Thermally activated Emergency Isolation Valves (EIVs) are critical components in refinery, terminal and distribution safety systems. Thermal activated shutoffs work like fuses in the piping that carries extracted fuels. When a fire occurs, the fuel flow is shut down, preventing the fuel from feeding the fire.
Historically, thermal shut-offs relied on fusible links made of metal alloy. Once the alloy melts, a spring-armed plug is released, which stops the flow of fuel. The problem with the fusible link design is that once triggered, the unit needs to be replaced and, likewise, cannot be field tested.
However, new technology for thermal shutoffs uses a Nitinol shape memory alloy system, originally developed for NASA space station applications. Nitonol’s shape memory effect changes certain metal alloys from one shape to another with temperature changes—a direct result of a transformation of the alloy’s crystal structure. The shape memory element senses the ambient temperature and, through a phase induction change, rapidly produces the force and motion to operate the shutoff.
When the thermal shutoff senses temperatures above the shape memory alloy’s actuation level, the shape memory element simultaneously vents pneumatic actuator air pressure and closes upstream supply pressure. A manual reset allows routine performance testing for safety maintenance programs.