PIPELINE PIGGING International Training & Development? 1 Piosiine PagingOBJECTIVES Upon completion of this section, you will: Understand the reasons for pigging a pipeline Learn why and how te pig during Pipelines construction Operation Inspection Maintenance and repair Renovation and rehabilitation How to design a pipetine for pigging Pipeline dimensions Pipeline materials Bends and off takes Connections and valves How to design and operate a pig trap and pig station Basic configurations Launchers and receivers Barrel and closures Signalers Offshore considerations Operating conditions International Training & Development ® 2 Pipeline SigaingBASIC PRINCIPLES Reasons for pigging a pipeline Safeguard assets and optimize efficiency General considerations Use of the correct type of pig and proper pigging program helps Maintain the integrity and optimum efficiency of the pipetine Safeguard both the environment and company assets Pipelines are designed and constructed based on the foliowing fundamental considerations tt must operate continuously Required throughput must be obtained with the least capital and the lowest operating costs Pigs play a major role in both obtaining and maintaining the above “two fundamentals” Help to obtain and maintain maximum efficiency by Removingany debris or foreign matter in the line Removingany deposits, either liquid or solid, that might build up and restrict flow Monitoring the operating and/or physical conditions of the line International Training & Development ® 3 Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Safequard assets and optimize efficiency General considerations Pigs play a major role in both obtaining and maintaining the above “two fundamentals” Help to maintain continuous operation by Removing any substance that might damage the pipeline process systems Helping lo prevent the formation of corrosion cells Providing timely information of any developing problems Providing data on any perceived problems to enable informed decisions to be made Providing an alternative to shutting down for stationary periodic testing Pipeline pigs help ensure that the pipeline is constructed properly and that it stays that way Pipeline efficiency and protection depend upon Pigging program Effectiveness of the pigs used Intecnational Training & Development ® 4 Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Safeguard assets and optimize efficiency Example 1: Effect of pipeline ID on pipeline efficiency Given: * A simple short, straight section of water pipe 12 inch (300 mm) diameter Determine: Flow rate reduction and pressure required to reestablish initial pressure if the inside diameter is reduced by 5% (15 m) by both a smooth and uneven internal deposit Solution: The flow rate reduction tor a smooth deposit at constant pressure is over 10%. To bring the flow rate back to its original level requires the initial pressure to be increased by almost 30% | If the deposit is uneven, the resulting turbulent flow will cause the pipe ID to be reduced by 18%, Flow rate would be reduced by i approximately 35% while the pressure to over come these /osses would need to be increased by more than 140%. International Taining & Development © 5 Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Safeguard assets and optimize efficiency Effect of corrosion One of the more common mistakes is to rely totally on corrosion monitoring and automatic corrosion control systems to decide when to run a pig Monitaring system reliahility depends upon where the probes, coupons and/or sampling points are located. This is difficult to achieve Sub-sea lines Land lines that have significant gradients Effect of channel and pitting corrosion Once pitting or channel corrosion has occurred, it is . unlikely that a pig will be able to remove the water that will accumulate in these recesses (Figure 1) Batch inhibition (running a slug of inhibitor between two pigs) is recommended as part of aay corrosion control program Intaraational Training & Development ® 8 Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Safeguard assets and optimize efficiency FIGURE 1: EFFECT OF CHANNEL AND PITTING CORROSION Government requlations United States Authorities having jurisdiction require that most new hydrocarbon pipelines must be designed to enable them to be pigged Other countries There are no known regulations Some countries require that licenses to construct and operate pipelines, are dependent upon them being able to be pigged International Training & Development ® 7 Pipeline Pigging A 4sBASIC PRINCIPLES Reasons for pigging a pipeline Practical needs Pigging is required during each phase in the life of a pipeline During construction Removing construction debris from the line Acceptance testing (water filling, de-watering, etc.) Commissioning During operation Pipe wall cleaning Condensate removal Product separation (batching) Applying inhibitors International Training & Developmen ® Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Practical needs Pigging is required during each phase in the life of a pipeline For inspection To check for physical damage (geometry) To detect corrosion, laminations or cracking Leak detection Sampling Line covering and spanning (sub-sea) For general maintenance and repair Corrosion inhibition Pre-inspection cleaning Decommissioning isolation Recommissioning Intornational Training & Development® Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Practical needs Pigging is required during each phase in the life of a pipeline During renovation/rehabilitation Gel pigging Applying in situ coatings Chemical cleaning Scale removal Cleaning for produce conversion Decommissioning Product removal Pipe wall cleaning Inspectian/testing Inerting Inesnational Training & Devalogment® 10 Pipeline PiggingBASIC PRINCIPLES Reasons for pigging a pipeline Practical needs It must be remembered that each pipeline is different, as they have different Diameters Lengths Contents Geometry Operating pressures and temperatures Materials Wall thickness Locations Contractors, owners