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'Pigs' play crucial role in pipeline maintenance

Oil refineries are highly reliant upon pipelines for their ongoing successful operation as the raw materials and finished products (crude oil and petroleum products) are usually transported by means of pipeline to and from the refinery. Pipelines are also arguably the most efficient method of fluid transport over long distances as, once installed, the running costs are significantly lower than alternative transportation methods. But pipelines must be maintained and that’s where the ‘pigs’ come into play.

‘Pig’ is the most widely-accepted term for any device inserted into a pipeline which travels freely through the line driven by the product flow. First used in the US in the early days of the oil extraction and refining industry, today more than 350 varieties of ‘pigs’ cover a full range of applications.

A Hak Industrial Services, the Alrode-based subsidiary of the Dutch A Hak BV, which specialises in plant shutdown and maintenance services for the petrochemical, refinery, pipeline and oil and gas industries, manager Ian Middleton says that the pipeline installations around the world are valued at about $200-billion.

“However, the regular maintenance and upkeep of this valuable asset is not always clearly evident,” Middleton says. “Pipelines are like motor vehicles which require regular servicing and, if this is not done properly, they will fall into a state of disrepair.

“Pipelines, depending on the products they convey, require regular pigging and main- tenance activities to ensure they remain in good working order. “Human nature, of course, tends to defer this kind of work, because pipelines are often out of sight, out of mind. “While this approach may not have any effect in the short term, lack of maintenance normally heralds costly trouble for the pipeline asset over the longer term,” he explains.

In the oil-extraction, conveyance and refining industry, the concept of ‘pigging’ a pipeline has often been questioned. Middleton says the two most fundamental reasons for carrying out ‘pigging’ are to ensure continuous operation and maximum efficiency of the pipeline over its useful lifespan.

“Specific ‘pigging’ activities during the life-cycle of a pipeline would usually include the removal of debris, hydrostatic pressure testing and drying of the line during the construction phase, maintenance ‘pigging’, pipewall cleaning, chemicals application during the operational phase, and product removal and inerting (the pressurised injection of inert nitrogen gas as a safety measure) during final pipeline decommissioning.

“Over and above these basic ‘pigging’ activities, we can today deploy ‘intelligent pigs’ to collect data on the internal state of the pipeline. From this information, refinery management or pipeline owners can make informed decisions that will ensure the integrity of a pipeline and extend its lifespan,” says Middleton.

‘Intelligent pigging’ is a highly-specialised operation. Its objective is to gather critical information such as the remaining wall thickness of the pipeline and the exact location of any problem areas. It is also used to conduct pipeline geometry surveys to prove the internal bore of the pipeline and to identify and locate mechanical dents, buckles or pipeline ovality.

“The information collected during this kind of survey is usually processed into an overall information-based evaluation of the state of the pipeline by the inspection vendor company. “This information is presented to the pipeline owner for input into a pipeline integrity management programme. “Geographic information systems are often also used to provide a user-friendly and powerful pipeline management tool.” A Hak Industrial Services specialises in plant shutdown and pipeline services for the oil and gas industries, providing the full range of pipeline ‘pigging’ and consulting services. Middleton says the company has performed many “challenging pipeline-pigging operations” both locally and abroad.

The company offers market-leading pipeline ‘pigging’ services to South African industry. As Middleton stresses, experience counts in this highly-specialised game and A Hak has successfully completed pipeline ‘pigging’ work for Sasol, Engen, Sapref, Caltex, Petronet and PetroSA, among the more prominent local producers. Recent pipeline ‘pigging’ operations executed by the company include the ‘intelligent pigging’ of three 12-inch fuel product lines in Secunda and the decommissioning of several subsea offshore transfer lines in Angola.

Middleton says the company is now busy with a large contract for the supply of pipeline pigging services for the precommissioning of new pipelines as part of the Sasol Turbo expansion programme. “The contract was awarded to us by Fluor Management and involves ‘pigging’, high- integrity cleaning and nitrogen blanketing ser- vices on the OBL section (outside battery limits) of the project. “Pipeline diameters range from 2 inches to 18 inches and our specialised services are required to meet Sasol’s high cleanliness specification for the commissioning of new pipelines.” The term ‘Pig’ came into being when a combin-ation of straw wrapped with barbed wire was first used to provide a crude pipeline-cleaning tool when the US oil industry was in its infancy. The name is a description of the sound made as the first barbed wire ‘pigs’ were dispatched. Later ‘pigs’ included bundles of rags. These were superseded by bundles of leather, which were superior as they were not only stronger, but swelled when wetted to provide a better seal inside the pipe- line and therefore achieved better cleaning results.