Pipe Bending Explanation

BY CRAIG BARNSHAW,MANAGING DIRECTOR, BARNSHAWS METAL BENDING, UKPipelines International — March 2012

Many pipe bending methods are available, with considerable overlaps in capacity. Deciding on a suitable option ultimately depends on quantity and the quality required. All the processes have been described below with a suggested range/suitability, etc. While some companies have quite successfully developed processes that exceed the ranges suggested below, having processes outside of these ranges is not common.

Pipeline Bending

Pipeline Global Buckling

Pipelines like other slender strcutures with compressive forces, can buckle globally if the axial compresssion goes beyond a certain level. Buried pipeline normally tend to buckle in upheaval direction (upheaval buckling) and exposed pipelines normally tend to buckle laterally (lateral buckling).

In most cases, evaluations relevant to the global buckling threat will already start taking place in e.g. feasibility studies carried out during the concept phase. With regard to global buckling, the system risk review and strategy development activity should be initiated by participating in such early studies.

Pipeline Buckling

Why Apply Thermal Insulation Coatings?

Assets such as offshore pipelines, risers, spools and subsea structures which transport liquid products may be required to maintain a minimum temperature while the product is being transported within the asset, particularly offshore. Some liquids such as oil and gas can leave wax or hydrate deposits if a minimum temperature is not maintained. These deposits can, over time, build up and block the asset/pipeline either reducing or completely stopping flow/production. External wet insulation can be designed and applied to ensure the reduction in product temperature is kept within a range so the risk of deposits during production is acceptable. Insulation can also reduce the frequency of pigging operations during the life of the asset.

During other operational events, such as pipeline shutdowns, the product is contained in a stationary state within the asset/pipeline while the process facility has other operations performed. Similarly, to avoid deposits during these shutdown periods external insulation can be designed and applied to ensure the reduction in product temperature is kept within a range so the risk of deposits during shutdowns is acceptable.

Vortex Induced Vibrations, a Swinging Problem

Pipelines at the bottom of the sea are susceptible to ocean currents. Even relatively calm currents can induce turbulences in the wake of the pipeline, which results in the pipeline to start 'dancing'. Pipe vibrations can trigger fatigue, with catastrophic fracture as a result. Consequently, when designing submarine pipelines, caution is being paid to avoid such vibrations. Our research engineers use powerful software to predict submarine pipeline stability.

“The engine of our Western economy is continually being driven by oil and gas”, says FilipVan den Abeele, Research Engineer at OCAS. “The steadily increased demand for fuel, however, obliges the oil companies to explore and produce new oil and gas fields at remote locations. Wells are currently being drilled sometimes more than two thousand metres deep."

Effective Corrosion Prevention Methods For Pipelines

Unprotected pipelines corrode, no matter where the pipeline is. If it’s buried underground, above ground or in water, it’s going to deteriorate. As 60% of our nation’s transmission lines approach their life expectancy of a half century, we’re hearing more and more about pipeline failures. This should not be a surprise. Without implementing safety measures and having a corrosion control program, corrosion makes transporting hazardous material unsafe.

Pipeline Corrosion

The origin of Intelligent Pigs

One of the most crucial aspects of pipeline operation is ensuring pipeline integrity. The intelligent pig has become an important tool for assessing the condition of a pipeline, and is set to become an even more integral part of pipeline maintenance as steps are made towards solving the ‘unpiggable’ pipeline puzzle. Pipelines International spoke with Doug Woodley to trace the origins of the intelligent pig and examine how it developed into the essential tool that it is today.

Early intelligent pig technology

Pipelines are normally pigged for one or more of the following reasons: cleaning, batching, displacement or inspection. Pigging has been around for a long time – some say the process dates back to Roman aqueducts – but the earliest ventures into retrieving information from a pig originated in 1959.

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.

