Control Valve Cavitation Solutions

Cavitation is the formation of vapor spaces (bubbles) in the control valve cavity resulting from a rapid change in pressure. When the bubbles move downstream and are exposed to a larger cross-sectional area, velocity decreases and pressure increases, the surrounding higher pressure causes the lower pressure bubble to implode, which causes shockwaves. These shockwaves can cause metal fatigue and cause excessive wear on the internals of the valve. As the bubbles collapse, they make a discernible sound with accompanying vibration, and the damage to a valve can happen quickly (weeks or months).

Cavitation is very destructive and may wear out the trim and body parts of the valve in a short time. Using hard internal materials provides a slight improvement but costs more.

Flowserve Valtek Cavitation Solution Control Valves prevent cavitation damage and minimize hydrodynamic noise even under the most severe liquid applications. Their unique, patented designs eliminate cavitation damage and provide straightforward maintenance and a long life even with demanding applications. 

For more information about Flowserve Valtek Control Valves in Florida, contact Instrument Specialties by calling +1 407.324.7800  or visiting https://isisales.com.

The Flowserve Valtek FlowTop GS General Service Control Valve

The Valtek FlowTop GS control valve (types V746 and V748) improves the reliability and uptime of production processes while minimizing operating and maintenance costs. Designed for general service applications, the FlowTop GS globe valve is a competitively priced, fully integrated valve-actuator-instrumentation package for continuous process flow loop control throughout the plant.

For more information, and to download a PDF cutsheet, visit this Instrument Specialties webpage.

The Flowserve Logix 3200 Positioner: Calibration Procedure

This video describes the calibration procedure for the Flowserve Logix 3200 positioner.

The Flowserve Logix 3200 Series Digital Positioner includes:

• Two versions: Basic & Advanced (Advanced includes pressure sensors to measure actuator pressure)
• HART Command 1, 3, 9, 33 & 48
• Burst Mode available to continuously transmit
• Position command analog loop current
• Final value of command after characterization
• Supply pressure (advanced), Temperature (basic)
• Stem position in percent
• Onboard temperature sensor to measure local positioner ambient
• Stroke speed limiter (configurable through HART)
• Stainless steel version available
• Enhanced Device Description for advanced signature diagnostics
• Step test, friction test, HRL, data logger

For more information, contact Instrument Specialties, Inc. by calling 407-324-7800 or visit http://isi.group.

Video of Valtek Packing Subassembly

The Mark One, from the Flowserve brand Valtek, is a globe valve intended for flow control of liquids or gases across a wide range of applications. The valve design provides high positioning accuracy, repeatability and tight shutoff. A wealth of special design and construction features make the Mark One a serious contender for almost any fluid control operation.

Share your control valve and valve automation requirements and challenges with an application specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Control Valve Flow Characteristics

Industrial Control Valve
Courtesy Flowserve - Valtek

Flow characteristics, the relationship between flow coefficient and valve stroke, has been a subject of considerable debate. Many valve types, such as butterfly, eccentric disk and ball valves, have an inherent characteristic which cannot be changed (except with characterizable positioner cams). Flow characteristics of globe valves can be determined by the shape of the plug head.

The three most common types of flow characteristics are quick opening, equal percentage and linear. The adjacent figure shows the ideal characteristic curve for each. These characteristics can be approximated by contouring the plug. However, inasmuch as there are body effects and other uncontrollable factors, plus the need for maximizing the flow capacity for a particular valve, the real curves often deviate considerably from these ideals. When a constant pressure drop is maintained across the valve, the characteristic of the valve alone controls the flow; this characteristic is referred to as the “inherent flow characteristic.” “Installed characteristics” include both the valve and pipeline effects. The difference can best be understood by examining an entire system.

Control valve flow properties
Courtesy Flowserve - Valtek

Equal Percentage

Equal percentage is the characteristic most commonly used in process control. The change in flow per unit of valve stroke is directly proportional to the flow occurring just before the change is made. While the flow characteristic of the valve itself may be equal percentage, most control loops will produce an installed characteristic approaching linear when the overall system pressure drop is large relative to that across the valve.

Linear

An inherently linear characteristic produces equal changes in flow per unit of valve stroke regardless of plug position. Linear plugs are used on those systems where the valve pressure drop is a major portion of the total system pressure drop.

Quick Open

Quick open plugs are used for on-off applications designed to produce maximum flow quickly.

This information provided courtesy of Flowserve Valtek. Share your control valve requirements and challenges with a valve specialist, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

The Valtek Control Valve: Understanding the Components

Flowserve (Valtek) control valves

Valtek control valves are also known for handling the most severe services: cryogenic, superheated steam, volatile and corrosive fluids, erosion, high pressure drops, vibration, cavitation, flashing, and high noise levels.

Valtek valves are equipped with spring cylinder or spring diaphragm actuators that provide the thrust and speed necessary to manage any service. Valtek four-way analog and digital positioners provide accuracy and response to handle the most exacting applications.

This video gives the viewer an understanding of the major components.

For more information, contact:
Instrument Specialties Inc.
3885 St. Johns Parkway
Sanford, FL 32771
phone 407.324.7800
fax 407.324.1104
e-mail: offices@isisales.com

Design and Construction of the Globe Control Valve (Valtek Mark One)

Globe control valve

A globe control valve is a specific type of valve used for regulating flow in a pipe. The design includes a movable plug, connected to a stem, which can be moved linearly to close or open the valve. Globe control valves are referred to as “linear” valves because of this movement, whereas ball valves and butterfly valves are referred to as “quarter-turn” valves. Generally, globe control valves provide better overall flow control than quarter-turn valves due to the design of their flow path.

The Valtek Mark One globe control valve is know for superior performance in liquid and gaseous services, while also permitting easy, fast and inexpensive maintenance to its major components.

The video below provides an excellent look inside a globe control valve (in this case the Flowserve Valtek Mark One).