Pipeline Pigging

pipeline pigging banner 1A PIG is a Pipeline Inspection Gauge.  PIG's scrape the inside of the pipeline and perform various maintenance jobs like cleaning, clearing, maintenance, inspection, dimensioning, process and pipeline testing operations on new and existing pipelines.  Smart PIG's inspect the integrity of the line for any potential problems.  Pipelines need to be cleaned regulary to prevent debris or buildup from occuring that may slow down the movement of the fluid inside.  The process of pigging is normally performed without stopping the flow of the product in the pipeline.  The diameter and lengths of the pipelines determine the pig size and tend to be much larger than in liquid processing and manufacture.  PIG launchers and receivers need to be installed at the approperate locations.

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Nomenclature & Symbols

Pipeline Pig Types

  • In-line inspection tool (ILI)  -  Also called intelligent pigs or smart pigs, that inspect the interior wall of the line.  When a pipeline is inspected through processes that examine the interior of a pipeline.  These pigs are used for: burial & coating, caliper, crack detection, internal inspection, leak detection, metal loss, line damage due to construction equipment.
    • Configurations  -  A pig that is used to gather data about the internal pipeline wall.
      • Camera Pig  -  A pig with a camera and light source recording the inside of the pipeline for visual inspections.
      • Geometry Pig  -  Designed to record conditions, such as dents, wrinkles, ovality, bend radius and angle, and occasionally indications of significant internal corrosion by making measurements of the inside surface of the pipe.
      • Mapping/ GPS Pig  -  A mapping pig uses technology, often inertia sensing, to produce a plan view of a pipeline’s route. 
  • Utility Pig  -  These pig perform simple mechanical functions, such as cleaning the pipeline, are called utility pigs.

    • Types
      • Foam  -  There is a wide variety of styles, drying, wiping and scraping pigs to accommodate almost any application.
      • Inflatable
      • Solid Cast  -  These pigs have the same flexibility and handling advantage of foam pigs.  The cups and discs found on steel pigs can offer excellent sealing which makes them very efficient as general purpose pigs for batching, displacement, and routine pipeline pigging operations.
      • Gel  -  Utility pig composed of a highly viscous gelled liquid.  These pigs are often used for pipeline cleaning.  Sometimes called gelly pigs.
    • Utility pigs are used for:
      • Batching Pig  -  A utility pig that creates a tight seal as it moves through the pipeline seperating liquids from gasses or other products being transpotred.
      • Cleaning Pig  -  Is used to remove solid or semi-solid debris or build-up inside a pipeline.
      • Cup Pig  -  A utility pig that is supported and driven by cups made of a resilient material such as neoprene or polyurethane.  At least one of the cups forms a piston-like seal inside the pipe.
      • Fill Pig  -  The pig runs through a pipeline during various testing processes like during a pipeline filling procedure.  The pig is propelled by a column of test water, ensuring that air in the pipeline is eliminated.
      • Gauging Pig  -  Utility pig permanently deformable by obstructions in the pipeline.  Upon retrieval from the line, the gauging pig provides evidence of the worst-case obstruction in a given pipeline segment.
      • Sealing Pig  -  Used to provide a good seal in order to either sweep liquids from the line, or provide an interface between two dissimilat products in the pipeline.
      • Sphere Pig  -  Can be solid or inflated to their optimum diameter with glycol and/or water.

 

Pipeline Pigging Procedures

Pigs were origionally used to remove any large deposits of wax or dirt to maintain a flow through the pipeline.  Today, pigging is required during each phase in the life of a pipeline.

DURING CONSTRUCTION

  • Removing construction debris from the line.
  • Acceptance testing (water filling, dewatering, etc.)
  • Commissioning

DURING OPERATION

  • Pipe wall cleaning
  • Condensate removal
  • Product separation (batching)
  • Applying inhibitors

FOR INSPECTION

  • Check for physical damage (geometry)
  • Detect corrosion, laminations or cracking
  • Leak detection
  • Sampling
  • Line cover and spanning (subsea)

FOR GENERAL MAINTENANCE AND REPAIR

  • Corrosion inhibition
  • Pre-inspection cleaning
  • Decommissioning
  • Isolation
  • Recommissioning

DURING RENOVATION/REHABILITATION

  • Gel pigging
  • Applying in situ coatings
  • Chemical cleaning
  • Scale removal
  • Cleaning for product conversion

