Edit How to Read a Load Chart

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How to read a load chartA crane’s load chart is the most important resource a crane operator must be familiar with for ensuring crane safety, and determining a particular crane’s lifting capacity. With all the different crane manufactures out there, it is imperative that the crane’s load chart be well understood.

Whether you are operating a boom truck such as a Terex, National, Manitex, Pioneer, Altec, or a rough terrain crane such as a Grove, Link-Belt, Manitowoc, Kato, or Tadano; it is important to keep in mind the similarities and differences between load charts. Ignoring these differences may lead to the overturning or structural failure of the crane.

 

Gross Capacity vs. Net Capacity

 The capacities listed in a crane’s load chart are not the actual loads that can be lifted on the hook. The values given in the charts are “Gross Capacities” or “Rated Capacities”. The actual load the crane can lift is referred to as the “Net Capacity”. The maximum load must never exceed the crane’s Net Capacity!


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.

 

These are called “Capacity Deductions”. The following are examples of

Capacity Deductions:

1) Weight of the main load block

2) Weight of the Headache ball or overhaul ball

3) Effective weight of Jib (Stowed or erected and not used)

4) Weight of all hanging cable

5) Weight of all rigging

6) Weight of Load


Remember there are many variations, depending on the manufacturer of the crane. Make sure to understand what the manufacturer determines are capacity deductions.

GROSS CAPACITY - CAPACITY DEDUCTIONS = NET CAPACITY

The rated capacity of cranes is divided into two groups.
The following are an example of capacity deductions in the crane’s load chart.

Crane Capacity Deductions

 

 

 

 

 

 

 

 

 

STRUCTURAL STRENGTH - This limit is based on actual strength of material, boom, jib, etc. Structural capacities in a load chart are distinguished by:
Shaded area, above a bold line, in bold type or marked with an asterisk *


TIPPING CAPACITY OR STABILITY
- This limit is based on stability of crane or the weight necessary to tip the crane over. Tipping capacities are below the bold line on thechart. It is of the utmost importance to determine which limit you are using. Each load chart will have a way distinguish the difference between the two.

 

Telescopic Boom Cranes

MAIN BOOM CAPACITY

The procedure for determining Net Capacity is as follows:

1) Determine weight of load to be lifted

2) Determine weight of rigging

3) Determine load radius, boom length, boom angle, quadrants of operation

IF THE ACTUAL LOAD RADIUS, BOOM LENGTH, BOOM ANGLE IS NOT LISTED ON CHART USE THE FOLLOWING PROCEDURES:

a) Radius - Use the next further radius

b) Boom length - Use next longer length

c) Boom angle - Use the next lower angle

4) Determine correct chart for crane configuration

5) Determine gross capacity

6) Determine~ the capacity deductions

7) Calculate net capacity

8) Compare the net capacity to the actual weight of the load if the net capacity is equal to or greater than the load, the lift can be made.

 

MAIN BOOM CAPACITY - Pinned Telescopic

On most cranes having pinned tip sections there are three different cases to consider when determining main boom capacity.

1) With the pinned section retracted (all boom lengths)

2) With the pinned section extended (boom fully extended)

3) With the pinned section extended (all boom lengths)


The procedures are as follows:

1) Pinned Section retracted: Same a telescopic

2) Pinned Section extended (boom fully extended): Same as telescopic except the gross capacity is now found in the column that shows full boom lens and fly section.


3) Fly extended (all boom lengths): Same as retracted (on most cranes, some cranes use two charts) except, the gross capacity is now found in the column that

show full boom length and fly section and depends on actual boom angle only, actual radius and boom length cannot be used.

 

Jib & Boom Extension—Types

The most common types of Jibs and Boom extensions for Hydraulic cranes are as follows:

EXTENSION CAPACITIES - Full boom length

The procedure for determining Net Capacity is as follows:

1) Determine weight of load to be lifted

2) Determine weight of rigging

3) Determine load radius, boom length (including extension), boom angle, quadrants of operation

4) Determine correct chart for crane configuration

5) Determine gross capacity

6) Determine the capacity deductions

7) Calculate net capacity

8) Compare the net capacity to the actual weight of the load if the net capacity is equal to or greater than the load, the lift can be made

 

EXTENSION CAPACITIES - Partial boom length

1) Same as full boom length except, the gross capacity is now found in the column that show full boom length and extension and depends on actual boom angle only, actual radius and boom length cannot be used.

 

JIB CAPACITIES - One Chart

1) Determine weight of load to be lifted

2) Determine weight of rigging

3) Determine jib type and length, jib offset, and math boom angle

4) Determine correct jib chart for type and length being used

5) For the correct main boom angle and jib offset read the gross capacity from the jib load chart. This chart gives both structural and tipping capacities

6) Determine the capacity deductions

7) Calculate net capacity

8) Compare the net capacity to the actual weight of the load if the net capacity is equal to or greater than the load, the lift can be made

 

JIB CAPACITIES - Two Charts

1) Determine weight of load to be lifted

2) Determine weight of rigging

3) Determine jib type and length, jib offset, and main boom angle

4) Determine correct jib chart for type and length being used

5) For the correct main boom angle & jib offset read the gross capacity from the jib load chart

6) On the Jib chart read the gross structural capacity of the jib based on jib offset & actual main boom angle

7) Select the proper main load chart for the quadrant you are working in

8) From the main boom chart check the tipping capacity listed for the actual length of main boom (do not include jib length) and the actual load radius (do not use boom angle)

9) The lower of those two numbers is to be used as the gross capacity of the crane

10) Determine the capacity deductions

11) Calculate net capacity

12) Compare the net capacity to the actual weight of the load if the net capacity is equal to or greater than the load, the lift can be made

 

JIB AND EXTENSION CAPACITIES - One chart

1) Determine weight of load to be lifted

2) Determine weight of rigging

3) Determine jib and boom extension type and length, jib offset, and main boom angle

4) Determine correct load chart for boom extension and jib combination

5) For the correct main boom angle and jib offset read the gross capacity from the jib load

chart. This chart gives both structural and tipping capacities

6) Determine the capacity deductions

7) Calculate net capacity

8) Compare the net capacity to the actual weight of the load if the net capacity is equal to or greater than the load, the lift can be made

 

 

FACTORS THAT REDUCE LOAD CAPACITIES PRODUCTION OPERATIONS:

Full load chart ratings may not apply when certain operations are being done:

1) Pouring Concrete

2) Steel Erection

3) Dragline, magnet, and clamshell work, etc.

 

SWING RATE:

Starting and stopping the swing to rapidly and will cause a side loading condition.

 

INCREASE IN LOAD RADIUS:

When load is applied the boom deflection will cause the load to drift away from the crane, increasing load radius.

 

SIDE LOADING:

Crane booms are designed for maximum strength downward not to the side. This is strictly forbidden by the manufacturer.

 

UNLEVEL CRANE:

All load charts are based on firm level ground. Below is an example of possible capacity loss due to crane being unlevel.

 

IMPROPER USE OF OUTRIGGER’S:

The load charts for carrier mounted or RT cranes are based on several configurations. It is very important to crane safety that the crane operator understands how the load chart distinguishes these.

1) On Outriggers – Straight down, Mid span, or fully extended

2) On Rubber – pick and carry, stationary or partially retracted outriggers may require a crane operator to use this chart. Keep in mind the crane chart for on rubber capacity contains capacities substantially lower than the crane chart for on outriggers.

Outrigger Stability

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