WSI
Delayed Coking Unit (DCU)
In recent years, fracking technologies and its supply of lighter crude has shifted the slate available to refiners. Despite this shift, heavy crude continues to constitute the largest portion of available feedstock and most likely will continue into the future. According to AFPM, the United States has the largest concentration of delayed coking units of any market in the world with more than 60 refineries using the technology to destroy vacuum residuals and increase distillate yields.[1] Prior to the delayed coking process, the eventual feedstock known as vacuum reduced crude (VRC) was processed through several units. First the originating crude has salts and dirt removed in the desalting process. Next, the crude distillation process heats the feedstock into initial products such as gasoline, jet fuel, light ends, and most importantly to the coker, atmospheric reduced crude. Finally, the atmospheric distillation process provides further separation leaving VRC to be moved to the delayed coker for processing.
Constructed first by Standard Oil of Whiting, Indiana in 1929, delayed coking is the only main process in a modern refinery that is a batch-continuous process. The DCU batch process produces solid carbon material known as petroleum coke primarily in a few forms: shot, sponge, and needle. Depending on the physical and chemical properties that the various forms of petroleum coke display, the coke can be used in a wide variety of ways including feedstock for the petrochemical industry, fuel grade material for the aluminum and steel industries or even used for gasification. In today’s market, approximately 80 percent of worldwide production is fuel grade petroleum coke.[2]
Coke Drum Materials and Process
The delayed coking process utilizes coke drums usually arranged in pairs that can range in size from small (15’ diameter) to large (>30’ diameter). The pairing of these drums allows for refiners to operate the process continuously dependent on unit feed rate, drum size, and throughput capacity. Designed and built to the ASME Section VIII, Division I, older drums were constructed of carbon steel but modern drums are fabricated from low carbon chrome-moly alloy steels internally cladded with 410ss or 405ss for internal protection from corrosion due to high sulphur. Specifically, most drums are fabricated using 1.25Cr-0.5Mo and 1Cr-0.5Mo alloy plate although there are numerous examples of construction using 2.25Cr-1Mo, 3Cr-1Mo, and C-0.5Mo materials.
The coking process is cyclical and typically begins with one drum of a pair being pre-heated from ambient temperature to ~250F-350F via steam injection and usually constitute to most significant amount of the cycle time. The next phase begins by feeding the drums ~750F-850F residual oil. This is followed by additional steam injections to promote the thermal cracking process. Lastly, water is injected to cool and aid in solidification of the coke product. The coke is then hydro-cut and the drum de-headed to unload the coke product into storage areas. The cycle times for the coking process can vary greatly from 9 hours to 36 hours and begins again in the subsequent drum of the pair. Most coker operators currently run cycle times of approximately 16 hours but cycle times have been observed as low as 10 to 12 hours. The shorter cycle times result in increased thermal cycles due to the shortening of the heating and quenching cycles.
Low Cycle Thermo-Mechanical Fatigue
Thermo-mechanical fatigue (TMF) is fatigue damage that occurs in components, such as the coke drums, due to coinciding exposure to cyclic mechanical strains and thermal cycles. TMF can occur in an environment that experiences cyclical temperature gradients in areas with complex geometries such as the coke drum skirt attachment welds or areas of dis-continuous material properties such as seam welds. The nature and magnitude of strains under TMF conditions are often very complex due to the number of variables involved in the delayed coking process. Coke drums of all materials are subject to low cycle thermo-mechanical fatigue, which causes accumulative damage, and most often thought to be the principal reason for bulging and subsequent cracking. Originally, Weil and Rapasky studied the phenomenon for 20 years beginning in the 1930’s asserting that radial bulging was found to be directly attributable to the quenching portion of the operating cycle.[2] They also observed severe bulging in the lower portion of the drums that experienced the highest quench rates producing high thermal gradients. Even today, the initiation mechanisms of bulging in coke drums is still not fully understood although we can mainly attribute them to thermal stresses. The area that is clear is that delayed coking’s thermal cracking process has a wide range of variables that affects the severity, growth rate, and frequency of bulging in the drums.
