How & Why Would an LPG (Propane) Cylinder Explode? LPG Tank Explosion
LPG cylinder or LPG tank explosions do not happen with any frequency. An LPG tank explosion or blast is actually quite rare. Gas cylinders can explode but not easily or often. Even trying to get an LPG cylinder-tank to explode intentionally is very challenging.
Now, you may be thinking that I am only saying this because I work for an LPG company.
How can what I say be true when you see reports of “exploding gas bottles” in the news with some frequency?
The issue lies with the erroneous reporting of the facts…
LPG Tank Explosion or Blast vs Gas Explosion - Can Gas Cylinders Explode
It is extremely difficult to get an LPG cylinder or LPG tank to blast or explode, even trying intentionally. An LPG tank explosion is a very rare event. Gas cylinders can explode but it is rare.
The real issue lies with poor reporting. Reporters have a habit of calling any explosion that involves bottled gas an "LPG tank explosion" or a “gas bottle explosion”.
However, what is usually taking place is an event that does not directly involve the gas bottle(s).
The typical scenario is a gas leak from a gas appliance, connection or fitting.
Gas from the leak accumulates within a confined space and that is what catches fire or explodes.
Because home LPG bottles are normally stored outside, the gas bottles or LPG tanks themselves are frequently untouched by the explosion or fire.
For example, there was a tragic accident a few years ago involving an explosion and fire.
The newspaper headline read “Gas Bottle Explosion” but the accompanying picture (see below) showed the gas bottles still standing there, next to the gutted house.
Ironically, the gas bottles (green arrows) were just about the only thing left intact.
Even the intense heat of the adjacent fire didn't make them explode.
BLEVE - Boiling Liquid Expanding Vapour Explosion
An LPG tank explosion is sometimes referred to as a BLEVE. BLEVE is the acronym abbreviation for Boiling Liquid Expanding Vapour Explosion.
If a pressurised gas bottle or vessel ruptures when the contents are above their boiling point, it is referred to as a BLEVE. A BLEVE does not necessarily involve fire. A prime example of this is a steam boiler explosion.
LPG (propane) bottle and tanks rarely BLEVE because of the Pressure Relief Valve that releases the excess pressure, preventing an LPG tank blast.
Does Shaking Cylinder Cause it to Explode
Shaking a cylinder does not cause it to explode.The only result from shaking a cylinder is getting tired arms, but it will not cause the cylinder to explode.
Evidently there is a fake video showing the shaking of a cylinder causing it to explode, but it is just a hoax.
LPG vs Natural Gas Explosion
Leaking gas in a house or other structure could be either natural gas or LPG.
Either scenario could result in a gas explosion and fire.
If there is a problem with an appliance or fitting, within the house, leaking gas can accumulate.
Regardless of the type of gas, the results would be the same.
This is one reason why you should have regular maintenance on gas appliances.
BBQ Gas Fire vs LPG-Propane Tank Explosion
BBQ gas fires very rarely cause a LPG-propane tank explosion. Faulty barbecues can cause gas fires, as gas BBQ maintenance is often overlooked.
This neglect results in hoses perishing, O-rings getting damaged or lost, old regulators leaking or gas knob valves starting to leak.
Gas leaks from poor connections, faulty gas regulators and damaged hoses are the most common causes.
Homeowners should regularly check for leaks with the soapy water leak test.
Preventing BBQ fires with good BBQ maintenance should be the focus.
The gas leak is rarely from the gas bottle itself and an actual gas bottle or LPG tank explosion, resulting from a BBQ fire, would be very unusual.
The fire will self-extinguish when the gas bottle runs dry, as barbecues should always be placed safely away from other flammable materials.
The gas bottle may have some scorch marks on it, but it is intact.
In my many years in the LPG industry, I have seen many BBQ fire investigation reports and photos.
In all that time, I have not once seen a homeowner’s BBQ gas bottle or propane tank that has actually exploded.
Not once. Never.
How Do Gas Stoves Explode? What are Some Precautions to Prevent it?
Gas stove explosions are rare. The important thing is to make sure the flame is lit, so that there is no accumulation of gas.
There are built in safety devices, such as a flame failure device, which is designed to stop gas going to the burner of a gas appliance if the flame is extinguished. These safety devices helps prevent a dangerous buildup of gas within the stove.