and operating philosophies _ Codes and comply with different authorities having jurisdiction Pig selection and pigging program must be tailored to suit the particular need as well as the characteristics of the individual pipeline and its operation International Training & Development ® 11 Pipeline PlagingBASIC PRINCIPLES Pigging during pipeline construction General considerations Pigging during construction is frequently performed on sections of pipelines that are shorter than the entire pipeline, often using compressed air as the means of propulsion Pigs perform best if they are run at or near constant speed, thus some means of speed control, other than constant input, is required, thus eliminating speed excursion” One method of maintaining constant differential pressure and thus a ear constant speed is to: Close the down stream end of the pipe section Pressurize the entire section Release pressure down stream as air is inserted upstream Differential pressure required to keep the pig moving may be only 70% of that required to start the pig moving Excessive and uncontrolled pig speed can be very dangerous International Training & Development ® 12 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction General considerations A means of restraining the pig at the receiving end of the pipe while releasing the pressure ahead of the pig is required, otherwise the pig will become a projectile Catching devices can be as simple as a field made pig catcher or as sophisticated as a manufactured pig trap Many contractors build temporary traps that are reused during pipeline construction (Figures 2 and 3) sedans Stina a wth ivr aeons = 3c ecole eine ‘Slots around srcumforence with minim teal ‘rae ‘area of pipeline late wah hale approximately SO% of pipe darseter tack welded or “boted to end FIGURE 3: TYPICAL PIG CATCHER WHEN DRIVING WITH WATER Intemational Training & Development ® 13) Pipeline FiggingBASIC PRINCIPLES Pigging during pipeline construction Debris removal stage During the construction of any new pipeline Debris, sand, stones, welding rods, rags will be /eft inside the pipe Wildlife like mice and rabbits will find their way inside in spite of the use of “night caps” All foreign materials must be removed prior to performing cleaning or gauging runs Type of pig used depends on following factors Pipeline diameter and Jength Topography Whether the pipeline is offshore or onshore Soil is sandy or rocky Several debris-removal pig runs may be necessary and, because of duty, it is good practice to use wear discs on the front of the pig if the pipeline is relatively long tatemnational Training & Development ®© 14 Pipeline P sgingBASIC PRINCIPLES Pigging during pipeline construction Debris removal stage Compressed air is normally used to push the pig through the pipeline Each end of the pipeline section is fitted with “test ends” or temporary pig traps Used to faunch and receive the pig Receiving end should be fong enough to accommodate debris Offshore, the pipeline is usually capped at each end and laid down on the sea bed, then tied-in at some /ater stage “Lay-Down” head Used at each end of the section is similar to the test end on a /and line, and is basically a very fong pig trap May have to hold a /arge number of different types of pigs that may need to be launched or received separately, thus requiring a complex manifold and complex pigging procedures. Normally, this is subcontracted to a competent pigging service company Inrarnational Training & Development ® 18) Pipetine PiagingBASIC PRINCIPLES Pigging during pipeline construction Cleaning stage Following the debris-removal pig runs, a wire brush pig is run through the pipeline to remove stubborn debris including mill scale, weld bead slay, etc., from the pipe wall Normally, more then one run of the cleaning pig is expected Compressed air is usually used to push the cleaning pig through the pipeline For a series of cleaning runs Launcher and received fest ends should be fong enough to accommodate the number of pigs used Manifold system, similar to that used offshore, may be required Initial gauging After debris removal and cleaning have been satisfactorily completed, gauging pigs are run International Training & Devalopmenc® 16 Pipeiine PlagingBASIC PRINCIPLES Pigging during pipeline construction Initial gauging Gauging runs are necessary to Determine that there is nothing protruding inside the pipeline which might cause an obstruction Ensure that the ovality of the pipeline is within accepted tolerances Pigs are fitted with a “gauging plate” Circular mild steel, usualiy an aluminum plate, that is machined to a specified diameter, typically 95% of the smaifest diameter of the installed pipeline If the gauging plate sustains any damage, an investigation shauld he carried out to establish the possible cause(s} of the damage and remedial action taken Gauging pigs are pushed through the pipeline usually with compressed air International Tesining & Ravelanment ® 47 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Initial gauging Aluminum gauging plates are usually installed between the pig seals Protects plates from any damage other than that caused by a reduction in diameter within the pipeline Gauge plates are made of either Soft aluminum to reduce spring back Cut into segments to help identify the shape of any restriction (Figure 4) FIGURE 4: TYPICAL SLOTTED ALUMINUM GAUGING FLANGE International Training & Devalopment® 18 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Initial gauging Once the obstructions have been removed it is. then necessary to rerun the gauging pig to verify that ali pipe diameter reduction have been removed from that section of pipeline Geometry or caliper pigging When the gauging plate is darnaged There is no way to determine what caused the damage impossible to determine the locatian of the fault In severe cases, the pig many not emerge at all and be stuck in the pipeline These inherent problems are overcome by using the “geometry” or “caliper” pig instrumented pig designed