DECOMMISSIONING

  • Product removal
  • Pipe wall cleaning
  • Inspecting/testing
  • Inerting

 

Pipeline Pigging standards

ASME Standards

  • ASME B16.5 - Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard
  • ASME B16.9 - Factory-Made Wrought Buttwelding Fittings
  • ASME B16.47 - Large Diameter Steel Flanges, NPS 26 Through NPS 60
  • ASME B16.36 - Orifice Flanges
  • ASME B31.4 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids
  • ASME B31.8 - Gas Transmission and Distribution Piping Systems

NACE Standards

  • NACE ISBN 51316-7023 - Methodology for the Evaluation of Cleaning Pigs on Sludge Deposits from Corrosion Pits
  • NACE ISBN 96034 - A Portable Pig Launcher and Receiver to Enable Maintenance and Smart Pigging of Production Pipelines
  • NACE ISBN 96035 - Use of Intelligent Pigs to Detect Stress Corrosion
  • NACE ISBN 96041 - Smart Pig Philosophy
  • NACE ISBN 96048 - Solid Gel Pigs for Cleaning Production
  • NACE ISBN 96049 - Intelligent Pigging: Policy, Recent Experience and Needs of a Petroleum Poerator
  • NACE SP0102 - In-Line Inspection of Pipelines
  • NACE SP0106 - Control of Internal Corrosion in Steel Pipelines and Piping Systems
  • NACE SP0204 - Stress Corrosion Cracking (SCC) Direct Assesment
  • NACE SP0206 - Internal Corrosion Direct Assesment Methodology for Pipelines Carrying Normally Dry Natural Gas
  • NACE SP0208 - Internal Corrosion Direct Assesment Methodology for Liquid Petroleum Pipelines
  • MTI Publication No. 14 - Manual on Closure Bolting for the Chemical Process Industries

 

Pipeline Pigging Glossary

A

B

  • Barred Tee  -  A tee or any fitting with a branch used in pipelines that is pigged and has a restriction bars welded internally preventing the pig from traveling down a branch connection.
  • Batching Pig  -  A utility pig that creates a tight seal as it moves through the pipeline seperating liquids from gasses or other products being transpotred.
  • Bell Hole  -  A bell-shaped hole dug beneath a pipeline to make room for a use of tools to perform an inspection, survey, maintenance, repair, or replacement of pipe section.

  • Blanching Line or Equalizer Line  -  Allows the filling of the launcher from both sides of the pig.
  • Bypass Line or Tie-line  -  This line is connected to the barred tee alowing the allowing the pigging line to continue flowing past the launcher/receiver.
  • Bypass Valve or Mainline Bypass Line  -  Opens and closes the bypass line, on the barred tee branch.

C

  • Calibration Digs  -  When an in-line inspection tool records an indication then a calibration dig, a bell hole or exploratory excavation, will be performed on a section of pipe.

  • Camera Pig  -  A configuration pig with a camera and light source recording the inside of the pipeline.
  • Cleaning Pig  -  Travels free through a pipeline along with product flow, brushing and scraping foreign matter, rust, dirt, and fluids from the inside surface of the pipes. Cleaning pigs help facilitate inspections and increase operating efficiency of a pipeline.
  • Cement Lined Pipe  -  Pipe that is internally coated with a mortar like compound that acts as a barrier between the carbon steel pipe and the process.
  • Closure or End Closure  -  A flange or hinged device connected to the major barrel used to open or close the launcher/receiver for pig insertion or retrival.
  • Concrete Coating  -  A liquid or semi-liquid covering that is applied to the surface of cured concrete to reduce the need for maintenamce and repair.   
  • Configuration Pig  -  Geometry pigs, camera pigs and mapping pigs are all types of configuration pigs which are any instrumented pig that collects data relating to the inner workings of the pipeline.
  • Corrosion  -  The thinning of a pipe wall that is typically caused by a chemical reaction from a corroding fluid or agent and is limited almost exclusively to metal products.
  • Corrosion Allowance  -  The amount of material in a pipe or vessel that is available for corrosion without affecting the pressure containing integrity.
  • Corrosion Inhibitor  -  A substance that slows down the chemical reaction rate of corrosion on metal that is exposed to the environment.
  • Corrosion Mapping  -  An ultrasonic method that identifies and maps corroded areas in a pipelineby yhe varying material thickness.
  • Crack  -  Cracks can come from fatigue, grith welds, or seam welds.
  • Cup Pig  -  A utility pig that is supported and driven by cups made of a resilient material such as neoprene or polyurethane.  At least one of the cups forms a piston-like seal inside the pipe.

