Erection, alteration, dismantling and commissioning
Domain 4 covers the highest-risk phase: putting the rig up, changing it, taking it down, and proving it is fit before first use.
Erection
- Erection, alteration and dismantling are done by trained riggers under the supervision of a competent person, following the manufacturer's instructions and the rigging plan.
- Supporting structure: confirm the roof slab, beam or parapet can carry the outrigger reactions. Unusual or heavy rigs need an engineer's check; spreader beams distribute point loads.
- Anchors and tie-backs: anchor to structural elements or approved cast-in anchors - never to parapets, handrails, pipes, ductwork or air-conditioning units.
- Counterweights: the calculated mass, purpose-made, fixed so they cannot be displaced, and marked.
- Ropes: correct diameter and length, correct reeving, terminations to specification, ropes free of twists; safety ropes anchored separately.
Alteration
Any change to overhang, back-span, counterweight, anchor position, rope length or platform configuration changes the loads. It requires re-inspection and, before use, re-examination and re-testing. A certificate issued for the old configuration does not cover the new one.
Commissioning before first use
- Function test of hoists, brakes, emergency stop, limiters and alarms.
- Load test to the specified proof load (commonly 1.25 times the rated load, per the Code or manufacturer).
- Examination by a competent examiner and issue of the certificate.
- Only then are persons carried.
Dismantling
Lower the platform to a safe level, isolate and lock off the power, slacken and remove ropes in a controlled way, and dismantle the rig with the same supervision. Secure the roof edge and prevent falls throughout.
Worked example
A team extends an outrigger overhang by 500 mm to clear a new fin. The counterweight no longer balances the increased moment, roof reactions rise, and the suspension rope may rub the fin. The rig must be recalculated, re-rigged, inspected, examined and load-tested before use - extending the beam and reusing the old certificate is a serious breach.
Traps
- Anchoring tie-backs to the parapet.
- Using loose weights as counterweights.
- Commissioning by function test only, with no load test.
- Reusing a certificate after alteration.
- Letting the platform carry persons during setting-up.