Tower Crane Load Charts & Lifting Capacity Curves — Reading the Spec for UAE Sites

The brochure says 16 tonnes. The schedule was built assuming 16 t. Then the lift planner pulls the load chart and the actual number at the planned 55 m radius is 3.4 t — and the precast panel weighs 4.8 t.

This conversation happens on UAE high-rise sites more than anyone wants to admit. The brochure rated max load is the capacity at minimum radius, near the slewing platform — it is almost never the number you’ll lift to. The number that matters lives further out the curve, usually at the jib tip, often a fraction of the headline figure.

The load chart is the only paper in the crane folder that tells you what the machine will actually do at the radius where your real lift sits. Reading it correctly is the difference between a lift plan that closes and one that loops back through procurement at three weeks’ notice. For the broader question of which crane to pick in the first place, see the tower crane selection guide. This article is about reading the chart once a crane is in the frame.

Why the brochure number is misleading

Every crane manufacturer markets on maximum lifting capacity. Yongmao sells the STT293 as “16 t,” Potain the MCT 385 as “16 t,” Zoomlion T7530 as “25 t.” These numbers are accurate at minimum radius, with the trolley parked as close to the mast as it can sit — useful for pour-bucket cycles near the base and lifts that only clear the perimeter of the mast. For everything else — facade panels, MEP modules, precast spandrels — the trolley is somewhere out the jib, and the capacity there is a fraction of the headline number.

A site engineer who specifies a crane by brochure capacity alone is buying the wrong machine roughly half the time. The right question is never what’s the max capacity? It’s what does this crane lift at the radius I actually need?

The two axes of a hammerhead load chart

A standard hammerhead (saddle-jib / flat-top) load chart is a 2D curve:

• X axis: radius — horizontal distance from the centre of the mast out along the jib, in metres. The trolley travels along this axis. Minimum radius is typically 2.5–4 m; maximum is the jib length (50, 60, 70 m, whatever’s configured).

• Y axis: capacity — the safe working load at that radius, in tonnes.

The relationship is inverse: as radius increases, capacity drops. Sometimes gently close-in, sometimes steeply at the tip. The exact curve depends on the crane’s structural design, jib bracing, hoist rope reeving (single-fall vs double-fall), and counter-jib ballast.

On a printed chart you’ll see two zones:

1. Constant-capacity zone (the “max load zone”) — from minimum radius out to typically 15–25 m, capacity is flat at the rated max. The crane lifts its full advertised load anywhere in this zone.
2. De-rating zone — from the end of the constant zone out to maximum jib radius, capacity drops along a curve to the tip load. This is where most real high-rise lifts happen.

Tip load — the most important number

Tip load is the capacity at maximum jib radius — the smallest number on the chart and the most important for high-rise lift planning, because the further out the hook reaches, the more of the floorplate one crane position can serve. For most modern hammerheads tip load is 12–18% of rated max at single-fall reeving:

Indicative — always read the actual OEM chart. The pattern is consistent: tip load determines whether the crane can serve the far perimeter of a high-rise floorplate, not the brochure max.

UAE site engineers regularly spec a “16 t” crane for a facade lift, then discover at lift planning that the panels are 3.8 t and tip load is 2.5 t. Three options at that point: shorten the jib (often impossible), add a second crane position (AED hundreds of thousands and weeks of programme), or step up to a larger crane.

Worked example: Yongmao STT293 at 70 m jib

A representative load curve for a Yongmao STT293 with the 70 m jib in single-fall reeving, UAE site conditions, no wind derate. Numbers indicative — verify against the OEM chart.

Read this carefully. The brochure says 16 t. At 30 m radius (a normal MEP-module or pour-bucket position) the capacity is 8.4 t. At 55 m radius (where you’d lift a facade panel from the perimeter of a high-rise) it has dropped to 3.6 t. At the 70 m jib tip, reaching the opposite corner of a wide floorplate, capacity is 2.2 t — 14% of the brochure figure. The “16 t” is honest. It’s just not the number you’ll lift to.

Reading a luffing jib chart

A luffing-jib crane adds a third dimension: jib angle. On a hammerhead the jib is fixed horizontal and only the trolley moves. On a luffing crane the entire jib pivots up and down, so radius is a function of both jib angle and trolley position.

The load chart becomes a 3D surface — in practice, several 2D curves stacked, one per jib angle (15°, 30°, 45°, 60°, 75°, 85° from horizontal). The same weight may be possible at multiple radii depending on angle; the operator effectively luffs the jib up to reduce working radius and unlock more capacity.

Practical implication: the lift planner must specify both radius and jib angle. “We’ll lift 4 t at 40 m radius” is incomplete — the crane might do it at 30° but not 60° because load-path geometry changes against the building. This is part of why luffing cranes carry higher operator-training requirements in the UAE.

