Lightning protection for a steel chimney

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Abey

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Sri Lanka
I live in Sri Lanka. Can someone help me with 2 questions please:
1. To protect a steel industrial chimney against lightning, do we need to install a lightning rod at the top of chimney and use a down conductor and ground it or is it sufficient to connect the grounded earth electrodes to the chimney from the bottom i.e. let the steel chimney act as the conductor?
2. Do you need a lightning rod at the top anyway as the steel chimney can be the conductor?
 
Sahib

Sahib

Senior Member
Location
India
Abey said:
I live in Sri Lanka. Can someone help me with 2 questions please:
1. To protect a steel industrial chimney against lightning, do we need to install a lightning rod at the top of chimney and use a down conductor and ground it or is it sufficient to connect the grounded earth electrodes to the chimney from the bottom i.e. let the steel chimney act as the conductor?
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The steel chimney may be used as the down conductor and if there are sections in the chimney, it should be ensured that they are electrically continuous by properly bonding them.
Abey said:
2. Do you need a lightning rod at the top anyway as the steel chimney can be the conductor?
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Not needed if the chimney is the tallest structure. But if the surrounding structures are taller, a lightning rod is to be provided to make the chimney the tallest.
 
gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Abey said:
I live in Sri Lanka. Can someone help me with 2 questions please:
1. To protect a steel industrial chimney against lightning, do we need to install a lightning rod at the top of chimney and use a down conductor and ground it or is it sufficient to connect the grounded earth electrodes to the chimney from the bottom i.e. let the steel chimney act as the conductor?
2. Do you need a lightning rod at the top anyway as the steel chimney can be the conductor?
Click to expand...

First, I am not an expert in lightning protection. However, I have seen the results of strikes and personally been within about 20 feet of one myself. Considering the amount of physical damage a strike can cause from air displacement as well as electrical effects, I'm not sure I'd want to count on the steel chimney to carry the current to ground. Depending on the diameter of the chimney, I might consider multiple down conductors and maybe even cross connect them every so often to try and prevent the strike from jumping to the chimney. Sort of like a Faraday cage.
 
L

LightningProtectionDesign

Member
Location
SW Florida
Abey said:
I live in Sri Lanka. Can someone help me with 2 questions please:
1. To protect a steel industrial chimney against lightning, do we need to install a lightning rod at the top of chimney and use a down conductor and ground it or is it sufficient to connect the grounded earth electrodes to the chimney from the bottom i.e. let the steel chimney act as the conductor?
2. Do you need a lightning rod at the top anyway as the steel chimney can be the conductor?
Click to expand...

I don't know what standard you would have to use in Sri Lanka, but the NFPA 780 has certain requirements for industrial stacks. It is considered a "heavy duty stack" if it is taller than 75' (23m), and has a cross sectional area of 500 in.2 (0.3m2). Do you know the height and size of the stack?
 
jaylectricity

jaylectricity

Senior Member
Location
Massachusetts
Occupation
licensed journeyman electrician
Smart $ said:
Being the original thread was nine months old as pointed out by i think it was mgookin, I'll let it slide into the nethers... :lol:
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Well, frankly I wish I had seen what you had posted. Being the one who started the other thread.

You can PM your thought to me and I'd appreciate it. Or whatever.
 
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