How To Compare Two Cranes Using Load Charts Instead Of Maximum Capacity

The maximum capacity is one of the statistics that appears on the spec sheet, in the sales brochure, and in most conversations about renting a crane, but it is also one of the least relevant when deciding which crane to employ for a specific lift. 

A 100-ton crane is only capable of lifting 100 tons under a specific set of conditions, such as minimum boom length, minimum load radius, fully extended outriggers, and a specified counterweight configuration. When the load moves farther from the crane, the boom extends over an obstacle, or the jobsite prevents full outrigger extension, the crane’s usable capacity can decrease significantly.

Two cranes with the same maximum capacity rating can perform very differently depending on the load radius, boom length, and configuration of the lift. The best way to determine which crane is more suitable for  a particular lift is to understand their crane load charts and then compare rather than relying on their maximum capacity ratings.

Load charts are technical documents that specify a crane’s rated capacity for different combinations of load radius, boom length, and operating configuration. Manufacturers provide these charts for crane operators, riggers, lift planners, contractors, and equipment buyers to determine whether a specific crane can safely perform a planned lift.

Reading and comparing load charts is an important task when selecting between two cranes because the comparison directly affects lifting capability, jobsite safety, project planning, and equipment selection. This article explains how load charts are organized and how to compare two cranes at the specific radius, boom length, and configuration required for a job.

Why Maximum Capacity Is A Misleading Comparison Point

The maximum capacity listed on a crane’s specification sheet is the best-case scenario, a set of conditions under which the crane can lift its maximum rated load. For rough terrain cranes, this usually involves the shortest boom section, minimum load radius, outriggers fully extended to their maximum span, and the full counterweight package installation. In real-world lifting operations, this is not the exact same set of lifts that the crane is called upon to lift.

Let’s say a contractor is looking at two 80-ton and 100-ton rough terrain cranes. On the surface, it seems the 100-ton unit is more powerful. However, where the lift needs to be 60 ft at a 30 ft radius, the rated capacity of both cranes at that lift and radius may be much more comparable than the numbers in the headline imply, such as for industrial equipment picks, precast concrete placement, or structural steel erection.

Depending on the boom geometry, counterweight design, and structural engineering of the crane, in some configurations, an 80-ton crane may be able to lift a higher rated load at a particular radius and boom length than a 100-ton crane. Maximum capacity indicates the maximum for one particular scenario. Load charts provide information to the operator about the crane’s capabilities for the entire spectrum of conditions it is likely to encounter in the field.

What A Load Chart Actually Contains

A crane load chart is a table that lists the capacities of a crane in pounds or kilograms and is divided into two main sections: load radius and boom length. The load for each cell of the matrix is the maximum load that the crane is certified to lift at that radius and boom length under the conditions listed at the top of the chart.

All load charts have governing notes indicating the outrigger configuration assumed, the counterweight configuration used, the type of boom used, and any deductions for wire rope or block weight. A crane with a number of outrigger configurations, counterweights, and jib configurations will have multiple load chart tables, each of which is valid only under the conditions specified.

OSHA 29 CFR 1926 Subpart CC requires the load chart to be on the crane at all times and that lifts be planned based on the load chart applicable to the actual configuration of the crane. A common cause of crane incidents is using the wrong chart, a serious safety violation.

The Four Variables That Govern Every Load Chart

• The distance from the center of the suspended load to the center of the crane’s rotation is called the load radius. The rated capacity decreases with the increase of the radius, and the decrease is not linear. With the increase in radius, capacity decreases rapidly, especially as the length of the boom increases, deflection and structural stress increase. 
• The vertical reach is determined by the boom length, and the lift geometry is defined by the combination of radius and Boom Length. The longer the boom sections, the greater the reach but the lesser the structural strength, and the greater the lever arm on the boom, which reduces the rated capacity at a given radius.
• One of the most important capacity variables is Outrigger Configuration. Rough Terrain cranes can be used with outriggers fully extended, partially extended, or on rubber tires. There are separate load charts for each condition. The widest base and highest rated capacity are achieved with fully extended outriggers. On-rubber operation rating capacity is usually 50-70% less than the full-outrig rating on the chart.
• The Counterweight Configuration has an impact on the overturning resistance of the machine. There are a variety of different configurations of cranes with modular counterweight systems, each with a different chart. Rated capacity will increase at longer radii with the addition of counterweight, but also the transport weight and outrigger ground bearing pressure will increase, which is an important factor on soft soils in the Gulf Coast region.

How To Read A Load Chart: Step By Step

When reading a load chart, the process is the same for each lift that is planned.