The math behind the curve — bending moment

The load chart isn’t arbitrary. It’s the crane’s bending moment envelope at the mast. Simplified:

Bending moment (kNm) = Load (t) × Radius (m) × 9.81

A 16 t lift at 10 m radius produces ~1,570 kNm of moment. The same 16 t at 40 m produces ~6,280 kNm — four times the moment for the same weight. Past a certain moment the mast, foundation, slewing ring and jib root bracing are over-stressed. The load chart is the curve along which moment stays within the structural envelope.

Two consequences:

1. Mast grade is driven by max bending moment — from the lift schedule against the chart, not the brochure rating. The L46A1 vs L68B sizing guide and L68B grade selection guide trace back to this number.
2. Foundation reaction loads come from the same moment envelope. Pad sizing (typically 6×6 m to 12×12 m) flows from the OEM’s reaction-force envelope, built off the load chart. The UAE sandy-soil foundation design guide covers how this lands on the pad spec.

UAE-specific derating — heat and wind

The chart you receive is the OEM’s structural envelope at nominal conditions. Three derates apply for UAE operations:

Heat and motor cooling

The hoist motor’s continuous rating drops as ambient temperature rises. European-spec motor packages are rated to ~40°C; UAE summer routinely hits 48–52°C. Brake fade, gearbox oil viscosity and motor winding temperatures all degrade. The structural chart doesn’t change, but duty cycle and lift speed do — continuous lifts-per-hour can fall 20–30% in July and August. UAE-spec cranes ship with enhanced cooling; worth specifying.

Wind derating

The OEM ships an operating-wind table alongside the chart:

• 0–9 m/s sustained: 100% capacity, full chart applies
• 9–15 m/s sustained: derate per OEM table — typically 70–85% of nominal, reduced speeds
• >15 m/s sustained or >20 m/s gust: stop lifting, prepare to weathervane

The 9–15 m/s band is where most UAE shamal-storm lifts get cancelled. The wind and shamal storm guide walks through the decision tree for marginal wind days.

Dynamic versus static lifts

The chart shows static capacity. Real lifts are dynamic — hoist acceleration, slew swing, brake stops and trolley motion all add transient load on top. The OEM publishes a dynamic factor table (typically 1.10–1.25) that must be applied as a multiplier on the lifted weight before checking against the chart. A 6 t panel at 1.15 dynamic factor needs 6.9 t of chart capacity at that radius, not 6.0. Forgetting this is a common lift-plan error.

Common UAE lift situations

Three situations come up repeatedly:

1. Precast facade at 55 m+ radius onto a 70-floor tower. The classic use a luffing crane or step up to 25 t call. A “16 t” hammerhead with 70 m jib delivers ~3 t at the tip — inadequate for heavy spandrel beams. A 25 t hammerhead or luffing jib gets 4–5 t at the same radius.

2. MEP module lift at 25–30 m radius. The hammerhead’s sweet spot — capacity is still 50–60% of brochure. A 16 t flat-top handles most MEP modules under 8 t.

3. Pour bucket near the base, radius 5–15 m. Max-capacity zone — full rated load every cycle, limited only by motor duty cycle. This is where the brochure number actually applies.

What site engineers get wrong

Five mistakes we see at quote-review stage:

1. Speccing by brochure max load, never reading the chart. Default mistake; catches up at lift planning.
2. Ignoring rigging weight. A 200–400 kg spreader bar plus slings and shackles is part of the hook load. Subtract it before checking the chart.
3. Forgetting the dynamic factor. Apply the OEM’s 1.10–1.25 multiplier before checking capacity at radius.
4. Not asking for the chart at the bidding stage. Most common quote problem. The chart belongs in the equipment file at quote, not at erection. If a supplier won’t share it pre-contract, that’s a flag.
5. Picking a jib length too short for the building geometry. A 65 m jib that almost reaches the far corner is worse than a 75 m that comfortably reaches — at marginal radii the tip-load math gets brutal. Either commit to the reach or rethink the crane position.

How HOE engineers use the chart at quote prep

When a contractor sends us a project — floorplate, floor count, critical lift schedule, wind region, crane position envelope — we run the actual lift schedule against the candidate cranes’ load charts. The output is a one-page summary: at each critical lift, what does each crane deliver with rigging weight subtracted and dynamic factor applied?

This often surfaces a crane cheaper than the contractor’s first pick because it has a smaller brochure capacity but a more favourable chart shape at the radii that matter. Or it confirms a larger crane is needed for two specific lifts — at which point the conversation shifts to whether those lifts can be re-engineered (smaller modules, ground-level pre-assembly, alternate crane position) rather than buying a 25 t machine for two lifts in a six-month project. The chart is the spec sheet that earns its keep.

Getting started

For load-chart support on a project you’re scoping — including the lift-schedule modelling described above — send the project parameters to inquiry1@hoe.ae or call +971 50 144 4810. For a quote on a crane already in the frame, the contact page routes to the right engineer. For a crane already on site that’s hitting capacity issues at unexpected radii — usually a wind, dynamic-factor or rigging-weight miss — the 24/7 breakdown line is +971 4 880 3079.

Full equipment list at /products; the broader crane selection conversation starts at the tower crane selection guide. The FAQs below cover the load-chart questions that come up most often at quote stage.