to measure the inside diameter of the pipeline Identify the focation of any nonconformity Provides a catalog of information on the entire pipeline International Training & Develooment® 19 Fipoline PiggingBASIC PRINCIPLES Pigging during pipeline construction Geometry or caliper pigging Pigs can survey a pipeline without making any metallic contact with the pipe wall Report can be used to locate and make all the repairs needed Rerun to provide a final report for the acceptance decision as well as a permanent record of the “laid” condition Pigging record Number of joints used between the launcher and the receiver Any changes in inside diameter (which may be due simply to changes in the wall thickness) Exact location of any joint which is outside the allowable tolerances for ovality Location of any protrusions into the pipeline Whether the valves are fully open International Training & Development ® 20 Pipeline PinginaBASIC PRINCIPLES Pigging during pipeline construction Geometry or caliper pigging Normally run During de-watering of the pipeline following hydrostatic testing Periodically during the operational life of the pipeline Hydrostatic testing After the pipeline section has been accepted as laid in good condition, it then becomes necessary to pressure test For leaks Ensure pipeline can be safely operated at the design pressure All pipelines are subjected to a hydrostatic pressure test Always prior to commissioning Pericdically throughout its life to Reconfirm integrity Upgrade MAOP International Training & Development ® 21 Pipeline PissingBASIC PRINCIPLES Pigging during pipeline construction Hydrostatic testing Important to ensure that the pipe is filled with a solid column of water Achieved by inserting a pig(s) in the launcher before pumping starts These upstream pigs ensure all the air is removed Regulating air vent valve is installed at the receiver to enable the movements of the pigis) to be controlled by the operator at the receiving end Air vents should be installed at all high points of the pipeline system Reasons for having to ensure all the air is removed Avoid pressure variations due to vapor locks Safety in the event of a failure since compressed air contains much more energy than water when under pressure Forward movement of pig is usually controlled by the input of the water but a regulating air vent valve may also be installed in the receiver lnternational Training & Development ® 22 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Hydrostatic testing In mountainous regions or locations where significant variations in elevation exist Any air trapped at the high points, eliminate the syphon effect and cause the static heads of the individual liquid columns which are thus created to become additive (Figure 5) Pressure required to drive the pig may then exceed the safe working pressure of the pipeline and/or the capacity of the pumps Vents are required at high points to eliminate trapped air ‘Static heads become adiva, Ht + H2 + HS etc may exzoed the lowable pressure FIGURE 5: SKETCH SHOWING. EFFECTS GF LIQUID WITH GAS POCKETS IN A PIPELINE loternationsl Training & Development ® 23 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Hydrostatic testing In the event of insufficient test water Test water can be moved from one section to another as each section is hydro tested Requires pre-installing pigs in each section of the pipeline before welding on the test ends Manifold piping is installed at each end of the test sections to allow the water to be transferred from one section to the next Procedure for moving test water from one section to another (Figure 6) Two pigs are installed in the test end and the first one is jaunched and pumped to the other end to complete the fine fill of the first section, (Both pigs remain in the pipeline during the pressure test.) internationsl Training & Development ® 24 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Hydrostatic testing Procedure for moving test water from one section to another (Figure 6) After the first section is tested, compressed air is typically used behind the second pig to transfer the line fill to the next section for hydrostatic test, simultaneously driving the first of the two pigs pre- installed in that section to complete the line fill of the second section B oh. Ll 3 Gye of Use pa ita nackte ene 3 =a ee sett gat LL, Ese eC ie 2 ae 13) Fst anim dered Ah 2, stern ng acon sein ving eg OS FIGURE 6: METHOD OF MOVING HYDROSTATIC TEST WATER FROM ONE SECTION TO ANOTHER international Training & Gevelepment® 25, Pipeline Pigging f iBASIC PRINCIPLES Pigging during pipeline construction Hydrostatic testing Procedure for moving test water from one section to another (Figure 6) Procedure is repeated until the entire line nas been tested When test water must be returned to the source from which it came Pigging process is reversed Pigs must be bidirectional so that they are effective in each direction When test water does not have to be returned to the source Any pig designed for de-watering, batching or swabbing is acceptable, except a foam pig Pigs might be a sphere mandred pig or one piece batching type pig Foam pigs are made of intercellular materials which allow fiuids to permeate through them and so are not normally suitable for line fill prior to testing International Training & Development 26 Pipetine PiggingBASIC PRINCIPLES Pigging during pipeline construction De-water Once the Aydrostatic test is completed. the water inside the pipe must be removed by a series of pigs pushed through the pipeline normally with compressed air For fong pipelines in arid regions Not uricommon for the pipeline to be Aydrostatic tested in sections Test water is transferred from one section of pipe to the next section during the de-watering operation First step in the de-watering operation is to study the features of the pipeline that may affect the de-watering operation. These include: Pipeline length, diameter and wall thickness Internal configuration and location of main line valves Piping configuration