Mobile crane classes, tonnage and radius

Truck-mounted loader cranes · city · rough-terrain · all-terrain · crawler cranes

Crane tonnage is a name, not a capability. A crane rated at 50 t lifts 50 t only at its minimum radius, on full outriggers, with full counterweight and the shortest boom configuration — a set of conditions that almost never describes a real lift. The number that decides which crane you need is the load at the radius and hook height you need it at. This page is about picking the class and building the enquiry; the crane owner quotes the job.

The classes

These are class ranges, not the specification of any particular machine. Models overlap at the edges and vary by manufacturer. Use the table to pick the class, then take the exact figures from the data plate and spec sheet of the machine you are actually offered.

The load chart, and why rated capacity falls off with radius

A crane resists the overturning moment of the load — the load mass multiplied by its horizontal distance from the crane's centre of rotation. Double the radius and you roughly halve what the crane can hold, and the fall-off is steeper than that once the boom is long and low. The load chart tabulates capacity against radius for each boom length and each configuration, and it is the only document that answers the question.

Three things routinely surprise first-time hirers:

• Deductions. The hook block, slings, shackles, spreader beam and any erected fly jib all count against the chart figure. The load available for your actual load is the chart figure minus all of it.
• Configuration. Part-extended outriggers, reduced counterweight, or a boom longer than the minimum needed each move you onto a different, lower line of the chart. A crane set up in a confined position is a smaller crane than the same machine set up in the open.
• Radius is measured at both ends of the lift. The governing radius is the larger of the pick radius and the set-down radius, not an average.

How to specify a lift

The four numbers

1. Load mass in kilograms, with an honest allowance for what you do not yet know — water in a tank, an unaccounted frame, packaging.
2. Radius from the crane's centre of rotation to the centre of the load, at the pick and at the set-down.
3. Hook height — the height of the landing point, plus the load height, plus the rigging height, plus clearance.
4. What has to be cleared — a parapet, a canopy, an existing structure, scaffolding, a live carriageway.

Where the crane stands, and what is under it

Outrigger loads are the whole crane plus the whole load through four pads, so the bearing pressure under a pad is high — far higher than the machine mass divided by its footprint suggests. Basements, podium decks, culverts, service trenches, shallow drainage and slab edges are all reasons to get the outrigger loads from the crane owner and have them checked before the date is fixed. Mats and pads are normal, not exceptional. Separately, confirm the crane can physically get to and turn into its standing position — access route, gradient, overhead obstructions and the swing circle of the counterweight behind the machine.

Overhead services and airspace

Overhead power lines impose exclusion distances and are a stop on the lift, not a caution. Height near an aerodrome, a heliport or a controlled approach brings aviation clearance into scope.

Duty cycle

A single defined lift, a day of repeated lifts and a crane standing on site for a month of intermittent work are three different transactions. Say which one you are asking for, because mobilisation and demobilisation are charged whether the crane lifts or not, and on the larger classes they are frequently the largest single line on the quotation.

UAE practice

• Cranes are hired wet. Operator, rigger and banksman come with the machine and their certification is part of the site approval, not an extra.
• Third-party inspection. The crane and every item of lifting gear carry their own certificates, on their own cycles. Gear used to lift people is inspected more frequently. Check the expiry dates against the lift date.
• Lift plan and appointed person. Anything that is not a routine repetitive lift needs a written plan and a competent appointed person. Sites and consultants enforce this.
• DCAA and aviation clearance. A tower crane in Dubai needs a Civil Aviation NOC, and height clearance can apply to a large mobile crane near an aerodrome or heliport too.
• Road movement. All-terrain and crawler cranes travel oversize: permits, routes, restricted hours and sometimes an escort. Counterweight and boom sections arrive separately on their own trailers, and their standing and unloading space is part of the site plan.
• Road closures and public areas are arranged through the roads authority and the municipality, with lead time.
• VAT at 5% applies to equipment hire.

Permit routes, certificate validity periods and working-hour rules differ by emirate, by authority and by free zone, and they change. Treat everything above as the questions to ask, not as a current legal position — confirm the requirement with the authority, the site and the equipment owner before the machine is booked.

What to state in the enquiry

• Load mass in kilograms, and what the load is.
• Radius at pick and at set-down, in metres.
• Hook height required, in metres.
• Where the crane can stand, and what the standing surface is.
• Obstructions to clear, and overhead services.
• Whether it is one lift, a day, or a period on site.
• Whether you have a lift plan and an appointed person, or need the crane owner to advise.
• Date, time window, emirate and site, and whether a gate pass or road permit is required.

Next

• Cranes on the marketplace — what is listed right now, and the specification points that move a UAE quotation.
• Telehandler classes — a rotating telehandler covers some lifts a small mobile crane would otherwise take.
• Crane operator certification in the UAE · DCAA NOC for a tower crane in Dubai

Other class references

Aerial work platforms · Excavators · Generators · Forklifts · Telehandlers