Pipeline Pre-Commissioning Procedure

Pipeline Pre-Commissioning Procedure

Figure 1: Typical Pigging Launcher Arrangement

LAUNCHING PROCEDURE

1. Check that the launcher barrel is isolated.
2. Close Trap Valve (9) and Kicker Valve (10) and associated valves (where installed) and bleed through the bleeder valves.
3. Open Vent Valve (2) on launcher barrel and check pressure in the barrel on pressure indicators P1 (1b) and (1c).
4. Open Drain Valve (3) on launcher barrel.
5. When launcher barrel is fully depressurised and drained, release the safety locking device on the launcher barrel trap closure door.
6. Open the launcher barrel trap closure door.
7. Check that the barrel is clean.
8. Insert the pig and pushed it as far as possible (pass the kicker line outlet) using the pig probe.
9. Close and bolt up the launcher barrel trap closure door and secure the security device.
10. Set the pig signaller XI (6a) and (6b).
11. Close the drain valves (3) on the launcher barrel.
12. Close the bleed valve on the kicker line.
13. Open the block valve (10) on the kicker line.
14. Slowly crack open the kicker valve (10) to fill up and equalise the line.
15. Close vent valve when launcher barrel is filled and equalised.
16. Fully open kicker valve (10).
17. Close the bleed valve between the trap valve (9) and block valve (9).
18. Fully open the block valve (9) and trap valve (9).
19. Close the isolation valve (8).
20. Product in line will force the pig into the barrel. The pig will trigger and trip the pig signallers XI(6a) and (6b), which will indicate the pig has gone through the launcher and on its way to the receiver.
21. Fully open the isolation valve.
22. Close the Kicker Valve (10) and the Trap Valve (9).
23. Depressurize the launcher barrel using Drain Valves (3).
24. When fully depressurised and drained, close Vent Valve (2) and Drain Valve (3).
25. Leave the launcher barrel isolated.
26. Inform the receiving party of the successful launch.

RECEIVING AND RETRIEVING PROCEDURE

1. Close Drain Valve (3) and open Vent Valve (2) on the receiver barrel.
2. Open Block Valve (12) and crack open bypass valve (12) to fill up and equalise pressure in the receiver barrel.
3. Close vent valves (2) and check pressure in the barrel on pressure indicators P1 (1b) and (1c).
4. Fully open block valve and trap valve (9).
5. Fully open bypass valve (12).
6. Close isolation valve (8).
7. Set pig signallers XI (6a) and (6b).
8. Receiver barrel ready to receive the pig. Tripping the signaller will indicate that the pig has already arrived in the receiver.
9. Fully open isolation valve (8).
10. Close trap valve (9) and bleed off pressure in the receiver barrel. Monitor on pressure indicator P1 (1b) and (1c).
11. Drain the content in the receiver barrel through drain valve (3).
12. When the receiver barrel is fully depressurized and drained, release the safety locking device on the receiver barrel trap closure door.
13. Check and remove debris for safe disposal.
14. Remove and check pig for any peculiarity.
15. Close the drain valves (3) and the vent valves (2) on the receiver barrel.
16. Leave the barrel isolated.
17. Inform and report successful retrieval and finding to the Focal Point.

Pipeline Construction

Pipeline construction is divided into three phases, each with its own activities: pre-construction, construction and post-construction.

Pre-Construction

Surveying and staking

Once the pipeline route is finalized crews survey and stake the right-of-way and temporary workspace. Not only will the right-of-way contain the pipeline, it is also where all construction activities occur.

Preparing the right-of-way

The clearly marked right of way is cleared of trees and brush and the top soil is removed and stockpiled for future reclamation. The right-of-way is then leveled and graded to provide access for construction equipment.

Digging the trench

Once the right-of-way is prepared, a trench is dug and the centre line of the trench is surveyed and re-staked. The equipment used to dig the trench varies depending on the type of soil.

Stringing the pipe

Individual lengths of pipe are brought in from stock pile sites and laid out end-to-end along the right-of-way.

Construction

Bending and joining the pipe

Individual joints of pipe are bent to fit the terrain using  a hydraulic bending machine. Welders join the pipes together using either manual or automated welding technologies. Welding shacks are placed over the joint to prevent the wind from affecting the weld. The welds are then inspected and certified by X-ray or ultrasonic methods.

Coating the pipeline

Coating both inside and outside the pipeline are necessary to prevent it from corroding either from ground water or the product carried in the pipeline. The composition of the internal coating varies with the nature of the product to be transported. The pipes arrive at the construction site pre-coated, however the welded joints must be coated at the site.

Positioning the pipeline

The welded pipeline is lowered into the trench using bulldozers with special cranes called sidebooms.

Installing valves and fittings

Valves and other fittings are installed after the pipeline is in the trench. The valves are used once the line is operational to shut off or isolate part of the pipeline.

Backfilling the trench

Once the pipeline is in place in the trench the topsoil is replaced in the sequence in which it was removed and the land is re-contoured and re-seeded for restoration.

Post Construction

Pressure Testing

The pipeline is pressure tested for a minimum of eight hours using nitrogen, air, water or a mixture of water and methanol.

Final clean-up

The final step is to reclaim the pipeline right-of-way and remove any temporary facilities.

Reference :  http://www.cepa.com/about-pipelines/pipeline-design-construction/pipeline-construction

PIPELINE MAINTENANCE: Magnetic leakage detection used to spot, measure pipeline cracks

A standard axial configuration high-resolution inspection vehicle. Click here to enlarge image

Magnetic flux leakage (MFL) inspection is the most commonly used tech-nology for the inspection of in-service pressurized pipelines. It is estimated that about 80% of line inspection missions are carried out using this technique. The technique is robust and reliable, and advances over the last 25 years have resulted in high resolution inspection systems that achieve accurate and repeatable measurement of defects in the pipeline. High quality inspection can be achieved with minimal disruption to daily operations.
The traditional use of MFL technology has been the detection and measurement of metal loss defects, primarily corrosion, and this is the inspection mission for which the technology is best known. What is less well known is that high resolution MFL technology can be used and adapted for the location and measurement of cracks in the pipeline, in circumferential and longitudinal directions.