at the ends of the line Changes in pipeline elevation Internal condition of the pipeline International Training & Mavainpment® 27 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction De-water Type of de-watering pig(s) used is based on Pipeline features previously discussed Air compressor’s ability of running the pig at a speed of at least 7 mph (1.6 kph) under these conditions Discharge outlet and connecting discharge pipe should be As farge as possible Fitted with a valve to enable the pipeline to be completely shut off or to be throttled to regulate the rate of discharge to safe levels Receiver end should be prepared for any violent surges of discharge water that may occur as the pig approaches the receiving end if some compressed air has by-passed the pig Pigging with compressed air or other gaseous medium, can be aighly dangerous and should only be carried out by fully qualified personne! Intarnational Training & Development > 28 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction De-water Foam pigs used to swab up Once the De-water pig(s) have been received, foam pigs are commonly used to swab up Water remaining in the pipeline low points Residual water adhering to the pipe wall Drying If the product to be transported in the pipeline requires a dry line (e.g., natural gas) then, after de- watering, the line can be dried using varicus techniques Drying Typical methods used to dry a pipeline include Blowing dry air through the line in conjunction with foam pigs Use of nitrogen “Vacuum drying” International Training & Development ® 94 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Drying Dry air and foam method Used mainly for onshore pipelines Capable of achieving a high degree of dryness and cleanliness that prevent contamination of most pipeline transported products Procedure First, ight weight polyurethane foam swab pigs are run with extremely dry compressed ait, typically with -90°F (-68°C) atmospheric dew point temperature These swab pigs wipe out and soak up the residual water, while the dry air absorbs as much water as it can under the existing conditions and carries it out of the pipeline Swab pigs are run continuously until they are received dry On long pipelines, this may require 200 to 300 runs international Training & Development ® 30 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Drying Dry ait and foam method Procedure The next step is to scratch loose the loosely- adhered rust and mill scale and break up any packed dirt that may have settled out of the hydro-test water This is achieved by running polyurethene foam bigs equipped with fine steel wire brushes on a continuous basis until they are received without any material packed into the bristles Additional foam pigs are run if it is necessary to remove the loose material that remains in the pipeline in the form of very fine dust Swabs are run continuously until they are received clean enough to meet a specified condition ot until some specified dew point is attained This phase may also require 200 to 300 swabs orernational Training & Development ® 31 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Drying Dry air and foam method Procedure Using super-dry air to propel ail pigs, the pipeline will be extremely dry when it is clean, as evidencev’ by the condition of the final swabs run through it Vacuum drying method Useiul in offshore pipelines Works on the principle that the boiling point of water is determined by the pressure Reducing the line to below atmospheric pressure causes the remaining water film on the pipe wall, and elsewhere, to boif Water is then removed form the line in the form of steam Process continues until it reaches some pre-determined dew point value Method is fong and expensive, but yields excelfent results International Training & Development ® 32 Pinging PiggingBASIC PRINCIPLES Pigging during pipeline construction Commissioning Definition Stage when the completed pipeline Filled with the product Brought to the point where it is ready for operation General considerations Almost always fnvelves the use of pigs and may often require “slugs” ot other substances such as methanol, glycol, diesel, etc., to be pumped through ahead of the product Slugs, if used, Contained botwcen two or more pigs Designed to avofd product contamination as, Particularly with hydrocarbons, there may otherwise be a risk of explosion or perhaps serious blockage due to hydrate formation Technique finally used will almost always be determined by the product(s) to be transported Due to its complexity, commissioning is aimost always entrusted to a qualified pigging service company International Training & Development? 33 Pipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Commissioning Water pipelines General considerations May not require de-watering after hydrostatic testing as the test water may serve to commission the line Potable water considerations If pipeline transports potable water Test water requires special treatment before being used as line fill Most countries have strict regulations covering the procedures to be used for potable water pipelines as well as laws governing the quality of the water coming from the pipeline Produce pipelines General considerations Method used to commission a product's pipeline depends upon the type of product to be transported Intemational Training & Development® 34.BASIC PRINCIPLES Pigging during pipeline construction Commissioning Product pipelines Most long distance product's pipelines carry refined products so it is usually necessary to remove the water prior to commissioning Since air will invariably be /eft in the pipeline the pigs must be abie to Separate the air from the product Separate the air from any other substance in the line which could create a hazard when exposed to air May require running several pigs, Perhaps in a “train” with say methanol or other water absorbing chemicals in “slugs” between the pigs Perhaps with slugs of an inert gas such as nitrogen interspaced between each different liquid or gas Intemational