Article: fusible plugs Location

[f81aa]

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[buiquyduong]

Hi

Pls send me documents above calculation and selection fusible plug system

Thanks!

[f81aa]

Hi buiquyduong:

A few days after Mohamed started a thread (

[link Point to another website Only the registered members can access]
Now, you are using a public post and I´m answering in the same way. What follows is a transcription of those messages exchanged in January 2012:

“Hi,

I am in the design of a fusible link activated deluge valves for an offshore platform.

Is there any way to calculate the depressurization time for the fusible loop?
So that i can calculate and choose the length of the fusible line accordingly to be in line with NFPA.
Do you have any guideline or sample calculation for the same?
What is the size of the restriction orifice for the instrument air charging line?
What is the best architecture for the fusible loop?
Do you have any samples for the fusible loop layout?

I know that i am asking too much. Please guide me or tell me where i can find out these if possible

Thanks in advance”


“Hi:

I see why you were asking for help. Your questions were about details that are not addressed in the fire protection books. Well, at least the ones I have read.

I proceed to answer your questions:

Is there any way to calculate the depressurization time for the fusible loop so that I can calculate and choose the length of the fusible line accordingly to be in line with NFPA?
I´m going to give you 4 methods for determining the depressurization time for tripping the deluge valve, you´ll determine which one fits your needs. If you already have a design, see what value you´ll get.

Keep in mind that water delivery time = trip time + transit time. Calculating water transit time is more difficult, but may be accomplished using a mathematical model developed by FMRC researchers. The model requires the system to be divided into sections, and may therefore produce slightly different results, depending on user input. Maybe other models are available but none comes to my mind.

SFPE Handbook of Fire Protection Engineering
Comments in the file, I´d say it´s my first choice, simple and made for fire protection.

Piping Handbook
If I had to go thru some math to support my results, this is what I´d use, it´s my second choice. It would be interesting that you´d compare this result with the one obtained following SFPE Handbook of Fire Protection Engineering.

Consequence Analysis of Chemical Releases
Even more math than in Piping Handbook, it´s my third choice.
Assuming that the pipe is like as closed vessel, neglecting that the compressor will try to keep the air pressure, we know that as time elapses, both the air mass flow rate escaping and the detector line pressure will decrease.
Find how much air is contained in your piping (quick formula in Pipeline Rules of Thumb Handbook).
Determine the initial air mass flow rate leaving the pipe. Say that 2 or 3 seconds went by and get the total mass expelled.
Considering the piping as a closed vessel, subtract mass expelled from initial mass contained in piping and determine new internal pressure for next iteration. Repeat until you reach the deluge valve trip pressure, which you must know. See how many iterations you performed and you will have your answer.

Pipeline Rules of Thumb Handbook
Similar to Consequence Analysis of Chemical Releases, it´s my fourth choice.

These 4 books have been posted different times in the Forum and are available in internet.

I am attaching some other files that might be useful.

Do you have any guideline or sample calculation for the same?
It was answered above.

What is the size of the restriction orifice for the instrument air charging line?
I think that the restriction orifice size for the instrument air is specified by the deluge valve manufacturer. At least it was the case with the manufacturer I was familiar with when I was involved with deluge systems. I am attaching some technical information of VIKING CORPORATION products.

What is the best architecture for the fusible loop?
I don’t know if there is a “best” architecture. It depends on the arrangement of the equipment one tries to protect, obstacles in the route chosen for laying piping, probability that piping might be subjected to mechanical damage, etc.

Do you have any samples for the fusible loop layout?
No, I don´t.

Well, to put all together took me more time than what I thought. Good thing that I had some free time during the holidays.

I hope that I have provided you with information that will help you.

Best regards”

The same files that this member had access to can be downloaded from:

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I hope this information will help you and others.

Regards