• First, check the table to be sure it is the correct table for the outrigger span available on the particular site, the counterweight installed, and whether the main boom or the jib is being used. If the site cannot be extended using the outrigger, then the full-extension table is not applicable.
• Secondly, determine the load radius, the horizontal distance between the swing centerline of the crane and the pick point. Take into account the maximum radius the load may swing out to when swung to a point further away from the crane.
• Third, calculate the length of the boom needed long enough to clear all obstacles between the crane and the landing site and to have sufficient clearance for rigging.
• Fourthly, find the intersection of the desired radius row and boom length column in the appropriate table. This is the crane’s capacity rating under those conditions.
• Fifth, deduct the weight of the total rigging assembly (hook block, shackles, slings, and spreader bars). The net load is the amount of load that can be used for the real pick. When the weight of the load plus rigging is greater than the rated capacity, the lift will not be performed safely with this crane in this configuration.

Comparing Two Cranes At The Same Lift Conditions

Comparisons should be made under the same conditions when comparing two cranes with load charts, meaning the same radius, boom length, and outrigger configuration. Comparing under different conditions will be meaningless. The correct process:

• Specify load weight with rigging, radius, tip height, and outrigger span for the particular site.
• Know the correct load chart table for each crane, depending on its setup
• Determine the rated capacity of each crane by looking it up at the defined radius and boom length
• When planning rigging jobs, deduct the rigging weight from the capacity of each crane to get the net usable capacity.
• The crane that has the higher net usable capacity under those conditions is stronger for that lift, no matter what the maximum rated capacity of the crane.

This can often be an unexpected outcome. A crane with a lower maximum rated capacity can be structurally designed with better performance in the middle of the radius, the boom geometry can be designed to be better at a certain angle, or the counterweight configuration can be designed to have a higher capacity further out on the chart. The only way to determine is to take the actual lift test.

Outrigger Configuration And Its Effect On Rated Capacity

The variable contractors tend to miss out on is the outrigger configuration. In congested urban areas, industrial streets, or in road projects where one side of the crane needs to be adjacent to a structure or traffic lane, full outrigger extension may not be possible. The rated capacities will be much lower on the partial extension load chart in these situations, and the crane will be required to operate at a reduced span.

The percentage of reduction in capacity due to the outriggers being extended varies depending on the crane. In general terms, a 50% outrigger extension will result in a loss of 30 – 50% of the rated capacity when compared to the same radius and boom length with full extension.

Operating on rubber can be 50 to 70 percent less than normal. If a comparison is made between two cranes in a site that has outrigger constraints, compare the partial extension tables, not the full extension tables, as there may be significant differences between the two cranes in relative performance under constrained conditions as opposed to ideal conditions.

Boom Configuration: Main Boom vs. Jib

Most rough terrain cranes have the option of having a jib configuration either as a fixed offset jib or a hydraulic luffing jib, which gives greater tip height and reach than the main boom. There is a load chart for each jib configuration, and the rated capacities on jib load charts are generally much lower than the rated capacities on main boom load charts for the same radius, due to the greater lever arm of the jib from the machine’s center of gravity.

If comparing two cranes for a lift where the jib is being used, the comparison should be based on the two cranes’ jib load charts under actual conditions, not the main boom load chart. The jib geometry may not be as optimized as the main boom geometry, which could lead to a relatively weaker jib chart for the crane.

When ordering a crane for a tall industrial structure, power generation plant, or bridge project that requires a crane’s jib to be used at a specific tip height and radius, always pull and compare jib charts at the tip height and radius the project requires

Technical Reference: Tadano GR800XL vs. GR1000XL

In the Texas and Gulf Coast market, the Tadano GR800XL (80-ton) and the Tadano GR1000XL (100-ton) are the two most popular rough terrain cranes that are compared. The difference of 20 tons on their spec sheet may seem like a lot, but the truth is that it’s not when you compare the load chart and test them under realistic conditions.

Load Chart Comparison at Common Working Conditions:

Representative of typical industrial equipment picks and typical structural steel placement: at 30 feet radius, 60 feet main boom:

• GR800XL rated capacity: approximately 47,000 – 52,000 lb
• GR1000XL rated capacity: approximately 58,000 – 65,000 lb

Longer reach at 50′ radius, 100′ main boom: picks over obstacles or in congested areas:

• GR800XL rated capacity: approximately 18,000 – 22,000 lb
• GR1000XL rated capacity: approximately 24,000 – 29,000 lb

Key Highlights:

• The GR1000XL’s benefit increases with the radius and boom length, as the increased weight of the counterweight and the outrigger spread provide a better tipping geometry at longer distances.
• The percentage difference between the two cranes at short radii and short boom lengths (where the maximum rated capacity is defined) is the greatest. When the working conditions are more typical of most commercial and industrial lifts, the difference is much less at mid-range.
• This is because the GR1000XL has a longer maximum boom length, making it the right tool for tip heights of over about 160′ on the main boom.
• The GR800XL’s lower transport weight (around 21,000 lb less) can help to alleviate the mobilization cost and the complexity of road permits for multi-move projects, which can help to compensate for some of the capacity benefits.