Training & Mavalonment® 36. hve PiggingBASIC PRINCIPLES Pigging during pipeline construction Commissioning Natural gas pipelines If the pipeline product is natural gas it is important that the mojsture content level within the pipeline be at a very fow level to prevent the formation of Aydrates One method of commissioning long distance gas lines (Figure 7) Inject nitrogen equivalent to 10% of the volume of the pipeline at atmosphere pressure prior to inserting the first pig A slug of methanol is then injected equivalent to 7.5D U.S. gallons per mile of pipeline (17.6D liters per kilometer} where D = pipe ID in inches, followed by the second pig Next, nitrogen equivalent to a minimum of 0.5 miles (0.8 km) of line when compressed to commissioning pressure is injected and prior to inserting pig three International Fraining & Development ® 38 Pipatine PiggingBASIC PRINCIPLES Pigging during pipeline construction Commissioning Natural gas pipelines Commissioning long distance gas lines continued (Figure 7) A secend slug containing the same votume of methanol as the first one is then injected followed by pig No. 4 That completes the “train” but a fifth pig may be sun if it is considered necessary to remove any excess methanol For fong fines, especially those offshore, the methanol is injected in the form ot a gel to provide a better seal as well as some lubrication FIGURE 7: TYPICAL PIG TRAIN FOR COMMISSIONING A GAS PIPELINE Intarnational Training & Oaveiopment® 37 Pipeline Pissing 4 i LeBASIC PRINCIPLES Pigging during pipeline construction Commissioning Crude oil pipelines Since many crude oif contain some water separators are normally installed as standard equipment at the destination point Thus, it is usually not necessary to dry the pipeline after the line has been de-watered Other pipelines lt is the product that determines the procedures to be adopted Commissioning procedures vary according to Material of the pipeline Product to be carried Governing codes Internal company policies international Tsining & Development ® 38 Fipeline PiggingBASIC PRINCIPLES Pigging during pipeline construction Commissioning Other pipelines Since combustible products need air in which to burn and a spark or compression to ignite the resulting mixture, it is these two aspects which generally command most attention Air is usually efiminated by using pig trains in conjunction with slug of other liquids or gases Base line surveys When the pipeline is filled with the product and the fine is at or near operating pressure, it is a good time to carry out an in-line inspection using a geometry pig Provides a base line for comparison will all future surveys identifies changes in the pipeline such as settling within the ditch or loss of support due to erosion (i.e., “spanning”) in sub-sea lines, which can expose the pipe to points of localized loading Intemational Training & Development ® 39 Pipeline PigaingBASIC PRINCIPLES Pigging during pipeline construction Base line surveys When the pipeline has been filed with the product and the line is at or near operating pressure, it is a good time to conduct an in fine inspection using a geometry pig Provides a base-line for comparison with all future surveys Helps identify changes in pipeline such as Settling within the ditch Loss of support due to erosion (i.e., “spanning” in sub-sea lines, which can expose the pipe to points of /ocalized loading that could result in damage to the bottom of the pipe or buckling Compare and locate damage that may have been caused by third parties operating over the pipeline but which did not create enough damage to cause a rupture at that time International Training & Development® 40. Pipeline PigaingBASIC PRINCIPLES Pigging during pipeline construction Base line surveys Provides vital evidence in the event of litigation Provides important data for monitoring the condition of the pipeline throughout the pipeline’s operating life When the pipeline is new and known to be in good condition, it is also and ideai time to run other instrumented pigs to provide a base line survey for comparison with future runs. These surveys include Metal loss (corrosion) pig Profile survey River crossings Earthquake areas! Permafrost areas Other potentially unstable locations Intemational Training & Development ® 41 Pipeline PigaingBASIC PRINCIPLES Pigging during operation Debris removal Pipe wall cleaning is essential to protect Investment Operational efficiency Applies regardless of whether the debris is Wax Scale Other form of solid material No one reason tor regularly pigging a line that is more important than any other, but one that should be Paramount and that is to prevent corrosion Free water, even in crude oil lines, collects in the bottom and must be both Swept out Inhibited International Training & Development? 42. Pipatine PiggingBASIC PRINCIPLES Pigging during operation Debris removal An inhibition program on its own is generally inadequate If pigs are not used to remove the surface debris such as dirt, sand, wax, corrosion products, etc., then water will collect under the debris and it wilt prevent inhibitors fromm working The same situation will arise if there are bacterial corrosion problems by sulphate reducing bacteria (SRB’s) Once the pipe wall experiences pitting corrosion It is difficult, if not impossible, to remove any accumulated water or debris from the pits Creates a progressively-worsening situation that may require a drastic and costly inhibition program to contain it Intannativnal Training & evelopment ® 43 Pipeline Plaging a ti netstat iaBASIC PRINCIPLES Pigging during operation Condensate removal Condensate drop-out Problem on many gas pipelines Rate at which it drops out depends up flow rate Condensate rarely blocks a line Settles out in low spots and reduces the effective bore This restriction causes the gas flow to increase locatly and pick up the condensate once more This situation is not acceptable Turbulence will cause an increase in the Pressure drop, thus reducing throughput The constant pick-up and