Lightning protection scheme for gas vent pipes

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Since the boiler room already has a well-developed lightning protection and grounding system, only protection against direct lightning strikes for the vent pipe section is provided. Relevant national standards require that: 1. In areas where ground lightning strikes may occur, buildings fall under Category 1 lightning protection buildings in any of the following situations: buildings where fire explosives and their derivatives are manufactured, used, or stored, and those where explosions or detonations caused by electric sparks could result in severe damage and casualties. (>Chapter 4, Article 4.2.1 of GB50057-2010) 2. A lightning rod should be installed at or near the top of the gas vent pipe; the tip of the rod should be at least 3 m above the top of the pipe, and its protection range should extend at least 1 m above the top of the pipe (Article 13.2.15 of Chapter 13 on civil engineering and electrical systems in GB50041-92). 3.11. The lightning protection of gas vent pipes shall meet the following requirements: ㈠ Metal pipes equipped with flame arresters may not be fitted with lightning rods, but shall be connected to the roof’s lightning protection system ； (ii) Non-metallic pipes and metal pipes without flame arresters that are outside the protection area of the roof lightning conductor shall be equipped with lightning conductors and connected to the roof lightning protection system. Site conditions: In this case, the boiler is 38 meters tall, with the vent pipe being 2 meters above the height of the boiler; thus, the total height is 40 meters. Assuming that the diameter of the vent pipe does not exceed 300 MM, calculations using the ball rolling method show that if the lightning rod is installed at a height of 38 meters, and a pre-discharge lightning rod is used, then its height should be 5 meters (including the lightning receptor). If an optimized lightning rod is used, the height needs to be increased to 6 meters. Note that different heights result in varying wind resistance coefficients, weights, and swing amplitudes for lightning rods; therefore, it is necessary to carefully select the appropriate height based on the site conditions. Given the existing direct lightning protection system in this boiler room, as well as the steel beams in the building, these steel beams can be used directly as the down conductors for the lightning rods.