Showing posts with label Flowserve. Show all posts
Showing posts with label Flowserve. Show all posts

Sunday, August 19, 2018

What Are Valve Positioners?

Digital Positioner
Digital Positioner (Valtek)
A valve positioner is used in combination with a valve actuator to precisely position a valve so that optimum flow accuracy may be achieved. The positioner does this by measuring a the process variable, comparing it to a desired condition (set point) and then pneumatically, electrically, or hydraulically changing the valve disc, globe, plug or ball position until the difference between the set point and actual position is zero.

Valve positioners are key elements in a closed loop control system where the final control element is a valve. They assist in maintaining tight control, overcoming the realities of imprecise calibration, differential pressure across the valve, valve wear and a host of other process control challenges.

A valve positioner responds to a signal from some type of master control system, typically a distributed control system (DCS), a programmable logic controller (PLC), or PID controller. The control system reads a signal from a process sensor (flowmeter, temperature sensor, pressure sensor, etc...) and compares that reading to the desired setpoint. A corrective signal, based on the difference,  is provided to the valve positioner which re-adjusts (if necessary) the valve position to bring the system in to equilibrium.

Valve positioners are available with pneumatic, electrical, electro-pneumatic, and digital operation. Here is a brief description of each:

Pneumatic
Pneumatic Positioner
Pneumatic Positioner (Valtek)
Pneumatic positioners receive pneumatic signals (3-15 or 6-30 PSIG). The positioner then throttles supply air to the valve actuator to move the valve to the required position. Pneumatic positioners are intrinsically safe and can provide a large amount of force to close a valve.

Electric
Electric valve positioners receive an electric signal, usually 4-20 mA, 1-5 VDC, 2-10 VCD or 0-10 VDC and generally drive the motors in electric actuators. They perform the same function as pneumatic positioners do, but use electricity instead of air pressure as an input signal.

Electro-Pneumatic
Electro-pneumatic Positioner
(PMV)
Electro-pneumatic valve positioners contain internal I/P (current to pneumatic) modules that converts the electrical input signal to a pneumatic output (4-20 mA to 3-15 PSIG for instance). Very similar to a pneumatic positioner except that its input is electrical.

Valve positioners are used throughout the process industries including power, pharmaceutical, chemicals, oil and gas, food and beverage, pulp and paper, refining and petrochemicals, pipelines, and many other processes.

For more information on valve positioners, contact Swanson Flo by visiting https://swansonflo.com or by calling 800-288-7926.

Wednesday, June 27, 2018

A Process Industry Stalwart - The Plug Valve

Flowserve Durco lubricated plug valve
Lubricated plug valve.
(Flowserve Durco)
This article will focus on one of the oldest and most reliable (when properly applied) industrial valve types - the plug valve.

Fluid process control operations commonly employ pumps, piping, tanks and valves as the means of transporting, containing and controlling the fluid movement through a system.

Valves, of which there are many types, provide control over the flow rate, direction and routing of fluids in a processing operation. Flow can be started, stopped or modulated between zero and full rate using a properly sized and configured valve. Some valves enable media flow to be diverted to a selection of outlets, in lieu of a single inlet and outlet pair. Specialized valves regulate inlet or outlet pressure, or prevent fluid flow from going in an undesirable direction. All of these capabilities are packaged into differing valve product offerings that present a very large selection array to a process designer or engineer.

Floserve Durco non-lubricated plug valve
Non-lubricated plug valve.
(Flowserve Durco)
Industrial flow control valve types are generally classified according to the structure or arrangement contained within the valve body that provides obstruction to fluid flow. Some of the common types are ball, butterfly, gate, globe, and plug. Surely, there are more valve types, and this article is not intended to list them all. Some of our previous blogs have discussed selection considerations for gate, ball and butterfly valves.

Plug valves, like ball and butterfly valves, span from fully open to fully closed positions with a shaft rotation of 90 degrees. The “plug” in a plug valve is installed in the flow path within the valve body and rotated by means of a stem or shaft extending to the exterior of the body. Plugs are tapered toward the bottom and are fitted to a seating surface in the valve body cavity that prevents fluid from bypassing the plug. An opening through the plug, the port, can be shaped to provide particular flow characteristics. There are two main types of basic plug, lubricated and non-lubricated. Lubricated plug valves have a cavity into which a sealant is injected. The sealant provides a renewable seal between the plug and the body, prevents internal leakage, and protects the seating surfaces against corrosion. Non-lubricated plug valves utilize an elastomeric body liner or a sleeve in the body cavity that is pressed in to the body of the valve by the plug's wedge-like shape,  with the result of reducing the friction between the plug and the body.

Plug valve considerations:
  • 90 degree rotation from open to closed provides fast operation.
  • With proper configuration, can be well suited for frequent operation.
  • Availability of corrosion resistant liner may provide comparative cost savings because valve body can be constructed of less expensive material.
  • Design is simple and employs a low parts count.
  • Valve can be serviced in place.
  • Generally, low resistance to flow when fully open.
  • Reliable leak-tight service due to tapered plug wedging action, replaceable sleeve, and injection of lubricant in some variants.
  • Potential issues of concern for plug valve application include a short list of items.
  • Higher friction in the plug closure mechanism may require comparatively higher operating torque than other valve types.
  • Without a specially designed plug, generally not well suited for throttling applications.
  • Rapid shutoff delivered by plug design may not be suitable for some applications where hammering may occur.
Share your fluid control application challenges with a valve and automation specialist. Leverage your own knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, June 20, 2018

A Peek Inside a Valtek Mark One Control Valve with Piston Actuator

Valtek Mark One Control ValveThe video below provides a look inside the Flowserve Valtek Mark One control valve and identifies its major components.

