How to Read a Load Chart
important resource a crane operator should be familiar with is a load chart.
This will ensure crane safety and knowledge of each crane’s lifting capacity.
There are many different types of cranes made by different companies and
manufacturers. Knowing how to properly read and understand a load chart is
imperative to the safety of the operator and the well-being of the cranes.
few different types of rough terrain cranes such as a Grove, Link-Belt,
Manitowoc, Kato, or Tadano will all have their own corresponding load charts.
You will also come across unique load charts during the operation of a boom
truck such as a Terex, National, Manitex, Pioneer, or Altec.
important to never swap load charts or reference a load chart that does not
belong to the specific type of crane you are using. This will help you as the
operator stay safe and avoid costly repairs.
Load Chart Explanation
You will find the
gross or rated capacities of a crane on this chart.
You can see that boom lengths of the crane are represented on the top row.
The operating radius are represented by the numbers in the left column.
The boom’s angle and radius are measured with the boom loaded and weight.
This is called the Loaded Boom Angle.
The intersection of the Boom Radius column and the corresponding Boom Length
or the intersection of the Boom Angle Column and the Radius or Boom Length
column will give you this crane’s “Gross Capacity”.
If the jib is stowed on the base of the boom you would deduct the “Stowed Jib
Deductions” row for each corresponding boom length.
Gross Capacity Versus Net Capacity
It’s important when
reading a crane’s load chart that you pay attention to the different types of
capacities it can carry. There is the “Gross Capacity”, “Rated Capacity”, and
The “Gross Capacity” and
“Rated Capacity” are not the actual loads the hook can lift. Be sure when
calculating the capacities that you always add the weight of the item being
lifted. This includes any weight outside of the crane whether it is mounted,
stowed on the boom, or hanging from the boom tip.
You will look to the
“Net Capacity” for the maximum load the crane can carry. To avoid damage or
structural failure the crane’s “Net Capacity” must never be exceeded.
The Gross Capacity
must include the weight of anything and everything that is mounted or stowed on
the boom of the crane or hanging from the boom tip. You will refer to the
weight of these items as "Capacity Deductions".
Capacity Deductions Include:
The Main Load Block’s Weight
Full Load Weight
Jib Weight (Whether it is
stowed, erected, or not being used.)
The Headache Ball or Overhaul
All Rigging Weight
Hanging Cable Weight
Always refer to the
load chart for what the manufacturer of your crane considers “Capacity
Deductions”. These will vary from crane type to crane type.
CAPACITY - CAPACITY DEDUCTIONS = NET CAPACITY
The following are
an example of capacity deductions in the cranes load chart. These items
represent the amount of weight you would deduct from the gross capacity to
determine the net capacity.
When lifting with
either the 24 or 40ft jib you will refer to the “Gross Capacities” in the crane
chart below. The “Gross Capacity” can be determined by selecting the jib and
boom angle you will be using.
The “Boom Extension”
may be referred to using different terms depending on which manufacturer’s load
chart you are using. The “Pinned Boom” is considered a jib, fly, or boom
extension. The names differ between each manufacturer’s chart whether you are
looking at a Link Belt, Grove or Terex but they ultimately mean the same thing.
The chart on the left
is common for Link Belt cranes where they use the term “fly”.
No matter what they
are referred to as the primary purpose of a jib, fly, or boom extension is to
increase the overall height a load may be lifted.
You will find the dimensions
of the crane in the illustration below. Refer to this information when
transporting the crane or setting it up in tight areas.
The “Line Pull”
simply refers to the amount of rope a drum will hoist for a given layer.
The available line pull and maximum
winch speed for the crane is represented in the image to the left.
Determining the of wire rope being
used, then how many parts of line, will allow you to determine the available
The available line pull on the crane
can be obtained by intersecting the two columns. The safe working load of the
wire rope and the line pull of the hoist drum can be found in this chart. On some
load charts you can find the available line pull for each layer of wire rope.
This can be very helpful, but it is not included on all load charts by each
Notice how as the wraps on the drum
increase, the line speed will increase while the available line pull decreases.
