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Gooseneck (Piping)

A gooseneck (or goose neck) is a 180° pipe fitting at the top of a vertical pipe that prevents entry of water. Common implementations of goosenecks are ventilator piping or ducting for bathroom and kitchen exhaust fans, ship holds, landfill methane vent pipes, or any other piping implementation exposed to the weather where water ingress would be undesired. It is so named because the word comes from the similarity of the pipe fitting to the bend in a goose's neck.

Gooseneck may also refer to a style of kitchen or bathroom faucet with a long vertical pipe terminating in a 180° bend.

To avoid hydrocarbon accumulation, a thermosiphon should be installed at the low point of the gooseneck.

material is taken from http://en.wikipedia.org/wiki/Gooseneck_%28piping%29

#pipeline #gooseneck

Commissioning of the Multi-Products Pipeline

Objective of the Commissioning

to bring the constructed / installed system to deliver the desired function

the pipeline commissioning means introducing crude/product/gas in the pipeline from originating station, filling the entire length and then start delivering to receipt system

What We Need Prior to Commissioning?

The pipeline and associated facilities are completed in all respect

All Fire and Safety equipments / facilities are tested and commissioned

Availability of dedicated communication

Statutory Clearances obtained

Availability of Product (HSD)/ Crude oil – Not less than line-fill

Required Manpower is placed at all locations

Availability of water and its disposal plan

Availability of a dedicated commissioning team

Critical Issues in Commissioning a Petroleum Pipeline

Movement of hydrocarbon in empty pipeline can generatestatic current

Hydrocarbon Vapor mixed with oxygen may lead to explosion

There may be formation of Air / Vapor pocket that may get compressed leading to rise in pressure

Air / vapor pocket may explode in receiving tank leading to damage of the tank roof seal

Leakage of any hydrocarbon may lead to fire or damage to environment

Commissioning of a Multi-Products Pipeline

Ensure the pipeline is ready in all respects for the commissioning

Ensure adequate product (HSD) is available for the commissioning (At least more than line-fill of a Pipeline section)

The pipeline or a section of the pipeline is pressurized with air (2 to 3 Kg/Sq-cm)

Pump a water column of about 500 kL to 1000 kL

Launch a Bi-Di Pig followed by 1000 kL to 2000 kL water

Launch second Bi-Di- Pig behind 1000 KL to 2000 KL water

Pump HSD at minimum flow

Track the movement of Pig

Vent the air at receiving end and maintain back pressure 3 to 4 Kg/Sq-cm

Monitor receipt of water at Receiving end – it may be disposed directly in to a protected pit or in a designated tank

Receive Ist Bi-Di Pig

Monitor the quantity and quality of water at receiving end

Receive second Bi-Di Pig

Once diesel or diesel mixed with water arrives, switch over to designated HSD Tank

Observe flow and pressure, once these become stable, the operation may be made normal and the pipeline may be declared as commissioned and handed over to Operation

material is taken from http://petrofed.winwinhosting.net/upload/15-18June11/13.pdf

#pipeline #multi-products #commissioning

How Does Decommissioning Work?

Decommissioning oil and gas installations can cost operators an average of $4-$10 million in the shallow water Gulf of Mexico. Thus when the US Department of the Interior Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) Gulf of Mexico OCS Region issued a new decommissioning regulation in September 2010, operators knew they'd take a hit.

NTL 2010-G05 requires wells that have not been used for the last five years to be to be permanently abandoned, temporarily abandoned, or zonally isolated within 3 years after Oct. 15, 2010. If wells are zonally isolated, operators have 2 additional years to permanently or temporarily abandon the wellhead. Plus, platforms and supporting infrastructure that have been idle for five or more years must be removed within 5 years as of the Oct. 15, 2010 effective date.

This new NTL on top of the typical volume of decommissioning work in the GOM will increase demand for contractors and, in turn, their dayrates.

According to a BOEMRE statement, the MMS (former name of the BOEMRE) conducted an Alternative Internal Control Review (AICR) of idle structures and wells on active leases in the GOM OCS in 2008. The review identified a significant number of idle platforms that need to be permanently plugged and removed. Why? Idle structures and wells could be damaged in a hurricane and cause an environmental disaster. Plus, damaged platforms and wells cost more to decommission than non-damaged wells.

How is Pipeline and Cable Decommissioning?

Pipelines or power cables may be decommissioned in place if they do not interfere with navigation or commercial fishing operations or pose an environmental hazard. However, if the BOEMRE rules that it is a hazard during the technical and environmental review during the permitting process, it must be removed.

