Fisher micro trims fall into two basic application categories: "Standard Service" and "Severe Service".
Standard Service Micro Trims
These are Plug-Characterized trims. Flow characterization is controlled by the plug.
(A)— Micro-Flow—Ultra low flow control. Linear flow characteristic. Plug-characterized, port-guided. Gas and liquid applications.
(B)— Micro-Flute—Low flow control. Bridges the gap between Micro-Flow and Micro-Form trims. Equal Percent flow characteristic. Plug-characterized, port-guided. Gas and liquid applications.
(C)— Micro-Form—Equal percent, contoured plug used in a variety of valve designs.
(D)— Micro-Flat/Form—General service gas or liquid applications where high rangeability (>200:1) is required.
Severe Service Micro Trims
Cavitation Isolation Trim—controls where cavitation occurs in the valve to minimize trim damage. Does not prevent formation of cavitation.
Cavitation Elimination Trim—trim design eliminates the effects of cavitation.
(E)— Micro-Flat Cavitation Trim—Cavitation isolation trim. Low Cv, is intended for use in angle valves only. Not recommended for use in globe valves. (F)— Multi-Stage Micro-Flat—Plug/Cage design with a series of flats on a common stem. High ∆P's and Cv's down to approximately 0.01. This is a cavitation elimination trim for use on liquids. Not intended for gas service. (G)— CAV III Micro-Flat—Cage-guided cavitation elimination trim. This trim is a CAV III multi-stage trim with the addition of a Micro-Flat style plug to provide staged performance at low flows. Allows CAV III staged cavitation control as low as Cv = 0.05.
