Hello Experts, I am working out cycle time for a multiple lifting operation using the LR-1600. The operations involve lifting elements of 20 MT from a certain location, swinging to the assembly point and then placing the elements in position. The radius of operation ranges from 22m to 24m. I am trying to see how much time would I have to account for the swing of the crane back and forth, to pick up the elements and then to swing back to lift the next one after assembly. The assembly comprises of 100+ elements and therefore the total swing time becomes significant. Looking into the Crane Specifications, I note the RPM mentioned. But, I assume that the speed of swing is not necessarily the same with load and without. Can anyone please help what time should each swing of the crane take? Thanks very much, in advance.
How far do you have to swing, what kind of obstacles are in the way? Are you lifting from the ground to 200' in the air, or from the ground to the ground 10' up? What kind of wind load on the "elements". Great big like a sail, or small physical size pieces? Take a long time to rig up each piece, or are they simple to rig onto? Is there a large change in radius from where they are built to where they set? If you have to do a lot of change in radius, that takes a lot more time than the swing. If its just pick one piece up, swing it 90degrees and set it down, you should be able to set one piece about every 10-15 minutes, depending on how long/ complicated each piece is to rig up, and how precise the placement is where they set it down. All that changes if you're walking the crane 20' each time, and the pieces are 15' wide and 150' long. If I'm just setting wood trusses on a house, I can set a truss every 2-5 minutes, but they don't weigh very much (under 200-500lbs) but thats using a small crane (small cranes move faster). All in all, it doesn't take very long to swing, rigging and unrigging the item and placement takes way more time than the actual swing of the load.
I don't know much about doing lifts but it seems like there would be too many variables to have a set time for swing and those variables could change throughout the day.
Many thanks and sorry for not giving better details. I am more used to metrics and I will try to explain as much as I can the work. We are using keystones to build a tower. Each keystone is an arc of 6m length (20´), 3m height (10´) and 300mm thick (12"). We are building rings that are decreasing in diameter to reach the top of the tower. Each ring is made of 3 or 2 keystones. The keystones weigh from 20 MT (40k lbs) to 14 MT (28k lbs). The crane position is fixed. The hook has to operate from the outer diameter of the tower to the point of the pick up of the keystones. The final height of the tower would be 80m (300´). To achieve this we will have to move 84 pieces. There will be no obstacles along the path of the swing as the path will be kept deliberately clear. Rigging of the keystones will happen at the ground. As we progressively build the tower, the unrigging will happen at the constructed height. In order not to lose time in crane travel, we are planning to keep the position of the rigging of the pieces fixed. An auxiliary crane will place the keystones in the lifting position for the LR1600. The swing time becomes significant as it has to swing back and forth a minimum of 84 times. Thank you, once again, for taking time to respond. I would very much appreciate any more valuable advice.
Thank you for your reply. I agree. The idea is to arrive at the maximum time for swing and adopt it as the outer limit duration for swing operations. Regards, Ram.
Are you looking for this info to bid the job? Sometimes the job just takes as long as the job takes. Stuff happens and changes along the way.
The liebherr lr 1600 swings at just less than 1 revolution per minute. If you only have 84 picks to make, thats less than two hours if you have to turn a 180 degrees each lift. If the tower is 300' tall, you're going to have 350' minimum of boom in the crane. Line pull is 39,000, so you'll have to have a minimum of two parts of line. So to lift a block from the ground to the top of the tower, will take reeling in at least 650' of cable. It only runs a max of 450' per minute, and you'll probably not be cabling up at full speed, with 40,000 lbs on the hook. So it will take two minutes to reel it all in, and another two minutes to reel it all back out for the next lift- four minutes of running cable vs. less than a minute of swing time. So- it will take longer to winch the block up and down, than it will to swing it into place. Since you can both winch and swing at the same time, the swing time isn't going to be the limiting factor, because it will take longer to winch it up, than it will to swing over into place. If I was guessing on the from the info you've posted. I'd say you would be doing well to average setting 3-4 blocks per hour. It will get slower the higher you get on the tower, and it depends how much bolting/ welding/ being precise with setting them down takes. I wouldn't be surprised if there were times when you can only get one or two blocks set in a hour, if they aren't fitting right or have troubles lining up or its a complicated rigging procedure. If I was configuring the crane, a short luffing jib would be really nice vs. just a main boom set up. 280' of main with a 80' luffing jib or so. That way you can just move the luffing jib to change radius for each block, and don't have to move the main boom.