The gas compressor station on the offshore platform can rise by 15 meters above the water surface or more, which puts it at under an increased risk of a lightning strike. Although this object is almost entirely made of metal (which means the ability to receive and remove lightning only due to its design), working with natural gas requires reliable lightning protection. In a bad scenario, lightning can lead to a large-scale technological and environmental disaster.
In one part of the station there is a high flare boom that can be used as an air terminal. But its height is not enough to cover the entire object with the protection zone, therefore, for lightning protection of the offshore platform, rod lightning rods from 8 to 20 m high are installed in different parts of it.
To prove the sufficiency of the solutions, the technical experts used the “Lightning Protection System Reliability Calculation Service” developed by OJSC “Energy Institute named after G.M. Krzhizhanovksy" (OJSC "ENIN"). As a result, the following were obtained: a value of reliability equal to 0.9938; the average time between breakthroughs, bypassing the defense - 1042 years. These are more than worthy indicators that demonstrate that the proposed lightning protection of the offshore platform is very reliable.
You will learn more about technical solutions from the news text.
Task
To calculate the lightning protection of a gas compressor station on an offshore platform located in the Caspian Sea.
Solution
The calculations are made in accordance with the following documents:
- Electrical 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 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.
The protected structure refers to special and hazardous to the environment in terms of lightning protection in accordance with IS, as well as to the 2nd category according to AD.
Description of the external lightning protection system of the offshore platform
The set of measures to provide the required lightning protection is offered by the following solutions:
- Installation of 3 rod lightning rods 8 m high. Lightning rods are attached to the metal structures on the platform.
- Installation of 2 free standing lightning rods 20 m high and one 18 m high.
- The pipe rising over the platform by 15 m acts as an air terminal.
The layout of elements in the lightning protection system and the grounding device is shown in Figure 1.
Figure 1. Plan with the location of lightning protection elements on the offshore platform
Calculation of lightning protection reliability in the program
The following source data are taken for the calculation:
The density of lightning discharges into the ground is 2 strikes / sq. km per year for the Caspian Sea.
The 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 reliabilityы |
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 |
Offshore platform |
8; 18; 15; 20 м |
0,9938 |
0,15 |
0,00096 |
|
once in 7 years |
once in 1042 years |
Accessories for lightning protection of an offshore platform
Chart 2 - List of materials needs
|
№ п/п |
Fig. |
Product item |
Product |
Quantity |
|
Система молниезащиты |
||||
| 1. |  |
ZZ-201-018 | ZANDZ Vertical lightning rod 18 m (galvanized steel; with embedded fittings for placing under the foundation) | 1 |
| 2. | |
ZZ-201-020 | ZANDZ Vertical lightning rod 20 m (galvanized steel; with embedded fittings for placing under the foundation) | 2 |
| 3. |  |
ZZ-201-008-3 | ZANDZ Vertical air-terminal mast 8 m with a set of 2 fastenings to the wall (stainless steel) | 3 |
Do you have questions about lightning protection calculations for a gas compressor station on an offshore platform? Please contact our ZANDZ Technical center!
See also: