Fuel tanks are an essential part of oil facilities. They are intended for storing various fuel types such as petrol, diesel fuel, or kerosene. These facilities are classified as Category II in terms of lightning protection according to RD 34.21.122-87 and may be protected both by standalone lightning rods and those installed on the tanks. The main task is to provide the respective operational safety of such facilities and properly chosen lightning protection systems.
The ZANDZ Technical Center has received a request to calculate the lightning protection and grounding system for fuel tanks. The specifics of the facility includes its location in sandy soils and closed-process (no respiratory pipes) operations. Let's consider a developed solution.
Lightning protection calculation
The activities were made in accordance with the Electrical Installations Code (EIC), Rev. 7, Chapter 1.7, SO 153-34.21.122-2003 "Guidelines for Arrangement of Lightning Protection of Buildings, Structures, and Industrial Utilities" (hereinafter referred to as SO), and RD 34.21.122-87 "Guidelines for Arrangement of Lightning Protection of Buildings and Structures" (hereinafter referred to as RD).
The facility is classified as Category 2 according to RD (zone B). According to SO 153-34.21.122-2003, fuel tanks are classified as special facilities hazardous for immediate environment; so, let's take protection level II with the reliability of not less than 0.95.
The protection zone calculation according to SO:
Lightning rods:
Cone height according to SO, Table 3.4:
Cone radius according to SO, Table 3.4:
Distance between the lightning rods:
54 м
The limit distance between lightning rods according to SP, Table 3.6:
м - m
Sagging height at 
:
To provide the protection zone of the desired reliability, horizontal section radius 
at the height 
is determined as follows:
Sagging height at 
:
To provide the protection zone of the desired reliability, horizontal section на высоте radius is determined as follows:
Lightning protection performance
Protection of buildings against lightning strikes is provided by using lightning arresters. Lightning arrester is a device that is elevated over the protected facility through which the lightning current goes into the ground bypassing the protected facility. It consists of a lightning rod that directly accepts the discharge of a lightning , a current collector, and a ground terminal.
Lightning protection of the facility is made using 4 x 10 m lightning masts ZZ-201-010-3 (2 m for attachment and 8 m to the top) on holders to the facility metal structure.
The metal structure of the facility is used as a natural current collector.
Grounding arrangement resistance calculation:
According to initial data, the estimated soil resistivity is taken as 3,000 Ohm∙m.
Horizontal electrode resistance:
Гор - Hor
wherein 
– is soil resistivity, Ohm·m;
is bar width of a horizontal electrode, m;
- is depth of a horizontal electrode, m;
– is total length of a horizontal electrode.
Vertical electrode resistance
Верт - Vert
wherein – is soil resistivity, Ohm·m;
– is length of the vertical electrode, m;
– is diameter of the vertical electrode, m;
– is deepening, a distance from the earth surface to the ground terminal, m;
wherein 
– is depth of the top of the electrode, m
Electrical impedance of the grounding arrangement:
ЗУ - GA
Исп гр - util
wherein 
– is number of sets;
– is utilization ratio.
Ом - Ohm
The estimated resistance of the grounding arrangement is 1.76 Ohm.
Grounding performance
Vertical copper-plated steel electrodes 3 m long are used as grounding arrangements. The copper-plated steel strip with a cross-section of 30x4 mm, combining all vertical electrodes is used as a horizontal ground electrode. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
According to RD, item 1.8, artificial ground terminals shall be located under the asphalt coating or in a unfrequented spots (on lawns, at the distance of 5 m or more from soil roads and pavements, etc.).
According to EIC, Rev 7., item 1.7.55, grounding arrangements for protective grounding of electrical installations for buildings and structures and the 2nd and 3rd categories lightning protection of these buildings and structures, as a rule, shall be common.
If there are concrete-steel constructions, they shall be connected to current collectors/grounding arrangement.
Grounding arrangements can be connected to the metal structures of the tanks using special clamp ZZ-005-064.
The location of the elements of the lightning protection system and the grounding arrangement is shown in a drawing in a separate file.
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Click here to view the diagram in full.
Условные обозначения - Legend
Table 1. List of required materials.
| Item No. | Fig. | Part number | Product | Amount |
| Lightning protection system | ||||
| 1 |  |
ZZ-201-010-3 |
ZANDZ Lightning mast, vertical, 10 m high, with a set of 3 wall fasteners (stainless steel) |
4 |
| Grounding arrangement | ||||
| 2 |  |
ZZ-005-064 |
29 | |
| 3 |  |
ZZ-11075-50 |
ZANDZ Copper-plated strip (30*4 mm/S 120 mm²; 50-meter bundle) |
6 |
| 4 |  |
ZZ-001-065 |
24 | |
| 5 |  |
ZZ-002-061 |
13 | |
| 6 |  |
ZZ-003-061 |
12 | |
| 7 |  |
ZZ-004-060 |
5 | |
| 8 |  |
ZZ-006-000 |
2 | |
| 9 |  |
ZZ-007-030 |
5 | |
| 10 |  |
ZZ-008-000 |
1 | |
Do you have any questions regarding grounding of a server room or other facilities? Please contact the ZANDZ Technical Center!
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