differ between clesd head sprinkler pattern and nozzle spray pattern for the same k factor

[mody2017]

Dear Members,
what is the difference between closed head sprinkler pattern and nozzle spray pattern for the same k factor?
my problem is that i have close head sprinkler network installed for a store and the HJ requested to replace this sprinkler by open head nozzle and when i mad a quick check i found this action can be applied,
the contractor said i cannot be replaced by the nozzles , it must replace the pipes ( even it has the same pressure, flow, and velocity?
i need a justification for the contractor?
your respond to my message is appreciated.

 

[MGXFP]

If you want an open nozzle system it must be a deluge type. That is a different type of fire sprinkler system than a wet pipe and one can't assume the two to be interchangeable by replacing the sprinklers with nozzles.

With open nozzles every nozzle in the system must and shall discharge at the same time. A wet pipe sprinkler system is only designed to have a certain number of sprinklers operate [not less than 5]. Reference NFPA 15.

Nozzles have different spray patterns than standard spray or extended coverage sprinklers. With nozzles you must account for the pressure, angle and k factor along with the density and area to determine the coverage. This shouldn't be an easy swap but an entire overhaul.

 

[mody2017]

thanks alot for your respond, but i conducted hydraulic calculation and ensured that pressure and every thing is OK and there is already deluge valve.
my problem with the contractor is the contracotr refuse to change the sprinkler with the same properties nozzles.

 

[MGXFP]

Just for reference, what type of store needs deluge systems with open nozzles?

I suppose I don't see the need for such a specialized system for mercantile.

 

[MatthewJWillis]

How many sprinklers were flowing in your calc verification?

R/
Matt