PIGGING

Aame B 31.8 Gas Transportation

“841.43 Functional Testing of Equipment and Systems.

As a part of commissioning, all pipeline and compressor station monitor and control equipment and systems shall be fully function-tested, especially including safety systems such as pig trap interlocks, pressure and flow-monitoring systems, and emergency pipeline shut-down systems. Consideration should also be given to performing a final test of pipeline valves before the gas is introduced to ensure that each valve is operating correctly.

863 INTERNAL CORROSION CONTROL

863.2 New Installations

When designing a new or replacement pipeline system, or additions or modifications to existing systems, measures shall be considered to prevent and/or inhibit internal corrosion. To preserve the integrity and efficiency of a pipeline in which it is known or anticipated that corrosive gas will be transported, the following factors should be included in the design and construction, either separately or in combination.

(a) When internal coating is to be used to protect a piping system(1) The coating shall meet the quality specifications, and the minimum dry film thickness shall be established to protect the facility from the corrosive media involved, based on the type of coating and methods of application.(2) Applied coatings shall be inspected in accordance with established specifications or

accepted practice.(3) Provision shall be made to prevent joint corrosion, such as cleaning and recoating or the continuing use of a suitable inhibitor when coated pipe or other components are joined by welding or other methods that leave the parent metal exposed.(4) The types of coating and pitting tools used should be evaluated and chosen to prevent damage to the internal coating if pigs or spheres are to be used.

(b) When a corrosion inhibitor is to be used as an additive to the gas streams (1) The equipment for the holding, transfer, and injection of the inhibitor into the stream shall be included in the design.(2) The operation of the injection program should be a part of the planning.(3) Sufficient test coupon holders or other monitoring equipment shall be provided to allow for continued program evaluations.(4) The corrosion inhibitor selected shall be of a type that will not cause deterioration of any components of the piping system.

(c) When a pipeline pigging system is planned(1) Scraper traps for the insertion and removal of pigs and/or spheres shall be provided.(2) Sections of pipeline to be traversed by pigs or spheres shall be designed to prevent damage to pigs, spheres, pipes, or fittings during operations.(3) Piping for pigs or spheres shall be designed to guide the tool and the materials they propel effectively and safely.(4) Provisions shall be made for effective accumulation and handling of liquid and solid

materials removedfrom the pipeline by pigs or spheres.

(d) When corrosion coupons, corrosion probes, and/or test spools are to be used(1) Corrosion coupons, probes, or test spools shall be installed where practical at locations

where the greatest

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potential for internal corrosion exists.(2) Corrosion coupons, probes, and test spools must be designed to permit passage of pigs or spheres when installed in sections traversed thereby.

(e) When gas is to be treated to reduce its corrosivity(1) Separators and/or dehydration equipment may be installed.(2) Equipment for the removal of other deleterious material from the gas should be

considered.

(f) The material of the pipe and other equipment exposed to the gas stream must resist internal corrosion; therefore,

(1) Materials selected for pipe and fittings shall be compatible with the components of the gas, the liquids carried by the gas, and with each other. A source of information on materials performance in corrosive environmentsis The Corrosion Data Survey, published by NACE.(2) Where plastic, nonferrous, or alloy steel pipe and components are used to prevent or control internal corrosion, such materials shall have been determined to be effective under the conditions encountered. [Seeparas. 842.611(b) and 849.611(b) for limitations on copper.](3) Erosion–corrosion effects from high-velocity particles at probable points of turbulence

and impingementshould be minimized by use of erosion-resistant materials, added wall thickness, design or

flow configuration,and size or dimensions of the pipe and fittings.

863.3 Existing Installations

A pipeline internal corrosion control program shall include, but shall not be limited to, the following:

(a) The establishment and evaluation of a program for the detection, prevention, or mitigation of detrimental internal corrosion should include the following:(1) Pipeline leak and repair records should be reviewed for indication of the effects of

internal corrosion.(2) When any part of a pipeline is removed and the internal surface is accessible for

inspection, it should bevisually examined and evaluated for internal corrosion.(3) If evidence of internal corrosion is discovered, the gas shall be analyzed to determine the types and concentrations of any corrosive agents.(4) Liquids or solids removed from the pipeline by pigging, draining, or cleanup should be analyzed as necessary to determine the presence of corrosive materials and evidence of corrosion products.

