Some details on the ignitor design would be helpful. Flares get naturally dirty and nasty so a clogged ignitor is not necessarily unexpected... Did someone send a bunch of liquid or other contaminants to the flare recently?

It may not be clogged but rather flat out damaged. Another possiblity is that part of the flare time has melted or otherwise been damaged and is now blocking the ignitor. Has anyone done an actual inspection or are you just assuming it is clogged?

yup..we already done do the actual inspection...3 pipelines are clogged..

1st, the input for ignition chamber are fuelgas and instrument air..the output of cos flame.

so this flame in pipelines are brought to the pilot to the flare. the clogged is at pipeline that brougth the flame.. so can you explain more how this clogged happen..

I have a very well experience related to flare system concerned with the design, construction and operation of that type of piping systems. The first trail was in 1985 when I was responsible to furnish a new 2 flare stacks with a new one Flame Front Generator, FFG using air/fuel ratio to create a flame to propagate through a pipe to ignite the flare tip which provided with a separate fuel line for igniting the pilots.

After erection completion of piping, and after adjusting air/fuel ratio used to make the flame propagation inside the pipes, I found that there was such damping to the flame, and inturn the tip still not ignited. After many trials, I discovered that the main causes of damping was the moisture due to ambient air located inside the pipes, and another cause was the sagging in that low size piping 3/4" & 1" in its midspan.

I dried the lines by purging a dry air, and I add an additional supports to avoid sagging, and at hence the system started to work.

Therefore the clog at your system may be due to moisture, sagging, or rust inside pipe, and I prefer to renew that piping.

cant we just unclog?

Could it be clogged from sooting? If you had a rich mixture in that line and a slow combustion taking place, you could get a lot of carbon formation. Do you think this could be a possible mechanism?