Field Welding of CRA Pipelines

T-Head Punj LloydMany gas fields contain dangerous levels of hydrogen sulfide gas – odorless, colorless, toxic and corrosive.  The Shah gas reservoir in Abu Dhabi contains 23% of the gas, as well as 10% CO2 requiring corrosion resistant piping from the well head to a processing facility.

One solution to transporting so called “sour” gas is to use standard steel piping internally lined with a corrosion resistant alloy (CRA).  This is usually Inconel 625 alloy (NiCrMo-3).  The pipe can be lined with a tube of this material which is inserted into the id and mechanically expanded.  Alternately, the id can be clad with a weld overlay.

It is imperative that root and hot pass do not melt any steel and dilute the continuous CRA clad surface.  The GTAW process is always used.

The contractor Punj Lloyd was awarded the welding project of welding hundreds of 16” and 24” selected the Magnatech T Model system with Pipemaster 516 Controllers.

Precision machining of the pipe end is required to create a “J” prep, where the land extension and Root face is cut into the Inconel clad layer, and does not include any carbon steel.  Two T-Heads were used on a single Guide Ring.  The ID required argon purging and a required interpass temperature of 177⁰C was maintained.

Unlike conventional carbon steel welding, CRA welding has certain unique features.  The joints need to be verified for traces of residual magnetism created by the cladding process.  If it is present, then demagnetization is mandatory.  The joints require thorough cleaning with lint-free cloth wet with acetone.  The fit-up process used special internal clamps with a back purging capability.  Throughout the welding process, back purging was maintained and a required limit on oxygen content less than 500 ppm was monitored with portable oxygen analyzers.  The root pass weld bead was inspected by videoscopy and the bead profile inspected by a Laser Optical Profile Measurement tool.  Defects were well under 1%.

Twenty four weld systems were used to double joint pipe in a yard for transportation to the work site.DSC04712

Orbital Welding Shell’s Quest Project “Green” Pipeline

shell 2The Athabasca Oil Sands Project (AOSP) is a joint venture between majority owner Shell Canada, Chevron Canada, and Marathon Oil Canada Corporation.  AOSP operates two mines.  No processing is done at the mines and the bitumen is transported in a diluted form by pipeline to the Scotford upgrader facility located 50 km northeast of Edmonton, Alberta.  The Scotford upgrader currently produces 255,000 barrels per day of synthetic crude.  This currently meets 10% of Canada’s requirements.

The proposed Keystone XL pipeline, to transport Alberta oil down to refineries on the Gulf of Mexico ignited a firestorm of controversy, and it was eventually blocked by President Obama.  Critics claim it encourages the use of “dirty” oil.  (Until recently, Canadian oil supplied 17% of US demand, the tar sands have been actively mined since the mid-60’s.)  The critics have several complaints, but a significant fact is that in “upgrading” the bitumen, large quantities of CO2 are generated.

Shell Canada is investing $1.4 billion in the Quest carbon capture and storage demonstration project.  It is designed to capture one million tonnes of CO2 annually from the company’s Scotford heavy oil upgrader.  The CO2 is converted from a gas to liquid, and transported by a new 60 km pipeline to a storage site.  To put this in perspective, one million tonnes of carbon dioxide is equivalent to the annual tailpipe emissions of 175,000 cars.  The Government of Canada and the province of Alberta are also providing funding for this initiative.

Gas and oil are typically extracted from deposits trapped by stone formations below the earth’s surface.  In a novel twist, captured CO2 will be injected into a sandstone formation, two kilometers down.  The CO2 is injected under pressure into the porous sandstone geological formation.  Once injected, the CO2 moves through the formation, but is trapped by an impermeable layer of cap rock overlying the sandstone storage.  This method of storing (sequestering) carbon dioxide is termed “structural storage”.  There is considerable experience with Carbon Capture and Sequestration (CSS) projects worldwide and the evidence is that carbon dioxide can be captured permanently in geological formations.  For example, the Norwegian Sleipner project, operating since 1996, has stored CO2 which is injected into oil wells to enhance oil recovery at this offshore oil fields.  Impermeable geologic formations have trapped oil and gas for millions of years, which provides confidence that carbon dioxide will be safely stored indefinitely.  Three sealing layers of rock exist at the Quest storage site.  Shell has decades of experience in modeling subsurface geologic formations during gas exploration, providing the company with unique expertise in storage site selection.

