Need Help (Phast 6.54): To find Flammable Mass

[Sanjay kumar G R]

Material is LPG.
Using TNT explosion model, but i need to find 'flammable mass in the cloud' to put as input.

Please guide me!

[aj2016]

Material is LPG.
Using TNT explosion model, but i need to find 'flammable mass in the cloud' to put as input.

Please guide me!

you can do a vessel simulation, and the in the summary report, go to explosion. there you can find the flammable mass in the cloud. other way is to use all the supplied mass in the inventory as flammable.
in any case, it wide accepted the multienergy method

[Sanjay kumar G R]

Thank You so much!

And i need one more help from you.

I wanna know whats the significance of fractional LFL concentration envelope in flash fire graphs in PHAST 6.54.??

Flash fire envelops shows the ranges for LFL and FRACTIONAL LFL. Please help me understanding what exactly the graph saying.

[aj2016]

Thank You so much!

And i need one more help from you.

I wanna know whats the significance of fractional LFL concentration envelope in flash fire graphs in PHAST 6.54.??

Flash fire envelops shows the ranges for LFL and FRACTIONAL LFL. Please help me understanding what exactly the graph saying.

LFL frac. means the fraction of the LFL of your interest. Sometimes you need to assess the distance reached of 0.5 LFL, sometime 0.25 LFL. in order to change the fraction value, go to:

Parameter tab > flammable parameters > LFL fraction to finish (the defaul value is 0.5).

[Sanjay kumar G R]

Thank You so Much aj2016.

By the way, why Vapour Cloud Explosion results are not for "Heat Radiation v/s Distance". Its only gives "Damage Pressure v/s Distance". Any explanation for this ?

Thank You

[aj2016]

Thank You so Much aj2016.

By the way, why Vapour Cloud Explosion results are not for "Heat Radiation v/s Distance". Its only gives "Damage Pressure v/s Distance". Any explanation for this ?

Thank You

in VCE you are interested in overpressures rather than heat radiation because the duration of heat effects are small.
If you are interested in heat radiation, you have to do a fireball model.
Fireball model requires more fuel mass, then the effects are more appreciable

[Sanjay kumar G R]

Then, can i assume the same for flash fire results also?? Because, even flash fire lasts for a lesser time.
As you know, flash fire results are of UFL, LFL & frac LFL concentrations and its distances.
Results wont provide us anything about radiation capacity of a flash fire. So, for a report, how can i conculde with flash fire envelope graph?

You been so helpful to me, Thanks a ton.

[aj2016]

Then, can i assume the same for flash fire results also?? Because, even flash fire lasts for a lesser time.
As you know, flash fire results are of UFL, LFL & frac LFL concentrations and its distances.
Results wont provide us anything about radiation capacity of a flash fire. So, for a report, how can i conculde with flash fire envelope graph?

You been so helpful to me, Thanks a ton.

the dispersione study is helpfull to assess the distances of the cloud of flammable gas. that cloud can reach some ignition sources (then you assess the overpressure values by TNT or Multienergy model).
The same cloud can be a jet fire, so you assess the thermal radiation contours.
Your flash fire chapter should be made with a dispersion envelope. if in that envelope there is an ignition source (a hot device, a furnace) than you will have an explosion.
on the other hand, if the release is immediately ignited, you will have a jet fire and you will show the thermal radiation