Foam pig
Source: www.pollypig.com

Horizontal Directional Drilling

HDD - A Brief Overview

Horizontal Directional Drilling techniques are used for the steerable installation of new pipelines, ducts and cables. The term applies to a crossing in which a pilot bore is drilled, and then enlarged to the size required for the product pipe. The drill path may be straight or gradually curved, and the direction of the drilling head can be adjusted at any stage during the initial pilot bore to steer around or under obstacles.

Normally launch and receipt pits are excavated so as to collar the hole and collect drill slurry and cuttings. These pit dimensions vary according to the size of the rig and conduit to be installed.

Installation of the product pipe or duct is usually a two-stage operation. A pilot hole is drilled along the required path to provide steering information, and the bore is then reamed in a single or multi-stage operation, depending on the ground conditions and project requirements, to a larger diameter to accommodate the product pipe. During the final ‘pullback’ stage, the product pipe is attached to the reamer by means of a swivel connector, and is pulled into the enlarged bore as the drill string is withdrawn.

Most guided horizontal boring machines use a drilling fluid, which lubricates and stabilises the bore, and also conveys the excavated material in suspension.

Pilot Bore – Starting at the entry point a drill head, suitable for the ground conditions, is drilled along the predetermined route with depth and alignment monitored continuously.

Design Procedures For Installing Deepwater PLEM

Robert T. Gilchrist Jr.
Shell Deepwater Development Systems Inc.
Houston

• Equations [221,894 bytes]

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.

Subsea PLEM

Energy Sector to Drive Demand for Spiral Welded Pipes and Tubes, According to New Report by Global Industry Analysts, Inc.

GIA announces the release of a comprehensive global report on the Spiral Welded Pipes and Tubes markets. Global market for Spiral Welded Pipes and Tubes is projected to reach 24.6 million tons by 2018, driven by economic recovery, level of activity in the energy sector, and intensifying pipeline construction activity.

Spiral welded pipes market, though encountering overcapacity conditions particularly in North America, is expected to witness steady growth in the upcoming years driven by the implementation of new pipeline projects. Investments in oil and gas exploration and production, which are influenced by prevailing crude oil & gas prices, have a considerable impact on the demand for spiral welded pipes and tubes. Resurgent world economy and consequent increase in the demand for industrial natural gas is expected to drive up momentum of the spiral welded pipes market.

How Does Offshore Pipeline Installation Work?

Laying pipe on the seafloor can pose a number of challenges, especially if the water is deep. There are three main ways that subsea pipe is laid -- S-lay, J-lay and tow-in -- and the pipelay vessel is integral to the success of the installation.

Buoyancy affects the pipelay process, both in positive and negative ways. In the water, the pipe weighs less if it is filled with air, which puts less stress on the pipelay barge. But once in place on the sea bed, the pipe requires a downward force to remain in place. This can be provided by the weight of the oil passing through the pipeline, but gas does not weigh enough to keep the pipe from drifting across the seafloor. In shallow-water scenarios, concrete is poured over the pipe to keep it in place, while in deepwater situations, the amount of insulation and the thickness required to ward of hydrostatic pressure is usually enough to keep the line in place.

Selection of Pipe Material For Low-Temperature Service

The selection of material for any specific environment is directly dependent on the material’s properties, especially those properties that are affected by that special environment.

Metal properties are classified in terms of Mechanical, Physical and Chemical properties. These are further subdivided into Structure Sensitive or Structure Insensitive properties. The following table describes these properties.

Tabel 1: Metal Properties

Pipe Stress Analysis: Basic Concepts

Introduction

 It is common practice worldwide for piping designers to route piping by considering mainly space, process and flow constraints (such as pressure drop) and other requirements arising from constructability, operability and reparability. Unfortunately, pipe stress analysis requirements are often not sufficiently considered while routing and supporting piping systems, especially in providing adequate flexibility to absorb expansion/contraction of pipes due to thermal loads. So, when “as designed” piping systems are handed-off to pipe stress engineers for detailed analysis, they soon realize that the systems are “stiff” and suggest routing changes to make the systems more flexible. The piping designers, in turn, make changes to routing and send the revised layout to the pipe stress engineers to check for compliance again.

