“Introduction – Processing natural gas before shipment in transportation pipelines is a necessity to meet the stringent entry requirements of pipeline operators.
In addition to removing water and other hydrocarbon components, high levels of sulphur can be a barrier to entry into a pipeline transportation system.
Sulphur exists in natural gas as Hydrogen Sulphide (H2S). If natural gas contains more than 5.7 milligrams of H2S per cubic meter, it is termed ‘sour gas’ .
H2S, or sour gas has highly corrosive properties that can cause embrittlement of steel pipelines through a process of sulphide stress corrosion cracking (SSCC). For this phenomenon to occur, free water (H2O) must be present in the pipeline together with high levels of H2S over a period of time.
SSCC is a significant risk that can lead to catastrophic failure of a natural gas transportation pipeline resulting in loss of containment of an extremely hazardous material. Obviously, this can give rise to significant safety, environment and commercial consequences.
The severity of the consequences, or process risk, may exceed the tolerable risk limits set out in an organisation’s health, safety and environment policy. They may also exceed what is deemed acceptable to the Regulator (the Health and Safety Executive – HSE, in the United Kingdom) in terms of the risk to workers and members of the public . From a commercial point of view, the loss of a pipeline system due to SSCC would likely result in significant financial impact as well as reputational damage for the organisation concerned.”