Photo: U.S. Coast Guard photo by Chief Petty Officer Angie Vallier

Crompion International replies to inquiries about how new stainless grades can safeguard people as well as product moving by rail

May 2015 - In the April Issue of Modern Metals, our story "Silver Bullet" caught the attention of Chicago-based mechanical engineer John Fischer. His follow-up questions allowed us to dig a little deeper into the problem-solving potential of a new cost-effective, high-performing stainless steel. This solution from the metallurgy side of the tracks is one the railcar industry might overlook despite numerous derailments of trains carrying crude oil products across North America, some involving fatalities.

These questions are especially timely in light of the most recent oil train derailment May 6 in a North Dakota town. Ten tankcars caught fire, forcing residents to evacuate. The same week, federal rail authorities rolled out long-awaited safety standards that focus on stronger tankcars and electronic braking systems.

Q: The article mentions that during a thermal event, Crompion International’s material offers greater heat resistance than other materials but isn’t it only the released crude oil that's burning and not what's still encapsulated in the tankcar?

A: One critical step toward minimizing the severity of a derailment involving crude oil or ethanol tankcars is to limit the number of cars involved. If spilled or released flammable liquids ignite, it is very important to keep nearby cars from overheating. Overheated cars can detonate and spread devastation beyond that of the initial accident with secondary explosions, fires and airborne metal projectiles. Because next-generation stainless steels have significantly lower thermal conductivity values, they can prolong heating periods over that of the carbon steels commonly used in tankcars. That affords first responders extra time to arrive on scene and douse cars with water and/or chemical foam to keep them cooler and prevent additional ignition.  

Q: How much different can the heat transfer characteristics be between the carbon steels in standard use today and Crompion’s stainless steel? 

A: When compared to the traditional grades of carbon steels currently used to construct tankcars, next-generation Cromgard stainless steels have 60 percent lower thermal conductivity value.

Q: Please reference the various types of crude oil being extracted as some are more volatile than others. How do Crompion’s grades of stainless steel for tankcar applications address the different levels of combustibility of crude oil?

A: It isn’t just a question of combustibility but of taking into account other issues such as corrosion resistance. The oils and liquids extracted in the U.S. and Canada during exploration and recovery operations have variable characteristics—some of which can originate within small geographical areas. These include viscosity, flammability, volatility and the chemical make-up of the liquids themselves. The chemical mix may contain different levels of sulfur and other corrosive elements. Crompion advocates the adoption of next-generation stainless steels for U.S. and Canadian tankcar standards to give shippers an optional material that is high strength, corrosion resistant and possesses a lower thermal conductivity value. The stainless grades currently approved for tankcars are Types 304/304L and 316/316L. These materials, while proven in other applications for 100 years, are outdated for tankcar applications because they do not guarantee the performance and economic advantages of modern stainless.

Q: The article mentions the slow adoption of materials in the rail industry. Is this from a commercial or a regulatory standpoint? Please expand upon the obstacles.

A: Cromgard has been actively engaged over the last several years in an educational and awareness campaign about the existence and availability of newer grades of stainless that are already recognized and approved by standards organizations like ASTM and API. Stainless steel has made inroads on applications for pipelines, freight railcars, offshore oil rigs and static storage tanks but, because the railroad industry and the federal government are such large organizations, related research and proposed improvements take time. We’re taking part in a comprehensive review of tankcar construction and safe transportation of flammable liquids to further educate the industry and the government, and secure approvals to offer these materials as a safer, more cost-effective option for future tankcar designs and standards.

For additional details, contact Ken Grantham, vice president, Crompion International, at 225/343-4219,  sales@crompion.com.