Propane tanks are recertified by a process that involves the propane tanks being inspected and also verifying the safety of the propane tanks including portable propane tanks at certain intervals and after certain dates have passed.
The recertification process of propane tanks includes performing a visual inspection for any severe rust or other damage and a pressure test of the main valve and the tank itself to ensure the tank is safe to use.
Trained professionals check the propane tanks for any dents, gouges, bulges, heat and fire damage, any damage to the welds, rust and corrosion.
If there is any severe rust or dents or gouges or bulges or heat and fire damage or damage to the welds or any severe corrosion the propane tank will not pass inspection and won't be recertified.
The inspector when recertifying the propane tank will also ensure that the ring on the bottom of the propane tank is in good condition and can hold the tank upright.
They will also inspect any labels and markings and ensure that any required markings and labels are in place.
The collar and valve will also be inspected and they will also ensure that the relief valve still works and is also not damaged.
A pressure check will be done on the tank and valve and they will use special tools to check for any leaks and perform a pressure test on the main valve.
Some propane tanks may also undergo more intensive volumetric expansion tests to determine the propane cylinder's expansion at a given pressure.
If the propane tank passes all tests then it will be recertified as being safe to use.
Once the propane tank is recertified, a new date will then be marked on the propane tank and it is then considered safe for use until the next re-qualification interval.
Propane tanks often require recertification between 5 to 12 years after the propane tank is manufactured, depending on the size of the propane tank and size.
The propane tank certifying company will also either add a sticker to the tank with the inspection date or stamp their own mark into the top of the propane cylinder.