Tuesday, February 16, 2016

Specialized Gate Valve For Control Applications

Sliding gate process control valve
Sliding Gate
Process Control Valve
Schubert & Salzer
Gate valves are widely employed throughout the industrial process control field to start and stop the flow of a wide range of fluids and slurries. The common construction of a gate valve, with a solid wedge or disc that moves perpendicularly to the direction of fluid flow, tends to limit the application of this valve type to processes where fully open or fully closed are the desired valve positions. The comparatively large travel range of the wedge from open to closed, combined with a need to close the valve slowly to avoid hammering, saddles the common gate valve with a slow operating speed. Holding the gate at a partially open position has potential to induce vibration in the fluid, resulting in noise and possible negative impact on the fluid transport system. For this reason, common gate valves are generally not used in control applications requiring flow modulation .

The limiting factors just described can be mitigated or eliminated with a modification to the gate configuration. Instead of a solid gate, two plates with matching orifice matrices are mounted in the fluid path. One plate is fixed and the other is moved by the valve actuator, sliding through a motion range that expands flow area by increasingly matching the orifice openings on the two plates. This gate valve design is often called a sliding gate valve and it is easily recognizable through its pattern of slotted openings on the gate.

Some notable features of the sliding gate valve:

  • Straight through flow path with little turbulence.
  • Flow is broken into multiple small streams by the orifice pattern, reducing the impact of the flow force on the valve trim.
  • Suitable for fluid control operation, not just fully open or closed.
  • Travel distance and time from fully open to fully closed is significantly reduced, when compared to common gate valve.
  • Quieter operation.
  • Long service life.
  • Suitable for lower viscosity, generally clean, fluids
Every valve design has applications where it will tower over others in terms of overall performance. The variable orifice control valve (sliding gate valve) will prove to be the best choice for certain applications. Share your fluid process control challenges with an industrial control specialist. Combining your process expertise with their product application knowledge is a sure way to produce positive outcomes.