This article is based around NZS 4541 – Automatic Fire Sprinkler Systems, a New Zealand Standard.
A fire sprinkler system is a series of sprinkler heads connected to pipe that is filled with water. That simple huh! I don’t think so.
A fire sprinkler system is a well designed system designed to put or control fires in properties. Each system is individually designed for the building in which it is going to be installed. Every aspect of the building and it’s contents is considered in the design. But, to understand a sprinkler system, we need to get back to basics.
There are 3 main component groups in fire sprinkler systems;
1. The water supply
2. The control valve set
3. The installation consisting of the pipes and sprinklers.
The Water Supply:
A sprinkler system is totally dependent on it’s water supply. The water supply can vary from a connection to the towns main to the installation of tanks and huge pumps. For the purpose of this article we are only going to deal with the towns main supply.
The towns main supplies the water to the system via an appropriately sized connection. This connection is normally valved at the point of connection so that it can be isolated if the need arises. The size of this connection is determined by the flow and pressure required for the correct operation of the system. This is determined by the hydraulic design – more on that later.
It goes without saying that the water supply is the most important part of a fire sprinkler system – no water supply, no fire sprinkler system.
I have been involved in the design of numerous fire sprinkler systems over my 40 years in the industry and it all starts with the water supply. The first thing to ascertain before you proceed with the either the design or installation is the quality of the water supply. I have known of instances when systems could not be installed because the water supply was not sufficient and was not capable of being improved by the use of pumps, reservoirs etc.
The Control Valve Set
Once you have the water supply to the building you need a control valve set.
This contains another isolation valve for the purpose of quickly shutting the down the system in the event of a false activation or after a genuine activation in order to allow the system to be reset. It also allows for the system to be shutdown for maintenance purposes.
At this point there is also an alarm valve which is a modified check valve. This serves the purpose of keeping the system charged with water and, owing to it’s special design, allowing for a hydraulic gong (water motor alarm) to activate when the system operates. This gives a local warning of the activation.
Located on this alarm valve is a large drain port (which is also valved) which allows the system to be drained as and when necessary.
We also have a DBA (Direct Brigade Alarm) which is an electrical device that monitors the state of the fire sprinkler system. It notifies the fire brigade when the system activates and also has a defect function that warns the service agent of any pressure drop or other potential problems.
If the system is pressurised above towns main pressure then there will also be a small system booster pump. There are also many other smaller ancillary valves.
The installation consisting of pipes and sprinklers
Above the control valves the system covers the entirety of the building with pipe and sprinkler heads. Each pipe is hydraulically calculated to make the most of the available water supply. The pipe weaves from the valves to it’s final point in varying sizes. The larger pipes are called mains and the smaller pipes are called ranges.
Each pipe is supported with seismically designed supports to maximise it’s ability to withstand earthquakes and other destructive forces.
There are now many different types of sprinkler heads and these need to be selected carefully to make sure they will do the necessary job. For instance, a sprinkler in an office may look, and act, dramatically different from one in a storage warehouse.
Sprinkler systems come in many shapes and sizes and not one size fits all! I have given you a brief tour through a sprinkler system but, by necessity, there are many items I have not covered. One of the major items I have not covered is the maintenance and testing of sprinkler systems and I hope to do this in a future article. Diesel Fire Pump