The first step to pipeline decommissioning in place requires a flushing it with water followed by disconnecting it from the platform and filling it with seawater. The open end is plugged an buried 3 ft below the seafloor and covered with concrete.

material is taken from http://www.rigzone.com/training/insight.asp?i_id=354

#pipeline #decommissioning

Subsea Tie-in System

Subsea flowlines are used for the transportation of crude oil and gas from subsea wells, manifolds, off-shore process facilities, loading buoys, S2B (subsea to beach), as well as re-injection of water and gas into the reservoir. Achieving successful tie-in and connection of subsea flowlines is a vital part of a subsea field development.

Subsea fields are developed using a variety of tie-in solutions. Over the past decade, FMC Technologies has developed a complete range of horizontal and vertical tie-in systems and associated connection tools used for the tie-in of flowlines, umbilicals and jumper spools sizes 2” - 36” and for single and multibore application. FMC’s horizontal and vertical tie-in systems have been extensively installed in many of the deepest, highest pressure and largest diameter subsea applications around the world.

Vertical Tie-in System

Vertical connections are installed directly onto the receiving hub in one operation during tie-in. Since the Vertical Connection System does not require a pull-in capability, it simplifies the tool functions, provides a time efficient tie-in operation and reduce the length of Rigid Spools.

Stroking and connection is carried out by the the Connector itself, or by the ROV operated Connector Actuation Tool (CAT) System.

Horizontal Tie-in System

Horizontal Tie-in may be used for both firstend and second-end tie-in of both flowlines, umbilicals and Jumper spools. The termination head is hauled in to the Tie-in point by use of a subsea winch. Horizontal Tie-in may be made up by Clamp Connectors operated from a Tie-in tool, by integrated hydraulic connectors operated through the ROV, or by non-hydraulic collet connectors with assistance from a Connector Actuation Tool (CAT) and ROV. Horizontal connections leave the flowline/umbilical in a straight line, and is easy to protect if overtrawling from fishermen should occur.

material is taken from Subsea Tie-in System_low res.pdf - http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QFjAA&url=http%3A%2F%2Fwww.fmctechnologies.com%2F~%2Fmedia%2FSubsea%2FTechnologies%2FTieInSystems%2FColleteral%2FSubsea%2520Tie%2520In%2520Systems_low%2520res.ashx%3Fforce%3D1%26track%3D1&ei=JhXuUrb6B4mPrQfo5YDoBA&usg=AFQjCNFjkS1ah2m-bzSTWjfoH7Jo02ZvMw&bvm=bv.60444564,d.bmk

#subsea #tie-in

Elbow and Bend in Piping

“All bends are elbows but all elbows are not bends.”

Infact, the pipe is bent to form an elbow. Elbows are pre-fabricated and are firm in design. There are issues with bends since the thickness at the bend radius reduces as we bend the pipe.

Sharp bends are normally called Elbows. Bends typically have a minimum bending radius of 1.5 times pipe radius (R). If this bending radius is less than 1.5R, it is called Elbow. Reference to any international / industry standard need to be traced. 1.5, 3 & 4.5 R are the most common bending radii in industry.

material is taken from http://wiki.answers.com/Q/What_is_the_difference_between_elbow_and_bend_in_piping

#pipeline #elbow #bend

Pipe-In-Pipe Technology

Flow Assurance

Insulation Capabilities

Pipe-in-Pipe Overview

Pipe-in-Pipe Offshore Construction

1. Fixed

suitable for majority of lay vessels

field joint uses bulkheads or swaged connectors, no movement between flowline and carrier pipe

permits vacuum in annulus

heat loss from flowline to carrier pipe through metal connectors

2. Sliding

S-lay & J-lay

uses a butt weld on carrier pipe and allows the flowline to move freely

flowline may or may not have alignment spacers

thermal insulation may be on the outside if flow-through-annulus active heating is used

3. Restrained

polymer bulkheads to hold insulation material in place

these bulkheads transfer the load during installation and provide concentric alignment

Deepwater Pipe-in-Pipe

Active Heating Pipe-in-Pipe

material is taken from http://www.deepsea-eng.com/sites/deepsea-eng.com/files/media/DeepSea%20Pipe-in-Pipe%20technical%20presentation.pdf

#pipe-in-pipe

Horizontal Directional Drilling - how it works

check that out!

#horizontal #drilling

The Emergence of the Horizontal Directional Drilling Industry in China

Currently, China is experiencing perhaps the fastest worldwide economic growth. With numerous monumental construction projects underway and an ever increasing population growth, China is utilising sustainable principles and methods for addressing their infrastructure needs.

