Mast climbing platform with a missing tie
A twin-mast mast climbing work platform is installed on an 8-storey building façade. The platform is 12 m long and rated 2,000 kg evenly distributed. Two workers (160 kg) and 900 kg of stone cladding are loaded at one end, leaving the other end empty. The manufacturer requires ties at every third floor, but the tie at level 3 is missing because the slab edge is being repaired. Wind is 25 km/h; the platform’s wind limit is 20 km/h. The emergency stop on the left mast has been intermittent, and the site engineer says ‘it will be fine for one more shift.’ The platform is currently at level 5. The access gate at level 5 is 1.1 m high and has no toe board.
1. Assess the load and wind conditions and decide whether the platform can be used for this shift.
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Total load is 160 + 900 = 1,060 kg, which is below the 2,000 kg rating, but the rating is for an evenly distributed load. Putting almost all the stone at one end creates a large eccentric moment; one mast and its ties take much more than half the load, and the deck may be locally overloaded. The load must be spread along the platform and secured, or the operation must use a smaller load. Wind is 25 km/h against a 20 km/h limit, so the platform must be stopped and the load secured. The combination of eccentric load, missing tie, and over-limit wind is a clear stop. Do not accept ‘one more shift’; lower the platform, unload, and do not re-enter service until the tie and emergency stop are restored.
2. Explain why the missing tie and intermittent emergency stop are not minor defects.
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The missing level 3 tie is a structural non-compliance. MCWP ties transfer wind and platform loads to the building; without one, the mast is unbraced over a longer height and can buckle or pull out. The installation is outside its design until the tie is restored and checked by a competent person. The intermittent emergency stop is also safety-critical: it may fail when someone needs it. Lock out the platform, remove the key, repair and test the emergency stop, and record the test. Do not operate with a bypass or with a ‘temporary’ tie unless the manufacturer or engineer approves it in writing. The site engineer’s verbal assurance is not adequate.
3. What is wrong with the level 5 access gate, and what must be done before use?
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The access gate is 1.1 m high and has no toe board. That is low enough for a person to fall over and offers no containment for tools or stone. The platform needs a full-height gate or guardrail with a toe board at every access point, and the gate must be self-closing or kept closed except when loading. Barricade the ground below, because dropped material is a dropped-object hazard. Check that the gate does not interfere with the platform’s movement and that the access route to the building is secure. Record the defect and do not use the platform until it is corrected.