Principles of inspection

The basic physics of the technique are very well known. The pipe-wall is magnetized axially by a pair of magnet and bristle rings at each end of the magnetizer vehicle. Any disruption to the flow of magnetic field in the pipeline steel, as caused by metal loss in the wall, will cause disruption to and leakage of the field. It is this leakage that is detected and measured by the sensors on board the inspection vehicle.
The axial configuration was initially chosen as the most practical engineering solution and because this configuration enabled the inspection vendor to detect and measure those defects that most commonly occurred in pipelines and were of the most concern to pipeline operators. There are some shortcomings in this technique when looking for defects that have a more longitudinal component. These shortcomings can be addressed by altering the magnetic configuration of the inspection vehicle.

Circumferential cracking

A standard grey scale output of inspection data from the PII tool. The girth weld can be seen in the center of the plot. Click here to enlarge image

The most common form of circumferentially aligned crack-like defect occurs within the girth weld. Girth weld defects, introduced during construction, can include incomplete weld passes, stop-start, unauthorized weld repairs, and cracking caused by inadequate heat treatment of the weld area.
As these defects are circumferentially aligned, and therefore at right angles to the flow of magnetic flux, they can cause a disruption and leakage of the field that is readily detected. However, the fact that these defects by their very nature are within a girth weld, poses significant technical challenges.
The girth weld itself presents a barrier to axial flux flow, causing a large disturbance to the signal, which can mask defects within the weld. In addition, and perhaps more significantly, the protrusion of the weld bead into the pipeline bore can cause the MFL sensors to "lift off" the inside of the pipe wall.
If the vehicle is traveling at normal pipeline speeds and the sensor design has high inertia, then a dead zone can be created both at the girth weld and for some distance downstream of the girth weld. This means that inspection vehicles cannot detect defects within the girth weld, and indeed for some distance beyond it. In some cases, this non inspected dead zone can be as much as 200 mm.
When a high resolution inspection vehicle was first developed by PII in the mid-1970s, these shortcomings in available technologies were recognized. The initial specification of the vehicle performance required that 100% of the pipeline be reliably inspected, including the girth weld and the area around it. So care was taken at the very start of the project to ensure that full inspection capability was not compromised by the presence of the girth weld.
The first problem, that of the large and sometimes confused signal generated by the weld, was tackled by using the very high magnetic field of the PII tool (necessary to saturate the pipe wall and generate repeatable signals from small defects). This, coupled with the very high sensor density of the high-resolution tool, means that the signal from normal girth welds is remarkably repeatable, and any abnormality in the weld can be easily identified.
Designing the sensor heads themselves to have very low mass solved the more serious problem of sensor lift-off. This design, coupled with very light spring suspension, means that the sensor carrier has low inertia and 'bends' with the weld bead, traveling over it smoothly rather than bouncing off the pipe wall.
The fact that all girth weld anomalies are by definition very short in the axial direction can pose problems for the analyst. It can be difficult to discriminate between the various types of defects that can occur in girth welds. The solution lies in the experience and training of data analysts. The first girth weld crack was identified and confirmed in the early 1980s. Since that time, we have located and confirmed more than 1,000 girth weld cracks in operational pipelines.

Longitudinal cracking

A further example of NAEC illustrates the view achieved by this technique. Click here to enlarge image

The extent of the flux leakage created by a pipe wall anomaly, and therefore the size of the signal collected by the in-line inspection device, is affected by the width of the anomaly. A circumferentially wide defect will set up greater opposition to the flux induced by the tool, and a larger signal will result.
The reverse also holds true. As a longitudinally aligned defect becomes narrower, its opposition to flux flow diminishes, and the resultant signal will decrease in magnitude. The extreme of this phenomenon is demonstrated by the fact that longitudinally aligned cracks cannot be detected using conventional magnetic flux leakage technology.
The result is that with inspection devices carrying only a few MFL sensors, a longitudinally aligned defect will not be detected. With high-resolution tools the high sensor density enables the defect to be detected, but the reduction of the signal strength can lead to an underestimation of the size of the defect.
The defects that have been recognized as present in some pipelines and designated as narrow axial external corrosion (NAEC) are very rare in PII's experience, as they are not only narrow but are longitudinally orientated, axially long and relatively smooth in profile.
Following the discovery of NAEC on one particular pipeline, the data from the previous MFL inspections of that line was examined closely by a PII-client team. Although it was confirmed that the inspection tool had collected data from these defects, the level of signal was such that the depth of the NAEC had indeed been underestimated.
An attempt was made to create algorithms that would recognize the character of NAEC, and correct the sizing model to compensate for the problem and predict depth more accurately. This project met with some limited success, but was found not to be 100% reliable for the purpose of establishing confidence in the condition of the pipeline, given the extent of the NAEC phenomenon.

Transverse field inspection

Samples of the Transcan data are shown alongside sections of the actual defects that were excavated and removed from the pipeline. Click here to enlarge image

If metal loss that is long and narrow will not produce signal strengths compatible with accurate sizing when the magnetic field is longitudinal, then another approach is to magnetize the defect in the orthogonal direction. This means that a tool had to be devised and constructed that would magnetize the pipe in the circumferential direction.
Theoretically, this means that the signal obtained will be far more prominent and will allow more accurate characterization. In addition, the axial extent of the defect should be clearer.
The idea of applying the magnetic field in the transverse direction is not new. AMF (formerly American Machine and Foundry) was probably the first to develop the idea as part of their mill inspection technology in the 1960-1970 period and patented a rotating transverse field system in 1978.
PII also examined it.
The reason these designs and prototypes never came to fruition was due to a limitation of the technology available at the time, rather than in the technique itself. Data in the 1970s was usually stored on reel-to-reel recorders, and displayed on UV sensitive paper. Given the advances in computing techniques, materials science, and electronics since then, confidence that a solution for the problem of long narrow defects could be achieved was high. However, without a commercial impetus, the technique was probably destined for obscurity. The discovery of NAEC and several long seam defect failures in North America provided the impetus to develop a commercially viable inspection system. A prototype, dubbed the Transcan tool was designed, constructed, and launched within a five week period and collected good quality data on its first inspection run of more than 200 km.
Analysis of the data and subsequent excavation revealed that the tool did provide an improved characterization of NAEC. This was particularly promising when considering that both the tool and the analysis technique were first attempts. The short times cales available for right-of-way access meant that only a limited amount of information could be gathered from field excavations, but the wealth of data obtained from the excavations carried out in 1996 means that extensive detailed correlation is possible.

