Unwetted wall Fire case - insulation factor

[Bill3752]

I have recently sized several RV's using the unwetted wall equation. I have not included an environmental factor, F, as I do when doing wetted wall cases. In addition, the primary manufacturer software I am using does not allow F to be input. However, I just reread API 521, page 16, which states

"The discharge areas for .... on vessels containing supercritical fluids ... exposed to open fires can be estimated using equation 5 (F'A'/sqrt P). In the use of this equation, no credit has been taken for insulation. Credit for insulation may be taken per Table 5 (the environmental factor table)."

I am correct in assuming that I should be taking credit for insulation?

 

[gr2vessels]

Obviously yes, you should take credit for insulation. Otherwise why would anybody bother to invent fireproofing and similar insulation materials?

 

[JoeWong88]

Well... there are several issues related to insulation. It is related to reliability of insulation and obviously link to the credit on Environment factor...

i) resist high temperature ( > 900 degC per API) and sustain fire for n hours.
ii) Corrosion under insulation
iii) risk of external mechanical damage
iv) Galvanic corrosion and mercury embrittlement of aluminum blind rivets
v) jet momentum (jet fire) may mechanically damage the insulation layer

Read more in Some Comments on Providing External Insulation as Protective Measure against FIRE