cooling water flows

[azcremers]

I am presently designing a cooling water flow for oil tanks. The local codes call for the design to take account of two different cooling water flowrates onto the tanks ('tan on fire' and 'neighbouring tank'). Without designing two different sizes (ID's) of cooling rings, I cant figure out how to achieve this. Did think about restricting flow via an orifice plate, but doubt this would work, as the restricted flow would not reach the end. Any suggestions?

 

[firedesignguy]

good day,

i am a designer of fire trucks, and would have to think that you could use a (how to descirde it ) a difusser plate within your water flow.

like a, preforadted screen, with a biger web of course, about 1/4" thick, this may allow air to get into the water flow for only a sec,(but may slow it down a bit) and should help to cool the water, you could also use a tank by-pass line ( witch will circulate the water within you water lkine if it is standing water like in atank or resivor) or a heat exchanger(used in engines cooling systems), the are available on the market from, acron, hale, waterous, darley, (company names)

it is nothing new and many cost 100-1000 dolars or so.

best of luck, hope i was some help.

cheers,

 

[acsajith]

Hi,

I am also woking in the same field. In my opinion restriction orifice will do the purpose but without seeing your scheme I will not be in a position to give any suggestion. You can also refer relevant NFPA codes.


regards,
Sajith
acsajith@yahoo.com

 

[gouveia]

I have also wondered about this in the past. I have never actually seen an installation that accomplished two flow rates. They usually just go with the higher flow rate.

But, I alway thought that a possible solution is to have two deluge valves. One could be extremely undersized and therefore create an extremely high friction loss. You could also run a few lengths of smaller piping from the deluge valve before tieing into you main loops. I would be curious to see what size the calculations require.

I suppose you could then setup some sort of logic in the fire alarm panel to determine which deluge valve to open.

Let us know what you come up with. Regards.

 

[DavidCR]

I´m courious about the water densities your code mentions. The type of tanks, size, contents, I suppose you are talking about fixed spray system, monitors, etc, ???.

I´d like to add some random points that hope may be helpful...

-I would ask if that code is reffering to minimun flow that the system must be capable to supply in order to consider the water demand, the system should be designed for the worst water consuming condition and not for several conditions.

-One should define a sensible worst fire scenario (worst water demand) following yor code.

-NFPA 15 5-5.3.7. Indicates that orifices plates shall not be used to balance spray systems.

-The more simple a deluge system is, the better.

-Water spraying on big tanks can be very water consuming and messy if oil spills are involved so try to design in a way the operation of spray systems can be controlled independently to apply water to the areas strictly required. For example API recomends to apply water to only tanks where paint is afected by heat or other danger symptom.

-If the tanks are located in convenient positions a monitor based sysems could be better that a spray nozzle deluge system. I would recomend to read some of API 2030, 2021, 2021-A, 2001 that may help to evaluate the usefullness of cooling systems.