Hook cracking

Encouraged by this success, PII refined the process still further to build an in-line inspection tool that would reliably detect and characterize long seam defects. This work was encouraged by one client who had experienced operational failures caused by hook-cracking in a 20-in. crude oil pipeline.
Defects, such as hook cracks and lack of fusion, have caused many in-service and hydrotest failures, especially in liquid lines subject to pressure cycling. Hook cracks occur when inclusions at the plate edge are turned out of the plane of the steel during the pipe manufacturing and welding process. These may pass the initial hydrotest, but fail later through fatigue-induced cracking. It is the turning out of the metal at the weld which gives the crack its characteristic "hook" or "J" shaped appearance.
Although such defects can be det-ected by manual non-destructive testing (NDT) methods, they have remained largely outside the domain of automated methods and in-line tools, which are used for the mass inspection of pipelines. Until recently, the only option was to hydrotest the line. This has limitations in as much as it gives an "all or nothing" or "yes/no" indication. It is not a quantitative technique.
Severe defects are identified through failure, but no information is conveyed about less significant defects which may themselves grow to criticality within a short time after the test. To ensure these defects are found, repeated testing at frequent intervals is required. In addition, following a hydrotest where there has been a failure, the line must be repaired and hydrotested repeatedly until there are no more failures. This is costly in terms of effort and lost throughput.
In this case, the service failures experienced in this 1500-km-long, 20-in. pipeline had resulted in a significant reduction in throughput for the pipeline, with subsequent loss in revenue, and a regulatory requirement to hydrotest the entire pipeline, at a projected cost of tens of millions of dollars.
In the spring of 1998, PII developed a high-resolution 20-in. Transcan tool carrying 400 primary sensors, which was laboratory tested and used to inspect 140 miles of 20-in. pipeline. The tool was successful. In order to validate the technology, the client excavated the reported defects and repaired and hyrotested the line. Two separate sections of the line, totaling 118 miles, were hydrotested to 125% MOP without failures.
More than 50 hook-cracks were detected by the tool and validated by "in the ditch" NDE. The smallest was 5-10% of pipe-wall thickness (Fig 11 and 12). In addition, many examples of lack of fusion and stitching, and three examples of cracks within dents were detected. Only two of the cracks verified would have failed a hydrotest at 125% MOP. The hydrotest requirement was lifted and following the inspection and repair of the remainder of the 1500-km line, full operating pressure was restored.
During the course of the remaining inspection, many hundreds of long-seam defects were revealed and repaired.
The Transcan has been used to inspect over 4,000 km of pipeline, and plans are to extend the range up to 42 in. and down to 8-in., with a 6-in. tool being a distinct possibility in the future.

Stress corrosion cracking

Given its sensitivity to axial features, would TFI be able to detect stress corrosion cracking? Recent work on behalf of the operator of a refined products line has shown some initial promise. Specifications of the line are seamless, 12-in. in diameter, 100 km in length, wall thickness of 6.35-7 mm X52 & X60 grade steel, and is 30 years old.
The pipeline had suffered from several failures due to stress corrosion cracking (SCC) and regulatory authorities required that the operating pressure be reduced from 90 bar to 60 bar and a program of hydrotesting be implemented. To investigate the capability of detecting SCC, a test program was undertaken on samples of defective pipe.
In parallel, a 12-in TFI tool was prepared for a trial run in the pipeline. The results from this run have been analyzed, and reporting will be followed up by proving excavations. The laboratory tests showed that it was possible to observe some colonies of SCC using the Transcan technique. However, as always, the true test is in the ability to discriminate these signals from other features in the line, such as manufacturing variations, corrosion sites, surface roughness, etc.
In parallel with this investigative inspection program, extensive testing was carried out on the Transcan tool using known colonies of SCC installed in a pull through string. TFI is not intended to be a primary inspection tool for SCC (ultrasonic tools probably offer the best performance here), but any success in this area is regarded as a bonus on top of its capability at inspection for axial metal loss features and defects in long seam welds.

Third party damage

During the inspection and subsequent repair of the 20-in. pipeline described previously, several instances of third party damage were located and confirmed. - Shown is an instance of third party damage uncovered on this pipeline.
As third party damage is the largest cause of pipeline failure in most countries, we feel that the technology has potential to allow pipeline operators to not only detect, but also characterize these kinds of defects. A development program has begun in the US with the Battelle Institute, the Gas Research Institute, and the Office of Pipeline Safety. This program should allow the development of a system for accurate location, identification, and characterization of this difficult-to-detect defect.
Crack-like defects in operating pipelines have long been the most difficult defect to locate using in-line inspection techniques. For many years, the pipeline industry has had to rely on the inexact science of hydrotesting to mitigate risk from failure due to cracking. New tools are superior to hydrotesting, technically and financially. ;

Acknowlegement

A slightly longer version with more illustrations was presented at the PII 5th Annual Pipeline and Pigging conference in Seville, Spain.

References

J. F. Keifner, "Installed pipe, especially pre-1970, plagued by problems", Oil and Gas Journal, pp 45-51, Aug 10, 1992.
API Bulletin on Imperfection Terminology (5T1), 9th edition, May 31, 1988.
R. D. Barton, US Patent 4072894, Rotating Pipeline Inspection Apparatus, 1978.
E. M. Holden, "Transverse Field - a new direction for inspection," Venezuelan Pipeline Conference 1999.
J. F. Kiefner, "Pressure Management Key to Problematic ERW Pipe", Oil and Gas Journal, pp 80-81, Aug 17, 1992.
P. Mundell, K. Grimes, "A new breed of intelligent pig for the detection of defects in the long seam weld of steel pipelines", Journal of the British Institute of NDT, Vol41, No2, February 1999.

How steel pipe is made?

Steel pipes are long, hollow tubes that are used for a variety of purposes. They are produced by two distinct methods which result in either a welded or seamless pipe. In both methods, raw steel is first cast into a more workable starting form. It is then made into a pipe by stretching the steel out into a seamless tube or forcing the edges together and sealing them with a weld. The first methods for producing steel pipe were introduced in the early 1800s, and they have steadily evolved into the modern processes we use today. Each year, millions of tons of steel pipe are produced. Its versatility makes it the most often used product produced by the steel industry.
Steel pipes are found in a variety of places. Since they are strong, they are used underground for transporting water and gas throughout cities and towns. They are also employed in construction to protect electrical wires. While steel pipes are strong, they can also be lightweight. This makes them perfect for use in bicycle frame manufacture. Other places they find utility is in automobiles, refrigeration units, heating and plumbing systems, flagpoles, street lamps, and medicine to name a few.