Area of Operation
Item Required by ANSI
B30.5-1.1.3 Load Rating Chart and OSHA 1926.1433.
As a crane operator,
you should always take the time to get familiar with the specific load chart of
the crane you will be using prior to operating. Each manufacturer has their own
load chart’s for each individual crane’s model and mounting configuration.
On the work area
diagram (chart) you will be able to determine the crane’s operational quadrants.
The diagram will clearly indicate the areas where no load is to be handled.
This chart also specifies the different working areas of the crane per the
Examples of different working area diagrams are shown below:
When trying to find the most
appropriate configuration and positioning of your crane you should always refer
to these diagrams. It will aid in determining the boom length needed to pick up
and lift a load and setting up near structures. This will help avoid damage and
aid in the safe operation of the crane.
When it comes to the wire rope, and
deductions are required, you will want to refer to the working range diagram.
The working range diagram to the right is separated into:
radius (vertical lines)
tip height (horizontal lines)
jib length (arched sections)
angles (angled lines)
area (prohibited area)
Load Chart Foot Notes
An important part of
understanding a load chart is to read the foot notes. These are especially
important to understand before operating the crane. Each crane will have
specific foot notes that pertain to that individual crane type. To ensure safe
crane operation read these notes carefully and following their instructions.
Outrigger / Crawler Extension
Crane load charts differ by crane
type. This is why it is important to read and understand each one
individually. In this case of the crane below you can see that this has many
lifting options where other cranes only have capacities listed for outriggers
fully extended and set. On this crane type you have the option of lifting:
- On tires
- Outriggers fully retracted
- Outriggers fully extended
- Outriggers intermediate extended
This is especially helpful when operating in small spaces. It will allow you
different options that you may not have with other cranes. However, due to
the options, the crane is considered less stable.
The wider you can
set your crane’s stance the further its tipping axis will be. This creates a
more stable crane. Luckily, some crawler cranes have the ability to extend
their tracks and widen their stance to improve the stability of the crane
when working over the sides.
RATING BASED ON PERCENTAGE OF TIPPING
TYPE OF CRANE
MOBILES ON ROUGH
manufacturers use the above percentages. Consult your specific crane’s
Depending on the
crawler crane’s load charts you may find different capactiies for crawlers
retracted and crawlers extended. Like outriggers the farther the tipping axis
the more stability.
On some cranes you
might find a counterweight. However, you will not find this on all cranes.
Specifically, boom trucks do not come equipped with a counterweight.
On Link Belt mobile
cranes you may find that their load charts show a variable counterweight
configuration. This allows the travel with lighter loads on public roads or
bridges where weight is a factor.
In order to gain
more capacity on your crane you need more counterweight. To stay safe avoid
operating a crane over the side without outriggers properly extended. This
will help avoid the loss of backward stability.
Stability (Tipping) vs. Structural
TIPPING CAPACITY / STABILITY
The tipping capacity
is based on the weight necessary to tip the crane over. It’s important to read
the load chart specific to the crane type you are using to determine the
tipping capacity. The tipping capacity is considered the stability of the crane
and can be found below the bold line. Each unique load chart has a way to
distinguish between the two.
This limit is based
on actual strength of material, boom, jib, etc.
You can find the
structural capacities in a load chart by checking the shaded area, above a bold
line, in bold type or marked with an asterisk *
FACTORS THAT REDUCE LOAD CAPACITIES
3 operations that may cause full load chart
ratings to not apply would be:
Dragline, magnet, and clamshell
All load charts are based on firm level ground. Below is an example of possible
capacity loss due to a crane being unlevel.
This is strictly forbidden by the manufacturer. Crane booms are designed for
maximum strength downward not to the side. This can cause the crane to tip.
It’s important not to rush the swing. Starting and stopping the swing too
rapidly and will cause a side loading condition and runs the risk of tipping.
INCREASE IN LOAD RADIUS:
An increase in load radius happens when a load is applied. The boom deflection
can cause the load to drift away from the crane.