From the Blog

En Route to Understanding AWS Codes for Rail Transportation

By PAUL BURYS, program manager at Raul V. Bravo + Associates Inc.

Reprinted with permission: The AWS Welding Journal

The U.S. railroad industry relies heavily on welding to produce transportation equipment that moves the people, products, and commodities that keep America continuously running. Freight is moved by rail, among other means, in the United States. According to a U.S. Department of Transportation report, the rail network accounted for approximately 28% of U.S. freight movement by ton-miles (for more details, visit railroads.dot.gov/rail-network-development/freight-rail-overview). In addition, American Public Transportation Association (APTA) ridership trends (transitapp.com/apta) shared the following information: “During the COVID-19 pandemic, public transit ridership has risen and fallen rapidly . . . These changes make it difficult for transit agencies that rely on monthly or quarterly reporting . . . To tackle this challenge, APTA and Transit have partnered to build a new resource for the entire industry, tracking demand for public transit and publishing estimates of ridership change in real time.” I believe the U.S. economy would simply not function without freight railroads moving commodities and passenger rail providing intercity and intracity transportation.

Over the past few decades, AWS codes and standards have been driving the safety, reliability, and quality of rolling stock manufacturing. From fabricating new locomotives employing EPA Tier4 engines and building light rail vehicles and diesel-electric multiple trainsets for urban transportation to the next generation of Amtrak Acela high-speed trainsets, manufacturers rely on AWS codes, standards, and specifications as the basis of manufacturing.

Rolling Stock Manufacturing

Nearly all aspects of the transportation industry utilize welding where failure could be catastrophic. These welds require high-quality standards to ensure safety, and AWS welding codes impact every portion of the manufacturing process.

Acquiring rolling stock can be time consuming. Initially, requests for proposals are released and manufacturers have an opportunity to meet with the prospective client, review the technical specification, and supply a proposal for construction. Then comes delivery, commissioning, and the warranty of new or rebuilt equipment.

Spotlight on Technical Specification

The technical specification released is the governing document detailing the construction methodology, reliability, safety, and performance specifications of the vehicle. Each technical specification is a unique set of characteristics detailed by the owner or transportation authority and governed by where the vehicle will be used.

For U.S. domestic transportation, the technical specification addresses that the manufacturer must perform the welding process using AWS codes and welding procedures and use qualified welders to perform the work. In addition to any welding requirements, the document details the specific processes that may or may not be used in construction; the materials used for construction; and any brazing, soldering, or joining techniques to be used. This technical specification is also conveyed to the subcontractors manufacturing components for the contract by the terms and conditions of the purchase orders released.

From the heating and cooling system (HVAC) to propulsion and auxiliary power supply modules, including collision elements, underframes, trucks, and high-voltage cabinets, to the seats the engineers and passengers use every day, virtually every system is impacted by AWS standards and practices spanning from initial engineering to final product delivery.

Each transit authority releasing a technical specification for the U.S. market requires the utilization of AWS codes and standards during the manufacture of locomotives and passenger rolling stock. Typically, and based on the material requested for the construction, the technical specification will request the use of AWS structural welding specifications, including AWS D1.1, Structural Welding Code — Steel; D1.3, Structural Welding Code — Sheet Steel; D1.6, Structural Welding Code — Stainless Steel; D1.2, Structural Welding Code — Aluminum, for use in design and fabrication; and D15.1, Railroad Welding Specification for Cars and Locomotives.

Additionally, in the technical specification and based on the application will be references to AWS B2.1, Specification for Welding Procedure and Performance Qualification; D17.2, Specification for Resistance Welding for Aerospace Applications; C1.1, Recommended Practices for Resistance Welding; and the Welding Handbook as well as pertinent ASME sections for pressure vessels.

Manufacturers outside of the United States may be using Japan Industrial Standards or DIN EN standards for welding and welder qualification when manufacturing domestic products in their home country or region, but technical specifications for the manufacture of most rail products for the U.S. market require AWS welding codes and standards be employed. Manufacturers may also provide comparisons of various standards to AWS codes, but the more stringent, and often AWS code, typically prevails for the purposes of the contract.

Materials and Processes Used in Construction

Locomotives, passenger rolling stock, and freight utilize a variety of materials and shapes in the fabrication and manufacturing process, from austenitic stainless steel, AISI 301LN and 304L stainless, and low-alloy high-tensile steel, such as A572, A588, and A606, to Association of American Railroads M-201 castings and aluminum sheet and extrusions. During the manufacture, welding procedures for dissimilar materials are often created and qualified for fusion welding of low-alloy high-tensile to stainless steel. Oftentimes corrosion mitigation must be addressed during manufacture, too, as multiple material types are combined in one vehicle.