History

People have used pipes for thousands of years. Perhaps the first use was by ancient agriculturalists who diverted water from streams and rivers into their fields. Archeological evidence suggests that the Chinese used reed pipe for transporting water to desired locations as early as 2000 B.C. Clay tubes that were used by other ancient civilizations have been discovered. During the first century A.D. , the first lead pipes were constructed in Europe. In tropical countries, bamboo tubes were used to transport water. Colonial Americans used wood for a similar purpose. In 1652, the first waterworks was made in Boston using hollow logs.
Development of the modern day welded steel pipe can be traced back to the early 1800s. In 1815, William Murdock invented a coal burning lamp system. To fit the entire city of London with these lights, Murdock joined together the barrels from discarded muskets. He used this continuous pipeline to transport the coal gas. When his lighting system proved successful a greater demand was created for long metal tubes. To produce enough tubes to meet this demand, a variety of inventors set to work on developing new pipe making processes.
An early notable method for producing metal tubes quickly and inexpensively was patented by James Russell in 1824. In his method, tubes were created by joining together opposite edges of a flat iron strip. The metal was first heated until it was malleable. Using a drop hammer, the edges folded together and welded. The pipe was finished by passing it through a groove and rolling mill.
Russell's method was not used long because in the next year, Comelius Whitehouse developed a better method for making metal tubes. This process, called the butt-weld process is the basis for our current pipe-making procedures. In his method, thin sheets of iron were heated and drawn through a cone-shaped opening. As the metal went through the opening, its edges curled up and created a pipe shape. The two ends were welded together to finish the pipe. The first manufacturing plant to use

Welded pipe is formed by rolling steel strips through a series of grooved rollers that mold the material into a circular shape. Next, the unwelded pipe passes by welding electrodes. These devices seal the two ends of the pipe together.

this process in the United States was opened in 1832 in Philadelphia. Gradually, improvements were made in the Whitehouse method. One of the most important innovations was introduced by John Moon in 1911. He suggested the continuous process method in which a manufacturing plant could produce pipe in an unending stream. He built machinery for this specific purpose and many pipe manufacturing facilities adopted it.
While the welded tube processes were being developed, a need for seamless metal pipes arouse. Seamless pipes are those which do not have a welded seam. They were first made by drilling a hole through the center of a solid cylinder. This method was developed during the late 1800s. These types of pipes were perfect for bicycle frames because they have thin walls, are lightweight but are strong. In 1895, the first plant to produce seamless tubes was built. As bicycle manufacturing gave way to auto manufacturing, seamless tubes were still needed for gasoline and oil lines. This demand was made even greater as larger oil deposits were found.
As early as 1840, ironworkers could already produce seamless tubes. In one method, a hole was drilled through a solid metal, round billet. The billet was then heated and drawn through a series of dies which elongated it to form a pipe. This method was inefficient because it was difficult to drill the hole in the center. This resulted in an uneven pipe with one side being thicker than the other. In 1888, an improved method was awarded a patent. In this process the solid billed was cast around a fireproof brick core. When it was cooled, the brick was removed leaving a hole in the middle. Since then new roller techniques have replaced these methods.

Design

There are two types of steel pipe, one is seamless and another has a single welded seam along its length. Both have different uses. Seamless tubes are typically more light weight, and have thinner walls. They are used for bicycles and transporting liquids. Seamed tubes are heavier and more rigid. The have a better consistency and are typically straighter. They are used for things such as gas transportation, electrical conduit and plumbing. Typically, they are used in instances when the pipe is not put under a high degree of stress.
Certain pipe characteristics can be controlled during production. For example, the diameter of the pipe is often modified depending how it will be used. The diameter can range from tiny pipes used to make hypodermic needles, to large pipes used to transport gas throughout a city. The wall thickness of the pipe can also be controlled. Often the type of steel will also have an impact on pipe's the strength and flexibility. Other controllable characteristics include length, coating material, and end finish.

Raw Materials

The primary raw material in pipe production is steel. Steel is made up of primarily iron. Other metals that may be present in the alloy include aluminum, manganese, titanium, tungsten, vanadium, and zirconium. Some finishing materials are sometimes used during production. For example, paint may be

Seamless pipe is manufactured using a process that heats and molds a solid billet into a cylindrical shape and then rolls it until it is stretched and hollowed. Since the hollowed center is irregularly shaped, a bullet-shaped piercer point is pushed through the middle of the billet as it is being rolled.

used if the pipe is coated. Typically, a light amount of oil is applied to steel pipes at the end of the production line. This helps protect the pipe. While it is not actually a part of the finished product, sulfuric acid is used in one manufacturing step to clean the pipe.

The Manufacturing
Process

Steel pipes are made by two different processes. The overall production method for both processes involves three steps. First, raw steel is converted into a more workable form. Next, the pipe is formed on a continuous or semicontinuous production line. Finally, the pipe is cut and modified to meet the customer's needs.

Ingot production

• 1 Molten steel is made by melting iron ore and coke (a carbon-rich substance that results when coal is heated in the absence of air) in a furnace, then removing most of the carbon by blasting oxygen into the liquid. The molten steel is then poured into large, thick-walled iron molds, where it cools into ingots.
• 2 In order to form flat products such as plates and sheets, or long products such as bars and rods, ingots are shaped between large rollers under enormous pressure.

Producing blooms and slabs

• 3 To produce a bloom, the ingot is passed through a pair of grooved steel rollers that are stacked. These types of rollers are called "two-high mills." In some cases, three rollers are used. The rollers are mounted so that their grooves coincide, and they move in opposite directions. This action causes the steel to be squeezed and stretched into thinner, longer pieces. When the rollers are reversed by the human operator, the steel is pulled back through making it thinner and longer. This process is repeated until the steel achieves the desired shape. During this process, machines called manipulators flip the steel so that each side is processed evenly.
• 4 Ingots may also be rolled into slabs in a process that is similar to the bloom making process. The steel is passed through a pair of stacked rollers which stretch it. However, there are also rollers mounted on the side to control the width of the slabs. When the steel acquires the desired shape, the uneven ends are cut off and the slabs or blooms are cut into shorter pieces.

