do it. We had years of experience with tight interior work."
It was a three crane lift with the 75 ton Fassi on one end and the two mini cranes on the other. They had to co-ordinate a lift straight up, then, as the united minis continued to hoist, Gary had to pause and follow up and in, swing his load as the stair top was lifted.
At some point the escalator had to be pulled back two feet. They had to boom up and raise the boom. "This is the real test of any crane; can it boom up with weight? Well, of course it can, our spider machines may be miniature, but they are still real cranes."
It could be close as the ceiling was only 9 or 10 feet high but Encore had another trick. "As long as the escalator remained high enough to sit on the upper floor, we could boom in or retract, and pull the load in that way."
Getting the mini cranes in position was the first job. "Jeff lifted them up with one of our 18 ton folders. With the dead stick pulled, he inched them through the beams into the second floor." The set up was better than planned, Lucas says.
The elevator on dollies was manoeuvred into position where the lifting points were below the hooks of the mini cranes. When it came to lifting, the escalator was raised an inch off the deck to see if all was well.
Adjustment was made on the hoists to level the frame and they were ready. "I started the cranes but only got a few feet before Cliff signalled full stop. We levelled again. Jim high, Jeff low. Two more feet, same thing." Don spoke to both operators explaining to Jim that he was too fast and had to slow down, and to Jeff that he was too slow and had to speed up.
The bottom skid lip finally cleared the rim. It jammed, however, when they tried to lower it into the concrete pocket. If the pit was built to the exact length required, then anything less than the perfect angle meant an increase in length that could be enough.
We thought the way to do it was to keep the escalator at the perfect angle and lower slowly, but together. It jammed again but, using a crowbar, it was given a tweak and it broke free and slid the last two inches into the pocket.
"Now we had a story to tell. We had made industrial history. Two 2.9 ton mini cranes had walked into a totally inaccessible area and done the same job we had a 50 ton do before. We owed a debt to the people we work with. Our equipment is top notch but it takes a good man to pull the best out of that iron."