drop-out at the same point could cause erosion problems Intarnational Training & Development ® 44 Pipeline PiggiangBASIC PRINCIPLES Pigging during operation Condensate removal When a section of line becomes saturated Condensate will be carried over to the next, and so on, until it arrives at the terminal Condensate arrival is always unexpected, and arrives in very large slugs Slug catchers Sized to handle the maximum likely volume When a slug exceeds their capacity, condensate overfiows to the processing plant and causes both damage and plant shut down Condensate drops out of untreated gas continuously Pigging is intended to remove condensate in a controlled and regulated manner, thus spheres are often used in spite of their poor sealing qualities Inteenationat Training & Development 45, Pipeline Figging cnnBASIC PRINCIPLES Pigging during operation Product separation “batching” Batching Used on multiproduct pipelines that transport different products in the same line at the same time Used for refined products such as petroleum, fuei oil, kerosene and jet fuel Interface mixing Product at the end of one batch mixes with the product at the head of the next Results in contamination, the volume of which will depend on such things as the Pipeline configuration Pumping rates Overall fength Batching pig inserted in between each batch of product Internationa! Training & Development? 46 Pipeline PiggingBASIC PRINCIPLES Pigging during operation Product separation “batching” Problem Getting the pig in between the batches and out again at precisely the right moment Spheres lend themselves to predictable and automatic handling, and thus are commonly used for batching in multi-product pipelines Batch inhibition Running a batch of inhibitor between two pigs ensures that the whole of the internal surface of a pipeline is wetted No way of guaranteeing complete coverage, especially at the top center or 12 o’clock position (Figure 8) FIGURE 8: POTENTIAL PROBLEM WITH BATCH INHIBITION lotarnationsl Teaining & Development ® 47 Pipeline PiggingBASIC PRINCIPLES Pigging during operation Batch inhibition Preferential corrosion Occurs in pipe that has only partly been wetted by inhibitor Metal loss that would have occurred over the entire pipe surface is concentrated on the small area that has not been wetted, thus making the situation worse, rather than better Recent corrosion problems Canada and the North Sea Point to the need for more effective inhibition to be carried out in addition to the usual injection systems Pigs are now under development that actually spray the inhibitor onto the internal surfaces of the pipe wall while the pipeline remains in operation International Training & Development® 48, Pipetine PiggingBASIC PRINCIPLES Pigging during operation Cleaning Crude oil pipelines Any type of pig will remove some of the wax Unless the right type of cleaning pig is used, a lot of wax will be left behind and smeared on the inside of the pipe wall Elastomer blades work weil to remove the wax from the inside surface and are self cleaning Pig by-pass Most cleaning pigs have a means for product by-pass through the pig Typically 5% of the total product flow passes through the pig Flow enters the back of the pig, pass by the cleaning devices and then exit through the front of the pig (Figure 9) International Terining & Mevelaament® 49 Pipeline PiggingBASIC PRINCIPLES Pigging during operation Cleaning Pig by-pass Lets the pig slip slightly in the stream so that the wax that has been removed can be floated away rather than be pushed into a solid mass Avoids the potentially serious problems that could occur if the wax arrives as a solid plug at the receiving trap Fw oe Bypace ff maine Ouuet 44 ™ coup aude FIGURE 9: BY-PASS PATH THROUGH A PIG BODY International Training & Development ® 50 Pipeline PiggingBASIC PRINCIPLES Pigging during operation Cleaning Natural gas pipelines Dust along with oil that may come from compressors can create an internal coating that will reduce the pipeline efficiency Type of cleaning pig is determined by the internal coating of the pipe Pig should not be equipped with cleaning devices that could damage or remove the coating Pig should be fitted with efastomer cleaning devices such as polyurethane blades to avoid damage to the coating Elastomer blades clean the internal coating and with repeated runs to polish the surface \f the pipeline is bare pipe Pig may be equipped with brushes that clean the inside of the pipe and with repeated runs create a smoother surface, thus increasing the flow efficiencyBASIC PRINCIPLES Pigging during operation Cleaning Product's pipelines Need cleaning to remove fine solids and water that may have settled from the product as it traveled the pipeline Any pig that seals in the pipe can be used to remove the water from the pipeline A better cleaning pig would be a pig with cleaning devices attached, such as Simple foam pig with strips of fine wire brushes bonded to the outside of its body Purpose built cleaning pig designed for that specific size of pipe which can be fitted with various cleaning devices so they can be replaced as the components wearBASIC PRINCIPLES Pigging during operation Cleaning Plant piping systems Pigging plant piping is similar to any other pigging 1 operation, but some aspects need to be monitored that are not a consideration in cross-country pipelines Elastomers on the pigs must be compatible with the products in the pipeline Piping must be carefully surveyed {i.e., elbows) to be sure that the correct pig is acquired for vt the intended purpose Since most plant piping is smai pigs, may not be available with spring loaded cleaning elements similar to the larger pigs Smaller cleaning pigs may use wheel type brushes that must be replaced as they wear Cleaning procedures may involve the use of cleaning or sterilizing fluids and should be fncfuded in the design and operation of the overall system International Training & Development® 53 Pipeline PiggingBASIC PRINCIPLES Inspection pigging Utility pigs Used during