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In this article, we will look at a little more detail on some passive and active fire safety features.
Revisiting defendable space.
Firstly, it would be appropriate again to emphasise the importance of defensible space. We have indicated that it should be a minimum of 30 metres. With many variables that could extend the space even further I.e. topography.
Fire services further break this defendable space area up into zones which generally looks at the level of management required. Also important as we need to manage the space effectively.
Reducing even fire-resistant plants within 10 metres of the building. If your protected building is to survive then there must be no avenue for direct flame contact.
Fire Resistant plants including small trees and shrubs will help to reduce the number of embers making it to your house.
The moral to the story is that the defendable space must be well thought out and managed.
Taking advantage of a well set up ring-main.
As mentioned in previous articles. The use of a ring main around the buildings you want to protect can substantially increase the effectiveness of emergency fire response.
When we think of a ring main, generally they are used around large factories and can include pipes as large as 250mm.
This diameter of the pipe and subsequent flows is much greater than anything we would need to use. Furthermore, the length of the ring main would be far less around our house. Thus much less scope for friction loss.
I’ve used 40mm poly piping around my house and it provides excellent pressure and flow through two 25mm lay flat hoses being used at once. This system does not run a fixed house mounted sprinkler system but does run two 14 litres a minute portable impact sprinklers.
The pump is a high pressure multistage electric motor and pump (150l/m with a 60-metre head).
We have tested this system with two 25mm lay flat fire hoses and the two impact sprinklers and achieve optimum flows from each. Another 25mm hose could have been added without any substantial flow or pressure loss.
Running a sprinkler system would require increased flow and a larger capacity pump. A twin stage fire fighting pump capable of supplying the number of sprinklers and hoses you intend to run. As
suggested in a previous article a diesel motor on a good quality twin stage fire fighting pump would be ideal.
The importance of planning.
It would be easy to go out and buy too much or too little equipment. So at a minimum, you need to work out the flow rate of all sprinklers and fire hoses. Taking into account any potential for friction loss. The more corners and bend you have in the system the greater the friction loss.
Once you understand what flows and pressures you to require them it will be easy to identify an appropriate pumping system.
Remember, you should have a main pump and a backup pump. The backup should be able to supply the system similarly to the main pump and also have a diesel motor.
It is ok to have an electric main pump but with a diesel backup generator and a diesel pump as a backup.
Such backup pumps should be linked into the system so if there is a failure then it’s just a matter of starting it and continuing firefighting. Even if you just need to connect a hose it can be very problematic during times of high stress associated with firefighting and emergency response.
Why a diesel motor on the pump.
As you probably already aware, petrol is much more flammable than diesel. A couple of decades ago the Country Fire Authority (Victoria) moved from petrol motors on their pumps to diesel motors. During firefighting operations, especially on days where the temperature is above 40 degrees celsius.
There was a number of reports of tankers fitted with petrol motors, failing at critical times. When firefighters lives were in real danger.
Petrol is not only more flammable than diesel but it vaporises at a much faster rate than diesel. The failed pump motors were attributed to the petrol vaporising before it made its way into the combustion chamber of the motor.
Thus the pump didn’t have fuel to continue operation. Therefore, the only option, in terms of safety, is a diesel or diesel-electric motor and pump.
One comment before we move on. If the economy is important – there are a number of good diesel fire fighting pumps available on eBay and other cut-price suppliers.
If very high quality is what you are after then suppliers of HATZ Diesels are ideal. Prices start at around $10,000 AUD. Yanmar are another very good brand and prices start at around $5000.
Back to the ring main and fixed building sprinklers.
Poly pipe is certainly more economical than copper or other types of piping. Even so, a registered plumber, who works on this stuff every day, will probably do a great job for you.
You could reduce the cost by digging the trenches for the pipe. In terms of riser for the sprinkler system. A plumber should perform this function.
The ring main, in most cases, will be used to supply the sprinklers, but be very careful when it comes to placement.
Plumbers aren’t always aware of the impact of heat and wind on systems. If you search for bushfire sprinklers on Google you will find numerous companies who can help you make informed decisions.
They often can provide products that have been specifically designed for protecting a building during a bushfire.
I noticed on the news last night (09/01/2020) that a number of houses survived when others burnt to the ground during the bushfires.
What was noticeable from the air was the amount of defendable space used by property owners that had their house survive. Most also had maintained green grass within this space. It’s certainly not the total answer but it does help.
There seem to be so many options when it comes to protecting your property. Even so, if you fail to plan you are likely planning to fail.
In the next article, we will take a little detour and look at what it takes to leave and not “stay and defend”.