Wednesday, December 23, 2009

Temporary site floodlights

Large construction sites usually need temporary floodlight towers (in addition to the temporary lighting inside the new buildings) to provide lighting efficiently for the general movement, safety and security on the external areas of buildings under construction.

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The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for the lighting tower units and the duration of the contract.

For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.

However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still be reused on future projects.

Careful dismantle the fixed height static towers at the end of the contract. Then the only extra materials that are required in at the next construction site is the foundation.

Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their own electric generator.

The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of construction materials and site clearing works.

A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium fittings.

A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting requirements.

If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the overall temporary electrical installation. The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at the required overall Illuminance.

These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.

Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant type due to its high lighting output per kW of power usage (approximately 125 lumens per watt). A tungsten halogen lamp would give only 22 lumen per watt. The capital cost of opting the hight pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to consider other factors also such as the running cost, installation cost and the lamp life.

At the end of the construction work, all these equipment except the tower foundation, can be dismantled and transported to other project sites for reuse.

Below is a picture of a small mobile floodlight unit:

Picture 1 - Mobile site floodlight unit

Read more on site electrticity at this post, Temporary Electrical Installations.

There is also more imformation on temporary lighting at this post, Temporary lighting installation.

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