Proper Selection Of Railcar Emergency Shutdown System

Leaky faucets in the kitchen sink are one thing.  A leak on a HazMat rail car filled with chlorine, sulfur dioxide, anhydrous hydrogen chloride, anhydrous ammonia, or methyl chloride is quite another.

Leaky faucets in the kitchen sink are one thing.  A leak on a HazMat rail car filled with chlorine, sulfur dioxide, anhydrous hydrogen chloride, anhydrous ammonia, or methyl chloride is quite another. 

A recent headline, “Rail Car Gas Leak Forces Evacuation,” underscores the danger of toxic chemicals such as hydrochloric acid that can burn people’s skin, eyes, and lungs when an uncontrolled leak occurs. The accident in Salt Lake City in early March sent plumes of the toxic gas into the air, forcing the evacuation of more than 6,000 people in the surrounding area. Such events, while rare, can happen. They are, however, highly dangerous to the community, people in the workplace, customers,  and can be challenging to operators charged with their management and prevention. In the case of rail tank cars carrying liquid chlorine, for example, it can be difficult and unsafe for operators to isolate and reach equipment leaks that can in turn cause serious harm. Traditional emergency shutdown systems require an operator to climb a ladder and/or cross an elevated gangway to reach the leak source on top of the car. With field-engineered or automated ball valve shutdown systems typically located upstream of the chemical tank car, reliability of valves and attendant safety of operators are often major issues.

Proper selection of an emergency shutdown system is vital, not only for its optimal performance, but also for that of the equipment and tasks with which it interfaces. Considerations for selecting such HazMat systems focus on several key considerations: Function, durability, safety, and service among them.

Newer technology today includes a remote valve actuator (RVA) system used on railroad tank cars carrying toxic chemicals such as liquid chlorine used for water treatment. The RVA automatically shuts down chemical flow right at the isolation valve on the railcar, versus farther downstream along the piping system without compromising human safety. Consisting of an air-driven actuator, and a manifold, the RVA system functions at the transfer valve on the tank car, as opposed to working downstream on vulnerable piping and hoses (as does the field-engineered automated ball valve) to eliminate potential leaks.

Typical chlorine unloading rack for railcars incorporating Midland valve actuator system.

The RVA system works essentially in either one or two ways. In the event that the remote system detects a leak, it triggers an actuator to automatically close the valve. Or if the operator detects a leak or wants to shut down the system for any reason, he can activate the system manually from where he is standing on the ground or loading rack, to trip the system that shuts down the transfer valves. An open and closed system verifies that it can operate each valve to ensure the integrity of the system. In addition to a shutdown plan, audible alarms at each loading point allow for audible warnings to notify employees in the vicinity of an incident. Such elements are part of a well designed contingency plan that includes daily testing as standard operating procedure.

Activation of the system should be safe, easy, and convenient for the operator. A push of a button is easier than physically having to gain access to the tank car, adjust torque correctly, and turn a valve in person, all while wearing protective equipment and breathing apparatus. The need for no human access to the car provides for protection against toxic chemicals.

Ease of installation and maintenance is also an important consideration.  So, too, are flexibility and compatibility with the wide range of the overall system’s valves and sensors, as well as that of the equipment of diverse suppliers and manufacturers. Selecting a remote system also requires taking materials of construction into consideration. All components exposed to varying weather conditions need to be durable and resilient. Parts made of stainless steel are longer lasting than those made of carbon steel and add to durability.  Command central in the control panel requires a durable enclosure for protection against hot and cold temperatures as well as wind, rain, and snow.

For sure, HazMat is never to be taken lightly. It can indeed be risky business. Proper selection of emergency shutoff systems, however, is one key to ensuring human safety.

More in Operations