Gate valve to actuate a spray system

[DavidCR]

A client has asked us to provide a spray cooling system for the walls of diesel fuel tanks in case of a neighbouring fire.

We have explained him that following NFPA 30 and the condition of the installation, type of tank, contents, separations, etc., a spray protection system is not a NFPA requirement. He has insisted that he wants a means to provide cooling, and that´s it. Our propposal is to desing rings of open nozzles following NFPA 13 and 15 with the respective water spray density, that can provide spray water on the sides of fire exposure of each tank.

We are used to design deluge systems with their respective deluge valve following NFPA 15 with automatic operation; but in this case, since there is plant personel and fire brigade 24 hr and we dont´t have a need to activate the cooling flow in a sudden way; I don´t see the need of a deluge valve with an automatic actuation system. Also considering that in the even of a fire, a manual valve located in a safe place would be enough to control the activation of the cooling spray on the exposed face of the tanks.

So I´m reckoning about not installing a deluge valve but only a gate valve (listed, indicating, etc.) to control the activation of the spray system manually. It keeps the system much simple and reliable. I´ve never done this and I don´t find a prohibition on NFPA to use a gate valve to control a cooling system, but I would like to hear the opinion of others on this.

 

[FFP1]

I have come accross this same situation at 3 different facilities. My advice is to make sure NFPA code does not require "exposure sprinklers" (primarily driven by the characteristics of the exposure, space separation and characteristics of the exposed structure) first. If this is the case, I agree with the manual open head deluge system if the customer wants the additional level of protection as long as the control valve is in a location which would be accessible during a fire involving the exposure........or you might want to consider a closed head system (antifreeze system) which is always active and would activate during a fire involving the exposure. You can make a case that this is an acceptable arrangement because the protection is not required by NFPA code; it is protection over and above NFPA code. In any case, I would have the project pre-approved by the authority having jurisdiction and possibly the insurance carrier for your customer. In my experience, the AHJ and insurance companies will accept the fire protection system (without the added expense and maintenance issues associated with deluge valves) if you explain the fact that the protection is not required by NFPA code and it is an added level of protection. ACE in the hole => let the AHJ and insurance company rep know the customer will not provide any protection for this exposure if they are required to use a deluge system.

I hope this advice is useful.