The eyes of the world are upon China as the country prepares for the 2008 Summer Olympics Games in Beijing, the 2010 World Expo in Shanghai, and the 2010 Asian Games in Guangzhou. These three major international events should be enough to continue the construction frenzy that the country is currently experiencing.

Even with its current growth, China’s safe water supply measures the second lowest in the world. Infrastructure-related issues such as this have driven the government to seek out emerging methods for installing and extending the useful life of existing underground utility networks. Underground utility networks are increasingly facing the need for upgrading and replacing; however, being out of sight generally results in a “reactive” solution for sustaining these systems. To meet this need, China is rapidly adopting trenchless technologies as an economical and minimally intrusive method for sustaining buried utilities. The most rapidly growing trenchless technology in China is Horizontal Directional Drilling (HDD).

Over the past few years, three professional trenchless technology societies have been established in China including: the China Shanghai Society for Trenchless Technology (CSSTT); China Beijing Society for Trenchless Technology (CBSTT); and the China Guangdong Society for Trenchless Technology (CGSTT). These societies have mandates to promote the adoption of trenchless construction methods through educational initiatives. With a mix of government and industry participation, these societies have conducted excellent and informative technical seminars in recent years. One private firm in particular, Hong Kong-based Balama Prima-Vermeer (China) Company Limited, has spearheaded numerous educational efforts regarding horizontal directional drilling throughout China.

SUSTAINING UNDERGROUND NETWORKS WITH HDD

Globally, horizontal directional drilling has made a significant impact in both the utility and pipeline installation industries over the past decade. Currently, HDD is a multi-billion dollar a year industry with hundreds of contractors and thousands of drilling rigs operating on five continents. Industry applications range across the civil engineering spectrum from the installation of utility conduits and natural gas pipelines, through municipal applications (i.e. water mains, gravity sewers), to environmental and geo-construction applications such as the remediation of contaminated sites, geotechnical investigations and diversion channels. Presently, the fastest growing segment of the HDD market is China. It is estimated that there are over 1,500 HDD rigs currently operating in the country with between 25 to 30 local manufacturers (although the top five account for 80 per cent of the locally made machines). Foreign rig manufacturers including Vermeer Manufacturing, Ditch Witch, American Augers, Case, and TT Technologies have had varied degrees of success in penetrating the local market. Today, HDD rigs of all sizes can be seen across various regions of China.

Horizontal directional drilling presents several advantages over traditional open-cut construction methods. One obvious advantage is that it is a trenchless technology. Installation of underground utilities in congested urban areas using open trenching methods can prove to be rather expensive, as the contractor must cautiously dig around existing utilities in order to achieve the required depth, subsequently impeding the operation. Furthermore, sidewalks, pavements, brick paving, sod, or other surfaces must be repaired or replaced. In addition, open-cut construction is often associated with higher user costs, including the interruption of traffic and the disruption of nearby commercial activities. With China’s large, congested population, horizontal directional drilling is even more attractive.

Government officials in China’s most wired city, Shanghai, have begun the onerous task of burying much of its 20,000 km above-ground utility network including telephone, fibre-optics, and electrical lines. The goal is to bury 70 per cent of the network by the year 2010. This is a difficult task given the mandate to preserve historical and cultural sites. Subsequently, horizontal directional drilling is rapidly becoming a preferred installation method because of its minimally-disruptive nature.

HDD SUCCESSES

China’s HDD achievements are competing at world levels by undertaking some of the most ambitious projects in terms of complexity, diameter, and distance. For example, an American-made Robbins trailer-mounted drill rig was instrumental in the completion of a 1.7 km (5,538 ft.) crossing of the Yangtze River in which a 400 mm petroleum pipeline was installed in difficult soil conditions. To further demonstrate HDD successes, projects in Shanghai and Fuzhou are described in the following paragraphs.

A gas pipeline installation project, which is the main pipeline of the West-East Gas Pipeline Project entering the first section of Shanghai region, was installed using HDD. Two multiple installations of 720 mm and 325 mm diameter steel pipelines were installed distances of 356 m and 361 m, respectively. A total of ten 720 mm and eight 325 mm pipes were installed. Shanghai Win-Market Trenchless Technology Construction Company Ltd utilised a Vermeer D200x300 Navigator directional drill rig to complete this project. The project commenced on June 25, 2004 and was completed on July 27, 2004. By utilising HDD, the installations were completed rapidly with minimal disturbance experienced in this congested urban setting.