The diversity of manufacturing utilized in the construction of locomotives, freight cars, and passenger rolling stock employs a multitude of processes such as gas metal arc welding (GMAW), short circuiting GMAW, shielded metal arc welding, flux cored arc welding, gas tungsten arc welding (GTAW), pulsed GTAW, submerged arc welding, resistance spot welding, resistance seam welding, laser beam welding, friction stir welding, plasma spraying, brazing and soldering, and bonding. Passenger rolling stock manufacturing historically used manual welding, but today we see robots with laser seam tracking and integrated positioners used to produce repetitive high-quality welds in locomotive frames and trucks. Robotics also play an increased role in resistance spot and seam welding of individual structural components for the fabrication of passenger rail car side sheets, roofs, and end sheets. Collision elements and heavy structural components are increasingly welded with automation, but oftentimes small details for joining and sealing roof and side structures still employ GTAW and soldering. Locomotives and heavy/commuter rail contain hundreds of feet of air brake piping and copper piping for use with air brakes as well as HVAC systems that are welded and brazed/soldered manually.

The Significance of AWS D15.1

Part of nearly every U.S. technical specification for the manufacture or remanufacture/overhaul of locomotive/rolling stock construction is AWS D15.1, Railroad Welding Specification for Cars and Locomotives.

AWS D15.1 was developed by the AWS D15 Committee on Railroad Welding to establish minimum standards for the manufacture and maintenance of railroad equipment and provide a comprehensive document for the industry. From D15.1-86 to the current version released in 2019, committee members consistently have strived to provide continuous industry input into the development of the specification from regulatory agencies, new technologies, and other specifications and codes for a comprehensive document covering welding, qualification, and inspection. Today, the document serves as a comprehensive collection of data for use in the railroad industry.

New Draft Document of AWS D15.3

The manufacture of passenger rail vehicles often employs resistance welding of steel and stainless steel to form the structure of the car. Stainless steel was used to manufacture tens of thousands of vehicles from the initial use by Budd Co., St. Louis Car Co., and Pullman-Standard to the current use by U.S. manufacturers for heavy and commuter rail applications. Resistance seam and spot welding, both manual and automated, have provided the strength and safety needed to meet stringent standards. Automated resistance spot welding of side walls allows for an as-welded aesthetic appearance desired by transit authorities. Some manufacturers now employ laser welding to connect the side structure framing to the exterior side wall sheet to minimize exterior weld appearance visible to the riding public. Resistance spot welding of side and center sills utilizes 301L stainless steel and can often be welded as thick as 3 or 4 ply of 0.187 in. (4.7 mm). The AWS D15D Subcommittee on Resistance Welding for Railroad Applications is addressing the need of specific resistance welding requirements found in the manufacture of passenger rail vehicles.

Historically, AWS C1.1, Recommended Practices for Resistance Welding, was used as the basis for resistance welding as were some requirements from AWS D17.2, Specification for Resistance Welding for Aerospace Applications, for qualification and testing. Once released, the new standard, AWS D15.3/D15.3M, Specification for Resistance Welding for Railroad Applications, will address current resistance welding technology for rail car manufacturing, procedures, qualification, testing, and inspection. The standard will also incorporate more-advanced inspection techniques, such as phased array ultrasonic testing, to utilize its full potential for resistance welding inspection.

Inspections Verify Compliance

AWS has promoted the Certified Welding Inspector (CWI) program (aws.org/cwi) throughout the decades, and the rail industry has acknowledged that CWIs are essential for manufacturing verification by incorporating the use of their knowledge and skills as a requirement in the technical specification. CWIs review procedures and qualification submittals for code compliance, verify the procedures are correctly employed by qualified welders, and inspect the final product. They work to address any nonconformities or discrepancies and work with the owner’s engineer and the manufacturer to resolve quality issues. From the initial submittals for vehicle construction to welding documentation reviews at first article inspections at the manufacturer and subcontractor facilities, the welding inspector provides a vital role in manufacturing.

Oftentimes during the initial phases of the manufacturing plan development and submittals, the CWI, welding engineer, and quality department work hand in hand on documentation review from the manufacturer as well as various component manufacturers, comparing submittals with technical specifications and requirements. During the manufacture, the welding inspector, both on the manufacturer’s side as well as the owner’s side, provide independent verification of procedures used during the fabrication process all the way to final inspection of components or the vehicle. CWIs verify the established essential elements and variables are used and the final product conforms to the engineering requirements, codes, standards, and technical specification.

Departing Thoughts

AWS codes and standards have widespread acceptance in the manufacture of freight and passenger rolling stock. Transit authorities, owners, and manufacturers have been incorporating AWS codes for the uniform construction of rail vehicles in the United States and abroad for decades. As the industry is constantly adapting to new products, processes, and technologies, committee members are bringing forward related discussions. As new technologies emerge to create faster and lighter vehicles, AWS codes and standards will continue to provide manufacturing safety in rail rolling stock, where failure is not an option.  WJ   

Fig 1 — An Alaska locomotive passenger train arrives at a platform.

PAUL BURYS (paulburys@rvba.com) is the program manager at Raul V. Bravo + Associates Inc., Reston, Va.; an AWS Senior Certified Welding Inspector; and an ASQ Certified Manager of Quality/Organizational Excellence. He also took the F40PH, truck frames, electrical multiple units, and carshell photos in this article. In addition, he’s a member of the AWS D15 Committee on Railroad Welding, D15D Subcommittee on Resistance Welding for Railroad Applications, and D15A Subcommittee on Cars and Locomotives.

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