JULY 29 ― The Institution of Engineers, Malaysia (IEM) has received some enquiries on the information circulating in social media, suggesting that petrol tank in a car can explode due to overheating when parked under the hot sun.

IEM is in the opinion that this is untrue and unlikely situation. Otherwise, there will be many such fire or explosions in hot desert areas. The day time temperatures in a desert can reach 50°C or more and this is much higher than the 40°C that we typically can experience in Malaysia.

Petrol tanks are built with many safety features. Such tanks are engineered to be liquid tight and would be pressure-tested. In order to prevent over pressurisation of the tank, it is equipped with a relief mechanism. In larger vehicles, these would be a fitted relief valve on the tank. Most cars would have a part built into the tank's cap. This is why the cap should be properly screwed back on after each refilling. When a cap is lost or damaged, it should be replaced with the original part from the manufacturer. Otherwise the tank would not have the proper relief if any inferior cap is used.

The cap should be slowly opened before refilling petrol, similar to opening a can of soda bottle. A bit of pressure is normal, as the relief is slightly above atmospheric pressure. But unlike a can of soda, there is no dissolved gas, hence the release of pressure will not continue for long and will not splash out like a pop drink.

Petrol tank are built sealed, so an ignition source would not get into the tank to start a fire. The most likely point of fire is when the cap is opened when the petrol is pumped.

The nozzle of the petrol pump is made with a low sparking metal, and this minimises the chance of sparks being made when it knock against metal parts in the car or tank. Fire can happen when a petrol tank is overfilled. Spilled petrol will vaporise quickly when it gets in contact hot surface ― such as hot tire or exhaust pipe after a long drive.

These vapours can be ignited by the hot surface or any flames. That is why smoking is prohibited in a petrol station.

Static charge will create sparks that could possibly ignite petrol during refuelling. Clothes made of plastic material tend to accumulate charges on one’s body on top of dry skin during the dry season. However due to the tropical climate, the low humidity factor is greatly minimised.

Drivers would sometime panic when they see the fuel needle reach “E” or when the fuel light flashes. However, when that happens, the car can still travel for approximately 50 km before it is totally out of fuel. This margin is almost universal for cars that meet the automotive engineering standards. On highways and trunk roads across the country, there should be petrol stations within that distance. This is one of the criteria used in planning petrol stations.

IEM is willing and ready to provide the technical expertise and clarification to the authority and relevant agencies where required.

* Tan Yean Chin is the President of The Institution of Engineers, Malaysia.

** This is the personal opinion of the writer and does not necessarily represent the views of Malay Mail Online.