construction and operations Used for cleaning and de-watering, etc. Intelligent pigs Referred to as “in-line inspection” (\LI) tools or “smart pigs” Provide information on the condition of the pipe and/or its condition Not sold but are the too/s that are used by specialized inspection-pigging companies to gather the data on the pipeline Data is analyzed to determine and report on the condition of the fine Many inspection surveys, especially those for metal Joss and geometry, ate usually run during or soon atter commissioning in order to provide a “base line” survey Enables subsequent inspections to be compared with original results and establishes the average rate at which any changes are taking place Internationat Training & Development® 84 Pipeline PigaingBASIC PRINCIPLES Inspection pigging Information provided by ILI services Diameter/geometry measurement Curvature monitoring Temperature/pressure recording Bend detection and measurement Metal loss/corrosion detection Photographic inspection Crack detection Wax-deposition measurement Leak detection Product sampling Detection of loose coating on the outside of a pipelineBASIC PRINCIPLES Pigging for general maintenance and repair General considerations Pigs are frequently used as part of a maintenance and repair program Uses include Batch inhibition (already discussed) Pre-inspection cleaning isolation Pre-inspection cleaning Pipeline cleaniiness For optimum performance, \LI tools require pipeline to be really clean Standard pigs are not capable of cleaning the pipeline sufficiently well, thus ILI survey may have to be aborted due to dirt or wax Requires a separate pigging program Specially designed pigs Normally carried out by the inspection company themselvesBASIC PRINCIPLES Pigging for general maintenance and repair Pre-inspection Cleaning Magnetic flux leakage tools With their powerful brush/magnets, remove the residual film of wax that has been /eft behind by the cleaning pig Residue fouls and can destroy iL| tool sensors Ultrasonic pigs Experience severe problems due to the attenuation of the signals by residual wax Routine maintenance Standard pig does not need to remove all the wax Thin film of wax left behind is beneficial Reduces friction factor Protects the pipe wall from corrosive productsBASIC PRINCIPLES Pigging for general maintenance and repair Isolation Pig seal within the pipe To travel through a pipeline, a pig should have an “interference fit” within the pipe bore to create a seal If the pig stopped within the line and fixed in some way, it is a means of isolating sections of the line for modification, maintenance or repairs A longitudinal weld bead can create a leak path past the seal Restraining the pig against differential pressure loads, especially in large diameter lines, is difficult Over-inflated spheres Used to provide a seal within the bore of a pipe which is being repaired, thus preventing any flammable products from being exposed to welding and cutting torchesBASIC PRINCIPLES Pigging for general maintenance and repair Isolation Hyperbaric spheres Special type of sphere, incorporating hyperbaric chambers, are used frequently in sub-sea tie-ins Due to their shape, have very limited area in contact with the pipe waif, thus can only be used where there is no differential pressure Sub-sea installation considerations Due to temperature and tidal changes it is often difficult to maintain a balanced pressure on either side of the pig, thus work has begun on the development of “high differential” pigs Pigs utilized consist of over-size polyurethane driving discs that are generally stacked closely together and often of varying hardnessBASIC PRINCIPLES Pigging for general maintenance and repair Plugging pigs Designed to stap at some pre-determined point Remotely actuated in order to create a seal Deactivated so that they may either Continue their journey Be reverse pumped back to their starting point Due to the difficulties in developing foolproof remote operations, most plugging pigs are Attached to an umbilical or “tether” Limitedto operations close to an access or “launch” point en Pipeline PiggingBASIC PRINCIPLES Pigging during renovation/rehabilitation Gel pigging “Gel pigs” “Not designed” but are “formulated” Can be made to almost any density Pre-formed pigs that are shipped to site within a metal mold (empty oil drum) Light foam that is sprayed into the line Most applications require it in jelly-like state (similar : to wallpaper paste) Material can be combined with a wide range of other 1 chemicals to perform other tasks, such as: Foaming and degreasing agents Corrosion inhibitors Cost considerations Large quantities are required Must be manufactured “on-site” Has a limited life since it is biodegradableBASIC PRINCIPLES Pigging during renovation/rehabilitation Gel pigging Application Useful in Removing “stuck” pigs Creating high-sealing pigs Temporary isolation of a pipeline for repairs Used as a major component in cleaning pipelines where the volume of debris to be removed after construction is too great for conventional methods Gel is trapped between pigs to form “slugs” which pick up the debris, hold it in suspension and literally carry it out of the line Other than when using pre-formed type of gel pig {which is, in effect, a “soluble” pig}, the formulation and work of gel pigging should always be carrfed out by qualified contractors International Training & Development ® 62 Pipoline PiggingBASIC PRINCIPLES Pigging during renovation/rehabilitation Applying in-situ coating General considerations Critical factors that influence the success of any coating project Surface preparation Coating selection Coating application | Wrong choice in any area may cause premature failure of the coating Surface preparation Essential to thoroughly clean the inside of the pipe to properly prepare its surface Must remove all deposits fromm the line that could interfere with the coating bond such as rust, scale and salts After cleaning, the line should be completely dry and under a purge of an inert gas to prevent