Zero cavitation in energy dissipation applications

Cavitation is fully avoided by means of multi-stage pressure reduction trim technology.

In the industries we serve there are various applications where high pumping pressures or hydraulic heads need to be reduced down to atmospheric pressure. Typically Cooling or Fire Water Overboard Dump, Pressure Equalization, Turbine Bypass etc. These applications are prone to cavitate which will lead to choking of flow, vibrations, high noise levels and damage to the valve and downstream piping.  

The risk of cavitation can be addressed in various ways dependent on the location, valve size, valve style /   inherent capacity and pressure conditions. On offshore platforms it is common to provide some static head downstream of the pressure control valve by means of a vertical elbow. In hydropower plants – for the same reason – preferably conventional sleeve or plunger valves shall have submerged discharges. Commercial literature and specifications mention “cavitation control”, meaning; the water jets are supposed to strike each other in the centre of the valve and away from metallic surfaces in an effort to prevent cavitation damage. In addition, venting pipes, air valves or a jump in downstream pipe size are required to reduce the impact of cavitation.

The above may be sufficient for mild applications, however, for moderate to high pressures and effective energy dissipation, cutting-edge technology is required. Without any secondary measures, Mokveld axial control valves completely avoid cavitation with a series of anti-cavitation trims in which the pressure is reduced over a number of small pressure reduction steps, avoiding formation of cavitation bubbles, as shown in the graph below. The trim will be customized to match the specific process conditions and hydraulic profile, and can consist of multiple trim sections with different Kc or Sigma cavitation index values.

Mokveld multi-stage pressure reduction trim technology

Mokveld anti-cavitation trim profile

Changing Hydropower and Water Markets

Rapid urbanization, climate change, increased customer demands and emerging digital technologies require 24/7 availability of hydropower and water supply. In recent history the main selection criterion for equipment to hydropower plants and water transmission systems was capital expenditure (initial cost). Repeated failures of the equipment however, led to dangerous scenarios at hydropower plants and reliability of water supply to industries and households was insufficient.

Critical applications call for custom made quality valves with 30 – 50 years product lifetime. With Mokveld engineered valve solutions, interconnection vaults in water transmission systems are simplified and reduced in size and cost. The number of valves and cost of operations (maintenance) will be reduced considerably; Mokveld provides single valve solutions for accurate control of low and high flow rates, bi-directional pressure and/or flow control and energy dissipation without cavitation.

Mokveld Axial Control Valve with anti-cavitation trim

Features and benefits of Mokveld axial control valves for hydropower and water applications

Direct features and benefits

  • Cavitation and its negative effects (vibrations, high noise level, damage to valve and downstream piping) is fully avoided by means of multi-stage pressure reduction trim technology.
  • No venting pipe, air valves or jump in pipe size is required to reduce the impact of cavitation.
  • Custom designed trim to suit the specific hydraulic profile of the system.
  • Operation of the control valve is not susceptible to debris in the medium: low maintenance / downtime.
  • Highly accurate control, also at initial opening. Minimum controllable flowrate is a factor 10 – 20 lower compared to conventional solutions.
  • Very low actuating force; small, low power actuators can be used, no gearbox required.
  • Actuator is positioned on top of the valve which means a smaller installation footprint.
  • Suitable for bi-directional flow or pressure control.
  • Reliable bubble tight shut-off

Indirect benefits

  • Smaller facilities: in addition to compact face-to-face valve dimensions, a straight length of 2x DN up- and downstream of the valve is sufficient for stable operation of the system.
  • Considerable cost savings are possible on the design of the downstream installation since secondary measures are not required or can be downgraded (tail water / stilling basin, additional energy dissipating structure, aeration, baffle plates, etc.).


More information

Mokveld engineering assistance

Mokveld engineers can provide support in an early phase of the project. With the correct parameters we size and select the right anti-cavitation trim tailored to suit your specific hydraulic system profile.