Mechanical Theory
and Principles of pipe line pigging
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CERT
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commercial, research and training arm of the Higher Colleges of Technology
(HCT), which is the largest higher education institution in the United Arab
Emirates. SINCE 1996
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Course Agenda
PIPE LINE PIGGING
8 - 8:55
9 - 9:45
9:45-10:15
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 Lecture 1
 Lecture 2
 BREAK
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Course content
• Introduction To Pipeline
• Introduction to Pigging
1- What pigging is
2-Why we need to pig a pipe
3- types of pigs
4-Pigging during construction
5-Pigging during operation
6-Different devices used in pipeline pigging
• Conclusion of Pigable pipeline
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Introduction to pipeline
Pipelines is the easiest way to transport all the petroleum products gas and crude oil
during production process ,refining and to export all of oil and gas products
from different countries all over the world
classifications:
Pipelines classified according to oil and gas fields by
* on-shore
* off- shore
And also according to operation based on design by
* Above ground pipeline
* Under ground pipeline
* sea pipelines
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Introduction to pipeline
Sea pipeline
Above ground pipeline
Under ground pipeline
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Descriptions of pipeline imperfections and
conditions
The following are descriptions of imperfections anomalies, defects, and conditions that are
found in natural gas transmission pipelines. The definitions have been obtained from different
technical references and dictionaries, but have been selected as relating to pipelines. The
descriptions are intended to be generic, but may apply to other structures and materials. The
ultimate goal is to provide a common language within the pipeline-pigging industry, world-wide.
Buckle:
A partial collapse of the pipe due to excessive bending associated with soil instability,
and slides, washouts, frost heaves, earthquakes, etc.
Corrosion:
a) general external: metal loss due to electrochemical, galvanic, microbiological,
attack on the pipe due to environmental conditions surrounding the pipe.
(b) general internal: metal loss due to chemical or other attack on the steel from
liquids on the inside of the pipe. Electrochemical attack can also occur on local cells, but this
condition is less frequent.
(c)
pit: local concentrated cell corrosion on the external or internal surfaces that
results from the generation of a potential (voltage) difference set up be variations in oxygen
concentrations within and outside the pit. The oxygen-starved pit acts as the anode, and the pipe
surface acts as the cathode.
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d) selective corrosion: a localized corrosion attack along the bond line of
electric-resistance welds (ERW) and flash welds (FW), that leads to the development of
a wedge-shaped groove that is often filled with corrosion products.
(e) stress-corrosion cracking: a progressive intergranular and/or transgranular
cracking that results from a combination of applied tensile stress, cathodic protection
currents, and a suitable corrosive environment.
Cracks:
a)fatigue: progressive cracking in the base material, weld, or weld zone, that is
caused by pressure cycling or oscillatory stresses associated with the operation of the
system.
(b) girth weld: cracks in the weld or weld zone of the butt weld that connect
sections of pipe.
(c) seam weld: cracks in the weld or weld zone of the longitudinal seam weld of
the pipe.
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PIGGING INTRODUCTION
Q. What are pigs and pipeline pigging?
A pig is a device inserted into a pipeline which travels freely through it, driven
by the product flow to do a specific task within the pipeline. These tasks fall into
a number of different areas: (a) Utility pigs which perform a function such as
cleaning, separating products in-line or dewatering the line; (b) Inline inspection
pigs which are used to provide information on the condition of the pipeline and
the extent and location of any problem (such as corrosion for example) and (c)
special duty pigs such as plugs for isolating pipelines.
Introduction
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PIGGING INTRODUCTION
Q. Why is it called “pigging”?
One theory is that two pipelines were standing next to a line when a pig went
past. As the pig travelled down the line pushing out debris, one of them made
the comment that it sounded like a pig squealing. The pig in question
consisted of leather sheets stacked together on a steel body. Without doubting
the authenticity of the story, it does indicate that these tools have been around
for some time. Another theory is that PIG stands for Pipeline Intervention
Gadget.
Introduction
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Why we need to pig a pipe
There are basically three reasons to pig a pipeline:
 To batch or separate dissimilar products;
 For displacement purposes;
 For internal inspection.
Pipeline pigs are used to prove flow diameter to maintain a continuous flow
through the pipeline.
Functions
•
•
•
•
•
•
•
•
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Separation of products
Cleaning out deposits and debris
Gauging the internal bore
Location of obstructions
Separation of products
Meter loop Calibration
Liquid Removal
Gas Removal
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Why we need to pig apipe
Functions
•
Pipe Geometry Measurement
•
Internal Inspection
•
Coating of internal bore
•
Corrosion inhibition
•
Improving Flow Efficiency
Section 3.1
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Why we need to pig a pipe
The pigs which are used to accomplish these tasks can be divided into three
categories:
Utility Pigs
which are used to perform functions such as cleaning, separating, or dewatering.
Inline inspection Pigs
which provide information on the condition of the line, as well as the extent and
location of any problems.
Gel Pigs
which are used in conjunction with conventional pigs to optimize pipeline
dewatering, cleaning, and drying tasks.
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Why we need to pig a pipe
The type of pig to be used and its optimum configuration for a particular task in a particular
pipeline should be determined based upon several criteria, which include:
The purpose
Type, location, and volume of the substance to be removed or displaced in conventional
pigging applications,
Type of information to be gathered from an intelligent pig run,
Objectives and goals for the pig run.
The line contents
The contents of the line while pigging,
Available vs. required driving pressure,
Velocity of the pig.
Characteristics of the pipeline
The minimum and maximum internal line sizes,
Maximum distance pig must travel,
Minimum bend radius, and bend angles,
Additional features such as valve types, branch connections, and the elevation profile.
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Types of pigs
*
Conventional Pigs
Inexpensive tools for removing troublesome debris from the pipeline
pipeline or batching dissimilar products.
Functions
- Cleaning
- Swabbing
- Batching.
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Types of conventional pigs
UTILITY PIGS
Utility pipeline pigs can be divided into two groups based upon their
their fundamental purpose:
Cleaning Pigs
which are used to remove solid or semi-solid deposits or debris from
from the pipeline.
Sealing Pigs
which are used to provide a good seal in order to either sweep liquids
liquids from the line, or provide an interface between two dissimilar
products within the pipeline.
Within these two groups, a further subdivision can be made to
differentiate among the various types or forms of pigs:
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Types of conventional pigs
Cleaning Pigs
Cleans the pipeline by removing solid or semi solid deposits
or debris.
Examples
- Mandrel pigs, foam pigs, solid cast pigs, spheres etc.
Sealing Pigs
Provides a good seal in order to sweep liquids or acts as an
interface between two dissimilar products in the same
pipeline
Examples
- Mandrel pigs, foam pigs, solid cast pigs, spheres
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Types of pigs
UTILITY PIGS
• Mandrel pigs
which have a central body tube, or mandrel, and various components
which can be assembled onto the mandrel to configure a pig for a
specific duty;
• Foam pigs
which are molded from polyurethane foam with various configurations
of solid polyurethane strips and/or abrasive materials permanently
bonded to them
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Types of pigs
Mandrill pig
Solid Cast pig
Solid cast pigs
Scraper mandrill pigs
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Types of pigs
GEOMETRY PIGS
A geometry / caliper pig is a configuration pig designed to
record conditions, such as

