Pig Launcher : The Well fluid produced on the Well head platform is to be processed either at an offshore Process Platform, or at an onshore facility. For this, the well fluid is to be sent to the processing facility through sub-sea pipelines. The production header joins the Pipeline, after a Pig launcher.
The Pig launcher is used for launching metallic pigs / spheres for cleaning the debris which accumulates inside the pipeline over a period of time. Pig receivers on other ends receives the pig
Pipeline pigging is a key part of maintaining the integrity of pipeline system. Pipelines required pigging at start and end of life.
Pipelines are normally pigged for
- Commissioning and decommissioning
- Cleaning or wax removal
- Inventory management, by sweeping out liquids, batching products etc.
- Corrosion and scale control
- Inspection of the pipeline
- Isolation and special operation
- Inline Inspection
- Pipeline Cleaning
The main instrumentation related to the pig launcher and pipeline is the Shutdown Valves, Motor operated valves, etc which isolate the production header and launcher from the pipeline section.
There will be pressure transmitters to monitor the pressure in the pipeline, local pressure gauges, and a Pig indicator for indicating the passage of a pig / sphere launched. A Pressure Relief Valve will also be there to protect the pig launcher from over pressure.
Pigs come in many different shapes and sizes; each requires care and attentions for its selections, design and size.
Utility pigs perform gaging of the internal bore, cleaning and debris removal, batch separations of products and sweeping of liquids from the line. Pigs can either be unidirectional or bidirectional
Types of Utility pigs
Foam:- moulded from polyurethane foam in various densities with various configurations of solids polyurethane strips or abrasive materials permanently bonded to the surface.
Elastomer:- moulded from solid elastomer.
Mandrel:- A central metal body with various components like cups, discs, wire, brushes, scraper blades , gaging plates attached.
There are four main types of gel that are used in pipeline applications
- Batching or separator gel
- Debris pickup gel
- Hydrocarbon gel
- Dehydrating gel
If used with conventional pigs, gel pigs can improve overall performance. Gel is normally a diesel based highly product but can be made with water and a range of chemical, depending on chemical compatibility requirements. Gel pigs can be susceptible to dilution and gas mixing
Sphere pigs are normally used to sweep liquids from gas lines. Sphere pigs are normally either from foam throughout or consists of elastomer skin inflated with glycol or water
Soluble spheres are sometimes used in crude pipelines and made from a microcrystallines wax and amorphous polyethylene that acts as paraffin inhibitors. Soluble spheres are broken up by crude oil and do not requires a receiver trap.