A second HDD project in Shanghai involved the installation of ten 220 mm diameter high density polyethylene electrical conduits over a distance of 800 m. A Vermeer D100x120 Navigator directional drill rig was used in this installation. By using horizontal directional drilling, these electrical wires are currently being installed with minimal disruption to surface activities and provide longer life due to lower longer term maintenance compared to above ground systems.

Horizontal directional drilling was used in Fuzhou, the capital of the Fujian Province, to install two potable water lines. A 500 mm steel pipeline and a 630 mm diameter high density polyethylene line were both installed a distance of 144 m across a river. This challenging project was completed using a Vermeer D33x44 Navigator directional drill rig. Using a trenchless method was the best approach in terms of preserving the environment due to minimal ecological disturbance during construction.

material is taken from http://trenchless-australasia.com/news/the_emergence_of_the_horizontal_directional_drilling_industry_in_china/001849/

#horizontal #drilling

Subsea PLEM and PLET

As the oil&gas field development move further away from existing subsea infrastructures, it become advantageous to consider a subsea tie-in of their export system with existing deepwater pipeline system offering spare transport capacity. This necessitates incorporating pipeline end manifolds (PLEM’s) at both pipeline ends to tie in the system. A PLEM is a subsea structure used to connect rigid pipeline with other subsea structure such as a manifold or a tree, through a jumper. It is also called a pipeline end termination (PLET), especially to serve as a support for one pipeline valve and one vertical connector.

material is taken from http://oilandgastechnologies.wordpress.com/2012/08/08/subsea-plem-and-plet/

#pipeline #ending #manifold

Application of Underwater Welding Process for Subsea Pipeline

While welding repairs or hot tapping onshore pipelines is a common occurrence, welding repairs on subsea pipelines is most often never even considered. However, the risks involved with welding subsea in-service pipelines underwater is present and needs to be managed by ensuring that, when conducted welding is performed in a reproducible and consistent manner.

The fact that electric arc technology could operate underwater has been known for over a 100 years. The first ever underwater welding was carried out by British Admiralty Dockyard for sealing leaking ship rivets below the water line in the early 1900s and the specific waterproof electrodes and the methods to use underwater were developed in Holland by ‘Van der Willingen’ in 1946.

INCREASING THE UNDERWATER WELDING PRACTICE

In recent years, the number of offshore structures, pipelines, and platforms being installed in deeper waters has increased. Some of these pipelines and structures will experience failures. Any repair for these on location will require the use of underwater welding.

When confronted with the issue of underwater welding, we often question: “Why should we consider underwater welding in the first place?” The immediate answer is “Why not?”

It's true; it is not a commonly-used technique and it does require meticulous planning, availability of highly-skilled tradesmen and tenacity to be successful. Even then, it is still a viable technique.

If the issues are analysed, there is no valid reason not to consider underwater welding, especially if production losses due to outage for repairs is punitive. Sunsea welding generally needs specialised welding knowledge combined with diving skills, which is more demanding than run-of-the-mill commercial divers can offer. Subsea welding covers areas of repairing pipelines, offshore oil platforms and ships.

Subsea welding also reduces the cost for the company by directly carrying out the welding work on location, saving time lost in production to the company.

Furthermore, because of the offshore exploration, drilling, and recovery of gas and oil in deeper waters today, it is necessary to have the capability to repair pipelines and the portion of drill rigs and production platforms which are deep underwater.

RISK AND PRECAUTIONS

Welding underwater can be a dangerous profession if precautions aren't taken. The main risks are electric shock and the possibility of producing in the arc mixtures of hydrogen and oxygen in pockets, which might set off an explosion. The other common danger is breathing nitrogen in the air mix, which is absorbed into the blood but not metabolised by the body at depths under pressure. This could turn into bubbles on ascent and paralyse the diver. Curiously, the risk of drowning is not considered in commercial diving because that is the first hurdle to overcome in this profession.

The quantity of dives, dive repetitiveness, depth of the operations, time spent underwater and the exhausting nature of a specific task increase these risks significantly. Appropriate safety measures are provided to the diver via emergency air or gas supply, stand-by divers and decompression chambers. The diving-related health and safety procedures are managed by strict governing guidelines and work procedures.

When subsea welding is completed, both the welder and the structures being welded are at risk. The welder has to be very careful to avoid receiving an electric shock. For this, adequate precaution is taken by insulating the welder and limiting the voltage of welding sets. Continuous control of hydrogen and oxygen build-up is managed by removal and kept away from the arc to minimise any potential explosion.

