Asphalt-concrete factory buildings are metal structures which can be used as natural lightning rods. But sometimes customers require to protect all equipment located on the territory by free standing lightning rods. ZANDZ Technical center has recently recieved such a task. Let's consider what solution was offered by our specialists.
Calculation example of an asphalt-concrete factory lightning protection
Object: asphalt-concrete factory
Figure 1 - Object plan
Task: Perform lightning protection and grounding system calculations for the asphalt-concrete factory.
Protection of buildings and structures against lightning discharges is ensured by lightning rods. A lightning rod is a device rising above the facility that diverts lightning current into the ground without entering the facility. It consists of a lightning rod which directly takes the lightning discharge upon itself, a down conductor and a ground electrode.
Solutions to meet the requirements for a lightning protection system:
1. Lightning protection is carried out in accordance with IS 153-34.21.122-2003., "Instructions for lightning protection of buildings, structures and industrial communications" (hereinafter IS) and AD 34.21.122-87 "Instructions for lightning protection of buildings and structures" (hereinafter AD).
2. The object refers to category 3 of lightning protection. System reliability must be not less than 0,9.
3. The lightning protection of the object is made with the help of 3 vertical detached air-terminal masts 5,7 m high (GL-21105G).
4. Installation of down conductors is carried out with the help of clamp GL-11703A on vertical surfaces. Distance between the clamps- from 0.8 up to 1.0 meter.
5. To connect rolled metal over the length and in the mesh nodes, a universal clamp GL-11551A is used.
6. All metal elements, placed on the roof must be connected to lightning protection mesh with the help of clamps GL-11545A. Stairs, railing are connected with the help of GL-11514 clamp.
7. Installation of a grounding device for each lightning rod, consisting of 2 vertical electrodes 3 m long, connected by a horizontal electrode (copper bonded tape of 30x4 mm) not less than 5 m long. The distance from the horizontal electrode to the object is not less 1 m, deepening 0,5-0,7 m;
8. In case of presence of the existing grounding device, they should be united into one grounding device in accordance with EIC p.1.7.55.
Calculation of protection zone in accordance with AD:
Lightning rod № 1, 2 (GL-21105G):
Air terminal mast № 1, 3 (GL-21105G):
Grounding device calculation resistance:
The design resistance of the grounding device is 2,54 Ohm.
Figure 2 shows the arrangement of equipment.
Table 1 gives the list of the required equipment and materials.
Figure 2- Arrangement of equipment for grounding and lightning protection on an asphalt-concrete factory
Chart 1 - List of need in materials.
Have you got any questions on grounding and lightning protection of factories? Please contact our ZANDZ Technical center!