Bulging in the Coke Drum
According to the 1996 API Coke Drum Survey, 57% of operators reported bulging in shell sections.[3] Furthermore, the drums that experienced bulging 87% had also experienced cracking. The severe low cycle thermo-mechanical load makes coke drums susceptible to shell bulging during the operation of the drum. The high stresses over time cause localized bulging and contribute significantly to cracking. The bulging is categorized as a deformation that forms partially or completely circumferential in the drum. The bulging can occur both inwardly (towards the ID) and outwardly (towards the OD) as well as be observed for rippling that may occur in the shell material. In most cases, the deformation of the bulge is measured for depth and sharpness indicating the severity and potential for recurring issues to the shell courses impacted. Localized bulging and the associated fatigue stresses caused by relatively minor distortion can have catastrophic impacts on fatigue life especially in cases where bulging occurs near circumferential weld seams.
Structural Weld Overlay for Life Extension Utilizing WSI Machine Technology
Beginning in the early 1990’s, WSI initiated the first Structural Weld Overlay’s (SWOL) in coke drums. With aid from partners in the industry, SWOL process was developed as an engineered repair method utilizing advanced techniques in laser mapping, fatigue analysis, and field machine welded execution. WSI SWOL extends the cyclical life of the drums by significantly slowing bulge growth rates and retarding crack growth with strategically designed weld deposits guided by analysis. Once properly assessed and designed, temperbead welding procedures are evaluated for use with WSI designed machine welding Gas Metal Arc Welding systems. These systems utilize state-of-the-art waveform controlled power supplies and are built by WSI engineers with sensor enabled parameter monitoring and digital control systems, the machine welding process has the ability to be effortlessly field modified to handle any geometry and difficult welding position unique to the drums. Utilizing the same equipment, WSI SWOL can be installed both to the ID or the OD of the drum depending on the compressive stresses that are needed to slow bulge rates and reduce bending stresses.
The WSI SWOL repair method has been implemented by owners experiencing low cycle thermo-mechanical fatigue in order to reduce inspection cycles, extend the life of the coke drums and gain greater predictability on operations. According to experts familiar with these issues, “long range studies have demonstrated how structural weld overlay repairs have lasted 10+ years, 3-5x longer than other repair strategies.”[5] The results observed in these cases are exceedingly reliant on a high quality overlay design, stringent control of the machine welding technique affecting the metallurgical properties, and precise control of the surface profile quality. In recent times, because more providers have entered the field the failure to adhere to these rigors throughout the process has had negative effects to the repair performance. In some cases causing damage to the vessel. Although the outcome is dependent on the rigor of design and quality of implementation, the WSI SWOL repair method has been found by owners to be both logistically and financially effective. Now with over a hundred field installations worldwide, WSI SWOL has proven that we are the world leader in coking unit life extensions.
WSI – The World Leader in Coking Unit Life Extension
Whether the coker needs to be repaired emergently or during a planned turnaround, WSI has unparalleled innovative leadership in the coking unit backed by proven results. WSI has the world’s largest portfolio of coker life extension projects and qualified procedures to handle coking unit specific challenges. Find out more about our coker life extension solutions and engineered technologies at WSI.
[1]American Fuels and Petroleum Manufacturers, AFPM. Technical Papers. Retrieved from https://www.afpm.org/data-reports/technical-papers.
[2]Weil, N. A. and Rapasky, F. S., 1958, “Experience with Vessels of Delayed-Coking Units”, Proceedings American Petroleum Institute, pp. 214-232, vol. 38
[3]1996 API Coke Drum Survey, 2003, American Petroleum Institute, Washington, DC.
[4]API 934J,2018, American Petroleum Institute, Washington, DC.