Lastly, the welder’s time under water is controlled by using saturation diving chambers and regular rest periods in between. Inspection of an underwater weld is very difficult and complicated when compared to surface welding, but as it is the only controlling process of the quality of the weld, it is always done. The weld is inspected very carefully to confirm that no defects remain.

There are many underwater welding schools located in different parts of the world, including Australia, to train commercial divers. Historically, underwater welding was restricted to salvage operations and emergency repair work with limited depths of less than 9 m.

WET WELDING - THE WAY TO GO

There are two well-developed major categories of underwater welding process: one is welding in a wet environment; the other is welding in a dry environment.

Working underwater to weld serves to provide a number of benefits. Firstly, there is no need to pull the structure out from under water to perform work. In addition, many structures like oil rigs and ship hulls may become damaged at sea, necessitating the need for immediate work below the surface.

Because of the poor quality and difficulty in the process of welding underwater in the past, welding in the wet environment was used primarily for emergency repairs in shallow water. For example, to weld a patch for short duration until a complete repair could be performed in dry docks. With more experience and the advent of special welding rods and the persistence of some ambitious individuals and companies improved results were achieved, which has made wet welding a common occurrence.

Today’s underwater arc welding is accomplished in much the same manner as ordinary arc welding the only variations being that the electrode holder and cable is well-insulated to eliminate any possible current leakage and electrolysis of the surrounding water and the coated water-proof electrodes are used so that the electrodes do not get wet.

The most commonly used wet welding technique is shielded metal arc welding, informally known as stick welding. The main differences in wet welding equipment versus onshore welding equipment is that wet welding uses DC current only.

AC is not used as it can electrocute the diver and it is difficult to maintain a welding arc underwater with AC. The inclusion of a single or dual circuit breaker switch and the use of double-insulated cables protect the diver from electrocution. The power source should be a direct current machine rated at 300 or 400 amperes. Motor generator welding machines are most suitable for underwater welding.

TYPICAL PIPELINE REPAIR METHOD

Typical repair methods, as described in DNV RP F113, are to use fittings for repairs and tie-in of submarine pipelines.

These fittings include: couplings, clamps, T-branch connections and isolation plugs. Mechanical means are used to connect fittings such as sleeves/couplings and T-branches to the pipeline and welding subsequently used to make the repair permanent.

The section on the strength of the mechanical attachments is also applicable to pipeline recovery tools. Couplings connect pipes by direct attachment to the pipe walls via mechanical means and welded. Flange joins pipes via thick, machined pieces of additional material that is welded to the pipe ends prior to installation. Clamps are fitted externally to the pipeline to prevent leaks or add strength. Hot-tap T-branch connections are fitted externally to the pipeline assembly even during operation. A pressurised pipeline is machined open to allow fluid flow through the branch. Pipeline isolation plugs or smart plugs are pumped with the pipeline fluid to the repair site and then activated to form an isolating barrier that can resist differential pressure.

The pipe itself represents the key member of the repair assembly with consequential limitations such as, but not limited to, pipe wall strength, surface irregularities, and deviations in shape. Fittings for sub-sea repair must be installed with caution to reduce the likelihood of damage. Coupling strength should be sufficient in resisting stresses from all relevant loads, within a factor of safety as defined in the standard.

AVOIDING PIPELINE DAMAGE

Pipeline damage after installation may be caused by internal and external corrosion, hydrogen-induced stress cracking, unstable seabed conditions, anchors, and dropped objects from the surface.

The risk of damage depends on the intensity of surface activities such as ship transport and offshore operations, depth, seabed conditions and the design of the pipeline itself. The extent of possible damage will vary from insignificant to a fully buckled or parted pipeline. Consequently, the repair and repair preparedness strategy depends on this.

The following steps have to be taken to select an appropriate repair method:

Detailed selection criteria – this can be location type and strength requirement of sleeve, sleeve design and fabrication mechanical attachment requirements, handling requirements; and,

A pipeline repair procedure manual.

This manual should include:

Avoiding burn-through, factors affecting burn through such as wall thickness, heat input, and operational parameters such as pressure, temperature and flow characteristics;

Prevention of hydrogen cracking concerns factors;

Selecting an appropriate procedure – welding procedure options, predicting required heat input, inter-pass temperatures, pre-heating and maintaining;

Proper electrode handling, welding sequence, and control of heat-input level;

Welder/procedure qualification;

Welder training;

Code and regulatory requirements (changes to API 1104);

Code requirements for weld deposition repair; and,

Inspection and testing.

material is taken from http://pipeliner.com.au/news/application_of_underwater_welding_processes_for_subsea_pipelines/063794/

#underwater #welding #diver

Pipeline Pigging

check that out!

