A contoured plug - the pig - pushes the product out of the pipe.
Every product which can be pumped can also be pigged.
- Open system: As and when required, the pigs are loaded into the system and then taken back out again after a pig clearing procedure. The system works as a one-way-principle.
- Closed system: The pigs stay in the system during their complete working life and do not have to be loaded into the system and then taken back out again.
A pig driven by a propellant can have a high kinetic energy. Pigging components and pipelines have to be designed for the load caused by these energies and the pig speed has to lie within certain limits so that the moving pig cannot cause any damage.
Especially when loading and unloading the pig possible risks must be reduced with suitable safety devices.
A good pigging result depends on following parameters:
- Pigging suitability of the pipeline
- Surface quality in the pipeline
- Quality of the pipe bends regarding pigging suitability
- Type of pipe connections
- Quality of the weld seams in the pipeline
- Pig speed
- Viscosity and other product characteristics
- Condition of the pig (pig new or worn?)
- Construction characteristics of the pigging stations
Pigging technology has existed for more than 100 years. The first pigging systems were designed for transfer of crude oils. Simple pig types were used to transfer the product out of the pipeline. For this application also intelligent pigs for pipeline inspection were developed.
The costs for a pigging system depend on its complexity as well as the cleaning degree required.
The price varies from several thousand up to several millions EURO. A pigging system which is exactly designed for the specific customer's requirement leads to enormous cost savings.
ROI period of a pigging system depends on the manufacturing costs as well as on the extent of cost savings. With high quality products and cost-intensive disposal of rinsing media a pigging system profits can be realised within a year or possibly even months.