How to fill a portable air tank | 4 Key points to remember

Mar 22, 2019
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How to fill a Portable Air Tank

Portable compressed air tanks are usually used to do a quick job on the go or to get a job done is areas where a compressor/electricity is not available. These tanks vary from 2 gallons in size to 10 gallons and hence are very much suitable for carry. Once you use the compressed air in them, they would have to be re-filled.

Generally, you can get your air tank refilled either at a Gas station, Garage or a Workshop; since they would definitely be having a compressor around. A point to keep in mind would be that these compressors (In a gas station, workshop) would be cranked to much higher PSI output than your air tank is rated at. So, you will have to adjust the pressure regulator on the compressor before you start filling.


Your portable air tank can be filled directly from a compressor or from another air tank which has compressed air. I will explain the steps involved in filling and will also let you know some points to keep in mind when you fill up your portable air tank.

Filling a portable air tank – Steps Involved :

How to fill a Portable air tank

Photo Credits : Amazon

As I have already mentioned, you can fill up your tank using a compressor or another air tank which contains compressed air. Let us consider filling the tank using a compressor. I will break it down into 5 steps.


1. Take the tank to be filled near the compressor and place it on the floor.


2. Arrange a hose with the proper quick connect coupling’s which connect to the discharge of the compressor and to the air filling valve of your portable air bottle.


Filling line - Quick Connect

Photo credits : Amazon

3. Check the initial pressure in your tank by looking at the pressure gauge on it. You should be        knowing the maximum pressure your air tank is rated to. This can be checked on the label stamped on your tank. For your safety, always make sure you fill the tank to 90% of the stated pressure.


How to fill a air tank - Gauge

Photo credits : Amazon


4. Connect the coupling on the discharge hose of the compressor to the filling nipple on your air tank. To do this, you will have to pull the quick connect and insert it into the filling nipple. You can ensure that the coupling has been connected properly by rotating the quick connect. If everything is proper, the quick connect coupling will rotate.


Air hose with coupling

Photo credits : Amazon


5. Now that you have completed all the above steps, its time to start the compressor. It is always a good idea to check the Lube-oil in the compressor (if it is a oil-filled compressor) by using the dip stick provided or by checking the level in the sight glass. Make sure that there is sufficient lube oil. Start the compressor by pressing the starter; keep an eye on the pressure in your air tank as well as the discharge pressure of the compressor.

It might take some time for your air tank to fill up depending on the size of your tank and also the capacity of the compressor. Usually, it will take anywhere from 3 minutes to 10 minutes, so be patient.


Although it all looks easy, there are some additional points which you should know before you fill any portable air tank


4 Additional key points to remember before filling an portable air tank


1. Condition of your air tank :

 Before you plan on filling your tank make sure it is in good condition. You can do this by visually looking for any crack, weak spots and signs of rust. A weak tank is a huge safety concern as it can lead to an explosion in the worst case. Usually, the cracks form at the bottom of the tank condensate tends to accumulate. Also, another place to check for cracks is at the welded joints. So always do this check before you fill your tank.


2. Draining  the condensate : 

Condensate is a huge problem for an air tank since it will definitely lead to rusting of your tank and considerably reduce its strength. Reduced strength of the tank means that your tank can no longer hold the pressure it is rated to. Whenever we compress air from the atmosphere, the moisture in the air also gets compressed. This moisture is now in vapor state since the temperature of the compressed air is high. When the air cools down the, so does the moisture; which leads to the formation of condensate.

You can drain the condensate once your tank is filled. To do this, find the drain valve provided on your portable air bottle. It will be located on the bottom. Gently open it and let all the moisture drain out. Close the valve once you see clean air coming.


3. How to know when your air tank is filled :

I normally prefer filly my air tanks to 90% of the rated PSI. Although, almost all the air tanks are tested to withstand a pressure which is 50% greater than its rated pressure. What this means is, if you have an air bottle which is rated to 100 PSI, the manufacturer would have tested the air bottle to hold a pressure of 150 PSI. But, keep in mind that these are ideal conditions and a new bottle when the tests would have been carried out. Over a period of time the strength of your bottle would have reduced depending on various factors, so it is always better to fill it to 90%. In the above example, you will need to fill it to 90 PSI.

Keep an eye on the pressure gauge on the air tank as well as the pressure gauge on the compressor. You would never know if the gauge on your air bottle malfunctioned. So, it is a good practice to see both the gauges. Both the gauges should roughly be at the same pressure. Once your air bottle reaches the maximum pressure, stop the compressor. Do not over fill your air bottle as this will lead to an explosion; unless the air bottle is fitted with a safety valve.


4. Storing your air tank after use :

Generally speaking, it is a good idea to drain all the air from the bottle before you store it for an extended period of time. Draining the bottle would ensure that the condensate is also removed along with any oil that would have carried over from the compressor during filling.

Try to find a cool place to store your air bottle if you plan on storing it with compressed air-filled. What would happen is, if you store the bottle in a hot place; the compressed air inside the bottle will expand. This would lead to an increase in pressure. Suppose you have filled your bottle to 100% rated pressure and considering a weak spot somewhere in the body, it will definitely lead to a crack. Hence, if you plan on storing your portable air  bottle filled; keep it in a cool place.


Now that you know how to fill a portable air tank; I hope you keep in mind all the safety factors that are described over here. I hope you have a better understanding regarding the procedure now. So are you ready to fill your air tank?

Hi there! I am Macklin, here I will share some ideas and tips that I know about Compressors, Pumps and related things. I am a Marine Engineer and my work mainly deals with Compressors, Pumps, Boilers and other auxiliary machines. In this blog I will explain the things that I know about Compressors and Pumps, I will try to post new things that I learn along the way.

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