Methane tanks are used for treating sewage water at integrated treatment facilities. They are intended for anaerobic fermentation of liquid organic waste to produce methane. Methane tanks are classified as a class C1a Zone according to RD 34.21.122-87, and it is important to provide the required lightning protection reliability. The ZANDZ Technical Centre has received a request to calculate the lightning protection for the methane tanks in Kemerovo Region. Let us continue with more detailed review of our offered solution.
Calculation of the lightning protection for the methane tanks in Kemerovo Region
Facility: Methane tanks in Kemerovo Region.
ПЛАН на отм. - PLAN at mark
Figure 1. Facility plan.
Task: To calculate lightning protection system for the methane tanks in Kemerovo Region.
Requirements according to the regulatory documents
Methane tanks are classified as Class C1a according to the EIC and RD.
According to Table 1 of RD, zone C1a includes Category II of lightning protection, which means that the tanks may be protected by both standalone lightning arresters and the ones installed on the facility.
Protection zone B of RD is taken as an estimate zone, since the expected number of lightning strikes per year for the facility is lower than 1.
The calculation of the lightning strikes per year to the facility is made in the software developed by OAO ENIN.
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 accepts the lightning discharge, a current collector, and a grounding electrode.
Solutions to meet the requirements to the lightning protection system of the methane tanks in Kemerovo Region:
The activities are made in accordance with the Electrical Installations Code (EIC), Rev. 7, SO 153-34.21.122-2003 Instructions for Arranging Lightning Protection of Buildings, Structures, and Industrial Utilities (hereinafter referred to as SO) and Arranging Lightning Protection of Buildings and Structures (hereinafter referred to as RD).
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- 2 x 10 m lightning rods are installed via their attachment to the wall of the methane tank. It is taken into account that 2 m of the height of lightning arrester are necessary for mounting;
- installation of 1 x 8 m lightning rod is carried out via attachment to the wall of the methane tank. It is taken into account that 1.5 m of the height of lightning arrester are necessary for mounting;
- attachment of the current collector made of a zinc-plated wire with a diameter of 8 mm from the lightning arrester along the methane tank wall is performed using clamps GL-11703A (installation step 0.6-1 m);
- protection radius and heights at which the protection zones are generated corresponding to zone B of RD are shown in the plan in a separate file.
A grounding arrangement is installed as follows:
- as horizontal grounding electrode made of a corrosion resistant steel zinc-plated bar with a cross-section 4 x 30 mm, laying depth 0.5 m around the site and 6 vertical electrodes (rods made of copper-plated steel with a diameter of 14 mm), 3 m long;
- interconnection of horizontal electrodes and with vertical electrodes is made using clamps ZZ-202-012;
- connection of current collectors with the output of a zinc-plated bar from the ground is made using clamps ZZ-202-013;
- design of the grounding arrangement corresponds to item 1.7.55 of the EIC. Grounding arrangements for protective grounding and grounding for lightning discharges are common.
Figure 2 shows hardware layout.
Table 1 includes the list of required hardware and materials.
Условные обозначения - Legend
Figure 2. Hardware layout for the lightning protection of the methane tanks in Kemerovo Region.
Table 1. List of material requirements.
Do you have any questions about lightning protection for the methane tanks or other facilities? Please, contact the ZANDZ Technical Center!