Further processing

• 5 Blooms are typically processed further before they are made into pipes. Blooms are converted into billets by putting them through more rolling devices which make them longer and more narrow. The billets are cut by devices known as flying shears. These are a pair of synchronized shears that race along with the moving billet and cut it. This allows efficient cuts without stopping the manufacturing process. These billets are stacked and will eventually become seamless pipe.
• 6 Slabs are also reworked. To make them malleable, they are first heated to 2,200° F (1,204° C). This causes an oxide coating to form on the surface of the slab. This coating is broken off with a scale breaker and high pressure water spray. The slabs are then sent through a series of rollers on a hot mill and made into thin narrow strips of steel called skelp. This mill can be as long as a half mile. As the slabs pass through the rollers, they become thinner and longer. In the course of about three minutes a single slab can be converted from a 6 in (15.2 cm) thick piece of steel to a thin steel ribbon that can be a quarter mile long.
• 7 After stretching, the steel is pickled. This process involves running it through a series of tanks that contain sulfuric acid to clean the metal. To finish, it is rinsed with cold and hot water, dried and then rolled up on large spools and packaged for transport to a pipe making facility.

Pipe making

• 8 Both skelp and billets are used to make pipes. Skelp is made into welded pipe. It is first placed on an unwinding machine. As the spool of steel is unwound, it is heated. The steel is then passed through a series of grooved rollers. As it passes by, the rollers cause the edges of the skelp to curl together. This forms an unwelded pipe.
• 9 The steel next passes by welding electrodes. These devices seal the two ends of the pipe together. The welded seam is then passed through a high pressure roller which helps create a tight weld. The pipe is then cut to a desired length and stacked for further processing. Welded steel pipe is a continuous process and depending on the size of the pipe, it can be made as fast as 1,100 ft (335.3 m) per minute.
• 10 When seamless pipe is needed, square billets are used for production. They are heated and molded to form a cylinder shape, also called a round. The round is then put in a furnace where it is heated white-hot. The heated round is then rolled with great pressure. This high pressure rolling causes the billet to stretch out and a hole to form in the center. Since this hole is irregularly shaped, a bullet shaped piercer point is pushed through the middle of the billet as it is being rolled. After the piercing stage, the pipe may still be of irregular thickness and shape. To correct this it is passed through another series of rolling mills.

Final processing

• 11 After either type of pipe is made, they may be put through a straightening machine. They may also be fitted with joints so two or more pieces of pipe can be connected. The most common type of joint for pipes with smaller diameters is threading—tight grooves that are cut into the end of the pipe. The pipes are also sent through a measuring machine. This information along with other quality control data is automatically stenciled on the pipe. The pipe is then sprayed with a light coating of protective oil. Most pipe is typically treated to prevent it from rusting. This is done by galvanizing it or giving it a coating of zinc. Depending on the use of the pipe, other paints or coatings may be used.

Quality Control

A variety of measures are taken to ensure that the finished steel pipe meets specifications. For example, x-ray gauges are used to regulate the thickness of the steel. The gauges work by utilizing two x rays. One ray is directed at a steel of known thickness. The other is directed at the passing steel on the production line. If there is any variance between the two rays, the gauge will automatically trigger a resizing of the rollers to compensate.
Pipes are also inspected for defects at the end of the process. One method of testing a pipe is by using a special machine. This machine fills the pipe with water and then increases the pressure to see if it holds. Defective pipes are returned for scrap.

Where to Learn More

Books

Pipe Characteristic Handbook. Williams Natural Gas Company Engineering Group. Pennwell Publishing. 1996.
Kirk Othmer Encyclopedia of Chemical Technology. John Wiley & Sons. New York: 1992.
Steel Pipe: A Guide for Design and Installation. American Water Works Association. 1989.

— Perry Romanowski

Reference : http://www.madehow.com/Volume-5/Steel-Pipe.html

Types of Pipe Flanges Used in Piping Systems

There are different types of pipe flanges  used in the piping systems depending upon the fluid, PT rating, material of construction, connecting equipment etc.  Below are the types of flanges used in piping based on facing

1) Flat Face (FF) Flanges:

These pipe flanges are used when the counter flanges are flat face. They are mainly used at connection to cast iron equipment, valves and specialties. This flat face flange has a gasket surface in the same plane as the bolting circle face.

Flange flat face FF

2) Raised Face (RF) Flanges:

These pipe flanges are the most commonly used flanges. The raised face thickness for 150# and 300# are included in the specified flange thickness and for higher rating they are not included in the flange thickness.

Flange raised face (RF)

3) Male-Female (M/F) Face Flanges:

These pipe flanges are better version of Raised face flanges.

Flange male female (MF)

4) Tongue-Groove (T/G) Face Flanges:

These pipe flanges are most reliable type of flange joint but are costlier than the other type of flanges.

Flange tongue groove joint (TG)

5) Ring Type Joint (RTJ) Flanges:

These pipe flanges are most reliable type of flange joint but are costlier than the other type of flanges. The Ring Type Joint flanges are generally used in high pressure (Class 600 and higher rating) and/or high temperature services above 800°F (427°C).

Flange ring joint (RG)

Reference : http://www.piping-engineering.com/pipe-flanges-types-systems.html

Design procedures for installing deepwater PLEM

Engineers planning to install a pipeline-end manifold (PLEM) as part of a deepwater flow line system must closely integrate design and installation procedures to ensure the equipment will run smoothly, predictably, and safely. Pipe tensions are high in deep water and installation vessels costly. Therefore, design of the PLEM and the corresponding installation procedure must be as simple as possible.
Shell Deepwater Development Systems, along with other companies, has used the approach and design outlined here.
They have been proven in the following flow line projects: Popeye (1,900 ft), Tahoe (1,500 ft), Mensa 6-in. intrafield flow lines (5,300 ft), and Mensa 12-in. interfield flow line (5,300 ft). All employed "second-end" PLEMs with mudmats, yokes, and vertical hubs.
The analysis strategy discussed in this article emerged over time after some PLEMs had to be modified in the field to run correctly. Problems encountered included:

• A PLEM with center of gravity too high as a result of late or unplanned equipment additions
• Extra measures required to land upright because of pipe torsion (twisting)
• Bent pipe that resulted from lowering too far with the PLEM held inverted.