Such “back and forth” design iterations between layout and stress departments continue until a suitable layout and support scheme is arrived at, resulting in significant increase in project execution time, which, in turn, increases project costs.

How Pipe Is Manufactured

Production of steel pipe is grouped into two general categories: WELDED and SEAMLESS. 

There are many methods of producing steel pipe in current use. However, most of the pipe produced in the United States is made by either the Continuous Weld, the Electric Resistance Weld, the Double Submerged Arc Weld or the Seamless method. 

Introduction to Hot Tapping & Line Stopping

What is a Hot Tap and why it is 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 Tees often to be used as branch and main pipe has the same diameters.
• Isolation Valve like gate or Ball Valve.
• Hot tapping machine which includes the cutter, and housing.

What Is Underwater Welding?

Many of us won't have heard of underwater welding, but it's actually a very important thing in many industries. Underwater welding includes a lot of different processes that join steel on offshore oil platforms, pipelines, ships, and in many other applications.

Underwater Welding

It can be done at regular or at high pressures, and can be done in a wet environment or a dry one. Let's take a look at some of the benefits and downsides of different kinds of welding underwater, and the uses of this interesting technique.

Underwater Pipeline Inspection

XPLISIT

Pipeline owners in the North Sea normally inspects their pipelines at regular intervals. On the outside the condition of the pipe as well as the close proximity of the pipe are of special interest. Free spans, debris, fish nets and World War II mines are states and objects that will be reported. In the eighties traditonal video cameras and storage on analogue video tape were the state-of-the-art technology giving huge amounts of video cassettes. Some of the oil companies even rented huge barnes to store analogue video tapes.

Back in 1988 Norsk Elektro Optikk (NEO) proposed to use line scan cameras and digital storage for pipeline inspection. The main advantage of this concept was a reduction in the amount of data and the volume requirement of the storage media. A second feasibility study was performed in 1993 and the main development project started in 1994.

Xplisit is a dicontinued product. Below is explained the principle of operation. A total system concept is also shown as well as some of the results.

New Standards to Control Pipeline Corrosion

Many factors can cause pipeline failures, including overpressure, weld resistance, joint issues and construction damage. Yet, in the last 15 years, almost 60% of oil and gas production pipeline incidents in Canada have been caused by internal corrosion.

Corrosion is the deterioration of a substance, usually a metal, due to interaction with its environment. Oil and gas pipelines are vulnerable to corrosion in part because of the use of carbon and low-alloy steels.

Adding corrosion inhibitors, or chemical substances that decrease corrosion rates, is one of the most effective methods to control internal corrosion of pipelines. However, no single inhibitor suits all situations, which creates a challenge for industry when it comes to selecting the best product for the job.

To help oilfield and refinery industries select and use the best corrosion inhibitors, Natural Resources Canada’s CanmetMATERIALS, CanmetENERGY-Devon laboratories and industry partners have developed five standards for the testing and use of corrosion inhibitors.

A close up of the CANMET corrosion test
flow loop at an operating oil wellhead

Pipeline Route Selection

Oil and gas pipeline routes are pivotal pieces of information upon which pipeline engineering depends. The route will define the pipeline size, terrain, soils, and engineering analysis requirements. Engineering assessment based upon agreed alignment selection criteria is an important part of a linear project. To be able to reach the best construction line and optimise its components, the phases – namely corridor, route, alignment, and construction line selection — should be studied in the given order.

Subsea Pipeline

New Deepwater Pipeline Concept

London: DNV has developed a new pipeline concept, called X-Stream, that can significantly reduce the cost of a deep- and ultra-deepwater gas pipeline while still complying with the strictest safety and integrity regime. X-Stream is based on established and field-proven technologies which have been innovatively arranged.

Asle Venås, DNV’s Global Pipeline Director,
presenting the X-Stream gas transportation concept