[5]Samman, M and DuPlessis, P. Refcomm 2017, Galveston. 10x Life Improvement in Coke Drum Life Using Weld Overlay
WSI
History of Power Boilers
With roots dating back to the 1700’s, steam-generating boilers have evolved greatly based on industrial and residential demand. George Babcock and Steven Wilcox were the first to patent their boiler design and later established Babcock & Wilcox Company in 1891. As the country grew, so did the need for utility companies to generate and distribute electricity to major cities and beyond. As demand grew, boiler steam temperature and pressure requirements also increased forcing manufacturers to design larger and more efficient boilers. In the late 1950’s, the industry responded with membrane tube wall designs that allowed for higher efficiencies, therefore paving the way for supercritical boilers that could generate over 1000 MW. Seamless carbon or Cr-Mo steel tubes were welded together using a steel membrane bar between the tubes, and formed into a large tube panel. This innovation eliminated the need for refractory, reduced construction cost, and increased the size of the boilers.
Tube Wall Challenges
The waterwalls made of tubes and membranes are constructed around the furnace enclosure. High-pressure water inside the tubes extract heat from the high temperature combustion gases on the fireside of the tubes. The waterwalls are subjected to thermal fluctuation, high temperature corrosion and particulate erosion corrosion attack. The waterwalls are constructed of ferritic steels to provide structural integrity as well as resistance to high temperature water and steam used in the heat transfer. Alternatively, the ferritic steels utilized did not necessarily deliver superior resistance to high temperature corrosion attack from oxidation although many times they performed adequately with predictable wall loss values. The Clean Air Act Amendments of 1990 forced operators to introduce low NOx combustion systems, in an effort to reduce the boiler’s harmful emissions of nitrogen oxides (NOx) emissions into the environment. This effectively created a reducing atmosphere in the lower furnace with low levels of oxygen and changed the corrosion mechanism from oxidation to erosion-corrosion by sulfidation. The result of these changes considerably increased waterwall wastage and forced operators to explore mitigating innovations.
Industry Proven Alloying Applications
Beginning in the early 1990’s, in response to the emissions legislation, WSI began researching alloying materials and innovative application methods to achieve longer life in the waterwall tubes exposed to high temperature corrosion and erosion-corrosion. Over the course of the next decade, WSI engineers patented several processes for application of corrosion resistant overlay (CRO) as well as identified various alloys for CRO including 309SS (Fe-24Cr-13Ni), alloy 625 (Ni-22Cr-9Mo-3.5Nb) and alloy 622 (Ni-22Cr-13Mo-3W) that would address the needs of power boiler operators. The necessary requirements for achieving maximum erosion & corrosion protection on the fireside of the waterwall is maintaining the lowest dilution rates of the weld deposit chemistry, retaining high relative Cr content throughout the weld deposit thickness and minimizing FE concentrations. WSI accomplished this with several CRO application methods built around the concept of achieving the lowest possible dilution for weld deposit chemistry with overlays exhibiting less than 10% dilution. These methods have been successfully utilized for many years to provide high temperature corrosion and erosion & corrosion protection for boilers.
Boiler operators sought to maintain their waterwalls in regular outage windows but experienced accelerated, and sometimes unpredictable, tube wastage from various erosion & corrosion mechanisms. WSI developed a field applied, machine welding approach that met ASME code requirements. Utilizing custom built and proprietary welding technology, a machine applied Gas Metal Arc Welding (GMAW) Unifuse weld metal overlay had the ability to substantially extend the service life of waterwalls. Applying custom programmed weld deposit sequences from the membrane to the tube crowns, the field applied machine Unifuse ensured industry best weld deposit chemistry, consistent thickness deposition across the entire tube, and productivity unachievable prior to the technology. WSI machine weld metal overlay is considered by the industry to be the standard for waterwall wastage in coal-fired boilers with 1000’s of field installed overlays, almost every coal fired boiler in the US has some form of WSI overlay installed.
