5 replies to this topic

[sandek]

Dear forum members

 

For  determining fire case relief load for an Air Fan cooler API 521 section 4.4.13.2.8.4 has given  below condition to consider bare tube surface as wetted area

(a) tube bundle height < 25 ft

( solid platform can sustain pool fire

© AFC outlet has control valve

 

In may case (LPG vapor to Liquid condensing) all above condition are met and accordignly required releif load comes out to be  very very large when total bare ture surface area is considered as wetted area

 

Request the learned members in this forum  to gude me if the approach is correct or i am missing something. 

 

Thanks & regards

[fallah]

sandek,

 

Please specify which equations and what constants (units systems) have been used for relief load calculation in AFC fire case...

[sandek]

fallah

 

Thanks for showing interest on the subject.

Below are more detail of the problem:

1. Tube OD x L x numbers 25.4 mm x 9144 mm x 2160 (6 row in 8 bundle)

2. formula used Q = C1 Aws   

[ This is Equation 20, C1 = 66,300, Aws = 1576 m2, exponent to Aws is taken as 1 as per API 521 section 4.4.13.2.8.4]

3. Latent Heat of Vap = 216.7 kJ/Kg

 

 (my apology for several spelling mistakes in my previous post)

 

rgds

[fallah]

sandek,

 

The reply to the first question in page 6 of 9 of the file included in following link might help you out to clarify the matter:

 

http://mycommittees....ments/521ti.pdf

Edited by fallah, 30 April 2015 - 08:50 AM.

[sandek]

Thanks fallah for the link.

 

It basically clarified the correct C values due ot chage in units.

 

My basic query here is to know the opinion of members regarding use of total bare tube area as weltted area for fire case relief load calculation in case on air fan cooler. 

 

For an existing RV, basis of the fire case relief load claculation is not found ( done 20 years back) but on  back calculation it appears that wetted area considers is appriox 2.3% of total bare tube area. On reviewing the existing design as part of modification scope (the AFC is the same ) the new load comes out to be exceeding the flare system capacity!!

What I am missing here?

 

rgds

 

sandek

[fallah]

 

It basically clarified the correct C values due ot chage in units.

 

My basic query here is to know the opinion of members regarding use of total bare tube area as weltted area for fire case relief load calculation in case on air fan cooler. 

 

For an existing RV, basis of the fire case relief load claculation is not found ( done 20 years back) but on  back calculation it appears that wetted area considers is appriox 2.3% of total bare tube area. On reviewing the existing design as part of modification scope (the AFC is the same ) the new load comes out to be exceeding the flare system capacity!!

What I am missing here?

 

 

sandek,

 

It might for that existing RV due to, say, having no control valve at relevant AFC outlet fire case hadn't been considered as credible scenario at that time...