flash rustingBASIC PRINCIPLES Pigging during renovation/rehabilitation Applying in-situ coatings Surface preparation Typical cleaning process involves scouring the inside of the pipeline with an abrasive material, such as flint, which is propelled in a low-pressure, high- velocity, stream of nitrogen Cleaning particles impact the wail of the pipe at a low angle chipping away the deposit Removed material is then carried through the line with the nitrogen, and collected at the outlets After abrasive cleaning, pigs and/or solvents are used to remove any remaining dust Cleaning process may uncover very thin hard deposits, such as magnetite, which are more economically cleansed with chemicals By removing rust or scale, cleaning may expose leaks that must be repaired before coating ae Binaline PlacingBASIC PRINCIPLES Pigging during renovation/rehabilitation Applying in-situ coatings Coating selection A wide variety of coatings have been used to internally coat in-place pipelines i Must have specific thixotropic properties to 1 enable the coating to be spread onte the pipe wall and then immediately “gel” to prevent it from running or sagging Two-part polyamide-cured epoxy coating Most commonly used coating Recommended for fines carrying Potable, fresh and salt water Crude oils Transportation fuels Natural gas Some solventsBASIC PRINCIPLES Pigging during renovation/rehabilitation Applying in-situ coatings Coating selection Final coating selection Should be discussed with a professional in-situ coating service company Good practice to install a test spool cleaned and coated under field conditions to assure compatibility with the intended service Coating application Achieved by placing the coating material between two pigs and propelling the “pig train” through the line Various types of pigs, including multiple cup-and- disc, bi-directional disc and spheres are used Coating thickness is determined by Size of the cup pigs Coating train speed er Pineline Piagina.BASIC PRINCIPLES Pigging duting renovation/rehabilitation Applying in-situ coatings Coating application Required coating thickness is achieved by Controlling the differential pressure across the : coating train and thus the train speed Nitrogen is used as both Driving force Back pressure Chemical cleaning Used when conventional pigging methods are unable to clean the line sufficiently Type of chemical{s), strength, contact time and overall procedures are dictated by the circumstances and each situation is different Vital to obtain professional advice before using this approach since mistakes may be irreversible and errors can be very costlyBASIC PRINCIPLES Pigging during renovation/rehabilitation Scale removal Scale can be removed by the proper use of Aggressive cleaning pigs Various grades of wire-brush foam pigs Utility pigs Equipped with brushes or steel blades Speciality pigs Specifically designed for purpose such as “Studded foam pigs” “Pinwheel pig” Typical deposits may include paraffin, asphaltene, sediments, silica, coke, iron, sulphides, calcium or other corrosive products that are often difficult to removeBASIC PRINCIPLES Pigging during renovation/rehabilitation Scale removal “Studded foam pig” Simple pipeline pig that can remove hard deposits from the interior of a pipe The pig, being symmetrical, permits travel in both directions which is important when cleaning industrial heaters and pipelines Body is formed of high-strength polyethylene, ‘polypropylene, rubber or polyurethane Flexibility and hardness of the body are adapted to the intended use Body has circumferential and longitudinal ribs, forming square recesses that retain an internally- threaded anchor Allows different types of studs to be screwed inBASIC PRINCIPLES Pigging during renovation/rehabilitation Scale removal “Studded foam pig” Studs are available in various sizes, shapes and hardness and are salected on the basis of Hardness of the deposit Extent of the build up Location of the deposit Pipe material Operation Pigs are inserted into the pipe and is propelled by a fluid, usually water Pressure acting on one end of the pig causes it to expand, which forces the studs into contact with the pipe wall and dislodging the scale oo oe Dinalice PloningBASIC PRINCIPLES Pigging during renovation/rehabilitation Scale removal “Studded foam pig” Operation When worn the studs are removed and replaced Stud height can be adjusted using shims Controls the rate of deposit removal Sets the amount of liquid by-pass around the pig body which flushes out the loosened deposits, reducing the possibility of blocking the pipe “Pin-wheel pig” Used on fonger and larger diameter pipelines Used as part of a service rather than being sold outrightBASIC PRINCIPLES Pigging during renovation/rehabilitation Scale removal “Pin-wheel pig” Consists of a number of heavy-duty polyurethane discs that have an outside diameter significantly less than the inside diameter of the pipeline Protruding radically from the circumferential edge of each disc are a number of steel pins with hardened tips that are radiused to prevent damage to the pipe wall Diameter across any two opposite pins is greater than the inside diameter of the pipeline Thus, when the pig is traveling through the fine, the pins are bent back at a slight angle This both assists in the cleaning action and also compensates for any wear None of the wax or scale removed from the pipe wall is pushed forward by the pig itself This is eft behind for remova! by another type of specialty pig as part of the overall programBASIC PRINCIPLES Decommissioning General considerations Decommissioning is still very much in its infancy Much discussion is going on about the methods and requirements for abandonment of pipelines Procedures for abandoning a hydrocarbon pipeline Product removal {nitrogen used to propel the pig) : Cleaning | inspecting/testing Inerting (nitrogen} In some countries, evidence of the condition of the Pipeline might be needed to obtain approval to abandon it, this may involve the use of one or more of the ILI tools