(b) Where it is determined that internal corrosion taking place could affect public or employee safety, one or more of the following protective or corrective measures shall be used to control detrimental internal corrosion:(1) An effective corrosion inhibitor shall be applied in a manner and quantity to protect all

affected portionsof the piping systems.(2) Corrosive agents shall be removed by recognized methods, such as acid gas or

dehydration treating plants.(3) Fittings shall be added for removal of water from low spots, or piping shall be positioned to reduce sump capacities.(4) Under some circumstances, application of a suitable internal coating may be effective.

(c) Internal corrosion control measures shall be evaluated by an inspection and monitoring program, including, but not limited to, the following:

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(1) The inhibitor and the inhibitor injection system should be periodically checked.(2) Corrosion coupons and test spools shall be removed and evaluated at periodic

intervals.(3) Corrosion probes should be checked manually at intervals, or continuously or intermittently monitored and/or recorded to evaluate control of pipeline internal corrosion.(4) A record of the internal condition of the pipe, of leaks and repairs from corrosion, and of gas, liquids, or solids quantities and corrosivity should be kept and used as a basis for changes in the pigging schedule, inhibitor program, or gas treatment facility.(5) When pipe is uncovered, or on exposed piping where internal corrosion may be anticipated, pipe wall thickness measurement or monitoring will help evaluate internal corrosion.(6) Where inspections, observation, or record analysis indicates internal corrosion is taking place to an extent that may be detrimental to public or employee safety, that portion of the system shall be repaired or reconditioned, and appropriate steps shall be taken to mitigate the internal corrosion.

A847.7 Testing for BucklesTesting for buckles, dents, and other diameter restrictions shall be performed after installation. Testing shall be accomplished by passing a deformation detection device through the pipeline section, or by other methods capable of detecting a change in pipe diameter. Pipe having excessive deformation which affects the serviceability of the pipeline facilities shall be repaired or replaced. Consideration should also be given to repairing excessive ovality which may interfere with pigging operation or internal inspection.

Interpretation: 14-6

Subject: ASME B31.8-1999 Edition, Paras. A834 and A842.27Date Issued: June 29, 2004File: 03-1792Question (1): A portion of the topsides between the riser hangar flange and the launcher/ receiver is specified as per B31.8 in lieu of B31.3 in order to maintain the constant inside diameter of the pipe for pigging. Does the pipe support attachment require a full encircling member in accordance with para. A834 since the portion of piping referenced above is not construed as a riser or a pipeline?

Reply: (1) Yes. We agree that the portion of piping you are considering is not a riser or a pipeline, but it is platform piping. Since para. A834 also covers platform piping, it does indeed require a full encircling member in order to be in accordance with ASME B31.8.”

PIG TRAPS/LAUNCHERS/RECEIVERSPig 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

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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 pressurised.

Hydraulically activated pipeline pigging

CHydraulically activated pipeline pigging (HAPP) is a pigging technology applied for pipeline cleaning. The basic principle is that a pressure drop is created over a by-passable pig held back against a pipeline’s fluid flow. The pipeline fluid passing through the pigs cleaning head is accelerated by this pressure drop forming strong cleaning jets. These jets are directed onto the inner wall in front of the pig removing all kinds of deposits. Generally this technology transforms kinetic energy of the pipeline fluid into a locally available differential pressure which in this case is used to create cleaning jets but can also be used otherwise.

Contents

Introduction to Pipeline Pigging

Pipeline pigs are devices that are inserted into and travel throughout the length of a pipeline driven by the product flow. They were originally developed to remove deposits which could obstruct or retard flow through a pipeline (Fig. 1). Today pigs are used during all phases in the life of a pipeline for many different reasons.

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Fig. 1 Cleaning pig in a pipeline

Fig. 2 Classification of pipeline pigs

Pigs used today can be divided into three categories (Fig. 2):

Utility Pigs, are used to perform functions such as cleaning, separating, or dewatering. In Line Inspection (ILI) Tools, provide information on the condition of the line, as well as the

extent and location of any problems.

Gel Pigs, are used in conjunction with conventional pigs to optimize pipeline dewatering, cleaning, and drying tasks.

