14.01.2020
A question for tower crane experts
The following question was received overnight from one of our readers regarding out-of-service tower crane trolley parking.
The question is: “We're all used to see conventional saddle jib tower cranes parked with their trolleys pulled in tight to the masts and their hooks raised. However I live near a job site where a pair of Wolffkran machines are parked every night with the trolley at the far end of the jib, furthest away from the tower and their hooks fully raised. A few years ago we had another site locally with three saddle jib cranes where every night the hooks were raised but all three cranes were parked with their trolleys mid way along the jib, this was on a MOD site.”
“I can understand if the trolley position helped with weathervaning, but is there another reason for the parked trolley positions?”
“Any one care to enlighten me?”
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emailed comment
Some tower cranes do place the trolley at jib end. Wolfe cranes with short jobs may state this. Go to operators manual.
Samuel Evans
Eric_L
I'm not a tower crane expert, but work for a manufacturer in the industry. My comment would be, when a manufacturer recommends a particular action, it's the result of hours of risk analysis, of study of different solutions, and of testing. Follow it. I know many of you will have a lot of experience, and something don't "feel" right to you, but for any particular model of any particular brand, they manufacturer knows more. Follow their advice, and if you can't for whatever reason, check with them first before going with another solution.
emailed comment
Hi Editor and thanks for your hard work! Regarding your request for answers on the following: The question was received overnight from one of our readers regarding out-of-service tower crane trolley parking.......
My answer in short is: as stated by the manufacturer, then by the site Lift Plan. In detail:- Prior to the crane installation all things have been taken into consideration including the manufacturer's out of service radius for the trolley included in A frame tower cranes or Flat Top tower cranes/hammer head, the location for the trolley can be set depending on any proximity structure being built and temporary works around it like access to top/stairs etc. The trolley needs to be left in clear space all around the crane were the crane can slew 360 degreens including swings and clearance space specified by best practices and standards like LEEA and LOLER98 and BS7121 in most cases a clearance of 500mm or more is needed from obstacles. Training Centers: Most training centers and instructors specify that a crane out of service needs to be maximum height and minimum radius but there is a but! The crane Cannot stay at maximum height as this can glue the hoist up to the stop switch and in the morning the hoist will not move, so on old cranes were this is not digitally done by a computer the crane operator actually goes up all the way till it stops then it hoists down a fraction 100mm+- to keep off the limit switch. When it comes to the trolley the experienced operator will go all the way in till it stops then trolley out 4 or 5 meters this is to keep the hook block away from the tower crane mast/tower sections and away from the crane cabin in some models as high winds can make the hook swing about damaging everything breaking glass in the cabin etc if close to the cabin but again only in some crane models but most new tower cranes are designed with this in consideration. Some cranes maybe left with a dolly weight to counterbalance the crane rear weight/ballast or the trolley is left all the way out to help counterbalance the top of the crane, but this only works in really long jibs like 70m or 100m jib, the manufacturers way would be a dolly weight with a specific designed weight for the specified parking radius, normally the closer to the cabin/tower mast the more weight there is, the more out on the radius the trolley there is less weight on the dolly. I hope it makes sense, if not I'm happy for any other questions I can help!
Regards Ricardo...
emailed comment
In response to the question about where a trolley is parked when the crane is out of service.
I've driven cranes for over 30 years a majority of them on Wolff cranes and on saddles I usually parked the trolley close to the tower. I was then told to park it at the other end of the jib with no explanation as to why it does not effect the free slew of the crane
As for parking it in the middle if that was a MOD site the drivers probably were told that was the radius to park up at
Bob L
emailed comment
If the tower crane is an smaller self erecting crane like an Igo 50, the trolley needs to be retracted past the first fold / hinge of the jib in case a problem occurs in the Pre-start checks & the crane needs to be folded for maintenance of repair.
B Cobbin=
Charmer
Good comments Mick, how you doing pal? How's Nottingham?
Dave Wolverhampton.
emailed comment
I have operated tower cranes for 48 years, saddle jibs are generally parked with the trolley at the heel end of the jib. When Wolff Kraan produced longer jibs, cranes became heavier because of the back ballast increased weight so the trolley was parked at the end for better balance. As long as the chains are removed this should not be a problem.
Any more questions please let me know.
Kind regards Mick Hart
Charmer
The last emailed comment, re the manufacturer guidelines, do you know these cranes and models, configuration,s ? Because I do and can make informed comments.
The 2 cranes mentioned are Wolffkran 6031fl models, 60m jib and 50m jib, the MOD project were Wolffkran 7532fl models with 65, 70 and 75m jibs, and trust me, these cranes need to be in free slew to weathervane, it's not just a manufacturer stating rubbish, it's actually safety critical for out of service conditions.
Get your facts before you make random comments, false or ignorant statements can cause untold confusion.
emailed comment
The crane you talk about it's the manufacture guidelines/ instructions! They seem to think when the crane is in free slew and its windy the crane moves easier! Basically its rubbish what they want, think of a sail! This blows around same as a flag no matter which direction its facing so it's going to move! Some companies insist on it as well.
Alan
Charmer
The comments emailed in are the most accurate, I work for this company, and have done for many years, i don't quite understand the thumbs down?
emailed comment
The manufacturer of the crane will specify the out of service conditions a crane must be placed in - in this case Wolffkran, state that the trolley must be placed at maximum radius where possible to assist in the balance of the crane to enable weathervaning.
However in certain circumstances, i.e site boundary or oversail rights the empty jib can oversail but not the hook block. Wolffkran will permit shorter radius parking, but this must be obtained first from Wolffkran.
The first 2 cranes mentioned are on a site large enough to enable maximum radius, the MOD project was a nuclear licensed project, therefore a physical blue line is placed around the licensed area of operations, out of service conditions did not allow a hook block to be outside of this boundary, so permission was granted to place the trolley at different radii on each crane, while staying within the blue line boundary.
Berkshire
Request for name to be withheld agreed
Michael Brown
I brought that to HTC's attention back in 2004. it states in the WollfKran manuals to park the trolleys there as it increases the effect of weather veining. ie when the cranes are out of service and free slewed the extra windage the trolley and block collect make it easier for the crane to slew with the wind. It is not as far as i know in any other manufacturers manual. Others prefer the trolley under the trolley rope motor or further back in, in this world with more trolley cameras then the trolley is positioned under the charging points at what ever point they are on the jib.