TCO, ROI, And Buying Guide: Applying Load Charts To Purchase Decisions

Direct implications of load chart analysis for total cost of ownership. An oversized crane for the job adds unnecessary acquisition cost, higher insurance premiums, increased transport and mobilization costs, and increased ground bearing pressure requirements, without providing the productivity benefit that is proportionate.

A crane that is consistently too small for the job at its working radius and boom length will be constantly operating at rated capacity, causing wear in the boom structure, fatigue in the wire rope, and stress on the hydraulic system.

The correct size selection, using load chart analysis under actual working conditions, results in the most cost-effective per-lift solution. When considering the purchase of an 80 ton and 100 ton rough terrain crane, the answer should not be “which one has the maximum capacity? It should be: “Which machine can we always use to carry our working loads at our working radii, at our working boom lengths, at our outrigger set-up with an appropriate margin, at what acquisition and operating cost?”

When buying a new crane, ask for the complete load chart, all outrigger configurations, counterweight options, and boom and jib combinations. Draw in all of the commonly used lift scenarios on the chart that apply to each crane. The crane that has your typical working load with a 15 to 25 percent margin below the rated load under those conditions is the correct size crane.

When buying used cranes, a published load chart is based on the condition of the crane when it was first certified. Actual safe working capacity may be less than chart values due to damage to the boom, deterioration of the wear pads, degradation of the wire rope, and deterioration of the outrigger wear.

When using a crane chart value from a used crane, always get a professional structural inspection of the boom section integrity, wear pads, wire rope condition, outrigger cylinder integrity, and load moment indicator calibration.

Local Market Conditions: Crane Selection In Texas And Gulf Coast Applications

There are certain lift conditions in the Texas and Gulf Coast crane market that are particularly beneficial for load chart literacy. In the case of industrial turnarounds, such as refineries and chemical plants, the picks are often made at a controlled radius within the process units where outrigger extension is limited by pipe racks, concrete pads, and other equipment. It is in these limited applications that the load chart comparison gives a different crane ranking than the maximum capacity comparison.

The ground conditions on the Gulf Coast are another factor. In the Houston metro area and coastal industrial area, soft soil, high water tables, and clay-heavy subgrades call for crane mat systems that impact the outrigger load distribution. More matting does not necessarily mean less matting. In some cases, more matting is needed because the more rated capacity a crane has, the more reaction force the outriggers will exert on the matting, and the more matting is needed to distribute the reaction force.

Once contractors become fluent at comparing loads, they can provide a more accurate crane specification when bidding a job, prevent mobilizing a larger crane, which will cost more for the project, and confidently determine when a smaller crane on their fleet will be able to lift a load that looks like it needs a bigger crane.

Operator And Rigger Training

OSHA 29 CFR 1926 Subpart CC states that the operator of the crane must be qualified to read and use the load chart for the specific configuration of the crane. Load chart reading is a fundamental skill in the NCCCO certification exams, and students learn to identify the correct chart, find the correct rated capacities at the given conditions, and apply the proper rigging weight deductions.

However, load chart misuse is one of the most prevalent factors involved in crane incidents. The most common mistakes are using a different outrigger configuration table, not accounting for rigging weight, and using a chart for an outrigger configuration that is different from the one being used.

Fleet managers should make load chart review a part of the pre-lift planning for all non-routine picks:

• Verify the chart that is applicable prior to writing the lift plan.
• Ask the rigger to check that the crane is set up as per the chart being used.
• Record the chart reference, rated capacity at lift conditions, rigging weight, and net available capacity in the lift plan.
• Explain to the operator what the rated capacity is for the particular pick that is going to be used before the lift starts.
• Do not allow changes to the field without replotting the chart under the new conditions: changes to the radius, boom extension, outrigger span changes, etc.

Load chart training that is part of the pre-lift culture results in measurable improvements in safe operations and fewer incidents due to capacity miscalculation.

Final Verdict: Load Charts Reveal the Right Crane for Every Lift

The right crane is not necessarily the one with the highest maximum capacity. Compare load charts using the actual load weight, radius, boom length, outrigger setup, counterweight, and rigging weight. For used cranes, also verify machine condition and chart applicability. Choosing based on real lift conditions helps ensure adequate capacity, safer operation, and better equipment value.

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FAQs

1. Can a lower-capacity crane outperform a higher-rated crane?

Yes, depending on boom length, load radius, counterweight, and operating configuration.

2. Why does load radius matter in crane comparisons?

As load radius increases, the crane’s rated lifting capacity usually decreases significantly.

3. Which load chart applies when outriggers are partially extended?

Use the manufacturer’s specified partial-extension or on-rubber load chart for that configuration.

4. How is rigging weight accounted for in a load chart?

Subtract the total weight of the rigging equipment from the crane’s rated capacity.

5. Does a used crane’s published load chart remain valid?

Yes, but the crane’s actual condition must be inspected to confirm safe operation.

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