Lightning Protection for Cold box

[zaza123]

I am working in Air seperation plant & we have a cold box. The cold box is tallest structure in our company. It is mettalic( but painted). Over the top of cold box is JIB crane which is taller than cold box. In my opinion Lightning rod which is connected directly to the Earthing Electrode is required for the Lightning protection of Cold box.The height of Lightning rod shall be more than the Jib crane height.
When asked to Consultant he replied that the Cold box is mettalic & base is grounded.
Is this explanation adequate or Lightning protection is really required.

 

[rbulsara]

I would think that at least the lighting rods (air terminals) are required on top of the jib crane structure and on top surface/perimeter of the cold box (depending up on the geometry and size of the area- look up NFPA 780). As long as the air terminals are firmly bonded (electrically) to the metal structure on top that is continuous and effectively grounded at the base, it would suffice. You do not need down conductors from the top the bottom.

The pointed rods/air terminals perform an important function in dissipating the electric charge as they build in the air, as I understand it.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

When transmitting high voltages, sharp points are avoided to prevent corona discharge. For lightning protection, you want the sharp points on the air terminals (lightning rods in the old days) to discharge the build-up of space charges with a corona like effect.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[zaza123]

For the air terminals the concept is clear, but i have read somewhere that the Air terminal shall be connected with the earthing cables & shall be grounded to a seperate Earth Electrode.
How good the resistance of the Structure shall be to ground the Lightning strike through its body, which ofcourse shall be painted.
Has anyone come across any lightning protection for coldbox