#pipeline pigging

How Does Pipeline Pigging Work?

While buildup in a pipeline can cause transmittal slows or even plugging of the pipeline, cracks or flaws in the line can be disastrous. A form of flow assurance for oil and gas pipelines and flowlines, pipeline pigging ensures the line is running smoothly.

The maintenance tool, pipeline pigs are introduced into the line via a pig trap, which includes a launcher and receiver. Without interrupting flow, the pig is then forced through it by product flow, or it can be towed by another device or cable. Usually cylindrical or spherical, pigs sweep the line by scraping the sides of the pipeline and pushing debris ahead. As the travel along the pipeline, there are a number functions the pig can perform, from clearing the line to inspecting the interior.

There are two main hypotheses for why the process is called "pipeline pigging," although neither have been proved. One theory is that "pig" stands for Pipeline Intervention Gadget. The other states that a leather-bound pig was being sent through the pipeline, and while it passed, the leather squeaked against the sides of the pipe, sounding like a squealing pig.

Engineers must consider a number of criteria when selecting the proper pig for a pipeline. First, it's important to define what task the pig will be performing. Also, size and operating conditions are important to regard. Finally, pipeline layout is integral to consider when choosing a pig.

Because every pipeline is different, there is not a set schedule for pigging a line, although the quantity of debris collected in a pipeline and the amount of wear and tear on it can increase the frequency of pigging. Today, pipeline pigging is used during all phases of the life of a pipeline.

TYPE OF PIPELINE PIGS

Although first used simply to clear the line, the purpose of pipeline pigging has evolved with the development of technologies. Utility pigs are inserted into the pipeline to remove unwanted materials, such as wax, from the line. Inline inspection pigs can also be used to examine the pipeline from the inside, and specialty pigs are used to plug the line or isolate certain areas of the line. Lastly, gel pigs are a liquid chemical pigging system.

Similar to cleaning your plumbing line, utility pigs are used to clean the pipeline of debris or seal the line. Debris can accumulate during construction, and the pipeline is pigged before production commences. Also, debris can build up on the pipeline, and the utility pig is used to scrape it away. Additionally, sealing pigs are used to remove liquids from the pipeline, as well as serve as an interface between two different products within a pipeline. Types of utility pigs include mandrel pigs, foam pigs, solid cast pigs and spherical pigs.

Inspection pigs, also referred to as in-line inspection pigs or smart pigs, gather information about the pipeline from within. . The type of information gathered by smart pigs includes the pipeline diameter, curvature, bends, temperature and pressure, as well as corrosion or metal loss. Inspection pigs utilize two methods to gather information about the interior condition of the pipeline: magnetic flux leakage (MFL) and ultrasonics (UT). MFL inspects the pipeline by sending magnetic flux into the walls of the pipe, detecting leakage, corrosion, or flaws in the pipeline. Ultrasonic inspection directly measures the thickness of the pipe wall by using ultrasonic sounds to measure the amount of time it takes an echo to return to the sensor

Specialty pigs, such as plugs, are used to isolate a section of the pipeline for maintenance work to be performed. The pig plug keeps the pipeline pressure in the line by stopping up the pipeline on either side of where the remedial work is being done.

A combination of gelled liquids, gel pigs can be used in conjunction with conventional pigs or by themselves. Pumped through the pipeline, there are a number of uses for gel pigs, including product separation, debris removal, hydrotesting, dewatering and condensate removal, as well as removing a stuck pig.

Because there now exist multi-diameter pipelines, dual and multi-diameter pigs have been developed, as well.

material is taken from http://www.rigzone.com/training/insight.asp?insight_id=310&c_id=19

#pipeline pigging

Pipeline Global Buckling

the picture is taken from Recommended Practice DNV-RP-F110 October 2007

#pipeline global buckling

Global Buckling

Temperature and pressure effects create expansion effective forces which may cause a pipeline to buckle globally. Pipelines installed on the seabed and left exposed have a potential to buckle globally and change configuration while a buried pipeline is designed to stay in place being restricted by the surrounding soil reaction forces.

The driving force for global buckling of the pipeline is the effective axial force, S, which represents the combined action of pipe wall force, N, and internal and external pressures, see Sec.5.2.2.The effective force for a restraint straight pipe, S0, constitute an upper bound axial load and is discussed in Sec.5.3.1.

