ESD is an acronym for Emergency Shut Down. There are many names used to describe Air Shut Off Valves for diesel engines. Regardless of what they are called, all shutdown valves have one major objective…to stop the airflow into the engine, forcing an engine shutdown. The most popular styles are the guillotine or swing-gate valves and the ESD style butterfly valves.
Within butterfly valves, there are many variations. Most manufacturers use stainless steel, aluminum or a combination of these metals. Some manufacturers use rubber O rings to help create a tight fit between the butterfly flap and the cylinder but rubber tends to harden over time and the seal or fit becomes vulnerable.
ESD strictly uses a metal on metal fit to seal off the airflow. Metal on metal alleviates any concerns about rubber O rings drying out and becoming ineffective over time.
Notice that the ESD Valve does not use a solid shaft running through the valve. Valves with solid shafts use metal screws to attach to the butterfly flap and over time can vibrate loose and be sucked through the engine. The ESD butterfly flap is pressed into the stems allowing for a secure fit without the risk of anything going into the engine.
The ESD revolutionary design uses two half-moon ledges inside the cylinder that act as a seal when the butterfly flap closes against them. Other valves that use a metal on metal fit are subject to contraction and expansion with dramatic changes in temperature. These changes can affect the seal when closure occurs, allowing air to pass through. The ESD Valves designed ledges prevent airflow even with contraction or expansion of the metal.