Beyond divers

Flow lines and pipelines that end in deepwater must be terminated with hardware that permits connection to other facilities, such as a PLEM to permit connection to other facilities. If installed upon completion of pipelay, the PLEM is termed a "second end" PLEM. A pipeline can be initiated with a first-end PLEM but this is an infrequently used technique and outside the scope of the present discussion.
A deepwater PLEM is beyond practical diving depths and must be remotely installable and designed to support robot execution of all planned and possible functions.
PLEMs discussed in this article have as a minimum a mudmat foundation for seafloor support and a vertical collet connector hub to receive a connection jumper.
The vertical hub removes any need to shift the pipeline laterally for connection and places the connection point well above the seafloor.
The PLEM can also be a platform for valves, taps, or instrumentation. And provision can be made for thermal expansion and pile foundations.
After installation, the PLEM can be accessed for repair or maintenance by removing the connection jumper and recovering the unit to the surface.
Installation of the PLEM starts with the configuration of the installed pipeline upon abandonment after installation by either S-lay or J-lay.
If S-lay, the pipeline is assembled horizontally aboard a vessel with several workstations, then guided downward over a stern-mounted, overbend support called a "stinger."
If J-lay, the pipeline is assembled by a single workstation with the pipe nearly vertical and no need for an overbend guide.
When the installed pipeline is abandoned to the seabed, it is fitted with an abandonment and recovery (A&R) head to prevent flooding and to allow attachment of the A&R wire.
There are two reasons for not attaching the PLEM at this point:

1. It is impractical to attach and maneuver the PLEM structure through the pipelay stinger (S-lay) or tower (J-lay).
2. It is prudent to lay the end of the pipe on bottom and assess the unconstrained top-of-pipe orientation before the PLEM is attached.

The PLEM weight, balance, and geometry are all designed to ensure it will have an intrinsic tendency to land with the correct orientation. Nevertheless, experience has shown it is essential to attach the PLEM in harmony with the observed top-of-pipe of the pipeline on the seafloor with the A&R wire disconnected or slack. The pipeline is lowered to the seafloor with the A&R wire. The cut length and top-of-pipe are assessed by ROV inspection. The pipeline is recovered to the side of the vessel in J-mode (pipe suspended with no overbend) and set in a hang-off receptacle or slips so that the A&R head can be removed and the PLEM attached.
With the PLEM attached, the entire assembly is lifted from the receptacle and lowered to the seafloor. If all goes well, the PLEM sled gently lands upright on the seafloor thousands of feet below the vessel

Design

The rigging to lower it connects to a yoke that applies the lift force to a pivot near the centerline of the pipe and above the center of gravity of the PLEM.
The placement of this pivot and the center of gravity of the PLEM are crucial to controlling the bending load on the pipeline throughout the running sequence and to achieving correct orientation of the PLEM on landing.
The center of gravity must be below the pipe centerline and the pivot should be just above the pipe centerline to ensure the PLEM will stabilize with the correct orientation for landing. The pivot is the local coordinate origin on the PLEM for dimensions and calculations.
Note that in Fig. 2, e_pipe and e_{plem t} are negative numbers. The analysis requires the yoke to fold flat on the PLEM. In one Shell installation, the yoke had to be shimmed on the front of the PLEM to deal with a center-of-gravity above the pipe centerline.
This article does not address this design complication of an inclined yoke.
The design shows an anchor flange used to connect the pipeline to the PLEM before welding. During welding, the structural connection isolates the PLEM/pipeline tie-in from the constantly flexing top of the suspended pipe.
Welding the PLEM to the pipeline minimizes cost and potential leak paths.

Equilibrium

Assessing the PLEM design involves modeling the running sequence with simple static vector-analysis methods to predict behavior of the PLEM stepwise through the procedure. Once the design clears this hurdle, more-sophisticated methods can optimize details. For the static vector analysis, some simplifications apply:

• Dynamic forces from vessel motions and PLEM-lowering movements are negligible.
• Pipe and cable shear loads are negligible. The suspended pipe and cable are modeled as catenaries. This tends slightly to over-predict pipe touchdown bending strain and under-predict pipe-top tension.
• The forces of the PLEM, pipe, and cable all act through the PLEM pivot.
• The PLEM is always aligned with the centerline of the top of suspended pipe (pipe deflection adjacent to the PLEM being negligible).

The heart of the analysis is the relationship of free-body forces on the PLEM during running

Bending load

For the analysis to determine the major forces, moments in the vicinity of the PLEM are nil because the only loads considered are vector forces acting through the PLEM pivot. There are moments within the PLEM and adjacent pipe, however, that are locally significant and these must be assessed. These moments occur because forces do not actually converge at a single point. The lines of force between the pivot, pipe axis, and PLEM's center of gravity. The top tension of the suspended pipeline plus the weight of the PLEM are suspended at the yoke pivot.
The reaction at the pivot is a force vector only; a pivot has no moment capacity. Moments result from the following:

• The eccentricity of the pipe top tension line of force from the pivot (pipe tension being applied in line with the pipe)
• Eccentricity of the PLEM center of gravity from the pivot.

These moments can only be resisted by a balancing moment in the suspended pipe. The pipe must be capable of providing the reaction moment without becoming over stressed. The forces, eccentricities, and reaction moment that must be in equilibrium are shown in Fig. 4 [83,601 bytes]. Moment about the pivot as a result of pipe-top tension (recalling that epipe is negative) is shown in Equation 5.
Moment about the pivot as a result of PLEM weight consists of two components: The transverse weight component times the longitudinal eccentricity (Equation 6), and the longitudinal weight component times transverse eccentricity as shown in Equation 7.
There is no moment because of cable tension because it is a vector that never has any eccentricity with respect to the pivot. Total moment about the pivot must sum to zero (Equation 8).
The bending load on the pipe to balance the moment load about the pivot is evaluated throughout the PLEM lowering sequence. The pivot and center of gravity of the PLEM must be located so as to avoid exceeding the moment capacity of the pipe.
Insofar as pipe strength will allow, the pivot should be located above and aft the PLEM's center of gravity and above the centerline of the pipe. At the start of running, the pipe reaction moment is most affected by e_pipe, the eccentricity of the centerline of the pipe from the pivot.
At the end of lowering the pipe, reaction moment is most affected by e_{plem l}, the longitudinal eccentricity of the PLEM's center of gravity from the pivot.
The sturdiness of the PLEM assembly can be increased by fitting the PLEM with a tailpiece of heavy-wall pipe (one or two joints) that will have greater moment capacity either to increase the safety factor or to allow greater eccentricity of the pivot.
Moment on the pipe from Equation 8 is conservative, as the deflection of the pipe because the moment tends to reduce the eccentricity and that in turn reduces the moment load on the pipe. This is an area in which a second round of more-sophisticated analysis can be applied to fine-tune PLEM design.