dents

wrinkles

ovality

bend radius

angle
Occasionally indications of significant internal corrosion is
recorded by making measurements of the inside
surface of the pipe.
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Types of pigs
De-waxing pig
Foam pigs
Ultrasonic corrosion
detection tool
Magnetic Flux leakage pig
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Types of pigs
intelligent pig
Gives the information on the condition of
pipeline as well as extent and location of
any problem in the pipeline
Functions
- Diameter/ Geometry measurement
- Curvature monitoring
- Temperature/pressure monitoring
- Bend measurement
- Metal Loss/Corrosion Detection
22
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Types of pigs
Types of intelligent pigging
 Photographic inspection Pigs
 Crack Detection Pigs
 Wax Deposition Detection Pigs
 Leak Detection Pigs
 Product Sampling Pigs
 Sampling Pig
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Types of pigs
In Line inspection Tools / Smart / intelligent Pigs
In Line Inspection provides information on the condition of the pipe and/or its
contents. With few exceptions, the In Line Inspection Tool itself is simply the tool
which gathers the data, which is then analysed by the engineers and technicians to
determine and report on the condition of the line.
Although the two most common requirements are for geometry/diameter
measurement and for metal-loss/corrosion devices, the information which can be
provided by these intelligent pigs covers a much wider range of inspection and
troubleshooting needs
which include:






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Diameter / geometry measurements;
Curvature monitoring;
Pipeline profile;
Temperature / pressure recording;
Bend measurement;
Metal-loss / corrosion detection;






