CNG means "compressed natural gas", i.e. it is a gas station.
The design of lightning protection for the CNG station site should protect the following elements: compressor modules, gas accumulator units, air cooling devices, and valve skids. Lightning strikes into each of the facilities may cause gas ignition and significant damage; therefore, it is desirable to redirect a possible lightning strike further away from the equipment.
To provide lightning protection of the CNG station site, standalone lightning rods are preferred. When using just four such lightning arresters, these structures are within the protection zone, while the installation of lightning arresters beyond the site fencing allows avoiding creeping discharges that are no less dangerous for the gas equipment than the direct lightning strike.
Let us study the example lightning protection for the CNG station site.
Task
To calculate the lightning protection and grounding for the CNG station site.
Solution
The lightning protection for the CNG station site was performed in accordance with the following regulatory documents:
- "Electrical Installations Code" (hereinafter referred to as the EIC), 7th edition.
- "Instructions for the installation of lightning protection of buildings, structures, and industrial communications" SO 153-34.21.122-2003 (hereinafter referred to as SO).
- "Instructions for mounting the lightning protection of buildings and structures" Working Documentation 34.21.122-87 (hereinafter referred to as the RD).
The lightning arresters are used to protect the buildings against lightning strokes. The lightning arrester consists of an interception rod, intercepting a lightning discharge, the main conductor cable, and the ground electrode. All these elements let us divert lightning current into the ground safely, without any damage to the protected facility.
The CNG site is a special facility hazardous for the surroundings in terms of lightning protection according to SO and to Category 1 according to RD.
Description of the lightning protection system for the CNG station site
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- 4 x 15 m standalone lightning arresters are installed.
- The lightning arrester design is intended for:
- 6th snow region according to SP 20.13330.2016;
- 6th snow region according to SP 20.13330.2016;
- 8-9 seismic region according to SP 14.13330.2014.
- Lightning arresters create protection zone B according to RD at the level of space over the high-pressure flares in the form of a cylinder (H = 2.5, R = 5 m).
A set of measures to ensure the necessary requirements for the grounding device of each interception rod is represented by the following solutions:
- Laying a horizontal ground electrode for current spreading in two directions with an angle of 90 degrees between them. Length of each ground electrode is 5 m. The ground electrode is made of a corrosion-resistant steel copper-plated strip with a cross section of 4x30 mm, the laying depth is 0.5 m.
- At the end of the horizontal ground electrode, one vertical electrode with the length of 3 m is installed in each directions. The foundation embedded part is used as the third vertical electrode.
- The vertical and horizontal electrodes, as well as the horizontal electrodes with the interception rod are connected using the clamps ZZ-005-064.
The location of the elements of the lightning protection system and the grounding arrangement is shown in Figure 1. The indicated protection zone corresponds to zone B according to RD.
Figure 1. Layout of lightning protection elements in the CNG station site
Components for the lightning protection system of the CNG station site
| № | Part number | Name | Quantity, pcs. |
| Lightning Protection | |||
| 1. | ZZ-201-015-В7-Сн7-С9 | ZANDZ Vertical lightning arrester 15 m (zinc-plated steel; with embedded parts for the foundation; 7th wind region; 7th snow region; 9th seismic region) | 4 |
| Grounding arrangement | |||
| 2. | ZZ-005-064 | ZANDZ Conductor connection terminal (up to 40 mm) | 16 |
| 3. | GL-11075-50 | GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle) | 1 |
| 4. | ZZ-001-065 | ZANDZ Copper-plated threaded grounding rod (D14; 1.5 m) | 16 |
| 5. | ZZ-002-061 | ZANDZ Threaded coupling | 9 |
| 6. | ZZ-003-061 | ZANDZ Termination | 8 |
| 7. | ZZ-004-060 | ZANDZ Guide head for jackhammer attachment | 4 |
| 8. | ZZ-006-000 | ZANDZ Conductive grease | 1 |
| 9. | ZZ-007-030 | ZANDZ Waterproofing tape | 4 |
| 10. | ZZ-008-000 | ZANDZ Attachment to the hammer (SDS max) | 1 |
Do you have any questions relating to calculation of the lightning protection and grounding of the CNG station site? Please, contact the ZANDZ Technical Center!
Related Articles:
