Pigging – Wikipedia

2023-10-20 23:31:01

Follow of utilizing pipeline inspection gauges or devices to carry out varied upkeep operations

A cleansing pig for a 710-millimetre (28 in) oil pipeline. The blue plastic disks seal in opposition to the within of the pipe to propel the machine and to take away free sedimentation or scale buildup. The black rectangles on the high and the round disks within the middle are magnets to draw and take away any free metallic objects within the pipe.

A cleansing pig for a 150-millimetre (6 in) oil pipeline. The wire brush encircles the shaft and scours the inside of the pipeline.

A scraper pig proven on the Trans-Alaska Pipeline System Guests Middle

In pipeline transportation, pigging is the follow of utilizing pipeline inspection gauges or devices, gadgets usually known as pigs or scrapers, to carry out varied upkeep operations. That is achieved with out stopping the circulation of the product within the pipeline.^[1]^[2]^[3]

These operations embody however aren’t restricted to cleansing and inspecting the pipeline. That is achieved by inserting the pig right into a “pig launcher” (or “launching station”)—an outsized part within the pipeline, lowering to the conventional diameter. The launching station is then closed and the pressure-driven circulation of the product within the pipeline is used to push the pig alongside the pipe till it reaches the receiving lure—the “pig catcher” (or “receiving station”).

Functions[edit]

Pigging is used to wash massive diameter pipelines within the oil trade. In the present day, nevertheless, the usage of smaller diameter pigging techniques is now rising in lots of steady and batch course of vegetation as plant operators seek for elevated efficiencies and lowered prices.

Pigging can be utilized for nearly any part of the switch course of between, for instance, mixing, storage or filling techniques. Pigging techniques are put in in industries dealing with merchandise as various as lubricating oils, paints, chemical compounds, toiletries, cosmetics and foodstuffs.

Pigs are utilized in lube oil or paint mixing to wash the pipes to keep away from cross-contamination, and to empty the pipes into the product tanks (or generally to ship a part again to its tank). Normally pigging is finished originally and on the finish of every batch, however generally it’s achieved within the midst of a batch, resembling when producing a premix that might be used as an intermediate part.

Pigs are additionally utilized in oil and gasoline industries to wash or clear pipelines. Clever or “Good pigs” are used to examine pipelines to evaluate their situation and to stop leaks, which might be hazardous or dangerous to the setting. They normally don’t interrupt manufacturing, although some product might be misplaced when the pig is eliminated. They will also be used to separate totally different merchandise in a multiproduct pipeline and to clear slugs of liquid from multiphase gasoline//liquid pipelines.

Pigging requires the pipeline to be designed to be pigged from the outset. If the pipeline comprises topological variations together with adjustments in diameter, butterfly valves, instrumentation, tight bends, pumps or lowered port ball valves, the pipeline can’t be historically pigged. In such situations, options resembling Ice Pigging could also be employed. Full port (or full bore) ball valves trigger no issues as a result of the within diameter of the ball opening is identical as that of the pipe.

Etymology[edit]

Some early cleansing “pigs” had been created from straw bales wrapped in barbed wire^[4] whereas others used leather-based.^[5] Each made a squealing noise whereas touring via the pipe, sounding to some like a pig squealing,^[6] which gave pigs their title.^[7]^[8]

In manufacturing environments[edit]

Product and time saving[edit]

A significant benefit for multi-product pipelines of piggable techniques is the potential of product financial savings. On the finish of every product switch, it’s doable to segregate the following merchandise utilizing a pigging sphere. Alternatively it’s doable to filter all the line contents with the pig, both forwards to the receipt level, or backwards to the supply tank. There is no such thing as a requirement for in depth line flushing.

With out the necessity for line flushing, pigging presents the extra benefit of rather more fast and dependable product changeover. Product sampling on the receipt level is quicker with pigs, as a result of the interface between merchandise may be very clear; the outdated technique of checking at intervals to find out the place the product is on-specification takes significantly longer.

Pigging will also be operated completely by a programmable logic controller (PLC).

Environmental advantages[edit]

Pigging has a major position to play in lowering the environmental influence of batch operations. Historically, the one means that an operator of a batch course of may guarantee a product was utterly cleared from a line was to flush the road with a cleansing agent resembling water or a solvent, and even with the following product. The cleansing agent then needed to be subjected to effluent therapy or solvent restoration. If a product was used to clear the road, it was essential to downgrade or dump the contaminated portion of the product. All of those issues can now be eradicated because of the very exact interface produced by fashionable pigging techniques.

Security issues[edit]

Pigging techniques are designed in order that the pig is loaded into the launcher, which is pressured to launch the pig into the pipeline via a kicker line. In some instances, the pig is faraway from the pipeline through the receiver on the finish of every run.^[9] All techniques should enable for the receipt of pigs on the launcher, as blockages within the pipeline might require the pigs to be pushed again to the launcher. Many techniques are designed to pig the pipeline in both course.

The pig is pushed both with a gasoline or a liquid; if pushed by gasoline, some techniques^[10] might be tailored within the gasoline inlet in an effort to guarantee pig’s fixed pace, regardless of the circulation stress is. The pigs have to be eliminated, as many pigs are rented, pigs put on and have to be changed, and cleansing (and different) pigs push contaminants from the pipeline resembling wax, international objects, hydrates, and so on., which have to be faraway from the pipeline. There are inherent dangers in opening the barrel to atmospheric stress so care have to be taken to make sure that the barrel is depressurized previous to opening. If the barrel shouldn’t be utterly depressurized, the pig might be ejected from the barrel and operators have been severely injured when standing in entrance of an open pig door. A pig was as soon as by chance shot out of the top of a pipeline and not using a correct pig receiver and went via the facet of a home 150 metres (500 ft) away.^[11] When the product is bitter, the barrel needs to be evacuated to a flare system the place the sour gas is burnt. Operators ought to put on a self-contained breathing apparatus when engaged on bitter techniques.

A number of pigging techniques make the most of a “captive pig”, and the pipeline is simply opened often to test the situation of the pig.^[12] In any respect different instances, the pig is shuttled up and down the pipeline on the finish of every switch, and the pipeline is rarely opened up throughout course of operation. These techniques aren’t frequent.

Pigging operations[edit]

See diagram on the best representing a pig launcher. In regular operation valves V2 and V4 might be open, all different valves and the door are closed and locked.^[13]

To launch a pig

Guarantee pig launcher is drained and vented. Unlock and open, then shut and relock the vent and drain valves.
Unlock and open door, load pig into launcher, shut and lock door.
Unlock and open valves V1 and V3, to create a circulation path via the launcher.
Partly shut ‘kicker’ valve V2 to launch the pig.
The launch alarm XA will point out when the pig has been launched.
Open valve V2 absolutely.
Shut and lock valves V1 and V3.
Unlock and open vent and drain valves. Permit launcher to depressurise and drain.
Shut and lock vent and drain valves.
Pig launcher is then prepared for the following pig to launch.

See diagram on the best representing a pig receiver.

To obtain a pig

Unlock and open valves V1 and V3, to create a circulation path via the pig receiver.
Partly shut ‘kicker’ valve V2 to induce circulation via the receiver.
The obtain alarm XA will point out when the pig has been acquired.
Open valve V2 absolutely.
Shut and lock valves V1 and V3.
Unlock and open vent and drain valves to empty the receiver.
Shut and lock vent and drain valves.
Unlock and open door, take away pig from receiver, shut and lock door.
Pig receiver is then able to obtain the following pig.

The pigging set up proven (proper) is called an Above Floor Set up (AGI). It’s a part of the UK’s National Transmission System for pure gasoline. It reveals two pig launcher/ receivers. There are on the finish of two 610-millimetre (24 in) diameter pipelines that carry gasoline beneath the River Thames between East Tilbury Essex and Shorne in Kent. Ought to one pipeline be broken, by a ship’s anchor for instance, that line might be remoted and the second pipeline permits gasoline to circulation throughout the river.^[14]

Mechanical interlocks[edit]

There are lots of stories of incidents during which operators have been injured and even killed whereas performing a pigging operation. Widespread causes of such occasions are:

opening of the closure door whereas the vessel continues to be pressurized;
opening of the principle course of valve whereas the closure door shouldn’t be absolutely closed;
opening of the closure door whereas a excessive focus of H₂S or different toxins stays contained in the vessel;
the vent valve remaining open whereas the vessel is being pressurized with its medium.

All these causes are straight associated to improper operation of the method valves and the closure door. A typical technique of avoiding these sorts of incidents is so as to add valve interlocks,^[15] which has been adopted by all international oil and gasoline working firms.^{[citation needed]}

Security throughout pigging depends on strict adherence to security procedures, which give detailed description of a protected valve working sequence. By bodily blocking incorrect operations, valve interlocks implement such sequences. Valve interlocks are completely mounted to each handbook and motor operated valves and the closure door. The interlocks block operation of a valve or door, except the suitable keys are inserted.

The precept of valve interlocking is the switch of keys. Every lock is supplied with two keys: a key for the locked open place and one for the locked closed place. Throughout an working process, just one key at a time is free. This key solely matches within the interlock belonging to the valve that’s to be operated subsequent within the working process. All keys are uniquely coded to keep away from the chance that valves might be unlocked at an inappropriate time.

These days clever interlocking options allow the combination of discipline gadgets like stress or H₂S meters in a valve interlocking sequence. This will increase security by integrating operator procedures^[16] with DCS and SIS security techniques.

Sorts of pigs[edit]

A pig on show in a piece of cutaway pipe, from the Alaska Pipeline

A pig launcher/receiver on a pure gasoline pipeline in Switzerland.

Gauging, separation and cleansing pigs[edit]

A “pig” is a software that’s despatched down a pipeline and propelled by the pressure of the product circulation within the pipeline itself. There are 4 most important makes use of for pigs:

Bodily separation between totally different fluids flowing via the pipeline
Inner cleansing of pipelines
Inspection of the situation of pipeline partitions (also referred to as an inline inspection (ILI) software)
Capturing and recording geometric data regarding pipelines (e.g., measurement, place).

One of the crucial frequent and versatile is the froth pig which is lower or poured out of open cell polyurethane foam into the form of a bullet and is pushed via pipelines for a lot of causes resembling to show the interior diameter of, clear, de-water, or dry out the road. There are a number of kinds of pigs for cleansing in varied densities from 32 to 160 kilograms per cubic metre (2 to 10 lb/cu ft) foam and in particular purposes as much as 320 kg/m³ (20 lb/cu ft). Some have tungsten studs or abrasive wire mesh on the skin to chop rust, scale, or paraffin wax deposits off the within of the pipe. Different varieties are absolutely or criss-cross coated in urethane, or there are naked polyurethane foam pigs with a urethane coating simply on the rear to seal and help in driving the pig. There are additionally absolutely molded urethane pigs used for liquid elimination or batching a number of totally different merchandise in a single line.

Inline inspection pigs use varied strategies for inspecting a pipeline. A sizing pig makes use of one (or extra) notched spherical metallic plates as gauges. The notches enable totally different elements of the plate to bend when a bore restriction is encountered. Extra advanced techniques exist for inspecting varied facets of the pipeline.

Clever pig[edit]

Clever pigs are used to examine the pipeline with sensors and report the information for later evaluation. These pigs use applied sciences resembling magnetic flux leakage (MFL) and ultrasound to examine the pipeline. Clever pigs may additionally use calipers to measure the within geometry of the pipeline.

In 1961, the primary clever pig was run by Shell Growth. It demonstrated {that a} self-contained digital instrument may traverse a pipeline whereas measuring and recording wall thickness. The instrument used electromagnetic fields to sense wall integrity. In 1964 Tuboscope ran the primary business instrument. It used MFL expertise to examine the underside portion of the pipeline. The system used a black field just like these used on plane to report the knowledge; it was principally a extremely personalized analog tape recorder. Till lately, tape recording (though digital) was nonetheless the popular recording medium. Because the capability and reliability of solid-state memory improved, most recording media moved away from tape to solid-state.

Capacitive sensor probes are used to detect defects in polyethylene pipe gasoline pipeline. These probes are connected to the pig earlier than it’s despatched via the polyethylene pipe to detect any defects within the outdoors of the pipe wall. That is achieved by utilizing a triple plate capacitive sensor during which electrostatic waves are propagated outward via the pipe’s wall. Any change in dielectric materials ends in a change in capacitance.^[17] Testing was performed by NETL DOE analysis lab on the Battelle West Jefferson’s Pipeline Simulation Facility
(PSF) close to Columbus, Ohio.^[18]

Trendy clever or “good” pigs are extremely subtle devices that embody electronics and sensors that accumulate varied types of knowledge throughout their journey via the pipeline. They range in expertise and complexity relying on the supposed use and the producer.

The electronics are sealed to stop leakage of the pipeline product into the electronics since merchandise can vary from being extremely fundamental to extremely acidic and might be of extraordinarily excessive stress and temperature. Many pigs use particular supplies in response to the product within the pipeline. Energy for the electronics is usually supplied by onboard batteries that are additionally sealed. Knowledge recording could also be by varied means starting from analog tape, digital tape, or solid-state reminiscence in additional fashionable models.

The expertise used varies by the service required and the design of the pig; every pigging service supplier might have distinctive and proprietary applied sciences to perform the service. Floor pitting and corrosion, in addition to cracks and weld defects in metal/ferrous pipelines are sometimes detected utilizing magnetic flux leakage (MFL) pigs. Different “good” pigs use electromagnetic acoustic transducers to detect pipe defects.^[19] Caliper pigs can measure the roundness of the pipeline to find out areas of crushing or different deformations. Some good pigs use a mixture of applied sciences, resembling offering MFL and caliper capabilities in a single software. Trials of pigs utilizing acoustic resonance technology have been reported.^[20]

In the course of the pigging run the pig is unable to straight talk with the skin world because of the distance underground or underwater and/or the supplies that the pipe is product of. For instance, metal pipelines successfully stop any important radio communications outdoors the pipe. It’s subsequently essential that the pig use inside means to report its personal motion in the course of the journey. This can be achieved by odometers, gyroscope-assisted tilt sensors and different applied sciences.^[21] The pig information this positional knowledge in order that the space it strikes together with any bends might be interpreted later to find out the precise path taken.

Location verification[edit]

Location verification is commonly achieved by floor devices that report the pig’s passage by both audible, magnetic, radio-transmission or different means. The sensors report after they detect the passage of the pig (time-of-arrival); that is then in comparison with the interior report for verification or adjustment. The exterior sensors might have Global Positioning System functionality^[22] to help of their location. A number of pig passage indicators transmit the pig’s passage, time and site, through satellite tv for pc uplink.^[23] The pig itself can not use GPS because the metallic pipe blocks satellite tv for pc alerts.

After the pigging run has been accomplished, the positional knowledge from the exterior sensors is mixed with the pipeline analysis knowledge (corrosion, cracks, and so on.) from the pig to offer a location-specific defect map and characterization. In different phrases, the mixed knowledge reveals to the operator the placement, kind and measurement of every pipe defect. This data is used to evaluate the severity of the defect and assist restore crews find and restore the defect rapidly with out having to dig up extreme quantities of pipeline. By evaluating the speed of change of a selected defect over a number of years, proactive plans might be made to restore the pipeline earlier than any leakage or environmental injury happens.

The inspection outcomes are usually archived (maybe in Pipeline Open Data Standard format) for comparability with the outcomes of later pigging runs on the identical pipeline.

In well-liked tradition[edit]

A pig has been used as a plot machine in three James Bond movies: Diamonds Are Forever, the place Bond disabled a pig to flee from a pipeline; The Living Daylights, the place a pig was modified to secretly transport an individual via the Iron Curtain; and The World Is Not Enough, the place a pig was used to hold and detonate a nuclear weapon in a pipeline.

A pig was additionally used as a plot machine within the Tony Hillerman e-book The Sinister Pig the place an deserted pipeline from Mexico to the US was used with a pig to move unlawful medication.

A pig launcher was featured within the season 2 episode “Pipeline Fever” of the animated present Archer, whereby Sterling Archer and Lana Kane are tasked with going right into a swamp and defending a pig launcher from radical environmentalist Joshua Grey.