Shop Applied Unifuse™ Panels for Fabrication
From time to time operators faced situations when high temperature corrosion and erosion & corrosion mechanisms accelerated waterwall wastage unpredictably and past ASME code allowable thicknesses. Operators facing larger areas of this condition needed panel replacement parts with alloying protection available for installation. WSI leveraged their field application experiences to develop processes and procedures for shop applied Unifuse™ weld metal overlay. The shop application meets ASME code and is delivered under WSI’s quality program.
Shop Applied Unifuse™ 360° Tubes for Fabrication
Boiler operators also experienced increased metal loss in the upper furnace components due to the fact that the metal temperatures of the superheater, for example, are much higher than those of the waterwalls. To extend the life of upper furnace components as well as increase fabrication options for waterwalls, Unifuse™ technology was patented by WSI resulting in a process for the fabrication of bimetallic tubes using a full fusion automated welded process. The patented process uses an initial uniform 360° GMAW weld deposit of alloying material followed by GTAW to smooth the overlay surface and temper the heat-affected-zone (HAZ) formed in the substrate steel during GMAW process. The completed Unifuse™ 360° tubes exhibit excellent ductility and toughness in the as-overlaid condition which allows fabricators to execute bends necessary to achieve various configurations without cracking. The majority of Unifuse™ 360° overlay tubes are fabricated for screen sections, superheater, reheater, and generating banks in the upper furnace of the boilers but panels can also be constructed based on boiler design.
WSI – Proven Results. Automatically.
With over 2000 total workscopes executed globally with Unifuse™ for power industry since 2000, WSI is the world leader in boiler life extension. Whether the boiler needs to be repaired emergently or during a planned outage, WSI has unparalleled innovative leadership backed by proven results. WSI has the most extensive portfolio of successfully completed, power boiler weld projects and qualified procedures to handle any boiler specific challenges. Find out more about our engineered services offering at WSI.
[1] Nicholas P. Cheremisinoff, Paul E. Rosenfeld, in Handbook of Pollution Prevention and Cleaner Production, 2010
[2] The National Board of Boiler and Pressure Vessel inspectors. Black Liquor Recovery Boilers
WSI
Black Liquor Recovery Boilers
The kraft pulping process was patented in 1884 and is the most common form of chemical pulping, at 80% of the total chemical pulping industry.[1] The economic viability of the entire process would not be possible without the black liquor recovery boiler (BLRB) used to reclaim the spent pulping chemicals discharged from digesters through a series of evaporators to increase their concentrations. The combustion gases are highly corrosive, particularly at temperatures necessary for operation above 900 psi. Resembling a large industrial boiler, the furnace is constructed with waterwall tubes in the furnace floor as well as on the sidewall. Black liquor is the waste liquor from the kraft pulping process and contains most of the original cooking inorganic elements and the degraded, dissolved wood substance.[3] The black liquor is a thick, viscous material with high hydrocarbon content that has traditionally been burned in a recovery boiler to generate heat and electricity to power the pulp mill. Organic compounds are burned to generate heat for producing steam for various processing applications within the mill. The resulting heat is a highly valued energy stream, producing power and heat for the pulp and paper mills, making many of them self-sufficient in energy. Combustion takes place under reducing conditions, transforming sodium sulfate to sodium sulfide and also forming sodium carbonate. Inorganic solids, such as sodium sulfide, sodium hydroxide, sodium carbonate, sodium sulfate, thiosulfate, sodium chloride and others, are melted in the furnace bed.
BLRB Furnace Sections Challenges
Burning the black liquor takes place in the furnace and requires oxygen to be mixed to self-sustain combustion. The furnace can be broken into two areas based on their functions, the lower furnace and upper furnace. In the lower portion of the furnace, the black liquor is sprayed in to intermix with combustion air and where the char bed accumulates and smelt is formed later draining out of this section. The molten smelt is removed from the furnace through water cooled spouts and a series of floor tubes that require corrosion mitigation and a prone to various cracking mechanisms. In the upper portion of the furnace, considered to be above the smelt bed, combustion completes as waterwall panels cool gases. In this area, corrosion is primarily due to sulfidation. Gas then flows out of the upper furnace through a screen section, superheater, generating bank, and economizer in most cases. In these various tube banks, the components are being subjected to high temperature erosion-corrosion.
