If there is one thing a chemical plant has in abundance it is tubes and pipes ranging in size from small to large diameters, and from standard carbon and stainless alloys to highly exotic custom-formulated alloys that require exacting weld procedures. Magnatech has a wide range of automated orbital welding systems. Whether your application calls for welding small diameter, thin wall instrumentation tubing or large diameter, heavy wall high pressure piping, we have an orbital solution.
Many manufacturing processes requires special alloy pipe; whether the need is to provide corrosion resistance or to withstand operation at high temperatures while maintaining ductility and creep strength. Automated orbital welding minimizes and precisely controls heat input, which is often critical to maintain the properties of these special alloys.
Maintenance welding can mean interrupting the operation of a large facility, resulting in profit losses by the hour. The high duty cycle of automated orbital welding minimizes the time required for maintenance operations by cutting weld time and virtually eliminating repairs.
Magnatech has proven solutions for petrochemical component fabrication, construction, and maintenance. We provide technical specialists for field training at the fab shop or job site.
Hydrogen reformers are commonly used in chemical plants and refineries. Natural gas is fed through superheated catalyst tubes to produce pure hydrogen, which is then used in a crude oil upgrading processor or as a feedstock for chemical production. The vertical catalyst tubes are heated in a furnace 1400-200 degrees F (760 - 1100 degrees C). The inlet and outlet pipes (headers) are located outside the furnaces.
Because of the expansion of the catalyst tubes, which can grow several inches in length, they must be connected to the headers with expansion loops, commonly called "pigtails" due to their geometry. Pigtails are commonly fabricated of austenitic nickel-chromium-based superalloys such as Inconel™ alloy 625, due to improved ductility and ability to withstand cyclical stresses, maintain creep strength, and avoid embrittlement. The pigtails are commonly welded to "sockolets", requiring a fillet weld. Mechanized welding is ideal to minimize heat input. However, minimal straight lengths preclude the use of many orbital welding systems.
John W. Page Welding Consulting Ltd. a specialty contractor based in Alberta, Canada, uses D-Heads to make 3-pass fillet welds on the sockolets. The compact D-Head fits within the minimal axial straight length of the pigtails. Heat input is precisely controlled by the computerized Pipemaster system.
Kubota Materials Canada Corporation manufacturers special heat resistant alloys which are centrifugally cast as tubes and fittings, in sizes ranging from 2.75 (70mm) to 14” (356mm) in diameter. These high carbon austenitic stainless alloys are used for fired heaters in the petrochemical industry, with typical service temperatures of 1400-2000 degrees (760 -1100 deg. C). Customers use these specialized materials for manufacturing plastics such as polyethylene from feedstocks. Frequently Kubota will be asked to fabricate tube lengths longer then the casting process allows, or to fabricate subassemblies such as U tubes and W tubes. The welds must all be made to meet B 31.3, sometimes with tight radial clearances between tubes.
Kubota uses multiple Magnatech systems to produce the x-ray quality GTAW welds their customers require. The compact radial clearance of the D-Heads allows multipass welds to be made in tight clearances which would make manual welding difficult.
The largest North American petrochemical facility must periodically shut down production trains for maintenance. One such operation is the replacement of steam cracking furnace tubes used in the production of ethylene.
The tubes used for furnace applications, such as steam crackers, have typical service temperatures ranging from 1400˚ to 2000˚ (760˚C - 1100˚C). To withstand these high service temperatures, a number of high-carbon austenitic stainless steel alloys are used, usually in the form of centrifugal cast tubes. Some common alloys for this application are HK-40 (0.4C-25Cr-20Ni) and HP-45 (0.4C-25Cr-35Ni). These alloys are specifically formulated for desirable properties, such as creep strength, but they pose significant welding problems.
Tube replacement requires large numbers of skilled and qualified welders for a short duration. A specific outage required 198 welds to be made on 3" (89mm), 1/2" (13mm) wall furnace tubes in a 30-day period. Past experience indicated that to do the task manually in the set time frame would require 32 welders. The problem was a shortage of welders in the area with the necessary skills. Another important factor was the time and cost associated with testing potential welders. Testing costs the company $500 per welder and in the past only one in four welders proved qualified. The application consisted of welding new tubes to new Y-fittings inside the confines of the furnace. The Y-fittings dictate a clearance between adjacent tubes of only 2-1/4" (57mm).
The company purchased the compact D-Head which only requires 2" (50mm) of radial clearance. Using multiple Pipemaster systems, the outage period was reduced by half. No defects were observed in the welds, and no costly cut-outs and rewelding.
Inspection of a large 50' (15m) diameter pressure vessel in a Canadian petrochemical facility revealed corrosion of 0.5" (13mm) beyond acceptable limits. Following excavation, the walls were mapped and the depth of weld overlay determined for each grid. Weld buildup had to meet ASME code standards and inspection criteria. Hundreds of kilograms of wire had to be deposited during the outage in a confined area as quickly as possible. A preheat requirement of 150˚C (300˚F) made for an extremely hot working environment for manual welders.
An FCAW weld procedure was qualified and Boilermakers trained in the use of the Pipeliner. Magnatech's Flx-Track was attached to the ID weld using magnets which allowed track installation and repositioning in minutes. The optional axial slide torch bracket combined with the long electronic steering stroke minimized track repositioning. By allowing the welder to remotely control the welding process away from the preheated surface, the job was done in record time.