Evaluation must for pipeline health

The early morning peace in the verdant Konaseema area between two branches of the Godavari river was shattered by a deafening noise and huge columns of flames as a Gas Authority of India Limited pipeline caught fire, engulfing the entire Nagaram village.      

     The leakage from the pipeline at Nagaram village supplying natural gas (NG) to the Nagarjuna as well as Godavari fertiliser plants led to the serious fire accident. The gas is said to have leaked from the gas trunk line causing the major explosion. The incident has raised the issues of accident prevention and safety awareness not only throughout India, but across the globe as well.

A technical team from the Andhra University which visited the site noticed human negligence as the cause as the leak was not taken into account even though it had been occurring for one week before the accident. It opined that the blast occurred not because of exploration but due to inadequate maintenance. Corrosion of the pipes would occur and ageing of the pipes was a reason for the accident but they should have been taken care of much in advance, the committee felt.
 “These pipes were laid as per international standards but safety measures were not followed while corrosion and ageing led to leakage”, the experts team said in its report. The team pointed out the need to maintain the pipes periodically, carry out pressure measurements and installing pressure indicators throughout the length. This should be undertaken at any cost to avoid human and cattle loss and to protect the eco system.

Through the decades, a variety of materials have been used to make natural gas pipelines.  The selection of materials varies with the date the pipeline was placed in service, the diameter and pressurisation requirements of the pipeline, and the characteristics of the local terrain.  The most common pipeline materials are steel pipes, cast iron pipes and plastic pipes.

A natural gas pipeline system may contain following elements: buried pipelines; above ground pipelines; compressor stations; isolation valves which can be manually, remotely or automatically activated; relief valves; pipe bridges or other supports; casing sleeves under road/rail crossing; leak detection system; pig launchers/receivers, and control system.

Hazards galore

Natural gas is a highly flammable substance, transported through cross country pipelines at high pressure often close to centres of high population or through areas of high environmental sensitivity. The NG pipeline system poses severe hazards for human beings and property in the vicinity. It is very clear in a majority of cases that human negligence is the root cause for these avoidable accidents. 

Pipeline incidents incur liabilities to pipeline operators, pipeline shareholders and owner of the volume lost. Such liabilities can range from cleaning up cost and damage compensation to criminal offences. Major liabilities are usually associated with major leak events without a reliable pipeline leak detection system. Therefore, investing in a proven and reliable leak detection system can help pipeline companies minimise the consequences of a pipeline incident. In order to have the correct response, within the shortest time possible, the leak detection system should: alarm a leak quickly after it occurs; provide accurate leak location and size estimates; and not generate false alarms under normal operating conditions including transients (such as due to valve open/close, pipeline start up and shut down).

To maintain the above performance standards, it is necessary for the pipeline operating companies and leak detection system vendors to work closely in order to make sure that:

n The field instruments are working correctly.

n The telecommunication systems are available.

n The leak detection system is optimised to current operating and instrument conditions.

n Alarms and anomalies are addressed timely.
n Operators have confidence in the leak detection system at all times.

An evaluation process to measure effectiveness of the current health of the pipeline and to prevent any failures in future is highly essential. A safety board consisting of technical experts, local public, noted NGOs formulated by law and should be given authority to supervise and indict the defaulters of safety, if any.
(The writer is Professor and former Director of Delta studies (Petroleum) Institute, Andhra University, Visakhapatnam, Andhra Pradesh)


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