BLRB Furnace Protection
Historically various methods of protecting the tubes were explored with limited success including pad welding with a stainless steel alloy, thermal sprayed coatings and others. Excessive dilution with manual pad welding generally resulted in 15 or 20% iron content in the alloy applied therefore significantly reducing the alloy’s resistance to high temperature erosion-corrosion. Thermal spray experienced spalling in some cases and in others sulfidation attack occurred to the carbon steel tubes under the coatings. WSI began researching alloying materials and innovative application methods to achieve longer life in the lower and upper furnace components exposed to the various forms of erosion & corrosion. Three application methods have been successfully installed meeting those challenges.
Utilizing custom built and proprietary weld technology, the machine applied GMAW Unifuse™ weld metal overlay had the ability to substantially extend the service life of recovery boiler waterwalls. Applying custom programmed weld deposit sequences from the membrane to the tube crowns, the field applied machine Unifuse™ ensured industry best weld deposit chemistry, accurate thickness deposition across the entire tube, and productivity unachievable prior to the technology. Utilizing 309ss to mitigate sulfidation attacks, BLRB operators have experienced longer life to waterwall panels. In addition, alloy 625, known to be highly resistant to environmentally assisted cracking and to thermal fatigue cracking, is an excellent candidate for Unifuse™ overlay for floor tube applications and water-cooled smelt spouts.
Shop Applied Unifuse™ Panels for Fabrication
From time to time operators faced situations when high temperature corrosion and erosion & corrosion mechanisms accelerated waterwall wastage unpredictably and past ASME code allowable thicknesses. Operators facing larger areas of this condition needed panel replacement parts with alloying protection available for installation. WSI leveraged their field application experiences to develop processes and procedures for shop applied Unifuse™ weld metal overlay. The shop application meets ASME code and is delivered under WSI’s quality program.
Shop Applied Unifuse™ 360° Tubes for Fabrication
To extend the life of upper furnace components, such as screen sections, superheaters, generating banks, and economizers, and increase fabrication options for waterwalls, Unifuse™ technology was patented by WSI resulting in a process for the fabrication of bimetallic tubes using a full fusion automated welded process. The patented process uses an initial uniform 360° GMAW weld deposit of alloying material followed by GTAW to smooth the overlay surface and temper the heat-affected-zone (HAZ) formed in the substrate steel during GMAW process. The completed Unifuse™ 360° tubes exhibit excellent ductility and toughness in the as-overlaid condition which allows fabricators to execute bends necessary to achieve various configurations without cracking.
WSI – Proven Results. Automatically.
With over 2000 total workscopes executed globally with Unifuse™ for furnaces since 2000, WSI is the world leader in boiler life extension. Whether the boiler needs to be repaired emergently or during a planned outage, WSI has unparalleled innovative leadership backed by proven results. WSI has the most extensive portfolio of successfully completed, BLRB weld projects and qualified procedures to handle any recovery boiler specific challenges. Find out more about our engineered services offering at WSI.
[1] Nicholas P. Cheremisinoff, Paul E. Rosenfeld, in Handbook of Pollution Prevention and Cleaner Production, 2010
[2] The National Board of Boiler and Pressure Vessel inspectors. Black Liquor Recovery Boilers
[3] Pratima Bajpai, Biermann’s Handbook of Pulp and Paper (Third Edition), 2018
WSI
FPSO (Floating Production Storage and Offloading Vessels)
An FPSO is a floating production system that receives fluids (crude oil, water and a host of other things) from a subsea reservoir through risers, which then separate fluids into crude oil, natural gas, water and impurities within the topsides production facilities onboard. Crude oil stored in the storage tanks of the FPSO is offloaded onto shuttle tankers to go to market or for further refining onshore.
