金属烟囱直接做接闪器和引下线的出处？

GB 50057-2010建筑物防雷设计规范中，第四章4.4.9条规定，金属烟囱应作为接闪器和引下线；另根据附加说明4.4.9条，只要金属烟囱厚度大于0.5mm即可防止雷击穿孔；
GB 50057-2010标准大量依据出自IEC标准BS EN 62305-3 2010,但在IEC标准中找不到原话，请问金属烟囱应作为接闪器和引下线的依据在哪里可以找到？
项目信息如下：国外项目管式加热炉，防爆区域zone2,烟囱顶部高度63米，33米处与钢结构螺栓连接，2.4米桩基，烟囱直径1.6米，厚7mm,桩基中心点直径12.3米，业主要求考虑防雷。
全是金属框架还那么大一个烟囱还要考虑防雷么，真让人费解，但要说服老外就得找国外标准，IEC62305全是关于建筑物与钢筋混凝土的，请问还有其它相关标准可以作为依据吗？

IEC标准中5.1.3条关于防雷系统的说明
5.1.3 Use of natural components
Natural components made of conductive materials, which will always remain in/on the
structure and will not be modified (e.g. interconnected steel-reinforcement, metal framework
of the structure, etc.) may be used as parts of an LPS.

5.2.4关于接闪器的说明
5.2.5 Natural components
The following parts of a structure should be considered and may be used as natural airtermination
components and part of an LPS in accordance with 5.1.3.
a) Metal sheets covering the structure to be protected provided that
– the electrical continuity between the various parts is made durable (e.g. by means of
brazing, welding, crimping, seaming, screwing or bolting),
– the thickness of the metal sheet is not less than the value t’ given in Table 3 if it is not
important to prevent puncture of the sheeting or to consider ignition of any readilycombustible
materials underneath,
– the thickness of the metal sheet is not less than the value t given in Table 3 if it is
necessary to take precautions against puncture or to consider hot spot problems,
b) Metal components of roof construction (trusses, interconnected reinforcing steel, etc.),
underneath non-metallic roofing, provided that damage to this non-metallic roofing is
acceptable.
c) Metal parts such as ornamentation, railings, pipes, coverings of parapets, etc., with crosssections
not less than that specified for standard air-termination components.
d) Metal pipes and tanks on the roof, provided that they are constructed of material with
thicknesses and cross-sections in accordance with Table 6.
e) Metal pipes and tanks carrying readily-combustible or explosive mixtures, provided that
they are constructed of material with thickness not less than the appropriate value of t
given in Table 3 and that the temperature rise of the inner surface at the point of strike
does not constitute a danger (for detailed information, see Annex D).
有张附表，PDF文件的就先不附上了。

5.3.5是关于引下线的说明，篇幅原因就不附上了。

5.4章中有两种接地形式，按照国标规范高于30m烟囱上部应该属于三类防雷建筑，下面防爆区属于二类防爆，但在IEC中不清楚怎么划分分类；

根据IEC标准5.4.3中说明For structures with extensive electronic systems or with high risk of fire, type B earthing
arrangement is preferable。
可以确定应按照TYPE B进行防雷接地，但桩基基础类型的防雷接地该如何做呢？是直接利用桩基螺栓作为接地体吗？
尽管这是属于业主的部分，但如果不符合规范我们就必须提供接地方式，是从桩基上焊接镀锌扁钢，按照间距不大于18米设2根还是3根作为引下线，并与大地连通么？

以上问题比较多，请高手帮忙解决，因悬赏区人气不旺，故在此寻求帮助，如果问题解决我会再贴到悬赏区，悬赏财富120，解决金属烟囱作为接闪器和引下线的出处的给予30奖励，没有出处但可以引据规范说明理由的给予50奖励，解决桩基基础接地问题给予40奖励，请大家多多帮忙！

另附上IEC 62305-3 2010规范，供大家学习。GB50057-2010太大了，给个连接http://down2.bzfxw.com/201106/GB 50057-2010 建筑物防雷设计规范.rar
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规范出处已找到：

6.10.1
Heavy-duty metal stacks having a metal thickness of

4.8 mm (3