Periodic inspection of gas cylinders: who carries it out and what are the steps?

Gas cylinders are not checked only once when they leave the factory. A proper understanding of the periodic inspection of gas cylinders helps dealers and filling stations keep their cylinders fit for circulation at all times, rather than being caught out when cylinders fall due. This article explains who carries it out, the usual steps and how to plan for it.

How does it differ from checks at the factory?

New cylinders are pressure tested one by one at the factory and delivered with batch records — see LPG cylinder pressure testing and inspection records when receiving a new batch of cylinders. Periodic inspection applies to cylinders that have been through many rounds of filling and transport, and assesses the effects of time and use: rust thinning the cylinder wall, dents from impacts, heat damage, worn neck threads and identification markings that have faded.

Who carries it out, and on what basis?

This is done by an inspection body that meets the conditions set by current regulations; dealers and filling stations do not certify cylinders as passing themselves. On the safety side, steel LPG cylinders must meet the technical regulation QCVN 04:2013/BCT of the Ministry of Industry and Trade. On the technical side, periodic inspection and testing of welded carbon steel cylinders are carried out according to TCVN 6294:2007. The specific sequence and rejection criteria follow the applicable standard and the inspection body’s procedure.

Common steps in the periodic inspection of gas cylinders

1. Receiving and sorting: record serial numbers, sort by capacity and owner, and set aside badly damaged cylinders early.
2. Emptying any remaining gas following a safe procedure, in a separate area, before the valve is removed.
3. External examination: rust, dents, bulges, cuts, signs of fire; welds, foot ring and collar.
4. Internal examination where the procedure requires it: rust, deposits and foreign matter inside the cylinder.
5. Checking markings and the neck: the data stamped on the collar is still legible and matches the records; the neck threads are not worn; the valve is the right type and still seals.
6. Hydrostatic testing at the test pressure set by the standard; a cylinder that leaks or deforms fails.
7. Weighing the cylinder and comparing it with the tare weight stamped on the collar; a loss beyond the permitted limit shows that the cylinder wall has worn.
8. Fitting the valve, leak testing and marking the result and the next inspection date; repainting if the paint coat has deteriorated.
9. Rejecting failed cylinders: destroy them as required so that they cannot be reused as gas containers.

How often is inspection required?

The interval is set by current regulations; ask the inspection body or the local authorities. The due date is shown on the cylinder; overdue cylinders must not be filled until they have been re-inspected and passed. How long a cylinder can be used depends on the results of these very inspections — see how long do LPG cylinders last.

How should dealers plan for it?

• Draw up a list of cylinders falling due by serial number, month by month — see LPG cylinder management for dealers.
• Collect cylinders in batches outside the peak season, so that you are not short of rotating cylinders when demand rises.
• Allow for a rejection rate based on previous rounds, so that you can order additional 12kg gas cylinders and 45kg cylinders in good time.
• Prepare replacement valves such as the LPG cylinder handwheel valve for cylinders with damaged valves.
• Transport them as you would full cylinders: empty cylinders still contain gas vapour, so close the valve and fit the cap.

Dealers planning to buy additional second-hand cylinders should read should you buy used gas cylinders, as most of the hidden costs lie in inspection.

Frequently asked questions

Written by the VietnhatGas technical and sales team — a batch manufacturer of LPG cylinders. This content is for reference; regulations and standards may change, so please check the current texts.