Inset pavement luminaires

How does Inset pavement luminaires work, step by step?

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   Step 1: The designer fixes the layout

   Where inset lights go, which functions they serve and how they are grouped onto circuits are set by the designer with the airport operator and agreed with the aviation regulator. Position on the ground is surveyed from the design, not judged on site, because these fittings define what a pilot sees. The civils and lighting contractors work to that setting-out and do not vary it. Any conflict found on site - a duct, a drain, an existing base - is referred back rather than resolved by moving the light.

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   Step 2: Install or core the base can

   On new pavement the base can is cast into the construction; on existing pavement it is installed by coring a hole to the required depth and diameter. Coring is a controlled operation: the core is taken cleanly, the arisings and water are collected rather than washed away, and any reinforcement or buried service encountered stops the work for a decision. The base is set with its top at the level the fitting requires, plumb and square to the surface, and held while the surround is placed. Getting the base level wrong is the mistake that cannot be corrected later.

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   Step 3: Form the duct and cable connection

   The base is connected to the circuit through ducts or a slot cut in the pavement, with the cable and isolating transformer installed by the lighting specialist. Slots are cut, cleaned, dried and sealed with the specified product so that they do not become a water path into the base. Where the connection runs to a chamber, the chamber is positioned so it can be reached for maintenance. Every route is recorded before it is covered, because the next team to work on this light will only have the records.

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   Step 4: Grout, seal and drain the base

   The base is grouted or sealed into the pavement with the product the specification names, mixed and placed to its stated working time and cured before trafficking. The seal has to accommodate the thermal movement between a metal fitting and the pavement around it without opening. Drainage of the base is provided as the design requires, because a base can that fills with water will fail electrically and will damage the fitting. On most projects this step, not the light, is where the durability of the installation is decided.

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   Step 5: Fit and set the luminaire flush

   The luminaire is bolted into the base with the specified fixings, torqued as the manufacturer requires, and set so that its top is flush with the surrounding surface within the specified tolerance. It is aligned to the design orientation using the setting-out, since these fittings are directional and their aiming is part of the design. The surrounding surface is finished so there is no lip, no depression and no ponding. Fixings, gaskets and seals are new items, not reused ones.

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   Step 6: Connect and prove under the operator's permit system

   The connection into the series circuit is made by qualified airfield lighting specialists working under the airport operator's permit-to-work, with the circuit isolated by the operator beforehand. This is high-voltage series circuitry and no one else goes near it. The fitting is proved and the circuit tested by those specialists, and the light is returned to service by the operator, who confirms it on the control and monitoring system. Until that happens the operator decides what restriction applies to the area.

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   Step 7: Clean, sweep and hand back within the window

   Coring produces slurry, cut slots produce dust and fixings produce small loose items, all of them foreign object debris on a trafficked pavement. Arisings and water are collected as the work proceeds, the area is mechanically swept and then walked, and fixings and tools are tallied and reconciled. Because inset work almost always happens in a night possession, this cleaning is planned into the window rather than added to the end of it, and the pavement is handed back jointly with the operator.

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   Step 8: Maintain, monitor and plan replacement

   Inset fittings are consumables in a way that other lighting is not. Lenses abrade, seals age, bases take water and fixings loosen under repeated loading. The operator monitors circuit and lamp status through the control system and inspects fittings physically on a routine cycle. Replacement is planned into possessions in batches rather than done one light at a time, because the cost of the closure usually exceeds the cost of the fitting. Records of each base, its position and its history make that planning possible.