There are many questions to ask when first looking at a job that requires a heavy lift crane.  Most of these questions revolve around the loads that will have to be picked up and set down, so we will start the questioning there. 

Usually the first question asked is: What is the heaviest lift?  Although this question is very important, it is not the only question that should be addressed.  Below are some more questions that should be asked before selecting a heavy lift crane:

What are the dimensions of the largest module that has to be set?

Asking the first question about dimensions will give a hint as to whether a jib attachment may or may not be needed at the top of the boom.  If a very large module is to be picked, then a fixed jib or even a luffing jib may be needed to keep the module away from the boom.  Another option is to increase the length of the boom to keep from getting “boom bound”.

What is the farthest the crane has to reach?

Figuring out the crane reach may actually set the boom and/or jib configuration of the crane.  This question will come with other questions such as:

Does the crane need to reach over a building? 

Is there critical infrastructure in the load swing path? 

Are there powerlines in the vicinity? 

The farther the crane has to reach, the more boom and/or jib will be required to make the reach.  This in turn reduces the overall capacity of the crane.  It is also important to keep in mind that in most cases, the farther you have to reach out reduces how close you can pick up a load.  Every crane chart has a minimum radius and it sometimes comes with conditions.  It is important to keep an eye on your minimum and maximum radii as you develop your plan.

What is the weight of the module at the farthest reach point?

Tying in with figuring out how far your crane needs to reach is: what capacity do you require at that radius?  After figuring this out and determining what size crane and configuration you need.  Be sure to go back and revisit other lifts you have to make to make sure this set up can make those lifts.  You may also want to refer to the wind charts to see if changing the configuration around a bit might give you a better allowable wind speed to work in.  It is important to note that just because the crane is capable of lifting 200T at 50 feet, does not mean it will have the ability to set 10T at 200 feet.

What type of rigging will be required to lift the module?

When I mention rigging, I’m not concerned with the exact size of the rigging, but more with the concept, height, and weight of the rigging.  If spreader bars are to be utilized or if the module is very wide, the rigging will have to be fairly tall and therefore increases the overall headroom.  The height of the boom tip is an important factor because it dictates your capacity, wind speed limits, the amount of crane rope deduction required, and minimum radius.  The overall weight of the rigging is also a concern since it is another deduction from the crane capacity.  There should be an adequate allowance for the rigging weight when sizing a crane in the proposal stage.  It is important to walk thru each type of lift to made with the particular crane and having a rigging concept prior to selecting the crane.

Are the weights of the loads estimated weights or actual calculated weights?

Finding out how the weights were determined is more about knowing what risk to take when sizing the crane than the loads themselves.  If the module weights are all estimated, then it would probably be prudent to not select a crane that is at 99 percent of its chart when picking the module.  However, if the weight of the module is known to be an actual weight, then using the full chart of the crane should be a possibility.  Keep in mind any critical lift criteria that your company may have when sizing a crane.  Some groups require a Professional Engineer to review lift plans for any lift above 95 percent.  Some companies or customers may prohibit from using a crane to 99 percent capacity.  It is important to understand the additional costs and reviews that may occur when planning a critical lift.

Going back to the very first question everyone asks, what is the heaviest load?  This question does set one thing, and that is the number of parts of line and the size of block required to make the lift.  These two important parts are critical deductions to make from the capacity of the crane.  The parts of line deduction will vary depending on the crane radius because it is determined by the boom or jib tip height.

We want to make sure you have a successful lift and that starts with proper planning and selecting the correct crane for the job.  We can help in this process by helping to create a lift plan and help size the correct crane for the job.  Here at The Dothea Group, we will do our best to meet your schedule needs and we will provide efficient, engineered solutions to better your project, improve safety, and increase your bottom line. 

If you are interested in learning more about our engineering services, contact us today.  We can partner with you to ensure a successful bid or project.