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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Temporary lighting installation

A construction site’s temporary electrical installation must also provide adequate lighting for the activities that are carried out at a particular workspace whether indoor or outdoor. Arguably more important than the light levels, the temporary lighting installation should be sufficiently safe for use and provided with adequate protection to prevent electrical shocks.

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1) Wire cages to prevent against mechanical damage should protect temporary light fittings at the construction sites. Damaged light fittings not only result in the repair cost, but they also present risks of electrical shocks to workers using them or those who are nearby. Precautions must be taken against the danger of electrical fires that because of damaged light fittings or the temporary supply wiring.

2) The temporary wiring supplying the lighting circuits should be connected to the special lighting section on the temporary switchboard. These circuits should be protected by 100 mA RCD (residual current circuit breakers).

3) Festoon lighting should only be used strictly in underground shafts, wells and tunnels. When this type of lights are used, the lamp holders should only be the moulded-on, non-removable type (the lamp holders are bonded or moulded to the wiring cables) and the lighting supply voltage is 32 Volts or below.

4) Either the temporary wiring or the newly installed permanent wiring may supply lift shaft temporary lighting. However, the light fittings used should be properly guarded against accidental mechanical damage and they should only be connected to the wiring using a lighting plug and socket. These lights should be installed at intervals of less than nine meters along the vertical length of the lift shaft. The control of the lift shaft lighting should be by means of two-way switches located near the shaft access points.

5) Normal duty lighting circuits are installed to provide general illumination for work and allow safe movement inside and around the construction site.

6) The installation of wiring for the temporary lighting should be carried out with proper supports and fittings to allow for wiring cables to be routed in ways that minimize obstructions, which can results in damage to the luminaries and wiring. These damages can present shock risks to the works and possibilities of electrical fires.

7) The use of lighting circuits supplied at safe extra low voltage levels (SELV - voltages less than 50 volts ac or 120 volts dc) is highly recommended for working in confined spaces where workers faces high possibilities of frequent contacts with temporary electrical equipment and wiring.

8) An illumination level of 10 lux is adequate for general movement within a building under construction. As an illustration, one length of 100 meter festoon light string fitted with 20 nos 100 watt lamps at 5 meter intervals will give a 10 lux over a rectangular area of 25 meter x 30 meter.

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

You can also see a few pictures of site floodlight at this post,  Temporary site floodlights.



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