Climbing Mast Sections Beside a 13.8 kV Line With a Gusty Forecast
At 07:45 the climbing crew is ready to add a 6 m mast section to a 60 m tower crane at a warehouse project. The crane stands 8 m from the boundary wall, and a 13.8 kV overhead distribution line runs parallel to that wall about 11 m from the mast centreline. The climbing procedure allows jacking up to 12 m/s wind 'measured at jib height'. The crane's own anemometer reads 8 m/s; the site weather station at 10 m is gusting to 13 m/s. The climbing unit's pressure gauge sits at 190 bar against a 210 bar limit. Two of the four tie-in pins for the new section show bright galling marks and will not seat by hand; a fitter proposes driving them in with a hammer. The rigger assigned to hold the tag line during the climb joined the company nine days ago and has never been on a climbing operation. The climbing supervisor wants the section in before the morning concrete pour starts.
1. Proceed with the climb or hold? Which wind reading governs, and what else supports holding?
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Hold. Three separate things point the same way and any one of them is enough.
Wind. The limit is written against the reading at jib height, so the governing instrument is the crane's own anemometer - but not as one instantaneous number. Jacking is slow and continuous, and the crane is at its most vulnerable while the mast is between sections, with the guide rails carrying load the pins normally carry. What matters is the gust, not the average. The station at 10 m already reads 13 m/s in gusts, and wind speed rises with height, so at jib height the gust is above 13, not below it. An 8 m/s reading on a cab anemometer that is partly shielded by the jib should not be used to overrule an open 10 m station. Treat the climb as outside the 12 m/s limit.
Pins. Galling means metal has transferred and the fit is no longer correct. A pin that will not seat by hand will not seat correctly by hammer either; you will burr the pin and the hole and the joint will bear on a fraction of its face.
Crew. A man nine days on site cannot be the tag-line hand on a climb.
None of these is a schedule problem. The pour waits; the crane does not climb in a gust.
2. The jib must swing over the line for the next section to be placed. What has to be in place before that happens?
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Not a judgement call made at the rail - a permit.
The clearance distance is not something to estimate from the ground or from memory. It comes from the approved lifting plan and from a permit-to-work agreed with the distribution utility, written down, signed and held on site. Before the climb resumes you need:
- The utility asked either to de-energise and earth the section, or to state in writing the minimum approach distance that applies with the line live, together with confirmation that the planned jib positions respect it. If it stays live, the plan must show the crane never enters that distance at any point, including jib deflection under load and the tail swing during the climb.
- A dedicated banksman with no other task, whose only job is watching the jib-to-line distance and who can stop the operation with one word on a dedicated channel.
- The climb re-sequenced so the jib is slewed to the side away from the line and pinned there for the duration of the jacking, rather than passing over it. Changing the sequence is usually cheaper than changing the clearance.
- The line treated as live until the permit says otherwise. Insulating gloves are not a substitute; on a crane, distance, isolation and earthing are the controls.
3. How do you deal with the galled pins and with the new rigger?
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Pins. They come out and go to the workshop - dressed and refitted, or replaced with the OEM part. A hammer is not a fitting tool. The objective is not to get the pin in; it is to get a joint that carries the design load across its full bearing surface, and a hammered pin does the opposite. Record the condition in the climb report and have the crane engineer sign off the joint before the next section is jacked, because those same pins are the ones that will be inspected when the crane is dismantled.
Rigger. He does not hold the tag line on this climb. This is not discipline, it is competence. He has nine days on site and no climb; a climb is not a training exercise. The mast is open, load is being transferred repeatedly between the hydraulics and the pins, and the tag line is the one control keeping the jib from swinging while the crane is not fully assembled. Put him on the ground crew on the exclusion perimeter today, and put him on the next climb as second man under a certified rigger. Once the climbing supervisor confirms his competence, he can take the tag line himself.
Write that into the training record. It is what turns 'he has been around a while' into documented, defensible competence for the next climb - and for the inquiry if there ever is one.