"Making a lift" is a term used to describe using a crane to lift and set an object. The object can be anything and the size determines the size of the crane.
A few years ago, we had a job removing a large conveyor in an industrial facility. The conveyor had been out of use for a few decades and the facility had budgeted the money for demolition.
I had spent the better part of a day measuring the critter. I had taken measurements of the structural members and using the information to determine the weight. Since the conveyor was so old, nobody had any idea of the weight of some of the components. I used wags to determine some of the weights and added a few percent to cover my butt.
Demolition is an entirely different aspect of what I do. In a way, it's a little sad to destroy something I know someone had been proud of building. I know how I feel after finishing a project. Then again, I've been doing this long enough to see things I've built reach the point a little destruction is necessary.
Television likes to show huge building being dropped with shaped charges. The event is filmed, rerun in slow motion and a 30 minute show is played dramatizing the explosion. The tough, nasty, boring part of the process is never shown. Days are spent tediously removing things of value, such as copper, and there are many things that don't require dynamite to dismantle. These things aren't glamorous, but they are part of the process.
Initially, everyone involved with removing the conveyor had determined a large crane was required. My boss, and I, examined everything and decided there was another way. We could remove the conveyor in pieces with a 50 ton hydraulic rig. We were given a purchase order number, so we started the process.
We spent most of the week removing the upper end of the conveyor. It had easy access and was isolated from any live components of the facility. It wasn't an open area, so we still had to use oxygen/acetylene torches to whittle away at components. There were a few larger sections, but they were easy to rig and let to the ground.
At the end of the week, there was a large section remaining that required one lift. It spanned two support columns, so there was only so much that could be removed without sacrificing the integrity of the truss construction. We had removed cover, belts, piping and electrical conduits. What remained was tough to reach, was at the limit of our crane capacity, and would require careful coordination to make a safe lift.
On the morning we removed the section, welders started the day welding some "pad eyes", which are steel clips with holes for shackles. While they were doing this, I moved the crane into the small area that was the only place I could reach the conveyor. I had spent the day before measuring distances and heights. It wasn't the best of areas for access, but I knew the crane would fit, but we'd have to spend some time preparing it for the lift. I would be swinging the load over two buildings, process equipment, piping and electrical trays.
I drove the crane up the narrow area to where it would sit. After extending the outriggers, the crew started placing cribbing (hardwood blocks) to compensate for the uneven concrete and to displace the weight. The wasn't any room for uh-ohs, so we took our time to make sure it was right. After I leveled the crane, I ran the boom out to the position it would be for the lift. I checked the computer; I would have around 2000 pounds of wiggle for the lift - if my calculations were correct. Since I had put a 10 percent safety factor on the weight, I felt comfortable.
I spent a few minutes going over everything in my head. I remembered running the calculations and still felt comfortable, since what we had already removed pretty well verified what I determined. Still, I had a nagging feeling. Mr. Murphy is the ruler of demolition. Mistakes are always dealt with unmercifully.
There's another thing about demolition. It's not like lifting something from the ground and then placing it somewhere higher. When you start from the ground, you probably already know the weight and if it's not correct, the crane computer will immediately shut down the controls if the capacities are exceeded. That's great on the ground. In the air, with something that has all of the supports cut away, losing the controls is a butt clincher at best and a disaster at worst.
I lifted the lifting slings, with shackles, so they could attach the section to the block. We had determined the proper length after using a level to determine the angle of the conveyor and adjusting the lengths to compensate for the unequal distances. They screwed the shackles to the pad eyes and I started winching the main block to take up the slack. A burner, and helper, moved an 80 foot manlift to the upper end so they could cut the upper section away from the supports.
The burner that would signal the lift gave me the signal to start placing a bind on the cables. He stopped me, gave me a signal to adjust the boom, and then continued his signal to tighten the winch line. I watched the scale on the display panel. When we hit about half the determined weight, the burner was satisfied with the tension and signaled for me to stop. He, and the burner at the upper end, started cutting away the supports for the conveyor.
I watched as the molten steel, and slag, showered to to the ground. A helper watched for fires. We had covered the top of a motor control building with fire blankets to keep the roof safe. It would be unfortunate to cause a fire in a building that had a few dozen 480 volt motor controls. Such a disaster would shut down the facility and end our stay forever.
After a few minutes, the burner on the upper end eased his manlift away. The burner on the lower end soon signaled to slowly start winching the block. I slowly pulled the control. Movement by sight was imperceptible, but I knew the line was winching due to the "tell-tale" on the lever, which clicked every few seconds. I watched the scale. It crept higher and higher. At around 4000 lbs from the maximum weight I could handle, the burner signaled for me to stop. For a second I thought he might have needed to cut some more, but he leaned into the conveyor and started to push it sideways. It was free. It was now mine.
He signaled me to start lifting. I slowly lifted the conveyor as he threw the tag ropes to the ground. The burner on the upper end did the same. The crew on the ground caught the lines and started swinging the section to clear the supports.
After I was high enough with the load, the burner signaled me to start swinging. I started the slow swing to my left. As I was swinging the load, the crew slowly walked with the load to keep it under control. When I knew the conveyor was clear, I started slowly lowering the load. I had to clear the equipment and the last building.
I finally cleared the last building and now had the load behind the crane. I lowered it to the ground. As the cables started getting slack, a burner was on top removing the shackles. Before I could lift the cables completely clear, the crew was starting to whittle away the steel to sizes that would fit into the metal dumpsters. The worst was over.
I lifted the cables and started swinging back towards what remained of the conveyor. We had more to do and it was almost time for lunch. I glanced at the large empty hole that used to be a conveyor. After seeing it for so many years, it was a strange sight to see it gone.