Generally for cleaning pigs, the cleaning force applied is the mechanical force between the pipe inner wall and the cleaning pig itself. This force is determined by the pig travel speed as well as by the hardness and shape of the cleaning edge: The faster the pig, the higher the cleaning impact on the deposits but at the same time only the surface of debris is scratched away. Therefore several, sometimes quite many, pig runs are required to clean a pipeline.Hydraulic activated pigs apply high pressure liquid jets either supplied by high pressure hoses (depended) or made available by the kinetic energy locally available. Depended hydraulic activated pigs are limited in reach due to the hose which needs to be inserted into the pipeline and guides the cleaning head.

HAPP principle

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Fig. 3 Components of a hydraulically activated power pig

A hydraulic activated pig consists of three units (Fig. 3): a brake unit, a seal unit and the cleaning head.

All units have openings that allow the entire fluid flow through the pipeline to bypass. The brake unit ensures that a hydraulically activated pig is held back against the fluid flow in the pipeline. The fluid pushes against the following seal unit, which channels it into the openings of the cleaning head. Seal unit and cleaning head pose a flow restriction resulting in a pressure difference across the pig. Thus the fluid is accelerated in the cleaning head's nozzles creating extremely powerful liquid jets. These jets are directed onto the pipe inner wall and remove any kind of deposits.

The brake unit ensures that the travel speed of the pig is many times slower than the fluid velocity thus allowing it to entirely remove deposits from the pipe wall before it travels across the cleaned surface. The deposits removed are immediately flushed downstream the pipeline with the main jet of the cleaning head which is directed in the middle of the pipeline. With all deposits removed from the pipe wall and transported downstream by the fluid flow there remains no risk of the pig getting stuck in debris accumulated in front of it.

References

Pigging Technlogy Review, page 36, World Pipelines Volume 9, Number 1 - January 2009 STOLTZE, Björn - Jet Power, World Pipelines Volume 8, Number 6 - June 2008

STOLTZE, Björn - A new pipeline cleaning technology: the hydraulically-activated power pig, Global Pipeline Monthly Volume 3, issue #11 - December 2007

STOLTZE, Björn - A new pipeline cleaning technology: Hydraulically activated power pigging (HAPPTM), presented at the Pigging Products & Services Association (PPSA) Seminar in Aberdeen, Scotland - November 2007

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Pipeline Inspection and Safety

In order to ensure the efficient and safe operation of the extensive network of natural gas pipelines, pipeline companies routinely inspect their pipelines for corrosion and defects. This is done through the use of sophisticated pieces of equipment known as pigs. Pigs are intelligent robotic devices that are propelled down pipelines to evaluate the interior of the pipe. Pigs can test pipe thickness, and roundness, check for signs of corrosion, detect minute leaks, and any other defect along the interior of the pipeline that may either impede the flow of gas, or pose a potential safety risk for the operation of the pipeline. Sending a pig down a pipeline is fittingly known as 'pigging' the pipeline.

In addition to inspection with pigs, there are a number of safety precautions and procedures in place to minimize the risk of accidents. In

fact, the transportation of natural gas is one of the safest ways of transporting energy, mostly due to the fact that the infrastructure is fixed, and buried underground. According to the Department of Transportation (DOT), pipelines are the safest method of transporting petroleum and natural gas. While there are in excess of 100 deaths per year associated with electric transmission lines, according to the DOT's Office of Pipeline Safety in 2001, there were 2 deaths associated with transmission pipelines, and 5 deaths associated with distribution systems. To learn more about pipeline safety, visit the DOT's Office of Pipeline Safety.

Pigging

From Wikipedia, the free encyclopediaJump to: navigation, search

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (January 2008)

This article is about the industrial process of pigging, for the sport see pigging (sport).

Pigging in the maintenance of pipelines refers to the practice of using pipeline inspection gauges or 'pigs' to perform various operations on a pipeline without stopping the flow of the product in the pipeline. These operations include but are not limited to cleaning and inspection of the pipeline. This is accomplished by inserting the pig into a 'pig launcher' - a funnel shaped Y section in the pipeline. The launcher is then closed and the pressure of the product in the pipeline is used to push it along down the pipe until it reaches the receiving trap - the 'pig catcher'.

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Pig - Pipeline Inspection Tool

Source: Duke Energy Gas Transmission Canada

If the pipeline contains butterfly valves, the pipeline cannot be pigged. Ball valves cause no problems because the inside diameter of the ball can be specified to be the same as that of the pipe.