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Photographic inspection;
Crack detection;
Wax deposition measurement;
Leak detection;
Product sampling, and;
Mapping.
Types of pigs
Magnetic flux detection
pig
Multi-channel
caliper pig
Geometric inspection
tool
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Dual diameter caliper
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Types of pigs
Geometry Pigs
(eg.-Kaliper Pig, Electronic Gauging Pig, Cal Pig, Geo Control Pig,
Deformation survey tool)
Curvature Monitoring Pigs
(eg.Gyrosystem, Inertial geometry Pig)
Pressure & Temperature Recording Pigs
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Types of intelligent pigging
Bend measurement Pigs
(eg. Bend Locator)
Metal Loss Corrosion Detection Pigs
Magnetic Flux Pigs (eg. Linalog, Magnescan,Corrocontrol
Corrosion detection system, Pipeline corrosion surveyor)
UltrasonicPigs
(eg Ultrascan, Microprobe, RPITT, Flow sonic)
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Types of pigs
Ultrasonic crack detection tool
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Types of pigs
PLUGS:
A plug is a specialist pig that can be used to isolate a section of pipeline at
pressure while some remedial work is undertaken.
The plugs can withstand pressures up to 200 bars typically.
The plug works by gripping into the line pipe and then having a separate
sealing system.
Lower pressure techniques include High Friction pigs, which provide a
barrier for de- pressurized systems.
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Types of pigs
High pressure plug pig
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Types of pigs
GEL PIGS
Gel pigs are a series of gelled liquid systems which have been developed for
use in pipeline operations, either during initial commissioning, or as a part
of a continuing maintenance program.
Most pipeline gels are water-based, but a range of chemicals, solvents, and
even acids can be gelled. Some chemicals can be gelled as the bulk liquid
and others only diluted in a carrier.
Gelled diesel is commonly used as a carrier of corrosion inhibitor in gas
lines.
There are four main types of gel that are used in pipeline
applications:
 Batching, or separator gel
 Debris pickup gel
 Hydrocarbon gel
 Dehydrating gel
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Types of pigs
Gel pig
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Types of pigs
GEL PIGS
As a liquid, although highly viscous, the gel can be pumped through any line
which will accept liquids.
Gel pigs can be used alone (in liquid lines), in place of batching pigs, or in
conjunction with various types of conventional pigs.
When used with conventional pigs, gelled pigs can improve overall
performance while almost eliminating the risk of sticking a pig.
Gel pigs do not wear out in service like conventional pigs.
They can, however, be susceptible to dilution and gas cutting.
Care must be taken, therefore, when designing a pig train that incorporates
gel pigs to minimize fluid bypass of the pigs, and to place a conventional pig
at the back of the train when displacing with gas.
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Piggable pipeline construction
Piggable pipeline design criteria
 Working site nature
 Transported crude oil nature
 Pipeline material component
Piggable pipeline start
Piggable pipeline End
construction
- According ASME B31.3 AND ASME B31.8 and according to
API oil pipeline design codes
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Piggable pipeline construction
The most essential item must be take action in
piggable pipeline construction is material selection
Material:
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* Barred Tees
* Long Radius Elbows
* Full Bore Valves
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Piggable pipeline construction
Barred TEE
Elbow 90 Long Radius
Ball valve full bore
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Pigging pipeline
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PIG TRAPS/LAUNCHERS/RECEIVERS
Pig traps are used for inserting pigs into a pipeline then launching, receiving,
and finally removing them without flow interruption.
Pig traps are not generally proprietary products and are usually made to a
specification drawn up by the user. However, pig trap closures are
proprietary products and form a critically important part of a pigging
system.
Safety is a major consideration in the selection of a closure.
All closures must have a built-in safety lock which prevents them being
opened while the trap is pressurized.
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Pigging operation
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Pigging operation
PIGGING ACTIVITY
B
A
FROM PROCESS
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Pigging operation
1. CLOSE main and bypass valves
2. Hydrocarbon free pig trap
3. Ensure trap valves hold.
4. INSERT pig and close trap
5. OPEN Main valve
6. Divert Flow thru Bypass.
7. Pig starts moving.
8. Close Main Bypass valves.
9. OPEN Station valve
10.COMMUNICATE w Receiver
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Pigging operation
PIG LAUNCHER
B
A
FROM PROCESS
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Pigging operation
1.
2.
3.
4.
5.
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Before Pig Arrives, OPEN Bypass and Main trap Valves.
When Pig is in trap, DIVERT flow thro station valve.
HYDROCARBON FREE the trap
PBU to ensure trap is isolated.
Open Trap & REMOVE Pig.
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Pigging operation
PIG RECEIVER
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launcher
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Receiver
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Prepigging Test
Preparing p/l spool pieces for pigging test
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SAFETY PRECAUTIONS
Increase the flow rate and line pressure, but do not
exceed safe limits of the pipeline.
Remove pressure from the line and vent or drain toward the launcher. Removing
pressure allows the pig to relax to its original shape and may cause it to back up
in the pipeline. Allow pres-sure to dissipate. After 15-30 minutes, re-pressure the
line in an attempt to drive the pig through the restriction. Repeat two to three
times.
Run a soft swab up behind the stuck pig to try to attain a positive seal. Repeat
step 1 above.
Consider ways to back the pig out of the line, returning it to the pig launcher.
This requires pressuring from the opposite end of the pipeline.
In a potable water line when pigging with a foam pig, super chlorinate (3000 to
5000 ppm) in a slug form to dissolve the pig.
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Devices Used In Pipeline Pigging
Pig detector
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Devices Used In Pipeline Pigging
suitable Pig
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Devices Used In Pipeline Pigging
Suitable air compressor
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Devices Used In Pipeline Pigging
High pressure Hydraulic pump
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