D

  • Dewatering  -  In order to remove all the water from the pipe after hydro testing, a pig needs to be sent through the pipeline, this pushes the water out.
  • Drag Force  -  The drag on a body as is moves through a fluid (gas or liquid).
  • Drain Pit  -  When the closure is opened the sludge and/or liquid can drain into the pit along with the drain line.  The pit can be drained by a vacuum ttruck or underground piping.  The pit is covered with a removable grilled lid to stand on.
  • Drain Line  -  Used to drain the major and minor barrels after the trap isolation valve in order to insert or remove the pig.
  • Drain Nozzle  -  A flange connected to the major barrel for the kicker valve.
  • Drain Valve  -  A valve at the bottom of the major barrel used to drain the line after the trap isolation valve.

E

F

  • Flow Rate  -  Measures the amount of fluid that flows in a given time past a specific point.
  • Fluid  -  A substance that deforms and changes position when put under stress.  Fluids can be both liquids and gases.
  • Foam Pig  -  A utility pig used for batching, cleaning, and removing products from the line..
  • Fretting Corrosion  -  Takes place where there is friction between two metal surfaces.

G

  • Gas  -  Able to be compressed to fit a confined space and expanded when released.
  • Gauging Pig  -  Utility pig permanently deformable by obstructions in the pipeline.  Upon retrieval from the line, the gauging pig provides evidence of the worst-case obstruction in a given pipeline segment.
  • Gel Pig  -  Utility pig composed of a highly viscous gelled liquid.  These pigs are often used for pipeline cleaning. Sometimes called gelly pigs.
  • Geometry Pig  -  Configuration pig are designed to record conditions, such as dents, wrinkles, ovality, bend radius and angle, and occasionally indications of significant internal corrosion by making measurements of the inside surface of the pipe.
  • Gouging  -  Mechanical removel of metal from the surface of the pipe.

H

  • Holiday  -  A discontinuity in painted or coated surfaces.
  • Hydro Test  -  This is a pressure test on pipelines and pressure vessels by filling them full of water, then pressurizing the line to check for leaks.  After the test dewatering is performed.

I.

  • In-line Inspection  -  When the pipeline is inspected by examining the interior of the pipe.
  • In-line Inspection tool  -  Devices, also called intelligent pigs or smart pigs, that inspect the interior wall of the line.
  • Inhibitor  -  Can reduce the corrosion rate by presenting a protective film.
  • Instrument Nozzle  -  Flanged or threaded outlets for instrumentation and relief valves on the launcher or receiver.  There can be multiple.
  • Instrumented Pig  -  Device or vehicle used for internal inspection of a pipe, which contains sensors, electronics, and recording or output functions integral to the system.  Instrumented pigs are divided into two types: configuration pigs, which measure the pipeline geometry or conditions inside the pipe surface; and in-line inspection tools that use non-destructive testing techniques to inspect the wall of the pipe for corrosion, cracks, or other types of anomalies.
  • Internal Corrosion  -  The thinning of the interior pipe wall that is typically caused by a chemical reaction from a corroding fluid or agent and is limited almost exclusively to metal products.

J

K

  • Kicker Line to Launcher  -  A line from the bypass line/tie-line to the front of the major barrel close to the closure.  When the kicker valve is opened, fluid pushes the pig past the trap isolation valve down the pipeline.
  • Kicker Nozzle  -  A flange connected to the major barrel for the kicker valve.
  • Kicker Line from Receiver  -  A line from the bypass line/tie-line to the back of the major barrel close to the eccentric reducer.  When the kicker valve is open, fluid passes to the bypass line and away from the launcher.
  • Kicker Valve or Upstream Isolarion Valve  -  Opening into the valve launcher behind the pig.  When opened, starts the pig on its way.

L

  • Launcher  -  Used to launch a pig past the trap isolation valve and down the pipeline.
  • Liquid  -  A specific volume and can hold any shape it is contained within.