Most FPSOs/FSOs are based on tanker ship hulls and can be secured to the sea bed via a variety of mooring systems, the choice of which is determined by the specific environment. They are suitable for a wide range of water depth, environmental conditions and can be designed with the capability of staying on location for continuous operations for 20 years or longer. [1]
The Customer Challenge
As part of their operation, FPSO’s have to be serviced by transport ships on a regular basis. These transport ships travel to the FPSO’s location and moor to the vessel to allow for safe transfer of the stored hydrocarbons in the FPSO.
To protect both vessels, fenders are used to cushion possible contact between the transfer shuttle and the FPSO. In challenging weather these fenders can abrade the protective coatings from the vessel shell which leads to salt water corrosion induced wall thinning. This issue creates a difficult choice for the customer. Either take the vessel out of production or make repairs at dry-dock, or find a way to repair the shells at sea. Many FPSO owners choose to make small scale localized repairs when the base material becomes too thin, but when larger affected areas are found, there is currently no viable repair while in-operation at sea available other than exchanging the plates or installing temporary patches.
The Best Solution: Unifuse Automated Welding for FPSO
For this customer, WSI evaluated the condition of the vessel and determined that by making modifications to one of their proprietary automated welding systems, they would be able to work within the inner hull of the FPSO while at sea to deposit layers of weld metal to restore the base metal thickness to design requirements. Because of the significant deposition rates achievable with this technology, justification for this approach vs. the dry-dock option was clear. The customer estimates that they experienced multi-million dollar savings by utilizing this innovative solution.
Although this WSI weld overlay technology is commonly used in refineries, petrochemical plants, pulp mills, and other industries where they use high pressure, high temperature pressure components, it is not very common in the shipping industry. Pressure vessels are typically constructed and repaired in accordance with the ASME Boiler and Vessel Code. Ocean going vessels generally utilize standards from the certifying agency, which impose compliance requirements on repairs to accommodate the ocean environment.
For this project, WSI had to manage a development program to test and verify welding procedures in accordance with the insurer’s requirements. These rigorous requirements ensure that the repair being implemented will result in a safe and reliable vessel. In addition to normal tests performed on procedure qualification samples, the testing protocol also included impact testing on coupons welded in simulated above and below the water line with varying water temperatures. In addition, WSI performed a local and global distortion analysis to ensure that the distribution of weld zones was done properly to manage residual stress and distortion.
To date, the majority of this scope has been completed with excellent safety, quality, and productivity results. This has been a significant financial win for the customer.
WSI – Proven Results. Automatically.
With over 2000 total workscopes executed globally with Unifuse™ for pressure components, WSI is the world leader in pressure equipment life extension. Whether the component needs to be repaired as an emergency or during a planned outage, WSI has unparalleled innovative leadership backed by proven results. WSI has the most extensive portfolio of successfully completed, field weld projects and qualified procedures to handle specific challenges. Find out more about our engineered services offering at WSI.
[1] Web Content MODEC. About and FPSO
WSI
The Fluid Catalytic Cracking Unit (FCCU) is one of the most important processes for converting lower value heavy oils into valuable gasoline and other lighter products such as distillate, butane, and propane fuels. The FCCU is a secondary conversion operation within more complex refineries that contribute the largest volume to the gasoline pool by catalytically cracking feedstocks that are too heavy to blend into the diesel pool. Various cracking techniques were pioneered in the early twentieth century but “the first FCC unit was built by M. W. Kellogg in Baton Rouge, Louisiana and was started up by operator Standard Oil in May 1942.” Two distinct configurations have emerged commercially since that time, side by side and stacked in terms of the locations of the reactor and the regenerator.
