Flame observed in continue venting Natural gas. 2

[Caprio]

During Rainy season ,flame observed for 2 to 3 minutes in cold vent gas stack.Is it a Normal situation or abnormal?
Natural gas continue venting through this stack with Nitrogen stream coming out from compressor casing in primary seal and secondary seal leakage stream.No flame is observed before even in Rainy season.My question is Why this flame appear? I hope,is not a dangerous situation? and what measures can we take if happen again?Please help me in this Regard.

 

[1503-44]

Not sure what you have there, but it does not sound entirely normal.
Gas + flame can always be dangerous, but sometimes it is just a pilot light. Gas without flame can build up to make high energy explosions, so gas without flame can be much worse than gas with flame. Hard to say what situation you have there. I suggest you have a professional investigate your particular installation and advise you how to proceed.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[NovaStark]

You may need to look at the design or operating manual of your system as it may be designed for flaring in a sense.

During rainy periods, static discharge can cause a such things. This is known to happen on the facility that I work in (and is a well known occurrence) but our vents are designed with this in mind.

 

[georgeverghese]

To prevent flashback during such accidental ignition of vent gas, there should be a continous purge of some inert gas or fuel gas into the flare header at a flowrate which prevents flashback. A low flow alarm on purge gas flow should also be enabled at DCS.
Also install a CO2 snuffing system to extinguish the flame when a flame is seen or detected via thermocouple.

 

[hacksaw]

Pipe size and pressure from the compressor casing, might be helpful.

When you say natural gas, are you talking about high percentage of methane, if so, what percent.

 

[LittleInch]

Most cold vents have some sort of flame arrestor on the end so that any lighting of the gas by spark, static or lightning doesn't track back down the pipe.

http://www.wermac.org/equipment/flame_arrester.html

As for why? well maybe your mix of inert gas to methane has changed?

Static / lightening can ignite a cold vent.

Some good advise above on what to do.

But continuous methane cold vents are usually worse than a lit flare for environmental issues.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hacksaw]

Make sure the compressor piping and the vent stack are properly grounded (earth grounds).
Purging is the vent stack is not commonly reqired.