Inspections and Assembly (3T and AGR)
What this domain covers
Inspections and Assembly (3T and AGR) tests how a tower is put up, how the assembly method protects the erector, and how inspection keeps it safe. 3T means through the trapdoor; AGR means advanced guardrail. You need to know the sequence, the limits and the records.
Core rules
- Assembly must follow the manufacturer's instructions and be carried out by competent people. Start with a firm level base, castors locked, correct base dimensions, braces and stabilisers.
- 3T assembly uses the platform trapdoor to reach the next level. The erector stands on a protected platform, opens the trapdoor, adds the next platform and guardrails, then closes the trapdoor. It relies on a suitable platform and trapdoor.
- AGR assembly places guardrail frames from below before the platform is occupied. This reduces the time spent working without guardrail, but the AGR must be the correct system and fitted in the specified order.
- Inspect before first use, before each use, at intervals required by your site or manufacturer, and after alteration, movement, damage or adverse weather. A competent person should record the results.
- Check base, castors, braces, stabilisers, platforms, guardrails, toe boards, trapdoors, locks and labels. Defects mean quarantine or dismantle.
- Do not mix 3T and AGR components unless the manufacturer permits it; do not skip stabilisers to save time.
Worked example
A team is building a tower where the first platform is too high to reach safely from the ground. They choose AGR: they assemble the base, fit the first platform, then attach the advanced guardrail frame from below before installing the next platform. They do not stand on an unguarded platform to fit rails. After assembly they check castors, stabilisers, rails and toe boards, and record the inspection. The reasoning is that AGR moves the guardrail installation earlier in the sequence, reducing exposure.
Traps that cost marks
Using 3T without a suitable trapdoor; fitting AGR after occupying the platform; relying on a weekly inspection only; not recording defects; and assembling without stabilisers because the tower is short.