Pigging has been used for many years to clean larger diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging systems is now increasing in many continuous and batch process plants as plant operators search for increased efficiencies.[1]

Pigging can be used for almost any section of the transfer process between, for example, blending, storage or filling systems. Pigging systems are already installed in industries handling products as diverse as lubricating oils, paints, chemicals, toiletries, and foodstuffs.

Pigs are used in lube oil or painting blending: they are used to clean the pipes to avoid cross-contamination, and to empty the pipes into the product tanks (or sometimes to send a component back to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is done in the midst of a batch, e.g. when producing a premix that will be used as an intermediate component.

Pigs are also used in oil and gas pipelines: they are used to clean the pipes but also there are "smart pigs" used to measure things like pipe thickness along the pipeline. They usually do not interrupt production, though some product can be lost when the pig is extracted. They can also be used to separate different products in a multiproduct pipeline.

Etymology

Pigs get their name from the squealing sound they make while traveling through a pipeline.[citation

needed] (Disputed: 'PIG' is an acronym derived from the initial letters of the term 'Pipeline Inspection Gauge')

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Pigging in production environments

Product and time saving

A major advantage of piggable systems is the potential resulting product savings. At the end of each product transfer, it is possible to clear out the entire line contents with the pig, either forwards towards the receipt point, or backwards to the source tank. There is no requirement for extensive line flushing.

Without the need for line flushing, pigging offers the additional advantage of a much more rapid and reliable product changeover. Product sampling at the receipt point becomes faster because the interface between products is very clear, and the old method of checking at intervals, until the product is on-specification, is considerably shortened.

Pigging Systems can also be operated totally by a Programmable Logic Controller (PLC).

Environmental issues

Pigging has a significant role to play in reducing the environmental impact of batch operations. Traditionally, the only way that an operator of a batch process could ensure a product was completely cleared from a line was to flush the line with a cleaning agent such as water or a solvent or even the next product. This cleaning agent then had to be subjected to effluent treatment or solvent recovery. If product was used to clear the line, the contaminated finished product was downgraded or dumped. All of these problems can now be eliminated due to the very precise interface produced by modern pigging systems.

Safety considerations

Pigging systems are designed so that the pig is loaded into the launcher, which is pressured up to launch the pig into the pipeline through a kicker line. The pig is removed from the pipeline via the receiver at the end of each run. All systems must allow for the receipt of pigs at the launcher, as blockages in the pipeline may require the pigs to be pushed back to the launcher. Some systems are designed to pig the pipeline in either direction. Most pigging systems are like this as the pigs must be removed, as many pigs are rented, pigs wear and must be replaced, and cleaning pigs push contaminants from the pipeline such as wax, foreign objects, hydrates, etc, which must

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be removed from the pipeline. There are inherent risks in opening the barrel to atmosphere and care must be taken to ensure that the barrel is depressured prior to opening. If the barrel is not completely depressured, the pig can be ejected from the barrel and operators have been severely injured when standing in front of an open pig door. When the product is sour, the barrel should be evacuated to a flare system where the sour gas is burnt. Operators should be wearing a self-contained breathing apparatus when working on sour systems.

A few pigging systems utilize a "captive pig", and the pipeline is only opened up very occasionally to check the condition of the Pig[2]. At all other times, the pig is shuttled up and down the pipeline at the end of each transfer, and the pipeline itself is never opened up during process operation. These systems are not common.

Intelligent pigging

Inserting a pig into a natural gas pipeline

Modern intelligent pigs are highly sophisticated instruments that vary in technology and complexity by the intended use and by manufacturer. An intelligent pig, or smart pig, is basically a computer that collects various forms of data during the trip through the pipeline. The computer part, consisting mostly of electronics, must be sealed to prevent leakage of the pipeline product into the electronics. Sealing is a very important aspect as the products in the pipeline can range from highly basic to highly acidic and can be of extremely high temperature. Many pigs use specific materials according to the product in the pipeline. Power for the electronics is provided by onboard batteries which also must be sealed from the product environment. Recording of data may be by various means ranging from analog tape in a reel-to-reel format, digital tape or solid state memory in more modern digital units.