Righting moment

It is essential to land the PLEM at the correct orientation. Designing a PLEM with the greatest possible positive righting moment to force the unit upright as it approaches the seafloor ensures the likelihood of this happening. For this part of the analysis, the PLEM is assumed to be out of orientation a full 90°. The problem is examined in the transverse horizontal plane and the vertical plane.
Fig. 5 [121,426 bytes] depicts the righting moment. The PLEM is rotated 90° out of correct orientation about the pipe axis. There are two forces trying to right the PLEM:

• The transverse component Wst, of PLEM weight Ws, a downward force applied at the center of gravity that is transversely eccentric to the pipe centerline. To be 100% accurate, yoke weight should be included in the PLEM weight and center-of-gravity calculations for this case. It may or may not be negligible.
• The transverse component T_oct, of A&R cable's bottom tension T_oc, an upward force applied at the yoke lift eye.

The yoke is assumed to be folded flat against the PLEM. The axis for the righting moment is the centerline of the pipe. Only transverse load components times their eccentricities contribute to righting moment. Longitudinal loads do not contribute to righting moment.
Equation 9 yields the transverse component of PLEM weight; Equation 10, the transverse component of cable tension; and Equations 11-13, the components and sum of righting moments about the pipe axis.
Note that transverse loads (and consequently the righting moment) are small when the pipe end is near vertical. It is not unusual for a PLEM to rotate one or more times during the descent.
Increasing the PLEM weight and the transverse eccentricity of the center of gravity can increase righting moment. The most efficient way of doing this is to add thickness to the steel mudmat.
Adjusting the longitudinal eccentricity can be achieved by differing the thicknesses of the fore and aft plates.
Increasing pivot eccentricity is usually not an option because pipe-reaction-moment capacity and pipe-top tension at the start of the installation control allowable pivot eccentricity.
PLEM weight is much lower than initial top-of-pipe tension so there is more scope to change the eccentricity of the PLEM's center of gravity.
This analysis case also provides a lateral design load for the yoke and pivots (applied at the cable connection to the yoke; Equation 14).

Bending load

In the 90° misoriented case, another set of loads induces moment in the pipe. In this case, moments are summed at the point of cable attachment to assess the moment load on the pipe. This moment must be balanced by a moment in the pipe. It is exactly orthogonal to the moment in the pipe induced by eccentricity from the pivot (Equation 15).
Shortening the yoke can reduce this moment load.
A long yoke is beneficial, however, at the end of the lowering sequence when the yoke lifts and another, more powerful, righting-moment regime comes into play.
The moments resulting from pipe and PLEM eccentricities from the yoke are still applied in a plane orthogonal to the moment described in Equation 15: They can be called moments y-y.
The moment y-y (Equation 16) resulting from pipe eccentricity from the yoke pivot was previously noted, in Equation 5.
Another moment y-y results from the longitudinal component of sled weight (Equations 17 and 18). The total y-y moment is shown in Equation 19.
The combined pipe moment with the PLEM running 90° misoriented is the vector sum of the z-z and y-y moments (Equation 20).
Evaluation of this load can indicate when the lowering should be stopped if the PLEM is out of orientation and the yoke has failed to lift. This will happen if the PLEM is oriented upside down and held that way by pipe torsion when it comes time for the yoke to lift.
It is possible to keep going until M_{pipe (90° misoriented)} exceeds M_{pipe allowable}. If the PLEM does not roll upright, the situation must be reviewed with particular attention paid to actual center-of-gravity location, righting moment calculations, and pipe torque.
If pipe torque is the problem, the PLEM is best recovered and reoriented about the pipe. Another possible strategy is to apply torque with an external force applied via a cable from the surface to a corner of the mud mat.
This method was tried with one of the three Mensa 6-in. PLEMs and proved to be futile. The PLEM eventually had to be cut free of the pipe and reoriented.

Other pipe stresses

Pipe outer fiber stresses resulting from the bending loads explained earlier can be calculated with Equation 21. Pipe stress resulting from pipe-top tension is shown in Equation 22; pipe stress resulting from hydrostatic pressure is compressive (Equation 23). The maximum outer fiber stress in the pipe is the sum of all three (Equation 24).

Example

Fig. 6 [119,190 bytes] presents catenary equations. Modeling of the PLEM running is step-by-step with use of a spreadsheet program such as Excel. The "Solver" add-in is useful because it automatically and quickly executes nested iterations.
The running plan will include defined variables (site conditions, PLEM weight, and geometry) and equal number of independent variables, which are determined by iteration, and constraints, and are test variables for the iteration cycles.
The iterated variables in this example are pipe catenary bottom tension and pipe catenary vertical height.
Following are the constraints by which the iterations are tested:

• Cable angle at the surface. This is set at 85° for every step and is an easy-to-monitor independent variable.
• PLEM depth. The analysis was run stepwise starting with the PLEM at the surface and 10 set predetermined depths.

For each step, the pipe catenary height must match the distance from the seafloor to the PLEM depth. The steps are unequal because PLEM-running geometry and loads change the greatest when the PLEM is near the seafloor and steps need to be closer together there.
The defined variables are:

PLEM: W_s = 20,000 lb; L_yoke = 6 ft; e_{plem l} = 0.5 ft; e_{plem t} = -1.0 ft (Yoke influence on center of gravity is negligible.) Pipe: OD = 6.625 in.; W.T. = 0.719 in.; e_pipe = 2 0.25 ft
Cable: OD = 2.875 in.; W_c = 12.5 lb/ft
Site: Water depth = 4,000 ft; seawater density = 64 lb/cu ft

Fig. 7 [77,549 bytes] shows a sketch of the problem. Fig. 8 [306,791 bytes] presents six representative plots of PLEM-running particulars generated by a spreadsheet model based on the equations discussed in this article and the small amount of problem information noted previously.