M

  • Magnetic Flux  -  This method can detect wall thickness from corrosion and pitting without affecting the pipe.
  • Major Barrel  -  The pig is inserted or removed from the major barrel and comes after the eccentric reducer.  Pipelines less than 8 inches in diameter, 2 inches larger, more than 8 inches in diameter, 4 inches larger than minor pipeline.  There is an eccentric reduce, flat on botton, connecting major and minor barrels.
  • Mapping Pig  -  A configuration pig used to produce an elevation and plan view of the pipeline route with collect data that can be analysed from the inertia sensing or some other technology.
  • Mass Flow Rate  -  The average velocity of a mass that passes by a point.
  • Metal Loss  -  Any anomaly in a pipe in which metal has been removed because of corrosion, gouging or other factors.

  • Minor Barrel  -  The pipe between the eccentric reducer and the trap isolation valve.  There is an eccentric reduce flat on botton connecting major and minor barrels.

N

O

P

  • Pig  -  Devices that are inserted into and travel throughout the length of a pipeline driven by a product flow. They were originally developed to remove deposits which could obstruct or retard flow through a pipeline.
  • Pig Signal Detector  -  A mechanical switch to verify that a pig has left the launcher or has entered the receiver.  Can also be placed along the line for locating the pig.
  • Pig Trap  -  A launcher and receiver.
  • Pig Trap Isolation Valve  -  The minor barrel is flanged to the isolation valve.  The valve allows the pig to leave the launcher or enter the receiver.
  • Pigging Efficiency  -  Is expressed in percentage and always less than 100%.

  • Pigging Valve  -  An alternative to conventional pig launchers. They are capable of launching and receiving foam, steel, and solid cast pigs in both cylindrical and spherical shapes.
  • Pitting  -  A non-uniform corrosion of a metal, not in the form of cracks, whereby a number of cavities, are formed in the surface.
  • Porosity  -  Happens when a contaminent or gas is absorbed into the weld puddle.
  • Pressure -  It is the force exerted perpendicular to the surface of an object and is expressed as force per unit area. 

Q

R

  • Receiver  -  Used to receive a pig after pasting the trap isolation valve from the pipeline.
  • Rectifier - Transformer  -  A device that uses electromagnetism to convert one current to another current.
  • Rupture  -  There are numerous reasons a rupture can happen, depending on the material: age, brittleness, corrosion, internal pressure, movement, etc.

S

  • Smart Pig  -  Collects information internally about the pipeline with electronic components.
  • Solid Cast Pig  - It is between a foam pig and steel pig having cups, disks or both and even brushes. 
  • Sour Corrosion: Hydrogen Sulfide  -  It is a flammable, poisonous gas, that occures naturally in some groundwater.  It becomes corrosive when dissolved in water.
  • Sphere Pig   -  These utility pig are made of rubber or urethane.  The sphere may be solid or hollow, filled with air or liquid.  The most common use of sphere pigs is as a batching pig.
  • Stress  -  The force per unit area of cross-section.
  • Stress Corrosion Cracking   -  The combined effect of tensile stress and a corrosive environment.
  • Sweet Corrosion: Carbon Dioxide  -  A weak acidic gas found in condensate, crude oil, natural gas, and produced water and becomes corrosive when dissolved in water.

T

  • Tensile Strength  -  The maximum stress a material can resist before it starts to elongate.
  • Transformer - Rectifier  -  A device that uses electromagnetism to convert one current to another current.
  • Trap  -  Pipeline facility for launching and receiving tools and pigs.

U

  • Ultrasonic Testing  -  Used to measure the pipe wall thickness perpendicular to the pipe.
  • Upstream Isolarion Valve or Kicker Valve  -  Opening into the valve launcher behind the pig.  When opened, starts the pig on its way.
  • Utility Pig  -  These pig perform simple mechanical functions, such as cleaning the pipeline, are called utility pigs.

V

W

  • Water Conductivity  -  The ability of water to conduct an electric current.
  • Water Cut  -  The ratio of water produced to the volume of total liquid produced.
  • Water Hammer  -  Occurs when a valve is suddenly opened or closed.
  • Well Integrity  -  An operation of technical, operational, and organizational solutions to reduce fisk of controlled release of formation fluids throught the life cycle of a well.

X

Y

Z

 

 

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