Flashing occurs when the pressure of a fluid passing through a valve is lower than the same substance’s vapor pressure. This causes the fluid to boil — otherwise known as “flashing.” “By reducing flow capacity and eroding the valve itself, flashing causes unplanned maintenance, reduced reliability and critical safety risks,” says Mike Semens-Flanagan, Global Engineering Director at IMI Critical Engineering (Birmingham, U.K.; www.imi-critical.com). The company has therefore developed a new valve enhancement technology called EroSolve Flashing, which aims to protect angle and globe valves against leakage and other issues caused by steam flashing. The EroSolve solution prevents low-travel operation and moves the fluid-path’s vena contracta downstream of the seating area of the valve, effectively protecting it against any damage. It also gradually reduces pressure through the introduction of special multi-path, right-angle-turned flow passages that prevent sudden acceleration of fluid velocity.
The EroSolve solution adopted special design concepts to specifically prevent damage by flashing. This technology has been developed not for general purpose, but specifically for flashing services. (Source: IMI Critical Engineering)
In angle valves, hardened trim material and an enhanced seat-plug design move flashing away from vital trim parts, and enable the valve to withstand severe conditions. The EroSolve variant designed for globe valves employs a seat basket that creates backpressure to reduce downstream velocity and pressure drop to avoid damage to the valve body — without requiring any piping modifications.
According to the company, this is the first dedicated and successfully demonstrated valve technology on the market aimed at mitigating problems related to flashing. EroSolve Flashing has been demonstrated in a combined-cycle power plant that had experienced erosion in its heat-recovery steam generators (HSRGs). Following the installation of valves equipped with EroSolve technology, there was no component damage reported after a year. In another demonstration, EroSolve valves were installed at a chemical plant in South Korea to replace boiler blowdown valves whose trim had not been specified for flashing conditions. The new valves are expected to last 2 to 4 times longer than the previous valves, resulting in a significantly lower cost of ownership, says the company.