The Flowserve Valtek® Mark One globe control valve is designed for liquid and gaseous services, and for permitting easy, fast and inexpensive maintenance.

The spring-cylinder actuated Mark One valve provides stiffness and maintains high positioning accuracy, repeatability, controlled high speed, and faithful response. The Mark One valve handles up to 150 psig supply air and has the thrust to shut off against much higher fluid pressures.

The Mark One valve is designed so the spring, supply air pressure and fluid pressure itself combine to produce exceptionally tight shutoff. A self-aligning seat ring further enhances the shutoff capability of the valve.

https://swansonflo.com
800-288-7926

Monday, March 26, 2018

Limitorque MX Actuator Users Instructions, Maintenance, and Spare Parts Manual

Flowserve Limitorque MX
The Flowserve Limitorque MX actuator controls the opening and closing travel of valves and other actuated devices. OPEN and CLOSED limits are protected by an absolute encoder that provides optical sensing of valve position and measures valve position in both motor and handwheel operation.

No battery or backup power supply is required. Output torque is derived from motor speed, temperature, and voltage. If the preset torque is exceeded, the motor shuts off. As a result of this reliable and advanced protection technology, all valve and other actuated devices are protected from potential damage from overload, improper seating, and foreign obstructions.

A range of control and network options is available and can be easily added to the control capabilities already available on a standard actuator.

You can download the Limitorque MX Electronic Actuator User Instructions, Maintenance, and Spare Parts Manual in PDF version from the Swanson Flo site here (8.5MB), or read the embedded version below.

Saturday, January 27, 2018

Flowserve Valtek MaxFlo 4 Eccentric Rotary Plug Control Valve

Valtek MaxFlo 4 Eccentric Rotary Plug Control Valve
The Flowserve Valtek MaxFlo 4 control valve is a high performance eccentric rotary plug valve designed for the process industry. It features a large capacity, standard hardened trim and superior shaft blow-out protection.

This valve is available in sizes 1 through 12 inches, ASME Class 150, 300 and 600 as well as DIN PN 10, PN16, PN 25, PN40 and PN63. An optional ISA 75.08.01 or DIN EN 558 series 1 long-pattern body makes this valve an easy drop-in replacement for a globe control valve. 

Founded in 1960, Swanson Flo has long maintained our position as an industry leader in process automation with unmatched project success leveraging industry preferred products and services. 

800-288-7926

Wednesday, November 8, 2017

Understanding Linear, Equal Percentage, and Quick Open Control Valve Flow Curves

Flowserve Valtek Control Valve
Flowserve Valtek Control Valve
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 figure below 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.

Equal Percentage
Control valve flow curves
Control valve flow curves.


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.

Friday, June 23, 2017

Lined Industrial Valves for Corrosive Service

Lined Durco Plug Valves
Lined Plug Valves
(courtesy of Flowserve Durco)
Lined valves use a fluoropolymer, plastic, or ceramic lining applied to all wetted internal parts of the valve.

Lined valves combine the excellent mechanical properties of metallic bodies with the corrosion resistance of fluorocarbons, such as PFA and PTFE.

Lining the intricately shaped inside surfaces of a valve is certainly an engineering challenge, especially to achieve a uniform thickness and the highest lining quality, without cavities or inclusions.

Lined Valves
Lined ball and swing check valve
(courtesy of Flowserve Atomac)
The special lining process guarantees tight bonding between the lining and the inside of the body.
This effectively prevents the lining from shearing off the body in part or being removed completely.

Ideal applications include highly corrosive applications within the chemical processing industry such as sulfuric and hydrochloric acid.

Lined valves are ideally suited for corrosive applications, requiring very reliable performance, tight shutoff, constant torque and no maintenance. These valves have gained extensive usage in many industries including power generation, pulp and paper, refineries, chemical process, pharmaceutical/bioprocessing and pollution control.

For more information on lined valves, visit Swanson Flo at http://www.swansonflo.com or call 800-288-7926.

Monday, April 17, 2017

Flowserve Valtek Valve Automation

The video below highlights several Swanson Flo automated Valtek control valves. Included in these systems are Valtek ShearStream segmented ball valves, Valtek Valdisk BX butterfly valves, Logix positioners, Valtek VR piston actuators, and StoneL Axiom valve monitors.


Swanson Flo is a premier valve and valve automation supplier located in Plymouth, MN with warehouse and fabrication facilities in Addison, IL, Indianapolis, IN and Menomonee Falls, WI.

Visit Swanson Flo at http://www.swansonflo.com or call 800-288-7926 with any valve automation project.

Saturday, March 18, 2017

Understanding Control Valves: The Flowserve Valtek Mark One

Control valves are an integral part of many process control loops. Understanding their basic operation is important for any process control professional. The following video demonstrates the reassembly of the Flowserve Valtek Mark One control valve and introduces the viewer to a control valve's main components.

There are a variety of styles of control valves. 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 to open and close is directed by a piston type, linear movement actuator. Generally, globe control valves provide better overall flow control than quarter-turn valves due to the design of their flow path.

For more information, a Valtek Mark One specification sheet is also included with this post.