Brochure

6 | Fisher
®
Cavitation-Control Technologies
Valve Selection and Design
When service conditions and the process loop design are fixed,
a control valve may have to operate at pressure conditions
that normally result in cavitation. In such instances, source
treatment will be needed.
Clearly, a single product design is not sufficient for the wide
variation of applications across multiple process industries.
Emerson Process Management uses multiple approaches
to address application-specific issues. A large selection of
Fisher cavitation-control technologies is utilized for clean and
dirty services.
Pressure distribution through Fisher Dirty Service Trim
in a NPS 16 easy-e
™
valve body.
Detailed view of the flow pathlines through the trim.
Application experience, knowledge of cavitation science,
and the effect of valve size, type, trim style, geometry,
and materials are all critical to providing reliable solutions.
Standard or custom Fisher control valves with anti-cavitation
trim can be used to control cavitation.
Fisher anti-cavitation trim styles utilize multiple techniques
such as pressure staging, jet formation control, and
flowstream manipulation to control cavitation and prevent its
damaging effects.
Materials of Design
Since the standard materials used in valve bodies are relatively
soft, selection for cavitation resistance must rely on factors
other than hardness. In general, as the chromium and
molybdenum contents increase, the resistance to damage
from cavitation increases. Thus, the chromium-molybdenum
alloy steels have better resistance than the carbon steels,
and stainless steels have an even better resistance than the
chromium-molybdenum alloy steels.
Materials commonly used for cavitating services are R30006/
CoCr-A, nickel-chromium-boron alloys (solid and overlays),
hardened S44004 stainless steel, hardened S17400 stainless
steel, and hardened S41000/S41600 stainless steel.
Matching Applications to Design