Converting a 9 Litre Fire Extinguisher as an Air Tank (Edit)

By Steven Rowlandson
Published 08-Jan-07 07:54 PM

After a hard trip the time consuming need of airing up ones tyres can be a royal pain in the preverbal. To increase the efficiency of any on board compressor, a decent sized air tank can speed up the process. Here we look at a common way to solve this problem using an easily obtainable 9 Litre Water type fire extinguisher.

Firstly, a lot of people panic, as large PSI and tanks can be dangerous, and quite rightly so, but they need to understand a fire extinguisher is designed to sit on a wall full of water pressurized to 100psi, the common pressure we use with a 4wd type air setup thanks to the readily available ARB Pressure switch which keeps the compressor going when the air pressure drops below 90psi and pumps it up to around 105psi.

The Actual conversion process is very simple. Discharge the Extinguisher by pulling the pin and squeezing the trigger. once empty, it might pay to unscrew the head of the tank and leave to dry out.

Next unscrew the hose and replace with a 3/8" BSP Quick connect fitting. We chose the Jamec style which handle mud and dirt better than the more common Ryco type fitting. These are not a common size but are obtain from a hydraulic / air fitting specialist, we got ours from Des Munday in Geelong, Victoria.

Now to fill the tank, you can simply connect any tyre inflator to the tyre valve on the side of the tank to fill it. We chose a little more long term and permanent solution by removing the 1/8 BSP Tyre Value and replacing it with a 1/8" -> 1/4" bsp reducer. This then allowed us to fit a 1/4 turn gate valve (to isolate the tank) and then a simple male Jamec Quick Connect to allow it to be an inlet to the tank.

The last trick, is to tape up the handle in the squeezed position to allow air to flow from the outlet.

We had our tank mounted in the back of the Nissan Patrol then Toyota Prado behind the rear seats out of the way. This was plumbed into the compressor via a simple hose fitting which was ran from under the bonnet to the rear of the vehicle. We also ran an Offroader Air Manifold under the bonnet with 2 x quick connects to allow us to run up to 3 hoses at once from the vehicle. The tank takes roughly 5- 7 minutes to fill with our Max Air compressor which means the first 2 tyres are inflated from 15psi -> 35 psi in roughly 30 seconds. This roughly halves our time to air up. We also combine this with the Air Transfer hose we use to transfer air stored in the spare tyre (at 55psi as per the placarded tyres maxiumum pressure) to one or both of the rear tyres. By combining these 2 methods, we can air up all 4 tyres in a matter of 2 minutes and be on our way. Much more efficent than the old 30 minutes we waired for the reliable but slow ARB compressor!

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