PHATHUTSHEDZO KHANGALE | Poor record-keeping exposes Joburg to gas disasters

As questions continue to linger over the explosion that rocked the Johannesburg CBD last month, city officials have claimed that it was a methane gas that triggered the blast. However, the officials said the source of the blast was still unknown.

This is a questionable finding that cannot be left unchallenged. The city’s own statement suggests that officials do not know who may be transporting methane through the city; hence it is difficult to trace the source. This, and several other factors, raise questions about the city’s competence in dealing with a disaster of such magnitude.

First, it is worth noting that following the explosion on July 19, city officials said they were caught by surprise after discovering an old active pipeline belonging to the municipality containing methane. It emerged that none of the city officials knew about the existence of the pipeline. That shows that the city may not have a proper record of all active gas pipelines in the city. It also raises a question as to whether another explosion similar to what was witnessed on Lilian Ngoyi Street could occur in the near future.

Some of these gases are invisible and odourless, but should something go wrong, their impact could be devastating.

For example, a gas such as carbon monoxide is invisible and odourless but if released into the atmosphere and members of the public inhale, it can lead to massive deaths. Other dangerous gases that could be transported include highly flammable gases such as hydrogen. Any small leak emanating from a gas pipe carrying hydrogen could literally burn down a major part of the city.

Joburg CBD is a densely-populated (residential) area and therefore it is dangerous for the city to not have a proper record of all gases being transported in the area as another possible explosion could lead to the loss of so many lives. The extent of the damage will depend mostly on the source of the explosion.

The fact that city officials have no clear idea of all activities happening in the vicinity of the Joburg CBD is chilling enough to make one shudder. There are greater chances that there could be more gas pipeline which the city is not aware of and not regulating.

In simple terms, an explosion occurs because the physical walls of the container, for example a gas pipe, fails to withstand the pressure exerted by the gas against the pipe walls.

If that is the case, the pipe diameter is much smaller compared to the distance between two parallel walls of the tunnel. Assuming that there was no accumulation of gas because the tunnel could be opened on the other side, one does not expect pressure to suddenly build up.

Another interesting point to note is that methane is normally flown at lower pressure. For a gas to cause damage witnessed in the Joburg incident, a gas pipe should have been at very high pressure, otherwise it would not have been capable of causing such damage.

In short, the discovery of an old pipeline which was supposed to be inactive raised a lot of eyebrows as residents would think that the city should have known if the pipe was still active or not.

One also doubts if the city even has a proper blueprint of the whole city. This exposes the city to the possibility of another disastrous outcome. Going forward, the city should urgently initiate a process to audit an underground infrastructure and ensure that they eliminate any possibility of old underground infrastructure being hijacked and used without their knowledge.

• Dr Khangale is a senior lecturer with the department of chemical engineering technology at the  University of Johannesburg.