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.

Multi-voltage electric actuators use auto-sense circuity to determine the supply voltage and condition it appropriately for internal use. Most multi-voltage actuators are capable of operating on a supply voltage range from 24- 240V AC or DC. Upon receipt of a continuous signal the motor runs until the valve is rotated 90 degrees. When the valve reaches the open or closed position an internal cam on the actuator strikes a limit switch and shuts off the motor. If the electric signal is lost mid-stroke the valve stays in mid-stroke position.
Sometimes upon loss of power it is necessary to have the valve fail to a certain position- ie “fail open” or “fail closed.” Electric actuators accomplish this by a battery backup, or battery safe return (BSR). Upon loss of power the battery backup kicks in and returns the valve to the desired position (i.e open or closed).
Multi-voltage actuators can also be throttled with the installation of additional circuity. This consists of an encoder as well as control and feedback logic. Changing the input signal (usually 4-20mA or 0- 10V) results in a corresponding and proportional change in the position of the valve.
Both of these features- battery safe return (BSR) and digital positioner (DPS)- are available as factory-installed options on Valworx multi-voltage actuators.
Some features that differentiate higher quality multi-voltage actuators include a brushless motor, a thermostatic heater to prevent internal condensation, a manual override mechanism, a weatherproof enclosure (normally IP 67/NEMA 4X or higher) and a dome positioner.

[ Ссылка ]

свернуть