Fisher Cavitation-Control Technologies ® Solutions to Cavitation Problems
| Fisher® Cavitation-Control Technologies Control Valve Cavitation Cavitation is a concern for plant operators and maintenance personnel because it can reduce plant availability and profitability. Cavitation not only decreases flow capability through control valves, but it may also cause material damage, excessive noise, and excessive vibration. A wide range of Fisher® cavitation-control technologies are available for clean and dirty service.
Fisher® Cavitation-Control Technologies | 3 Science of Cavitation Cavitation and Choked Flow Q, GPM Cavitation is a purely liquid flow phenomena—gases cannot cavitate. Choked flow may occur as a result of cavitation. Choked flow occurs when the normal relationship between flow and increased pressure drop is broken. With choked flow, an increase in pressure drop by decreasing the downstream pressure does not result in more flow through the restriction.
| Fisher® Cavitation-Control Technologies Effects of Damage Factors Affecting Cavitation Damage Material Damage Cavitation doesn’t always cause damage when it occurs. The extent of cavitation damage is a function of the following factors: Physical damage to a control valve due to uncontrolled cavitation is a concern because of the high maintenance cost, inconvenience, unpredictability, and unplanned downtime. Damage can consist of a mechanical and selective chemical attack on the material surface.
Fisher® Cavitation-Control Technologies | 5 Emerson Innovation Excessive Noise and Vibration Fisher® Technology Development Cavitation can cause unacceptable noise and vibration. Although the noise associated with a cavitating liquid can be quite high, it is usually a secondary concern when compared to the material damage that can exist. Cavitation is frequently described as sounding like gravel in a pipe, but the character of cavitation noise can vary widely.
| Fisher® Cavitation-Control Technologies Matching Applications to Design 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.
Fisher® Cavitation-Control Technologies | 7 Plant Designs that Prevent Cavitation Cavitation Coefficient Process Loop Design The Fisher cavitation coefficient indicates the potential for damaging cavitation in a control valve. It is dependent on several factors: Flow conditions that will produce damaging cavitation can often be avoided at the design phase of a project by giving proper consideration to service conditions and the process loop design.
| Fisher® Cavitation-Control Technologies Are You Willing to Take the Risk? FIELDVUE™ Performance Diagnostics Reliable Cavitation Control Reliability is a key requirement for all process facilities. FIELDVUE™ digital valve controllers installed on Fisher cavitation-control valves protect your process by giving a view of operating characteristics such as supply pressure, control signal, friction, and seat load.
Fisher® Cavitation-Control Technologies | 9 Cavitrol™ III trim is used for cavitating liquid applications in various globe and angle valve bodies. Cavitrol™ III trim can effectively eliminate cavitation damage. The cage contains a multitude of specially shaped holes; the hole shape reduces fluid turbulence. In addition, the holes are radially aligned to flow from one restriction to another. This action is pressure staging, dividing the total drop into smaller increments.
| Fisher® Cavitation-Control Technologies GX Valve with Cavitrol™ III Trim lowers hydrodynamic noise and vibration by utilizing a proprietary drilled-hole shape and spacing. The special hole technology and flowdown design reduces and isolates cavitation to prevent damage. Cavitrol III technology is used without altering the integral GX bonnet design. n 1-stage trim n Globe body n ASME Class 150, 300 n DN 25, 40, and 50 (NPS 1, 1½, and 2) n Flow-down design n 27.
Fisher® Cavitation-Control Technologies | 11 Cavitrol™ III Micro-Flat Trim is a combination of distinct technologies. The cage, plug, and seat ring are designed and manufactured as a unit. The benefit is cavitation control for high pressure drops at very low flow rates. The trim package also incorporates a protected seat for long shutoff life.
| Fisher® Cavitation-Control Technologies Micro-Flat Trim utilizes a cavitation-control mechanism consisting of special flow paths to prevent impingement on critical trim components. Micro-Flat trim is intended for low-flow applications in the flow-down direction only. The trim design does not eliminate cavitation but controls where it occurs to minimize damage. Micro-Flat trim features a protected seat design to maximize seat life in cavitating environments.
Fisher® Cavitation-Control Technologies | 13 NotchFlo™ DST Control Valve utilizes a multi-stage, axial flow path where fluid flow is parallel to the axis of the plug and cage. Pressure reduction occurs throughout the length of the plug. Individual stages are not exposed to the full pressure differential. NotchFlo DST trim uses a series of flow restrictions and expansions to control the pressure drop of the fluid.
| Fisher® Cavitation-Control Technologies Dirty Service Trim (DST) provides cavitation-control for applications with entrained particulate that could potentially plug the flow passages or cause severe erosion damage to conventional anti-cavitation trim. The DST design uses a combined axial and radial flow path that features large openings allowing particulate up to 19 mm (¾-inch) in diameter to pass through the valve.
Fisher® Cavitation-Control Technologies | 15 CAV4 Control Valve with Cavitrol™ IV trim has an expanding flow area design. Each of the Cavitrol IV trim stages has a successively larger flow area. The result is very efficient operation because more than 90 percent of the overall pressure drop is taken in the initial stages where there is little danger of cavity formation. Consequently, a relatively low inlet pressure to the final stage is achieved.
| Fisher® Cavitation-Control Technologies Dirty Service Trim for Outgassing (DST-G) is a multi-stage control valve trim design. It is used in services where the fluid has dissolved gases that are released from solution due to a reduction in pressure. The fluid may also contain entrained particulate. DST-G is mainly used in refining, petrochemical, and oil and gas applications. Outgassing can cause two types of damage. One type is cavitation, as discussed previously.
Fisher® Cavitation-Control Technologies | 17 461 Sweep-Flo Angle Valve is self cleaning with an expanded outlet. It is typically used in the chemical and hydrocarbon industries where cavitation control is required for residual oils that experience coking, have high particulate content and viscosity, and may outgas. This cavitation-control valve construction consists of carefully designed flow paths that control impingement, and material selections aimed at maximizing corrosion and erosion resistance.
| Fisher® Cavitation-Control Technologies Vee-Ball™ Control Valve with Rotary Attenuator combines the efficiency of a rotary valve, with the energy absorbing capability of special trim, to provide improved performance for demanding applications. The Fisher rotary attenuator design can be utilized in liquid service to reduce cavitation and vibration effects. The Vee-Ball with rotary attenuator has high application versatility and provides long service life.
Fisher® Cavitation-Control Technologies | 19 V260B Ball Valve with Hydrodome Attenuator provides improved performance for demanding applications such as pump bypass and pipeline take-off. The attenuator trim is designed for liquid service to help eliminate or reduce cavitation and associated pipeline noise and vibration. The V260B is a full bore ball valve designed with features for optimized pressure, flow, and process control.
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