What happens if vapor condense in flame arrestor

[ENG-RAY]

Hi all,

Can somebody tell me what can happen if Liquid collects in a pipe with deflageration flame arrestor ?
or if liquid condenses in a tank breathing valve with flame arrestor? Can we say it will not be effective anymore?
we are a polymer plant and most of our storage tank breathing valves are heat traced. The question was that what will happen if the heat tracing fails. We can somehow confirm that there will be no polymer in breathing valve but solvent may condense in pipe or breathing valve. The Liquid will not be that much to affect the set point of breathing valve but I am not sure what will happen to flame arrestor which normally designed for gas.
Tanks are atmospheric and have blanketing and breathing valves which open into atmosphere.

 

[Latexman]

If the liquid is condensed monomer, from a tank of monomer with a non-volatile inhibitor, then it will probably polymerize and plug the flame arrestor.

If the liquid is condensed solvent, it will probably have very little affect.

Good Luck,
Latexman

 

[TiCl4]

ENG-RAY,

Your flame arresters should be designed to disallow liquid accumulation. Placing an in-line flame arrester (FA) between the tank vent nozzle and the vent valve allows liquid to return to the vessel. If you have the FA above the vent valve, then liquid accumulation may drip back onto the vent valve - not good. Solvents are only a concern here if the liquid accumulation may change the opening pressure of the vent valve. Usually these outbreather valve will crack open at least once per day - this event normally should allow some of that liquid to drain back into the tank.

With monomer service, as LI stated, you have the risk of even a very little bit of residual monomer polymerizing and plugging the vent valve or flame arrester. This is a slow process normally - the "Acrylate Esters" storage and handling guide recommends 6-month PMs for flame arresters. I'd recommend you have at least a 6-month, if not more frequent, PM on the vent valves and flame arresters to check for buildup. There does not appear to be an immediate risk if heat tracing is non-functional.

 

[georgeverghese]

Deflagration and detonation flame arrestors are in many cases ineffective(other than in clean, dry and non corrosive applications) and in reality are a major safety risk. Wherever possible, replace with a liquid seal drum or continuous inert gas purge or fuel gas purge for vent gas collection systems to prevent flashback.

 

[ENG-RAY]

thakas all. Unfortunately it is not possible to replace flame arrestor. It is a regulatory requirement to install it when we have even EX-Zone 2 in tank. last inspection shows no accumulation of liquid and no plugging in pv vent. But actually it does not prove anything because we have heat tracing and the question is what happens if we do not. As said we had liquid in flame arrestor ( although the line has heat tracing) in pipe which is connected to flare. (Each tank has a pipe connected to flare and a pv vent which opens into atmosphere) and our notified body ( TÜV inspector) insist that flame arresstor is not effective if liquid condensed in it because it has been designed for gas! I doubt it !

 

[pierreick]

Hi,
Consider to read the document attached and consult vendor to provide a solution ( Tracing could be steam tracing and electrical tracing)

https://paradoxintellectual.com/upl...lame_arresters_in_piping_systems_api_2028.pdf

Note : If your system is plugged you are going for trouble as explained by latexman ( Polymer and lack of inhibitor). I had a Phenol tank collapsing because steam tracing was not effective on a vent line.
A regular check is a must until you get a definitive solution , to me should be every month or less (regular task for maintenance and operation crew) .
To be considered the treatment of the gas at the outlet of the vent line using a TO (thermal oxidizer ) or a wet scrubber and the removal of the flame arrester .
Pierre

 

[georgeverghese]

Where regulations require flame arrestors to be used, and you expect it to get blocked, you can install a rupture disk in parallel with the FA. Check if the regs actually require a wiremesh type FA; if not, a liquid seal drum is also a flame arrestor.

 

[ENG-RAY]

Thanks all for your help.

 

[TiCl4]

I think a parallel system is overkill for this service. Just PM the flame arresters and vent valves on a regular basis. I want to emphasize this - monomer buildup and plugging of flame arresters is not a fast event. We check our vents monthly and flame arresters every 3 months. We have no heat tracing at all on any on the vent lines. With decades of experience here, the only monomer of over half a dozen bulk monomers we have that has ever developed headspace polymerization worth mentioning is styrene.

 

[pierreick]

Hi,
For those interested with the subject Monomers (acrylic esters) , please consider the link attached .

https://www.dow.com/content/dam/dcc...and-storage-of-acrylic-esters.pdf?iframe=true

Enjoy the reading
Pierre