1. ## Supplied Air

Hello Everyone

We have a 1999 American Lafrance rear mount arial with supplied air to the tip. It has a 4500psi tank larger than an M cylinder. Does anyone know of a formula to figure out how much air time wise is left in tank,( for example sake if it has 2000psi left).

Thanks,
SABIL732

2. To answer your question you will need to know the size of your cylinder and the rate at which air is being used per minute.

Here is a formula that can be used to calculate the duration of an "M" cylinder.
Gauge pressure in psi minus the safe residual pressure (usually 200 psi) times 1.56 divided by the flow rate will give you duration of flow in minutes. For example, an M cylinder of oxygen with a starting pressure of 1,200 psi, minus the safe residual pressure of 200 psi gives 1000psi X 1.56 equals 1,560. If you flow 5 liters per minute you will have 312 minutes of flow.

The 1.56 factor is related to your cylinder size. A smaller cylinder has a smaller factor, a larger cylinder, such as an "H" clinder, has a larger factor of 3.41.

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