Reference : http://www.ogj.com/articles/print/volume-96/issue-44/in-this-issue/general-interest/here-are-design-procedures-for-installing-deepwater-plem.html

GIS-Enabled: Modeling Simplifies Pipeline Route Selection

The implementation of a Geographic Information System (GIS) can have a profound effect on management of large water and wastewater infrastructure assets. A GIS-enabled Suitability Model can be used to aid engineers and analysts in the selection of routes in large linear projects, greatly enhancing quality control while minimizing environmental impact.
This innovative technology was employed by URS on a recent project undertaken on behalf of the City of Austin, TX. The city was called upon to expand its water and wastewater infrastructure in a limited time frame, driven by rapid growth in the southeast area of the city, particularly along and east of IH 35. The city evaluated the existing Austin Water Utility (AWU) Long-Range Master Plan and determined that the best approach was to establish the South IH 35 Water/Wastewater Infrastructure Improvements Program, which would be committed to fast-track design and construction of key water and wastewater infrastructure projects.

The South IH-35 Program includes 13 miles of water transmission main and three miles of wastewater interceptor.

The City of Austin brought in URS as Program Management Consultant (PMC) to ensure the South IH-35 Program was successful. URS began with preliminary engineering design of 13 miles of water transmission main, three miles of wastewater interceptor, a 20 mgd pump station, and an elevated storage tank.

Pipeline Route

Determining the route of a pipeline is one of the most critical elements in the development of a linear infrastructure project. The cost and impact of the project are directly related to the quality and success of the routing process. The primary objective is to select a location that is cost-effective, environmentally appropriate, and meets the needs of the project.
Traditionally, potential routes are sketched on paper and a set of criteria is developed for the evaluation of those routes. Criteria generally include environmental hazards, physical barriers, challenging road crossings, a count of affected properties, and the length of the project area.
The handful of probable, or likely, routes are tweaked to avoid critical flaws and evaluated with a scoring matrix. Viable options are selected from a brief desktop study of real estate, rights-of-way, significant environmental features, highway crossings, and length. The potential routes are then evaluated in more detail. The elements of any scoring matrix vary by project and the needs of the owner but some general criteria are cost, environmental impacts, public disruption, number of required easements, and technical challenges. Each route is evaluated objectively and scored. The scores determine the route that best meets the overall needs of the project.
This method of routing evaluation has been employed for as long as water pipelines have been used to transport drinking water to the public. However, advances in technology have improved the evaluation process, and GIS has provided some of the most dramatic changes.

New Approach

GIS specialists and modelers at URS developed a GIS-enabled Suitability Model that was employed in the South IH-35 project. Once constituted, the model does the route analysis based on information provided by the modeler. The process begins with a map of all constraints that comprise the evaluation criteria for route analysis. These evaluation criteria are the same as those used in a traditional route analysis: cost, environmental impacts, public disruption, number of required easements, technical challenges, etc. Each criterion is assigned a suitability value based on a scale of 1 to 9, with 1 being the most suitable and 9 being the least suitable. Each criterion is then weighted based on project requirements, specific concerns, and values of the owner. Some features such as critical habitat or historic resources can be designated as avoidance criteria or "no-go" areas. All suitability criteria are summed to form a suitability surface.
From the suitability surface, an optimal path for the water pipeline is determined by applying an optimal path algorithm. By applying the algorithm, the model takes a stepwise approach between a starting and ending point and it proceeds to calculate the most suitable route between the points by evaluating the criteria from the suitability surface. The optimal path algorithm focuses on minimizing constraints (i.e., crossing streams) and maximizing opportunities (i.e., paralleling property boundaries or existing infrastructure) that were previously defined in the suitability model.

The Austin project included construction of an elevated storage tank and associated pipe lines flowing to and from the tank.

In Austin, the GIS-enabled Suitability Model was used for route evaluation of the South IH-35 Program's 13 miles of water transmission main (WTM). In keeping with a compressed schedule, the PMC employed several techniques to accelerate the work, including subdivision of the WTM into 21 segments for analysis, with those segments eventually regrouped into 17 design projects. To keep the program on schedule, a fully analyzed pipeline route was given to each design firm upon notice to proceed with design. The GIS-enabled Suitability Model was used to define a route for the transmission main in order to provide a consistent methodology for all projects in an efficient and timely manner.
Early on in the process, the PMC began gathering the necessary data to develop the study area base map. At the same time, it conducted aerial surveys as well as windshield tours of the program area to allow engineers and analysts to gain a deeper understanding of the program area that would be modeled. The analysts met regularly with the AWU and the City of Austin staff as well as area developers to determine the needs of each group. Evaluation criteria were established and a cumulative suitability surface was defined upon which the analysts and engineers applied the optimal path algorithm to define the WTM route for the South IH-35 Program.

Path Evaluation

The Suitability Model provides a pipeline alignment that is rough and follows the model input criteria directly. However, the world does not exist in the GIS-created block units of the model. So, it is typical to go through an evaluation of the model route and make minor adjustments. Much of the time, the evaluation reveals minor differences requiring small adjustments in straightening out the route or improving its fit along property and easement boundaries.
For the South IH-35 Program, the typical minor adjustments were made, particularly in one area along IH-35 where the model was seeking to avoid congested areas within a retail development. The design team determined that a route aligned with the South IH-35 right-of-way would better serve the needs of the AWU than a model-generated route away from the right-of-way line.

Versatility of the Model

The GIS-enabled Suitability Model is adaptable to a wide variety of linear projects. It has proven to be effective in improving efficiency in route evaluations and is well suited to large, complex projects - particularly those providing a corridor alignment - that normally would require many weeks of evaluation and several iterations of available routes. The model also is useful for rural environments that are difficult to evaluate visually.
On the IH-35 project, the GIS-enabled Suitability Model provided a significant benefit over traditional ranking matrix evaluations in terms of cost and time efficiency. It allowed for adjustments to criteria to be evaluated quickly and easily by simply adjusting the suitability criteria and re-running optimal path routing.

Reference :  http://www.waterworld.com/articles/print/volume-29/issue-4/departments/automation-technology/gis-enabled-modeling-simplifies-pipeline-route-selection.html