Reducing Pressure across Valves in Stages - Emerson Automation Experts

Reducing Pressure across Valves in Stages

In the third video in cavitation reduction series, Cavitation Mitigation Part 3 (2:52), Emerson’s Melissa Niesen describes how pressure reductions can be done in stages to avoid cavitating conditions in the liquid flow through a pipe.

Melissa explains how Cavitrol III trims for Fisher globe and angle valve bodies can reduce the pressure in stages to avoid cavitation. From the Cavitrol III Trims data sheet:

One-stage trims are normally used where the pressure drop is below 99 bar (1440 psi); two- and three-stage trims are normally used where the pressure drop is between 99 and 207 bar (1440 and 3000 psi). The Cavitrol III trims are frequently used in pump recirculation and startup systems in the power, process, oil production, chemical refining, and other industries.

A little over 1-minute into the video, Melissa shows the difference between a high-pressure valve with an equal percentage trim versus one with a Cavitrol III 2-stage trim. The video shows a big difference in the amount of noise and vibration mitigated by the 2-stage trim.

You can join with fellow valve experts and members of Emerson’s Fisher Valves & Instruments team in the Valves track of the Emerson Exchange 365 community.


  1. hasan jafari says:

    We have a control valve for dif. Pressure about 1200 psi and 67 m3/h
    Can you help us?

  2. Jim Cahill says:

    Hi Hasan, Thanks for your comment and yes we can help you. Send me an email at with your company and location and I’ll connect you with one of our control valve specialists… thanks!

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