Most crane quotations go wrong before the first email, because the enquiry describes the building instead of the crane. Here is what to measure, what to send, and which details change the price most.
Start with the load, not the crane
Capacity is the maximum mass the crane is rated to lift, and it includes everything hanging from the hook: the load, the slings, the spreader beam, the magnet, the grab and the bucket. Buyers routinely specify the weight of the product and forget the tackle. A 12 t casting in a 1.5 t lifting beam on a 0.4 t spreader is a 14 t lift, and a 12 t crane cannot do it legally or safely.
Two more things belong in the capacity decision. First, is the heavy lift occasional or routine? A 20 t lift once a month on a crane otherwise handling 5 t is a different machine from one doing 20 t every hour. Second, does the load have to be lifted off-centre, or with a long spreader? Off-centre loading twists the bridge and increases the load on one wheel, which is a structural issue, not a hoist issue.
Write down: heaviest load + tackle + spreader, and how often. That is the first line of a specification.
Span is measured between the rails, not across the building
Span is the centre-to-centre distance between the two runway rails the crane travels on. It is rarely the same as the building width, because the runway beams sit inboard of the columns, and a typical difference is 1–2 m. Getting this wrong by 500 mm produces a crane that either cannot be installed or has a hook that cannot reach the far corner.
If you do not have a drawing, measure between the two rail centres of the existing crane, or between the web centres of the two runway beams. If there is no crane yet, give us the building width and the column details, and we will propose a span that keeps a sensible hook approach at both ends. Hook approach — the distance from the hook to the nearest wall or column — is what actually determines whether the crane is useful in your bay, and it is the number nobody asks about until the crane arrives.
Lifting height and the headroom you forgot to measure
Lifting height is the distance from the floor to the hook at its upper limit. Measure it as height above the floor you actually work on, and be careful with pits, raised platforms and mezzanines — a crane that clears the main floor can still be unable to lift a load out of a pit.
Then measure the space above the crane. The top of the crane to the lowest obstruction (roof truss, purlin, light fitting, duct, sprinkler pipe) is your headroom, and it decides whether a standard hoist fits or you need a low-headroom machine. On a single girder crane, lowering the hook height by 300–600 mm with a low-headroom hoist usually costs less than any alternative, and raising a roof costs far more. If the measurement is tight, send a photo of the obstruction with a tape measure in the frame.
Duty class: the number that moves the price most
Duty class describes how hard the crane works, not how heavy the load is. It is expressed as A1–A7 in the Chinese classification, FEM 1Am–2m, or ISO M3–M7, and all three describe the same idea: the number of load cycles, how fully loaded the crane runs, and how long it runs each day.
Some sense of the range: a maintenance crane lifting a few times an hour is A3–A5. A production crane in a two- or three-shift workshop is A5–A6. A grab crane in a waste plant, a ladle crane in a foundry, or anything with the hook moving continuously is A6–A7. The same 20 t crane at A5 and at A7 will differ substantially in motor sizes, reducer rating, brake size, rope safety factor, wheel material and girder stiffness — and in price.
Specifying a light duty class for heavy duty work is the most expensive mistake in this list, because the failure arrives after the warranty conversation has already gone badly. Tell the supplier what the process does, not what class you think you need. A supplier who will not classify the duty with you in writing is a supplier to be careful with.
The details that decide whether the quotation is usable
Once the four numbers are clear, add these. They take ten minutes and save weeks:
- Power supply — voltage, frequency and phases at the site. 380 V / 50 Hz is standard in Vietnam; 415 V / 50 Hz and 440 V / 60 Hz also occur. Tell us if the supply is from a generator or unstable, because that changes the panel and the drives.
- Control position — pendant (operator on the floor), radio remote (operator walks with the load), or cabin (operator above, looking down). Each changes the crane and the price.
- Environment — indoor or outdoor; dusty, humid, corrosive or coastal; explosive atmosphere; food-grade area; high ambient temperature. A crane in a coastal yard in Vietnam needs a different paint and protection system from one in a dry inland workshop.
- Operating hours — shifts per day and days per week, plus the number of lifts per hour if you know it.
- Site constraints — door sizes and the route into the building, because the crane has to get in. A 30 m bridge girder will not go through a 3 m door, and planning the shipping split after the order is how schedules slip.
- Destination port — so the offer can be given FOB, CIF or DAP with a real number rather than a guess.
A checklist you can copy into your enquiry
- Crane type (overhead single girder / double girder / gantry / other)
- Capacity: heaviest load + tackle, in tonnes, and how often it occurs
- Span: rail centre to rail centre, in metres
- Lifting height: floor to hook at upper limit
- Headroom above the crane, and any obstruction above it
- Duty: shifts per day, lifts per hour, continuous or intermittent
- Control: pendant / remote / cabin
- Travel distance along the runway
- Power supply at the site
- Indoor or outdoor, and the environment
- Destination port and required delivery date
- Photos: the bay, the existing crane nameplate, the obstruction above
Send that and any competent supplier can quote properly in a day. Send "we need a 5 ton crane" and you will get a price that is wrong in one direction or the other — usually both.
Questions about your own project? Send the capacity, span, lifting height and duty and we will tell you honestly what we would specify — send an inquiry or message us on Zalo.