Lightning Protection on Cold Vent Boom at Wellhead Tower

The original post gives no hint as to whether it is the structure that is burned or whether there was a flammable material inside it that burned.

Two ways of reducing the probablility of lightning strike on a metal structure come to mind:

1. erect a taller, earthed, conductive structure somewhere nearby, so that the lightning takes a preferential path by that route
2. re-make the structure in something non-conductive.

http://cr4.globalspec.com/thread/45769/Why-You-Shouldn-t-List-Your-Email-Address

All measure to dissipate lightning can only prevent structural damage to vent stack; however even the vent stack is grounded properly it will catch fire (if explosive misture is present in atmosphere) as result of lightning b/c source of ignition is available.

I'm the R&D guy for a company called Flare Ignitors. As such I usually start fires instead of preventing them but my first instinct tells me that you need to look for a lack of ground on the boom. Are you not flaring these emissions?

if the structure is built to endure the gasses that burn and it is shaped to allow convective hot gas flow, as in a chimney, you have in effect, a flare that is allowed to vent unburned to the atmosphere, that lightning ignited in the rainstorm.

If it is not designed to tolerate this, if the flammable gasses flashed back to the wellhead and were able to ignite any gas/fluid at that point, if could become permanently lit until the fluid/gas runs out, which may allow it to burn for a long time, depending on leakage etc.

One would like to think a steel structure standing in salt water does not need lightning protection as long as the joints are welded, or otherwise very conductive. If it is bolted and the joints are corroded then you could easily get arcing around any badly conducting joint = an ignition point. This is in effect a bad ground, as RDGRNR said.

An experienced lightning guy would be able to tell you this, in fact, any experienced tower builders should be aware of this. Can you call the guys who designed and built your rig and ask?

There are static charge dissipators that are available for the top of masts on sailboats. They look rather like a chimney sweep's brush but made of stainless steel. I had one on my last boat but I have no data about the effectivity. The boom would have to be well grounded for this to work.

http://www.jmsonline.net/lightningstatic-dissipator.htm

You would probably have to put up a pole that would raise the dissipator above any flare / flame.

Remember the "cone of protection" is roughly a cone 45 degrees from the top of the highest conductor on the rig. Anything outside that could still be struck.

Finally, any particulates flowing in the flame might cause a triboelectric charge. So grounding the boom properly is absolutely manditory.

A non conductive gas can carry a static charge, and cannot be effectively grounded.I would recommend an alternating ion generator to neutralize the potential of the gas.

Whether Lightning Protection required for Flare Structure of FPSO ?