For a certain expansion force, the pipeline will buckle globally. For a partially displacement controlled condition, this implies that it will find a new equilibrium by moving perpendicular to the pipe axis at the same time as the pipe will move axially, feed-in, from both sides towards the buckle. The level of axial force to initiate this global buckling depends on:

pipe cross section properties

lateral resistance

out-of-straightness in the pipeline

lateral triggering force (e.g. trawling)

A straight column will buckle according to the classical Euler buckling formulation. As the out-of-straightness in the column increases, the level of axial force required to buckle it will be reduces. This effect, away from the buckle, is illustrated in Figure 2-1.

The out-of-straightness may be caused by:

small imperfections on the seabed like the pipeline resting on rocks

global imperfections as uneven seabed

curvature in the horizontal plane purposely made or random from installation

To illustrate the global buckling of a section in a pipeline, the following idealised sequence of a pipeline with free end expansion can be used :

Prior to applying pressure and temperature, the effective force will be limited to the residual lay tension. The effective force variation will be tri-linear; from zero at the pipeline ends with a linear increase proportional to the axial resistance to the soil, until it reach the residual lay tension H. It will then be constant until it reaches the decay from the other side, see lower curve of Figure 2-2.

When the temperature or pressure increase the compressive effective force will increase to maximum S0, This will vary along the pipeline as the temperature and pressure decrease along the line. At the pipe ends, the load will still be zero, see upper curve of Figure 2-2. A snap shot from a short section is now selected for closer examination in Figure 2-3.

The buckling development is described in Figure 2-3.

Note also that the post-buckling load, point B above, may not be reached directly but through a continuous development. This may imply that higher force close to the buckle is achieved prior to reaching B, that may trigger another buckle.

material is taken from Recommended Practice DNV-RP-F110 October 2007

#pipeline global buckling

Hot Tapping Gas Pipeline

informative but mute. check that out!

#pipeline hot tap

Hot Taping & Line Stoping

the picture is taken from http://www.wermac.org/specials/hottap.html

#pipeline hot tap

Introduction to Hot Tapping & Line Stopping

WHAT IS HOT TAP AND WHY IS IT MADE?

Hot Taps or Hot Tapping is the ability to safely tie into a pressurized system, by drilling or cutting, while it is on stream and under pressure.

Typical connections consist:

Tapping fittings like Weldolet®, Reinforced Branch or Split Tee. Split Tee often to be used as branch and main pipe has the same diameter

Isolation Valve like gate or Ball Valve.

Hot tapping machine which includes the cutter, and housing.

Mechanical fittings may be used for making hot taps on pipelines and mains provided they are designed for the operating pressure of the pipeline or main, and are suitable for the purpose.

There are many reasons to made a Hot Tap. While is preferred to install nozzles during a turnaround, installing a nozzle with equipment in operation is sometimes advantageous, especially if it averts a costly shut down.

REMARKS BEFORE MADE A HOT TAP

A hot tap shall not be considered a routine procedure, but shall be used only when there is no practical alternative.

Hot Taps shall be installed by trained and experienced crews.

It should be noted that hot tapping of sour gas lines presents special health and metallurgical concerns and shall be done only to written operating company approved plans.

For each hottap shall be ensured that the pipe that is drilled or sawed has sufficient wall thickness, which can be measured with ultrasonic thickness gauges. The existing pipe wall thickness (actual) needs to be at least equal to the required thickness for pressure plus a reasonable thickness allowance for welding. If the actual thickness is barely more than that required for pressure, then loss of containment at the weld pool is a risk.

Welding on in-service pipelines requires weld procedure development and qualification, as well as a highly trained workforce to ensure integrity of welds when pipelines are operating at full pressure and under full flow conditions.

HOT TAP SETUP

For a hot tap, there are three key components necessary to safely drill into a pipe; the fitting, the Valve, and the hot tap machine. The fitting is attached to the pipe, mostly by welding.

In many cases, the fitting is a Weldolet® where a flange is welded, or a split tee with a flanged outlet (see image above).

Onto this fitting, a Valve is attached, and the hot tap machine is attached to the Valve (see images on the right). For hot taps, new Stud Bolts, gaskets and a new Valve should always be used when that components will become part of the permanent facilities and equipment.

The fitting/Valve combination, is attached to the pipe, and is normally pressure tested. The pressure test is very important, so as to make sure that there are no structural problems with the fitting, and so that there are no leaks in the welds.

The hot tap cutter, is a specialized type of hole saw, with a pilot bit in the middle, mounted inside of a hot tap adapter housing.