The FCCU experiences are wide variety of damage mechanisms
With much of the installed equipment base originally constructed in the 1940’s and 1950’s, component upgrades and revamps occur frequently. The FCCU reactor and regenerator is commonly constructed from 1¼Cr-½Mo or 2¼-Cr 1Mo alloy steels. After years of service at temperatures near or sometimes well above 1000°F, the units suffer from a wide range of aging related service degradation including thermal fatigue, graphitization, temper embrittlement, sulfidation and creep. They can also experience a wide range of corrosive mechanisms such as colythionic acid stress corrosion, naphetanic acid corrosion, ammonium chloride corrosion, and hydrogen damage such as hydrogen induced cracking and stress oriented hydrogen stress induced cracking. This wide variety of damage mechanisms created in the process lead to internal components needing replacement. Learn about WSI’s HP GTAW automated welding for FCCU reactor and regenerator head replacements.
Managing concerns for head replacements
Head removal to change out reactor and regenerator internals are common but come with a myriad of challenges during reinstallation that affect welding. The first of which being the weld joint fit-up that cultivates two primary concerns, weld induced distortion in the pre-assembled head and the degree of out of roundness in the existing aged Cr-Mo material shell section. The head section can experience a variety of weld induced distortion mechanisms during removal and reinstallation of the internal components such as angular changes, bending, and buckling. Coupled with the potential for out of roundness of varying degrees from past service of the shell section, preparation for mechanical fit up becomes an immediate challenge in the sequencing of the installation. The fit up and potential for deformations then affects the design of the proper bevel selection. With material thicknesses exceeding 1”, best practice is to design the joint for a double sided compound bevel groove. The doublesided compound bevel joint design provides a substantial decrease in weld deposit volume as well as decreased residual stresses and potential for longitudinal shrinkage. The doublesided joint design requires backgouging to assure complete through-section fusion at the root, prompting the next challenge, access from the ID of the unit. Whether a single sided or double sided joint is selected, access to the ID of the unit is required in order to install a corrosion resistant overlay to the seam and reinstall refractory. In some cases, the clearance between the cyclones and shell ID can be less than 8” making manual welding of the groove joint and the weld metal overlay virtually impossible. Under these clearance constraints, weldability to the groove becomes the next challenge to address. Typically in these access constrained areas, keeping the arc length or tip to work distance consistent with manual welding, even for the highest skilled welders, is extremely difficult and often leads to lack of fusion issues at the root. Exacerbating the constraint issue is the fact that these welds are generally under elevated pre-heat creating extremely harsh work conditions as well as making the weld efficiency slow and prone to quality issues.
WSI’s HP GTAW™ Machine Welding for Head Replacement Seams
WSI’s Hot-PulseTM GTAW process delivers superior weld quality, increased productivity rates and reduced risk to personnel versus conventional welding methods. By utilizing a proprietary system of wire pre-heating, precise dabbing mechanics, and tightly controlled parameters the machine HP GTAW™ process minimizes the propensity for porosity, improves grain refinement and is significantly less susceptible to weld defects in critical field joints. Engineered with access constraints in mind, the slim profile of the equipment envelope can travel between the cyclones and shell ID. WSI’s machine HP GTAW™ welding technology combines unparalleled deposition rates with superior weld puddle control, subsequently delivering the highest weld quality with far less personnel risk in congested work areas like the ID of the reactor. This allows FCCU operators to utilize the highest quality double compound bevel joint design without the personnel or quality risks associated with manual welding. WSI’s machine HP GTAW™ provides weld deposits with superior volumetric and mechanical properties versus SMAW. The mechanical properties achieve improved ductility which make the finished weld deposit less susceptible to fracture under low cycle fatigue conditions. Simply stated, WSI’s HP GTAWTM process is faster, safer, and better than the currently used conventional welding methods for replacing heads on reactors or regenerators.
WSI – The World Leader in Pressure Equipment Life Extension
Whether the FCCU needs to be repaired emergently or during a planned turnaround, WSI has unparalleled innovative leadership backed by proven results. WSI an extensive portfolio of successfully completed, complex groove weld projects and qualified procedures to handle FCCU unit specific challenges. Find out more about our engineered services offering at WSI.
[1] J, Gary, et al. Petroleum Refining Technology & Economics – 5th Ed.
[2] Hydrocarbon Processing Magazine, July 2017. FCC process history
