Recently ZANDZ Technical Center received a request to carry out lightning protection of the warehouse of ammonium nitrate in Magadan Region. The substance is stored in portable metal containers installed in 3 rows. Ammonium nitrate is a fire hazard and explosive substance, therefore, for its safe storage, it is necessary to ensure reliable protection against direct lightning strikes of at least 0.9.
To protect the warehouse with such reliability, it is enough to use two existing lighting poles with a height of 10 m and additionally install two free-standing lightning rods with a height of 14 m. Having placed the lightning rods in suitable places and performed the calculation in the Service for calculating the reliability of a lightning protection system, we managed to obtain a reliability value of 0.938. This indicates that the measures taken for lightning protection of the warehouse of ammonium nitrate are sufficient.
Find out more from the news text.
Task
To calculate lightning protection of a warehouse of explosive substances at a deposit in the Magadan Region.
Solution
Calculations of lightning protection 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 (hereinafter IS).
- Instructions on 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.
The protected structure belongs to the 2nd category according to the AD and to the special ones that pose a danger to the immediate environment in accordance with the IS.
Description of an external lightning protection system for a warehouse of explosive substances
The set of measures to provide the required lightning protection is offered by the following solutions:
- Two existing lighting poles 10 m high are used as lightning rods
- To protect the spotlights on a lighting mast 10 m high, a rod lightning rod 4 m high is installed, which is welded to the fence (it is taken into account that 1 m of the height of the air terminal is taken for fixation). Taking into account the air terminal, the mast height is 14.7 meters
- In addition, installation of two free-standing lightning rods with a height of 14 meters is carried out.
- Lightning rods are designed for the III wind region according to SNIP 2.01.07-85 *.
Each lightning rod requires a grounding device in the form:
- Laying of a horizontal ground electrode for current spreading in three directions with an angle of 90 degrees between them. The length of each ground electrode is 5 m. The ground electrode is made of copper-bonded stainless steel with the cross-section 4x30 mm (GL-11075), laying depth - 0.5 m.
- One vertical electrode 3 m long is fixed in each direction at the end of the horizontal ground electrode.
- Connection of vertical and horizontal electrodes, as well as horizontal electrodes with a lightning rod is carried out with the help of clamps ZZ-005-064.
The location of the lightning protection system elements is shown in Figure 1.
Figure 1. Plan with the arrangement of lightning protection elements
Calculation of reliability of lightning protection in the program
The following source data are taken for the calculation:
The density of lightning discharges into the ground is 1 strike/ sq. km per year for the Magadan region.
he results of lightning protection calculation performed by the software, developed by OJSC "Energy Institute to the name of Krzhizhanovsky" (OJSC" ENIN ") are given in table 1.
Table 1 - Results of lightning protection calculation
|
№ |
Object |
Lightning rod height, m |
Protection reliability |
Number of strikes into an object, year-1 |
Number of breakthroughs into the object, year-1 |
|
Period of srikes, year |
Period of breakthroughs, year |
||||
|
1 |
Explosives warehouse |
14 and 14.7 m |
0,938 |
0,021 |
0,0013 |
|
every 48 years |
every 769 years |
Accessories for lightning protection of a warehouse of explosive substances
Chart 2 - List of materials needs
|
№ |
Fig. |
Product item |
Product |
Quantity |
| Lightning protection system | ||||
| 1. |  |
ZZ-201-014 | ZANDZ Vertical lightning rod 14 m (galvanized steel; with embedded fittings for placing under the foundation) | 2 |
| 2. |  |
ZZ-201-004 | ZANDZ Vertical air-terminal -mast 4 m (stainless steel) | 2 |
| Grounding device | ||||
| 3. |  |
ZZ-005-064 | GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil of 50 meters) | 6 |
| 4. |  |
GL-11075-50 | GALMAR Полоса омеднённая (30*4 мм / S 120 мм²; бухта 50 метров) | 3 |
| 5. |  |
ZZ-001-065 | ZANDZ Copper-coated threaded grounding rod (D14; 1.5 m) | 8 |
| 6. |  |
ZZ-002-061 | ZANDZ Threaded coupler | 5 |
| 7. |  |
ZZ-003-061 | ZANDZ Starting tip | 4 |
| 8. |  |
ZZ-004-060 | ZANDZ Driving head for a jackhammer | 2 |
| 9. |  |
ZZ-006-000 | ZANDZ Conductive grease | 1 |
| 10. |  |
ZZ-007-030 | ZANDZ Waterproof tape | 2 |
| 11. |  |
ZZ-008-000 | ZANDZ Header for a jackhammer (SDS max) | 1 |
Do you have questions about the calculation of lightning protection of a warehouse of explosive substances? Please contact our ZANDZ Technical center!
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