The hot tap cutter is attached to a cutter holder, with the pilot bit, and is attached to the working end of the hot tap machine, so that it fits into the inside of the tapping adapter.

The tapping adapter will contain the pressure of the pipe system, while the pipe is being cut, it houses the cutter, and cutter holder, and bolts to the Valve.

HOT TAP OPERATION

The Hot Tap is made in one continuous process, the machine is started, and the cut continues, until the cutter passes through the pipe wall, resulting in the removal of a section of pipe, known as the "coupon".

The coupon is normally retained on one or more u-wires, which are attached to the pilot bit. Once the cutter has cut through the pipe, the hot tap machine is stopped, the cutter is retracted into the hot tap adapter, and the Valve is closed.

Pressure is bled off from the inside of the Tapping Adapter, so that the hot tap machine can be removed from the line. The machine is removed from the line, and the new service is established.

HOT TAP COUPON

The Coupon, is the section of pipe that is removed, to establish service. It is very highly desirable to "retain" the coupon, and remove it from the pipe, and in the vast majority of hot taps, this is the case.

Please note, short of not performing the hot tap, there is no way to absolutely guarantee that the coupon will not be "dropped".

Coupon retention is mostly the "job" of the u-wires. These are wires which run through the pilot bit, and are cut and bent, so that they can fold back against the bit, into a relief area milled into the bit, and then fold out, when the pilot bit has cut through the pipe.

In almost all cases, multiple u-wires are used, to act as insurance against losing the coupon.

LINE STOPPING

Line Stops, sometimes called Stopples (Stopple® is a trademark of TD Williamson Company) start with a hot tap, but are intended to stop the flow in the pipe.

Line Stops are of necessity, somewhat more complicated than normal hot taps, but they start out in much the same way. A fitting is attached to the pipe, a hot tap is performed as previously detailed. Once the hot tap has been completed, the Valve is closed, then another machine, known as a line stop actuator is installed on the pipe.

The line stop actuator is used to insert a plugging head into the pipe, the most common type being a pivot head mechanism. Line stops are used to replace Valves, fittings and other equipment. Once the job is done, pressure is equalized, and the line stop head is removed.

The Line Stop Fitting has a specially modified flange, which includes a special plug, that allows for removal of the Valve. There are several different designs for these flanges, but they all work pretty much the same, the plug is inserted into the flange through the Valve, it is securely locked in place, with the result that the pressure can be bled off of the housing and Valve, the Valve can then be removed, and the flange blinded off.

LINE STOP SETUP

The Line Stop Setup includes the hot tap machine, plus an additional piece of equipment, a line stop actuator. The Line Stop Actuator can be either mechanical (screw type), or hydraulic, it is used, to place the line stop head into the line, therefore stopping the flow in the line.

The Line Stop Actuator is bolted to a Line Stop Housing, which has to be long enough to include the line stop head (pivot head, or folding head), so that the Line Stop Actuator, and Housing, can be bolted to the line stop Valve.

Line stops often utilize special Valves, called Sandwich Valves. Line Stops are normally performed through rental Valves, owned by the service company who performs the work, once the work is completed, the fitting will remain on the pipe, but the Valve and all other equipment is removed.

LINE STOP OPERATION

A Line Stop starts out the same way as does a Hot Tap, but a larger cutter is used,.

The larger hole in the pipe, allows the line stop head to fit into the pipe. Once the cut is made, the Valve is closed the hot tap machine is removed from the line, and a line stop actuator is bolted into place.

New gaskets are always to be used for every setup, but "used" studs and nuts are often used, because this operation is a temporary operation, the Valve, machine, and actuator are removed at the end of the job.

New studs, nuts, and gaskets should be used on the final completion, when a blind flange is installed outside of the completion plug. The line stop actuator is operated, to push the plugging head (line stop head), down, into the pipe, the common pivot head, will pivot in the direction of the flow, and form a stop, thus stopping the flow in the pipe.

COMPLETION PLUG

In order to remove the Valve used for line stop operations, a completion plug is set into the line stop fitting flange (Completion Flange).

There are several different types of completion flange/plug sets, but they all operate in basically the same manner, the completion plug and flange are manufactured, so as to allow the flange, to accept and lock into place, a completion plug.

This completion plug is set below the Valve, once set, pressure above the plug can be bled off, and the Valve can then be removed.

Once the plug has been properly positioned, it is locked into place with the lock ring segments, this prevents plug movement, with the o-ring becoming the primary seal.

Several different types of completion plugs have been developed with metal to metal seals, in addition to the o-ring seal.

material is taken from http://www.wermac.org/specials/hottap.html

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