Difference between Cavitation and Flashing of a Valve?

Discuss about Difference between Cavitation and Flashing of a Valve.

Requirements for occurrence of cavitation and Requirements for occurrence of Flashing :

  • Cavitation in a control valve:

    • Occurs only in liquid service.
    • Is the two-stage process of vaporization and condensation of a liquid.
    • Downstream the valve (orifice area), there is an increase in velocity because of a decrease in pressure. This takes place in the vena contracta.
    • If the pressure in this vena contracta is lower then the vapor pressure of the fluid, vaporization (boiling: also known as flashing) occurs.
    • Vapor bubbles go downstream where the velocity decrease, and the pressure recovers.
    • The vapor bubbles then collapse or implode and can cause severe mechanical damage to valves and piping.
    • Cavitation can cause a Choked Flow (critical flow) condition.