One process used to upgrade the bitumen to lighter synthetic oil involves hydrocracking where steam, methane gas, and a catalyst are combined with the bitumen under high pressure.  The chemical reaction produces hydrogen, which is then used to convert the heavy oil into lighter crude by a process called “hydrogen addition”.  But carbon dioxide is a byproduct of the process.  The Scotford upgrader currently releases three million tonnes annually into the atmosphere.

The Quest facility pipes CO2 gas into a vessel containing Shell’s patented ADIP-X amino-based capture technology, which absorbs the CO2.  The solution is then piped to a stripping tower where heat and pressure release the CO2, which is then piped to a compressor station.  The compressor turns the gas to a liquid that can be transported by pipeline.

 

Welding at 5 o'clock

Pipeline Construction

The construction of the 60 km 12” pipeline posed significant challenges.  Because the pipeline would be transporting liquid CO2, the welds had to meet Charpy impact testing of 60 joules at -50⁰ C as pipeline construction for this project was generally through farmland, with several marshy areas.  Work was done through a winter ith temperatures reaching down to -30⁰C.

Shell contracted with Aecom Technology’s Flint division (formerly Flint Energy Services Ltd.) for the pipeline project.  A standard 30⁰ bevel was used as delivered from the mill.  A gap was maintained between pipe ends, and a 1.6 m land was used.  The root and hot pass were done using 8010 electrodes welding double down.  Two additional fill passes and a cap pass were made using the flux-cored process. The contractor used Magnatech Pipeliner FCAW systems based on prior experience renting from John W. Page Welding Consulting.  John also provided his experience and technical support during the project.  The fill and cap passes were carried out using the Magnatech Pipeliner.  The Magnatech Pipeliner is a “bug and band” type system.  A guide ring is first mounted on the pipe and the weld Head is quickly installed on the guide ring using a push button switch.  Welding is carried out in a double-up progression.  The welder starts the weld at six o’clock and welds clockwise to 12 o’clock.  The Head is declutched and rapidly repositioned to six o’clock and the pass completed welding to 12 o’clock in the counterclockwise direction.

A side boom mounting on a diesel generator, lowered the tent over the joint.  The Pipeliner power supply, water recirculator, and gas bottle were mounted on a steel plate attached to the tent frame.  The entire welding system was contained in the tent, with only a power cable from the generator required.Shell

Hobart Brothers’ Corex filler wire was used on the 12 in. pipe, 1.3 mm diameter alloy E71T-9.  For the 12 in. X-80 pipe, filler wires used were Lincoln Pipeliner G-80M (E101T1-GM-H8) and the ESAB Dual Shield II 101-TC (E80T-a-K2).  A mixed gas of 75% Argon, 25% CO2 was used.  A preheat of at least 100⁰ C was required.  Although two weld heads can be simultaneously used for welding a pipe joint, the small diameter 12” pipe made it less practical for more than one bug on a pipe.  Typical time for the six passes was between 53 – 62 minutes, substantially less than manual welding.

The pipe material was specified to meet the low temperature toughness requirements for liquid carbon dioxide transmission.  During procedure testing, it became evident that to achieve the requisite mechanical properties in both the weld metal and Heat Affected Zone (HAZ) that mechanized welding was required.  The uniform torch rotation speed prevented variations in heat input.  Manual welding with semiautomatic FCAW torches had consistently failed testing in the HAZ.

“Tie in” welds at river or road crossings required welding to an existing pipeline that is already strung beneath the obstacle and often has a heavier wall thickness.  Tie in welds required welding to the existing string in the ditch.  The welding system and tent were lowered into the ditch to perform the welds.  A total of ten systems were used, with several tie in crews.

ID Welders Delivered

Magnatech has Model 442 delivered five ID welders to a contractor specializing in reworking critical valves used in electrical power plants.

Main Steam Isolation Valves (MSIV) are used to throttle the steam flowing into a steam turbine generator.  These massive valves are critical for safety, and must close within seconds in the event of a steam line break.  They also allow maintenance to be performed on the steam turbines.

