Valworx Explosion Proof Butterfly Valves Wafer Style - Positioner

Butterfly valves utilize a disc to block or enable fluid flow. The disc is connected to a stem which in turn is connected to a handle (for manual operation) or a motor for automatic use.
The most common type of butterfly valve is the concentric, resilient seated. Sealing is accomplished by the disc compressing against an elastomeric main seal. Construction and materials are relatively low cost, and the design is scalable. However, since sealing relies on compressing an elastomer, temperature and pressure capability is usually limited to around 150 psi.
Concentric butterfly valves are available in ductile iron, cast iron or PVC construction. Ductile iron has better corrosion resistance and lower temperature capability while cast iron costs less. PVC is usually used for potable water or corrosive applications.
Higher performance butterfly valves use geometric offsets to seat the disc directly against the valve body and axially compress the seal. This type of design is more difficult to manufacture and costs more than concentric butterfly valves but can withstand higher temperatures and pressures.
Some features that differentiate higher quality butterfly valves include a stainless steel disc, higher quality bearing materials (PTFE or graphite), and ductile iron (vs cast iron) valve body for concentric valves.
Explosion proof actuators are for use in potentially flammable environments. They are specially designed so they will not act as an ignition source and are certified as such. In practice this means not only will an explosion proof actuator suppress any spark or ignition source, but the enclosure must also be able to contain an internal explosion with no flame or spark escaping.
In the US the most common certification is the UL Class/Division standard, where Class refers to the type of explosion hazard (gaseous (Class I) or dust (Class II)) and Division refers to whether or not the hazard is normally present (Div I) or not normally present (Div II).
The EU generally uses the ATEX standard which classifies application by environment (type G for gases and type D for dusts) and zones which roughly correspond to the UL system. In addition, there is a third standard, IECEx, which is intended to be for global use. It is an industry standard (as opposed to a government one) and is quite similar to ATEX. However, unlike ATEX, EU countries are not required to adopt it.
Explosion proof design techniques include circular field joints to better withstand explosion pressures, long faying surfaces to suppress flame travel and internal compartmentalization to ensure explosion containment.
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