Fire Protection tank

[ifran31]

Dear members,

What are the design guidelines in the design of Fire Protection tank (fixed and floating roof)?

thanks in advance,
R.B (Mechanical Engineer)

 

[BigInch]

Use a fixed roof.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[Latexman]

What BI said. An API-620 tand would do nicely.

Good luck,
Latexman

 

[MJCronin]

ifran31...

You want to review NFPA 22 "Standard for Water Tanks for Private Fire Protection", 2008 Edition.

All NFPA-22 tanks are fixed roof.......they are to be filled only with water.

This guideline contains information on tank sizing and design, quality requirements, inpection and periodic testing.

The tank must be matched to the pumping system and meet performance requirements defined for the specific installation.

NFPA-22 tanks can be expensive to keep warm in cold climates !!

Tell us more about your installation !

 

[ifran31]

Good morning experts,

thank you for the message you sent for my preoccupation cited above

Concerning firefighting calculation, I opted the following codes:

- NFPA 11, 15 et 30

- API650 édition (Annex C)

The worst case scenario is:

The worst case is to calculate the firefighting flow (cooling and foam) of a tank independently of the other tanks.

Firefighting flow calculation

Calculation conditions

- The Crude oil is classified as Class II Liquid as per NFPA 30 Chapter 1-7.3.2.

- Fuel flash point is between 100 º F (37.8 º C) and 140 º F (60 º C).

- Product is crude oil,

- Diameter of the tank is 67020 m,

- Height of the tank is 17.18m,

- Nominal capacity of the tank is 50000m3,

As per NFPA 30 table 2-7:

The radius of the imaginary circle is the radius taken from the shell of the tank supposed to fire more then 15m

The formula is = 67.02 / 2 + 15 = 48.5 m

The (02) adjacent tanks are outside the imaginary circle that requires no cooling.

Tank on fire

1)Cooling water :

As per NFPA 15 Item 4.3.1.3

Required water flow (6.1 l / min / square meter) of the surface of the shell IN TOUCH OF FIRE OR THIS IS ANOTHER AREA (OTHER THAN THE TOTAL AREA OF THE SHELL)

Q1 = 6.1 x 67.02 x 3.14 x 17.18= 22065 l/min Or 1324 m3/h !!!!!!!!!!!!!

This flow seems very right to cooling the shell of the tank supposed on fire

2)Foam:

a.Calculate the total area of the roof of the tank

S1 =3528 m²

b.Calculation of the internal surface ofter foam dam

S2 =3403 m²

c.Calculation of the internal surface of foam dam

Premixture flow rate (water + emulsifier) necessary for the production of the foam

As per NFPA 11 TABLE B-1

12.2 liter / min / m ² of the annular surface between the shell and the foam dress.

Q2pm = 12.2

S = 12.2 x 126 = 1537 L/min 93 m3/h (water + emulsifier)

Water flow is 94% with 6% emulsifier

Q2 = Q2pm x 0.94 = 93 x 0.94 = 88 m3/h

Please your comments

Thanks and have a nice day
R.B (Mechanical Engineer)

 

[ifran31]

My installation is to protect floating roof tanks (six (06) tanks), the tanks presents the same capacity (50 000 m3) and the same liquid (crude oil), the type of roof is a floating roof double deck,

My concern is to choose the code to calculate the flow of cooling water and foam,

At the moment I am not familiar with the NFPA code, in my small experience, I have only used the French codes

Thanks
R.B (Mechanical Engineer)