Flashing Solutions – Angle Control Valves
Control valves – used in applications involving liquids in high pressure or high pressure drop conditions – are highly susceptible to damage from flashing or cavitation.
Flashing occurs in the liquid flow when the internal pressure of the liquid falls below the vapour pressure and remains below it. During this phase vapour bubbles form and flow with the liquid downstream at increased velocities causing erosion to valves and piping.
Whilst the valve outlet pressure and vapour pressure are not directly controlled by the valve, the best approach for flashing medium is to choose control valves that minimise its effects.
SchuF Anti flashing control valve features:
- Particle Impact Prevention The SchuF Angle control valve Model 74BS is an accelerating flow angle body design with flow to open characteristics. Installed in a tank or vessel the outward opening disc moves any potential flashing to the exit seating area of the valve. Flashing then takes place outside of the valve and the kinetic energy is dissipated into a special tank or vessel.
- Velocity Reduction Valves with expanded flow areas downstream of the vena contracta are beneficial as the erosive velocity is reduced. SchuF Angle Control Valves – either as a flow to open “X-Flash”, or flow to close “ToughFlash” design – can be provided with an expanding choke tube or customised outlet. This allows pressure to increase and minimizes velocity.
- Hardened Materials & Surfaces Correct selection of both the body and trim material can go a long way to reducing the effects of flashing and cavitation. The synergetic effects of erosion and corrosion in flashing water applications can be minimised by selecting a low alloy steel. For more complex flashing media, a wide choice of hard trim materials from ceramic to tungsten carbide, stelliting or surface coatings are available to protect the valve.