Three different questions
- Working. The wind the machine may lift in, from the manual for that model. If the manufacturer gives no figure at all, section 14.92(4) fixes it at 50 km/h (30 mph) — and lower whenever a load cannot be handled safely.
- Erecting, climbing and dismantling. A considerably lower figure, because the structure is not complete and sections are hanging in the air.
- Out of service. What the crane must be left in when nobody is on it — jib free to weathervane, and the machine set up as the manual requires.
Section 14.92(6) says it in the Regulation's own words: a tower crane must not be erected, operated or dismantled when the wind exceeds the upper limit the manufacturer specifies for erection, operation or dismantling.
The erecting limit is the one that gets misread. People quote the working figure because it is the one they know, then plan a lift around it. On our own machines the limit for erecting, climbing and dismantling is well under the figure they work to in service, and the job sheet carries the erecting figure rather than the working one for exactly that reason.
Where the number comes from
The manufacturer's manual for that specific model. Not the standard, not a rule of thumb, and not the other crane in the yard — 2 machines from the same maker may not share a figure, and you cannot assume they do. If somebody quotes you a wind limit without naming the model, they are guessing.
How the wind gets measured
Section 14.92 requires an anemometer mounted on the crown, apex or operator's cab of every tower crane, with a readout the operator can read from the controls. A forecast is for planning; the anemometer is what stops the lift. CSA Z248 sets a fallback of 32 km/h (20 mph) for erecting, climbing and dismantling where the manufacturer gives no figure — considerably more conservative than the 50 km/h the Regulation falls back to for lifting.
What to do with the forecast
Check it against the erecting limit before anything leaves the yard, not on the morning. A lift that has to be stopped halfway because the wind came up is worse than one that was never started, and mobilising a mobile crane twice costs more than waiting a day.
Related guides
- Notice of Project for a tower crane in BC — what has to exist before the first section leaves the yard.
- Tower crane inspection requirements in BC — which sections of the Regulation apply, and who is allowed to do the work.
- All of our tower crane guides — inspection, maintenance and paperwork in British Columbia.