how to Read Load Chart

How to read a Crane Load Chart

Load Chart Explanation | Calculate Net Capacity | Jib Capacities | Crane Dimensions | Determining Line Pull | Area of Operation | Range Diagrams | Foot Notes | Outrigger Extension | Counterweights | Structural vs. Stability

A crane's load chart is the most important resource a crane operator should know for ensuring crane safety, and for determining what a particular crane is capable of lifting. With all of the different crane manufacturers 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, or Altec, a rough terrain crane such as a Grove, Link-Belt, Manitowoc, Kato, or Tadano, it is important to keep in mind that though many cranes have similarities in their load charts, they also have many differences. Ignoring these differences may lead to the overturning or structural failure of the crane.

Load Chart Explanation

This chart illustrates the gross or rated capacities of a crane. The numbers on top row represent boom lengths of the crane The numbers in the left column represent operating radius Loaded boom angle (means the boom's angle and radius is being measured with the boom loaded with the weight indicated in the chart) The gross capacity of this crane can be determined by either following the radius column and interesting boom length, or following the boom angle column and intersecting the radius or boom length column. The "Stowed jib deductions" row is what you would deduct if the jib was stowed on the base of the boom for the particular boom length.

Gross Capacity Versus Net Capacity

The capacities listed in a cranes 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". Capacity Deductions:

Weight of the main load block•Weight of the Headache ball or overhaul ball•Effective weight of Jib (Stowed or erected and not used)•Weight of all hanging cable•Weight of all rigging•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 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.

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Jib Capacities

The gross capacities in the crane chart below are to be used when lifting with either the 24ft or 40 ft jib. By selecting the jib and the boom angle you will be able to determine the gross capacity lifting on the jib.

Whether you are using a Grove load chart, a Terex load chart or a Link Belt load chart you might see different terms used for the boom extension. Manufacturers refers to the pinned boom extension on their crane chart as a jib, fly, or boom extensions. These are pretty much the same things, they just could not agree on a name. This crane load chart on the left is a typical load chart for a Link Belt to use when you are lifting with the fly. Even though these important items for cranes have many other uses, keep in mind the primary purpose of a jib, fly, or a boom extension is to increase the overall height a load may be lifted.

Dimensions

The illustration below shows the dimensions of the crane, this type of information would be necessary for transportation purposes and for setting the crane up in tight areas.

Line pull

The amount of rope a drum will hoist for a given layer.

This illustration represents the available line pull and maximum winch speed for the crane.•To determine the available line pull first determine the type of wire rope being used, then how many parts of line.

•

Intersect the two columns and you will get the available line pull on the crane. This chart takes into consideration both the line pull of the hoist drum of the crane and the safe working load of the wire rope. Some load charts include the available line pull for each layer of wire rope.

•

As wraps on the drum increase, the line speed will increase -however available line pull decreases.•




Area of Operation

Item Required by ANSI B30.5-1.1.3 Load Rating Chart and OSHA 1926.1433. The work area diagram (chart) identifies operational quadrants and must clearly indicate the areas where no load is to be handled. This chart also shows how the manufacturer separates the different working areas of the crane. It is always necessary to get familiarized with the specific load charts of the crane prior to operating, since each work area diagram is specific to the crane model and mounting configuration. Examples of different working area diagrams are shown below:

Range Diagram

These diagrams assist a crane operator in determining the most appropriate configuration and positioning of the crane. This diagram will show the boom length needed to pick up and lift a load. The range diagram is also helpful when setting up near structures. When deductions for the wire rope are required, a good place in the load chart to assist in making calculations for this would be the working range diagram. The working range diagram to the right is separated into:

Load radius (vertical lines)•Boom tip height (horizontal lines)•Boom jib length (arched sections)•Boom angles (angled lines)•Caution area (prohibited area)•

Load Chart Foot Notes




The foot notes in a load chart must also be understood prior to operating the crane. Each cranes load chart will have specific foot notes pertinent to the particular crane type that must be taken into account to ensure the safe operation of the crane.

Outrigger / Crawler Extension

Many cranes have load charts that only have capacities listed for operations on outriggers fully extended and set. However, this particular crane chart has an option of lifting:

On tires•Outriggers fully retracted•Outriggers fully extended•Outriggers intermediate extended•

Using less than fully extended outriggers can be essential in confined spaces. However, the crane will be substantially less stable. The wider the crane's stance, the further to the tipping axis, the more stable the crane. 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

CAPACITY CHART RATING BASED ON PERCENTAGE OF TIPPING

TYPE OF CRANE %

LOCOMOTIVE 85%

CRAWLERS 75%

MOBILES ON ROUGH TERRAIN

on outriggers 85%

on tires 75%

COMMERCIAL BOOM TRUCKS

on stabilizers 85%

*Check your crane. Above percentages not used by all manufacturers

Counterweights

Some crawler crane load charts also have different capacities for crawlers retracted and crawlers extended. Like outriggers the farther the tipping axis the more stability. Many cranes especially boom trucks do not come equipped with a counterweight. Some cranes come with a standard counterweight. However, some cranes load charts such as this Link Belt mobile crane have variable counterweight configurations. This allows the carrier to travel with a lighter load to comply with weight restrictions on public roads by not hauling the extra weight around. Or work in places such as bridges where the extra weight of the crane is a factor. More counterweight will give you more capacity. For the sake of crane safety operating a crane over the side without the outriggers properly extended can lead to loss of backward stability with the counterweights installed.




Stability (Tipping) vs. Structural Strength

TIPPING CAPACITY / STABILITY

This limit is based on stability of crane or the weight necessary to tip the crane over. Tipping capacities are below the bold lineIt 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.

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 *

FACTORS THAT REDUCE LOAD CAPACITIES PRODUCTION OPERATIONS

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

Pouring Concrete•Steel Erection•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

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