The Role PIGs Play in Maintaining Pipelines
Cleaning pipelines has always been a crucial part of the oil and gas industry. The earliest methods of cleaning out the network of pipes that carry crude oil, natural gas, or other products involved bundles of straw wrapped in wire that would be inserted into the pipes. It is widely believed that the sound this caused may have reminded technicians of the squealing sounds made by pigs. Hence, today’s term for the equipment used to clean and maintain pipelines, “PIG,” which stands for the Pipeline Inspection Gauge or Pipeline Intervention Gadget, can further explain how the equipment got its name.
Whatever they’re called, PIGs are pivotal to the oil and gas industry wherever pipelines are used. With advances in technology, PIGs are now able not only to clean a pipeline, but to gather detailed information about the condition within the pipe itself. Smart technology allows this new generation of instruments to check corrosion, cracks, and defects within the network to prevent downtime or contamination of the product.
PIGs, PIG Launchers, and PIG Receivers
PIGs are one part of the cleaning process, but they don’t work alone. PIG launchers and receivers are the places where the PIG enters or exits the pipeline. In simplest terms the PIG enters at the launcher, and exits at the receiver; however, most systems today are bidirectional, which means that if there is a blockage in the pipe, the PIG can still be removed from the site where it entered.
The launchers and receivers are highly programmed to meet the specific needs of the pipeline network. There are multiple features within each system. Some launchers can manage multiple PIGs, and the system can be configured horizontally and vertically. The launchers and receivers work to safely interface the lower-pressured outside world with the high-pressured pipeline.
The Benefit of PIGs
There are four key benefits of using PIGs in pipelines:
- Cleaning and Maintenance – the PIG scrapes away buildup and debris to improve efficiency and prevent damage to the network
- Separation – when handling two different products, the PIGs prevent contamination or the need to flush out a pipeline, thus saving money and time
- Inspection – instead of wondering what is happening within the pipeline, PIGs can be configured to transmit data back to users
- Positioning and Monitoring – Once engineers know that the pipeline has a problem, the PIG retains the data to provide information about where the defect is located within the system. Rather than digging up healthy sections of the system, it targets the exact location. If there is a trouble section that doesn’t need to be immediately replaced, the PIG allows it to be monitored over time to track the progression of the damage.
How PIG Launchers and Receivers Work
Although PIG launchers and receivers are customized for a particular system, there are many steps that are common to all systems. When using a launcher, the pipeline operator closes the isolation valve and kicker. In a liquid system, the drain valve and vent valve are opened to allow air into the system to displace the liquid. In a gas system, the vent is opened to let the launcher reach atmospheric pressure. The PIG launcher should be drained to 0 psi, then the trap door is opened, but the vent and drain valves are also open. The PIG is loaded. After the closure seals and surfaces have been cleaned and lubricated, the trap door is closed and secured. The operator closes the vent valve and equalizes pressure in the isolation valve, then it is opened. The PIG is ready to be launched. Once the PIG is launched, the isolation valve and kicker valve are closed.
The PIG does its work and reaches the receiver, which will need to be pressurized. The bypass valve and isolation valve are fully opened, while the mainline valve is closed partway. When the PIG arrives at the receiver, the isolation and bypass valves are closed, but the drain valve and vent valve get opened. The trap needs to be depressurized to 0 psi in order to let the PIG be removed. The closure and seals are cleaned and lubricated, then the trap door gets shut and secured. The receiver is then returned to its original condition.
STI Group can provide a full array of PIGs, PIG launchers, and PIG receivers, designed to help keep pipelines operating at peak performance levels.