Required Ventilation to control Isobutane Flammability...PLEASE HELP

[YousufAli]

Hi

We make Extruded polystyrene foam. I was looking in to converting to a butane based blowing agent from a HCFC based one. I was looking at possible leaks of Isobutane from the die area. One scenario was that the blowing agent came in to the extruder but for some reason the gel did not and the die released 100% of the blowing agent.

If 60 kg of isobutane is used under s.t.p that comes to around 26000 liters of butane. If this is emitted out of the die in to the factory ( 90x30x10 meters). Also as the blowing agent is leaking in a specific area those that make a difference to its flammability. Will this be flammable? the LFL is 1.8% UFL is 8.4%. And if so how much ventilation will i need to counter this. Basically i just need some help in the calculation and i ll be set. I just need a approximate but safe answer.

Thank you very much

If you need any more details please ask

 

[StoneCold]

Ok
Since you use kg and Liters I assume you are not in the USA. I am so I will give you advice from that point of view. Honestly it would be easier to start with a new facility, design for Class 1 Div 1 electrical and an H3 chemical processing area. Then worry about ventilation to dillute the release of iosbutate. An old facility could be modified but I think you still need at least classified Electricial, 6+ air turnovers an hour, and fill in any sumps or trenches that you have. You also ought to have fire suppression that can deal with the isobutane, ideally foam or fog suppresion. I don't mean to make it sound impossible, but I would stick to the HCFC blowing agents or go to a nonflammable agent if it was me.

Regards
StoneCold

 

[moltenmetal]

Is this release a normal situation or an upset condition?

How fast will the release happen? In a minute? A second? A day?

Are there any sources of ignition present in the immediate area?

 

[mbt22]

BS EN 60079, part 10 I think, contains a calculation method for this. Assuming that you're thinking about area classification, dilution ventilation to limit the formation of a flammable atmosphere typically requires high air change rates (I've seen between 40 and 200 air changes per hour).

Matt

 

[YousufAli]

Replying to moltenmetals questions:
I am trying to take into consideration the worse possible scenario so lets say 26000 liters of butane leak instantly (in a second).

Yes there definitely are sources of ignition

Also mbt22 where can i find BS EN 60079, part 10. Could you please give me a link.

Thanks to everyone who contributed really appreciate it.

 

[mbt22]

The link to buy the standard is below.

Personal opinion, though, 60 kg of LPG rapidly released into a building feels an impractically large amount to disperse below the flammable limit by dilution ventilation. To dilute your 26000 litres of gas to 20% of the LFL needs 7200 m3 of gas, or a quarter the total building volume.

Matt

 

[ports394]

For Class 1, Div 1, we use 10 air changes per hour.

Overall you may be under the LEL, but what about localized pockets of higher concentration... ie near the leak.

Sweeping gasses is also a good alternative.. If you have some sensors to detect the leak, immediately sweeping the equipment with CO2 would be a good idea...