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Letdown Systems

Superior severe service valves for use in single-state and multi-stage letdown systems

In most process plants there are single- or multi-stage letdown systems between the furnace / reactor and the final end product. These systems reduce the pressure of the flow while maintaining the integrity of the media. By reducing the pressure, energy is released in several stages to stabilize flow before arriving downstream to the required product conditions or extrusion process.

Both control and isolation valves can be used in letdown systems depending upon media and process conditions. While reducing high pressures and / or velocities, these valves can be subject to not only turbulence, vibration and noise, but abrasion, corrosion and viscous sludge. Because these applications endure rough wear, routine maintenance and inspection have traditionally been a major concern with linear control and isolation valves. Quarter-turn severe service ball valves and rotary control trims have proven performances in these rigorous applications.

Also associated around the separators are essential control valves. Often these valves are utilized in the leveling and de-pressurization systems that are connected to the separators. MOGAS control valves with FlexStream® rotary control technology usually have an overall footprint that is considerably smaller than the traditional linear control valve options, saving costly design space for extra piping.


Letdown System Process Flow Diagram
  1. Primary Letdown Pressure Control
  2. Manual Isolation Pressure Control
  3. Reactor Effluent Emergency Block
  4. Secondary Letdown Pressure Control
  5. Manual Isolation Pressure Control
  6. Secondary Pressure Control Emergency Block
  7. Product Emergency Block