Over time, the valve seats degrade due to thermal stresses, corrosion and other factors.  These massive valves cannot be simply removed for maintenance in a workshop.  They must be reworked in-situ.  The valve actuator is removed, along with the top of the valve body.  The valve seat is located 4-6’ below.  A fixture is mounted on the top of the valve.  This locates the machining tool precisely to machine out the original valve seat, which is usually stellite material.

The machining tool is removed, and a weld overlay system mounted on the precision fixture.  An overlay of Inconel 625 material is made which requires repetitive overlapping passes, and a number of layers.  A video camera allows the operator to view the weld area.  The valve seat area is shaped like the “bell” on a trumpet. The torch can be quickly angled to keep it 90 to the valve body, as it moves from bottom to top of this “bell” (see photo.)  The welding Head is designed so that the function of the Arc Voltage Control and torch cross seam adjustment slides can be interchanged with a switch on the Head.

Following sufficient weld buildup, the weld Head is removed, and the machining tool reinstalled to cut the weld buildup into the precise geometry of a new valve seat.

What began as a request to improve existing equipment, turned into replacing most of the system. The contractor had already replaced power sources from

Model 442 cladding head
Model 442 cladding head

Orbital Welding Systems For Use In The Aerospace Industry: How Magnatech Can Help!

The Aerospace Industry counts on consistent welding with Orbital Welding

Orbital welding systems are used in the aerospace industry for high-quality welds on hydraulic lines, brake lines and fuel lines, among other applications. Orbital welding involves the joining together of two pieces of metal tubing or piping without the use of a fitting to keep the two pieces still, creating a much better result than welding the pieces manually. During this welding process, an orbital weldhead rotates an electrode and electric arc around the joint, creating a sturdy, precise, long-lasting weld. In essence, orbital welding brings stability and control to the entire process.

Orbital tube and pipe welding systems are the go-to option if weld quality or consistency is difficult to achieve due to a lack of skilled welders or weld defects, as well as challenging weld positions like vertical and overhead welds. Orbital welding uses the GTAW (Gas Tungsten Arc Welding) technique to create accurate welds on tubes and pipes (diameters up to 170mm and walls up to 3.5mm thick). Orbital welding also eliminates the need for threaded and mechanical fittings that need to be maintained or replaced. Orbital welding offers some major benefits over manual welding, such as:

  • Higher quality
  • Greater consistency
  • Greater productivity
  • Much more reliable

Because it prevents material distortion due to the precise control of heat input, orbital welding is suitable for many different types of materials such as: stainless steel, carbon steel, Inconel, duplex stainless, nickel alloys, copper and copper alloys, and titanium.

Developed more than five decades ago, orbital welding systems became more widespread during the 1980s thanks to lightweight, portable power sources. Portable orbital welding equipment enables welders to complete jobs on-site faster and in a more convenient manner. Modern-day orbital welding systems can be controlled by state-of-the-art computers that store specific welding parameters to use as needed for a particular type of welding job. Once the welding parameters have been programmed into the computer, it will perform welds with little to no operator input.

Computer-controlled orbital welding systems offer identical welds time after time, reducing the possibility of low-quality or defective welds. There are many industries served by automated orbital welding systems, including:

  • The aerospace industry
  • The pharmaceutical industry
  • The nuclear industry
  • The wastewater treatment industry
  • The semiconductor industry
  • The shipbuilding industry
  • The dairy industry
  • The food and beverage industries

With many years of experience manufacturing dependable equipment for orbital welding applications in the aerospace industry, the skilled team at Magnatech is dedicated to designing and manufacturing products that help make a welder’s job less physically demanding. We offer a large selection of welding models and equipment for the aerospace industry, provide expert guidance for operators and deliver timely, affordable service.

At Magnatech, our reputation for excellence has helped us win contracts to supply specialized automated orbital welding systems for use with turbine engine component fabrication, repair and overhaul projects. Thanks to our knowledgeable network of sales reps and distributors, we have worked hard to become THE people to call if you are in need of effective orbital welding solutions that meet or exceed aerospace welding standards in United States, Europe, the CIS countries, and the Middle East. For more information, please call +1 860-653-2573 today or click here to request a FREE quote.