What Pig Launchers and Receivers Do
Pig launchers and receivers play a crucial role in the operation of hygienic, sanitary, and process pigging systems. They serve as essential components for safely introducing pigs into the pipeline and propelling them to and from their source and destination.
They also safely store the pig when it’s not in use (when they’re not travelling through the pipeline and actually ‘pigging’), and enable flushing and effective CIP of the pig (or pigs). These are the key functions of pig launchers and pig receivers.
How PIG LAUNCHERS AND PIG RECEIVERS Work
Depending on the application, pigs can be propelled by gases such as nitrogen, compressed air or carbon dioxide, or sometimes by water, cleaning fluid or even the next batch of product.
Also known as pig stations in process pigging systems, pig launchers and pig receivers consist of specialist valves which control the pig propellant, and hence the pig.
The pigging system process is usually semi or fully automated.
Pig detectors, such as the HPS AccuTect are non-intrusively mounted on the exterior of the pipeline. They’re located a specific distance from the pig launchers and receivers, and send a proximity signal to the software or control system providing continuous tracking of the pig’s location.
The precise distance the AccuTect pig detectors are located depends on a number of factors, but it is usually based on enabling the pig to slow down sufficiently once having passed the detector and the propellent being shut off or propellent pressure reduced.
The pigging sequence itself is extremely quick. Opening and closing of the valves in the launch and receive stations is carefully controlled and ensures the pig is propelled through the line with utmost safety, eliminating any risk of product contamination.
It also ensures clean in place (CIP) or normal processing can resume once the pigging sequence concludes.
Usually, the pig launcher stores the pig when not in use, and includes a housing to contain the pig. This housing is slightly larger than the pig itself, enabling the flow of water or cleaning fluids around the pig for CIP.
Furthermore, the housing is engineered for the safe removal of the pig, whether for inspection or replacement purposes. In HPS systems, the housing’s design allows for safe access to the pig even while normal processing operations are ongoing. This ensures that there is no disruption to production in the event that a pig needs changing.
Safety is of paramount importance, and HPS systems are equipped with an array of robust safety features.
For instance, HPS pig systems incorporate interlocks and mechanisms that the pig and its housing can only be accessed when it is deemed safe to do so. These safety measures may vary depending on the specific system, but they serve as fail-safes, preventing an operator from attempting to open a launch or receive station while a pigging operation is in progress. In such cases, either the housing will remain locked, preventing access, or the system will immediately depressurize to ensure operator safety.
Returning the Pig
While the pig launcher introduces the pig into the process line, the pivotal role of the pig receiver is to send it back again when it has reached its destination. It’s worth noting that all HPS pigs are bi-directional, so can travel in either direction along the pipe (some manufacturers produce pigs that can only travel in one direction, which severely limits pigging system design and efficiency, particularly regarding automation).
Pig receivers are purposefully configured to swiftly, securely, and efficiently facilitate the pig’s return journey with minimal disruption to the line. They typically have a simpler design compared to pig launchers since they do not serve as a storage space for the pig, eliminating the need for a pig housing. However, it’s worth noting that exceptions exist. Certain pigging systems, such as multi-destination and double-pig systems, may incorporate housings in both the launch and receive stations. In such cases, the two types of stations closely resemble one another in design and function.
Good quality pigging system design is one of the most important factors of pigging system implementation.
This is because nearly all pigging systems are bespoke; designed specifically around a particular process and application. This level of customisation extends to pig launchers and receivers, which are intricately designed based on variables such as the propellant type, liquid being processed, pipeline dimensions, pigging sequence, pig type, and more.
Additionally, there are also specialist designs of pig launchers and receivers, aimed at eliminating any ‘dead space’ and maximising product recovery to the fullest extent possible. Therefore, there’s a wide variety of these pigging system components available – please contact HPS for further information.
For a visual demonstration of different pigging systems in action, please take a look at these pigging system demonstration videos.
Should you seek additional information regarding pigging system design, pig launchers, pig receivers, or any other aspect of liquid product recovery, please do not hesitate to contact us.