Is it necessary to carry out lightning protection of fire water tanks? It would seem that the container is made of steel, inside it there is only water, no combustible substances: can it be interesting for lightning? It turns out it can.
The reason is that fire tanks are not just steel tanks, but rather complicated technological complexes, including an electric heating system and pumping equipment. It is these elements that need to be protected from lightning. It is impossible to allow a significant lightning current to flow through the pipes to the pump station, damage the heating elements, and put the functional and control and electronic equipment at risk of failure
How to reliably protect fire tanks from lightning? Around them, a closed grounding contour is made of a horizontal electrode and vertical electrodes at the points where the grounding tape is connected to the tank. The lightning current received by the air terminal is diverted to such a ground electrode, which reduces the risks of damage to technological systems. This is the most reliable way of lightning protection of fire water tanks.
Let's look at the listed solutions for lightning protection and grounding on the example of a project carried out by the ZANDZ Technical Center.
To calculate lightning protection and grounding of fire tanks with a volume of 1044 m3 each. The protected structures refer to ordinary from point of view of lightning protection in accordance with IS and to category 3 according to AD.
The calculations are made in accordance with the following documents:
- Electric Installation Code" EIC 7th ed. (hereinafter - EIC).
- Instructions for organization of lightning protection of buildings, structures and industrial communications" IS 153-34.21.122-2003
- Instructions for lightning protection of buildings and structures" AD 34.21.122-87 (hereinafter - AD).
Protection of buildings from lightning strikes is carried out with the help of 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.
Description of the external lightning protection system of fire tanks
The set of measures to provide the required lightning protection is offered by the following solutions:
- The installation of 6 rod lightning rods with a height of 4 m. Lightning rods are welded to the fence on the tank.
- The metal body of the tank is used as a down conductor.
The set of measures on the provision of the necessary requirements to the grounding device is presented by the following solutions:
- A horizontal ground electrode is laid around the tanks. The ground electrode is made of corrosion-resistant copper-bonded stainless steel tape with the cross- section 4x30 mm, laying depth 0.5 m, distance to the wall of the building- at least 1 m.
- In places of installation of lightning rods, a horizontal ground electrode is connected to the metal structure of the tank and a vertical electrode 3 m long is installed.
- The horizontal electrodes are connected to each other and the tank is connected to the metal structure using the clamp ZZ-005-064.
The layout of elements in the lightning protection system and the grounding device is shown in Figure 1. Protection zone corresponds to zone B of the AD.
Figure 1 - Plan with the layout of lightning protection elements and grounding device
Зажим - clamp
Полоса - tape
Figure 2 - Installation of a clamp for metal structures of the tank
Figure 3- Marking of holes for the clamp
Accessories for lightning protection and grounding of fire tanks
Table 1 - Materials requirement list
Lightning protection system
|1.||ZZ-201-004||ZANDZ Vertical air-terminal -mast 4 m (stainless steel)||6|
|3.||GL-11075-50||GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil of 50 meters)||2|
|4.||ZZ-001-065||ZANDZ Copper-bonded threaded grounding rod (D14; 1.5 m)||12|
|5.||ZZ-002-061||ZANDZ Threaded coupler||7|
|6.||ZZ-003-061||ZANDZ Starting tip||6|
|7.||ZZ-004-060||ZANDZ Driving head for a jackhammer||3|
|8.||ZZ-006-000||ZANDZ Conductive grease||1|
|9.||ZZ-007-030||ZANDZ Waterproof tape||2|
|10.||ZZ-008-000||ZANDZ Header for a jackhammer (SDS max)||1|
Do you have questions about the calculation of lightning protection of tanks containing not only fire and explosive substances, but also such a “simple” liquid, like water? Please contact our ZANDZ Technical center!