Certified Pig Traps

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The Important Role Played by Certified Pig Traps

In the oil and gas industry, the word “pigging” has a very different meaning as what most people might suspect. In this environment, it describes a process in which a snug-fitting mechanical device is inserted into a pipeline and then propelled along its length under pressure in order to perform some set task. So named, because of the squealing noise it makes due to contact with the pipe’s walls, certified pig traps are required, first to launch the pig and later to retrieve it once it has completed its task.

These launch and retrieve units are designed to be connected into the ends of a pipeline and, while operating normally, they are sealed by a door and kept empty by means of a bypass valve. One of the main advantages of the pigging process, whether used to clean a pipeline or to check its integrity, is that the use of certified pig traps makes it unnecessary to interrupt the flow of product in the line during the operation. Once the pig has been placed in the launcher, the valve is opened to fill the trap with the product, at which point the pig can be propelled into the pipeline to begin its journey.

To ensure that the launch and retrieval processes will operate safely and smoothly, the traps must be designed to form a perfect seal with the main pipeline. In addition, their design and structure must be able to withstand the resulting pressure when opened to the main pipeline. Certified pig traps should comply with the mandatory Pressure Equipment Regulations (PER), as well as meeting the related requirements of the South African National Standard SANS 347.

The pigs also need to need to be manufactured to precise specifications and, while they are available in a number of standard sizes and configurations, in many cases, they need to be designed and purpose-built by an engineering company that specialises in this field. One such company is Oleum Process and Pipeline Services, who also manufacture the necessary PER certified pig traps.

The latter are of three basic types and which of these will be necessary will depend on whether the pig is to be launched horizontally, vertically, or at an inclined angle. Of the three types, the horizontal traps are generally preferred for their ease of operation. However, for those situations in which a lack of sufficient space may preclude a horizontal launch or retrieval, either a vertical or an inclined unit will be the only practical option.

Whether the launcher or receiver is vertical, horizontal, or inclined, the basic design is quite similar. A certified pig trap consists of a major barrel of larger diameter than the pipeline, a minor barrel of the same diameter as the pipeline, and a reducer barrel that connects the two. The major barrel is a sealed access door through which the pig is inserted or removed, while a ball valve at the end of the minor barrel isolates the trap from the pipeline when not in use.

Pigging is vital to pipeline maintenance and safety. It requires certified pig traps manufactured to the highest standards, for which Oleum Process & Pipeline Services are so well known.

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