Some stoves also have auto re-ignition, that can relight the burner if it goes out.
There are also timers built into some of the starters, that cut-off the gas if it doesn’t ignite within a very few seconds, preventing the accumulation of gas and any possible explosion.
Gas stoves explode only if the safety devices fail and the stove is unattended, as you would smell the gas.
No gas accumulation equals no gas stove explosion.
Tradespeople Incidents with Other Gases
Gas bottle explosions involving tradespeople, and welding in particular, are almost certainly not LPG.
Acetylene gas used in oxy acetylene welding, which is very volatile, is frequently the culprit.
Pictures of a completely destroyed plumber’s truck are almost assuredly acetylene related.
Pictured above is the result of an acetylene gas bottle explosion in a tradie's van.
However, the media just reports “gas bottle explosion” without specifying the gas.
The result is that many people falsely assume it was an LPG tank explosion.
The Media Just Loves to Report Exploding Gas Bottles or Propane Tanks
It should come as no surprise that the media is fond of reporting “exploding gas bottles”, even if it did not actually occur. It just sounds so much more exciting and dramatic than “BBQ fire”.
Most of us have heard the news media expression: “If it bleeds, it leads!”
And it would not be an exaggeration to say that the media likes to sensationalise the news.
After all, that’s one way they keep their audience interested.
Pressure Relief Valves Prevent LPG Tank Explosions
So, why are gas bottle or LPG tank explosions so rare?
Gas bottles have been around for about 100 years.
Over that time, the gas industry has had a lot of time to perfect the safety features of gas bottles and valves.
Arguably, the single most important safety feature of a gas bottle is the Pressure Relief Valve.
It’s actually a valve within a valve.
The Pressure Relief Valve is incorporated into the main gas valve on the bottle, as shown in the accompanying picture.
If the pressure of the gas inside the bottle increases, as the result of a fire or other heat source, the pressure relief valve releases some of the gas to relieve the pressure.
The typical cylinder would probably only burst with pressures over 6895 kPa or 1,000 PSIG.
That's about 5x the normal pressure.
The typical pressure relief valve setting is 2585 kPa or 375 PSIG.
So, the cylinder would never actually go above this, as the valve would open and lets some gas escape, limiting the pressure inside the cylinder.
Even at 54°C (130°F), the pressure would only be 1794 kPa (257 PSIG).
So, not only wouldn’t it approach bursting pressure (≈ 1,000 PSIG) but, under normal circumstances, it would never even reach the 375 PSIG required to trigger the pressure relief valve.
No pressure build up means no risk of an LPG tank explosion.
Pressure Relief Valves Writ Large
All LPG vessels have pressure relief valves, even the very large ones.
A recent accident showed the wisdom of this inclusion.
A B-double LPG road tanker, full with 63,000 litres of LPG, was involved in a crash with a car.
The car crossed the centre divider and hit the tanker head on.
This ruptured the diesel tanks of the truck resulting in a massive fire.
The prime mover (tractor) section of the truck was destroyed. It even melted the tyres. See image above.
However, the tanker trailers remained intact, even though the exteriors were scorched (they were originally white) but there was no LPG tank explosion.
The contents were safely removed after the fire was extinguished.
This is a testimony to the design safety incorporated into all LPG vessels.
The Exception - Sub-standard Gas Cylinders
In some countries, there are problems with substandard gas cylinders that do not meet the manufacturing and safety requirements.
The typical problem is an insufficient regulatory mechanism and/or a lack of enforcement. For example, both India and Pakistan have struggled with this issue in recent years.
Be sure to only buy gas cylinders from reputable suppliers. If the deal is too good to be true, there is probably a reason. Steer clear of any cylinder that is odd looking or non-standard in any way.
The problem can be even worse with CNG - Compressed Natural Gas. CNG cylinders for vehicles have a much higher operating pressure so any cylinder with substandard manufacturing is more likely to fail.
Whilst one should always take care when using gas, there is no reason for an irrational fear of a gas bottle blast or propane tank explosion.
Gas bottles, with their Pressure Relief Vales, have a very effective safety system.
The result is that gas bottle explosions are extremely uncommon in most countries.
The real concern should be the proper maintenance of gas appliances and fittings.
Comments, questions or feedback?
The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.