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The technology used to accomplish the service vary by the service required and the design of the pig, each pigging service provider may have unique and proprietary technologies to accomplish the service. Surface pitting and corrosion, as well as cracks and weld defects in steel/ferrous pipelines are often detected using Magnetic Flux Leakage (MFL) pigs. Other "smart" pigs use ultrasonics to detect pipe defects. Caliper pigs can measure the "roundness" of the pipeline to determine areas of crushing or other deformations. Some smart pigs can combine technologies such as MFL and Caliper into a single tool.

During the pigging run the pig is unable to directly communicate with the outside world due to the distance underground or underwater and/or materials that the pipe is made of. For example, steel pipelines effectively prevent any reliable radio communications outside the pipe. It is therefore necessary that the pig use internal means to record its own movement during the trip. This may be done by gyroscope-assisted tilt gauges, odometers and other technologies. The pig will record this positional data so that the distance it moves along with any bends can be interpreted later to determine the exact path taken.

Location verification is often accomplished by surface instruments that record the pig’s passage by either audible or gravinometric (or other) means. The sensors will record when they detect passage of the pig; this is then compared to the internal record for verification or adjustment. The external sensors may have GPS capability to assist in their location or even to transmit the pig’s passage, but the pig itself usually cannot use GPS as it requires being able to “see” (in satellite terminology) the satellites.

After the pigging run has been completed, the positional data is combined with the pipeline evaluation data (corrosion, cracks, etc) to provide a location-specific defect map and characterization. In other words, the combined data will tell the operator the location and type and size of each pipe defect. This is used to judge the severity of the defect and help repair crews locate and repair the defect quickly without having to dig up excessive amounts of pipeline. By evaluating the rate of change of a particular defect over several years, proactive plans can be made to repair the pipeline before any leakage or environmental damage occurs. pigging is very impotant for industrial point of view vipin sharma bhadamai hathras

Pipeline inspection gauge

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A pig in a cutaway pipeline

A "Pig" launcher/receiver, belonging to the natural gas pipeline in Switzerland.

A pipeline inspection gauge or pig in the pipeline industry is a tool that is sent down a pipeline and propelled by the pressure of the product in the pipeline itself. There are four main uses for pigs:

1. physical separation between different liquids being transported in pipelines; 2. internal cleaning of pipelines;

3. inspection of the condition of pipeline walls (also known as an Inline Inspection (ILI) tool);

4. capturing and recording geometric information relating to pipelines (e.g. size, position).

The original pigs were made from straw wrapped in wire used for cleaning. They made a squealing noise while traveling through the pipe, sounding to some like a pig squealing. The term "pipeline inspection gauge" was later created as a backronym.

One kind pig is a soft, bullet shaped polyurethane foam plug that is forced through pipelines to separate products to reduce mixing. There are several types of pigs for cleaning. Some have tungsten studs or abrasive wire mesh on the outside to cut rust, scale, or paraffin deposits off the inside of the pipe. Others are plain plastic covered polyurethane. Pigs cannot be used in pipelines that have butterfly valves.

Inline inspection pigs use various methods for inspecting a pipeline. A sizing pig uses one (or more) notched round metal plates that are used as gauges. The notches allow different parts of the plate to bend when a bore restriction is encountered. More complex systems exist for

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inspecting various aspects of the pipeline. Intelligent pigs, also called smart pigs, are used to inspect the pipeline with sensors and record the data for later analysis. These pigs use technologies such as Magnetic flux leakage (MFL) and ultrasonics to inspect the pipeline. Intelligent pigs may also use calipers to measure the inside geometry of the pipeline.

In 1961, the first intelligent pig was run by Shell Development. It demonstrated that a self contained electronic instrument could traverse a pipe line while measuring and recording wall thickness. The instrument used electromagnetic fields to sense wall integrity. In 1964 Tuboscope ran the first commercial instrument. It used MFL technology to inspect the bottom portion of the pipeline. The system used a black box similar to those used on aircraft to record the information.

A pig has been used as a plot device in three James Bond films: Diamonds Are Forever, where Bond disabled a pig to escape from a pipeline, The Living Daylights, where a pig was modified to secretly transport a person through the Iron Curtain, and The World Is Not Enough, where a pig was used to move a nuclear weapon through a pipeline.

A pig was also used as a plot device in the Tony Hillerman book The Sinister Pig where an abandoned pipeline from Mexico to the United States was to use a pig to transport illegal drugs.

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