Showing posts with label process control valve. Show all posts
Showing posts with label process control valve. Show all posts

Friday, February 23, 2018

Industrial Diaphragm Valves

sectional drawing weir type diaphragm valve with pneumatic actuator
Section drawing of diaphragm valve, weir type,
with pneumatic actuator.
Image courtesy Gemu Valves, Inc.
Diaphragm valves are named for the means employed in their design to restrict the path of fluid flow through the valve. Most valve designs employ a rigid solid shape which is repositioned in the fluid path to regulate flow. Diaphragm valves are somewhat unique in their use of a flexible material that is deformed by a moving part connected to the valve operating mechanism. The diaphragm acts as the flow restrictor and seat. It also isolates the valve bonnet and stem from the flowing media.

The fluid path and diaphragm positioning and seating enable this valve type to be used for throttling or simple stop operations. They are generally tolerant of particulate matter entrained in the media. Selecting body and diaphragm materials that are compatible with the media are primary elements of achieving a successful application. The diaphragm is a wearing part and should be inspected periodically and replaced when necessary.

Diaphragm valves for industrial use are available in a range of materials and sizes to accommodate light through heavy duty applications.
  • Suitable for inert and corrosive liquid and gaseous media when proper valve body and diaphragm materials are selected
  • Bonnet and valve bodies available in metal or plastic construction
  • Insensitive to particulate media
  • Valve body and diaphragm available in various materials and designs
  • Compact design
  • Automation via pneumatic or electric means
Share your fluid process control challenges with valve application specialists. Leverage your own knowledge and experience with their product application expertise to develop an effective solution.

Thursday, July 27, 2017

Valve Positioners

industrial valve actuator with positioner
Valve positioner installed on pneumatic actuator
Courtesy Crane ChemPharma Energy
Valve positioners can provide process operators with a precise degree of valve position control across the valve movement range, as well as information about valve position. A relationship exists between applied pneumatic signal pressure and the position of the valve trim. The relationship between the two elements is dependent upon the valve actuator and the force of the return spring reacting to the signal pressure. In a perfect world, the spring and pneumatic forces would reach equilibrium and the valve would return to the same position in response to an applied signal pressure. There are other forces, however, which can act upon the mechanism, meaning the expected relationship between the original two elements of pressure and position may be offset. For example, the packing of the valve stem may result in friction, or the reactive force from a valve plug resulting from differential pressure across the area of the plug may be another.

While these elements may seem minor, and in some cases they are, process control is about reducing error and delivering a desired or planned output. Inclusion of a positioner in the valve assembly can ensure that the valve will be set in accordance with the controller commands.

Each positioner functions as a self-contained small scale control system. The first variable in the positioning process is the current valve position, read by a pickup device incorporated in the positioner. A signal which is sent to the positioner from the control system, indicating the desired degree of opening, is used as the setpoint. The controller section of the positioner compares the current valve position to the setpoint and generates a signal to the valve actuator as the output of the positioning process. The process controller delivers a signal to the valve, and then the positioner takes that signal and supplies air pressure required to accomplish the needed adjustment of the stem position. The job of the valve positioner is to provide compensatory force and to act as a counterbalance against any other variables which may impact valve stem position.

Magnetic sensors can be employed to determine the position of the valve stem. The magnetic sensor works by reading the position of a magnet attached to the stem of the valve. Other technologies can be employed, and all have differing ways of overcoming degrees of inaccuracy which may arise with wear, interference, and backlash. In addition to functioning as a positioner, control valve positioning devices can also function as volume boosters, meaning they can source and subsequently ventilate high air flow rates from sources other than their pneumatic input signal (setpoint). These devices can positively affect and correct positioning and velocity of the valve stem, resulting in faster performance than a valve actuator solely reliant on a transducer.

The inclusion of a positioner in a control valve assembly can provide extended performance and functionality that deliver predictable accurate valve and process operation. Share your valve automation requirements with a knowledgeable specialist and combine your process knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, June 7, 2017

Metal Diaphragm Valves - Best Applications

pneumatically operated diaphragm valve industrial valve
Diaphragm valve, pneumatically actuated
Courtesy GEMU
There are more valve selection options available than one can count. Differing types, sizes, materials, and other special characteristics distinguish each and every product as unique in its own way. Matching the design and performance strengths of a particular valve to the requirements of an application may require some investment in time and research, but the payback can be years of trouble free performance.

Diaphragm valves are beneficial for applications requiring hermetic isolation of the valve bonnet and stem from the media. The diaphragm serves as the isolating barrier. The valves are generally tolerant of particulate matter entrained in the media, and provide good shutoff and throttling capability. Body and diaphragm materials should be selected that are compatible with the media.

Body styles are either weir or straight through design. Straight through body styles offer a less restricted flow path than the weir type, but diaphragm movement in the weir style is reduced. Diaphragms do wear and will need to be replaced at some point. Valves should be installed with good service access.

There are many variants of diaphragm valves, broadening their suitability for a wide range of industrial applications. Share your fluid process control challenges with application specialists, combining your process knowledge with their product expertise to develop effective solutions.

internal diagram of weir type diaphragm valve
Weir body style diaphragm valve
Coutesy GEMU

Monday, May 22, 2017

Introduction to Valve Parts or Components

cutaway view forged steel gate valve
Cutaway view of a forged steel gate valve
Courtesy Crane-ChemPharmaEnergy
Although there are many different classifications of valves specific to their respective functions, there are standard parts or components of valves you may find regardless of the classification. They are the valve body, bonnet, trim, seat, stem, actuator, and packing.

The Valve Body is the primary boundary of a pressure valve which serves as the framework for the entire valve’s assembly. The body resists fluid pressure loads from connected inlet and outlet piping; the piping is connected through threaded, bolted, or welded joints.

The Valve Bonnet is the opening of the Valve Body’s cover. Bonnets can vary in design and model, is built using the same material as the Valve Body, and is also connected to the entire assembly through threaded, bolted, or welded joints.

The Valve Trim collectively refers to all the replaceable parts in a valve, e.g. the disk, seat, stem, and sleeves––all which guide the stem as well.

The Valve Disk allows the passage or stoppage of flow. Disks provide reliable wear properties and differ in what they look like per valve type. For example, in the case of a ball valve, the disk is called a ball, whereas for a plug valve it is a plug.

The Valve Seat(s) or it’s seal rings provide surface seating for the disk. For example, a globe valve requires only one seat and this seat forms a seal with the disk to stop flow.

The Valve Stem provides the proper position which will allow the opening and closing movement of the Valve Disk. Therefore, it is connected to the Valve Disk on one end and the Valve Hand Wheel or the Valve Actuator on the other.

The Valve Yoke is the final piece in the valve’s assembly; the Yoke connects the Valve Bonnet with the actuating mechanism. The Valve Stem passes through the top of the Yoke which holds the Yoke or stem nut.

There are countless variants of valve designs, sizes, and configurations. These basic parts will be found on most, but the particular form and arrangement of the part may provide an advantage when employed for a particular application. Share your industrial process valve requirements and challenges with a valve specialist. Combine your own process knowledge and experience with their product application expertise to develop an effective solution.

Thursday, May 11, 2017

Rack and Pinion Actuator - Double Acting vs. Single Acting

pneumatic valve actuator
Pneumatic rack and pinion valve actuator
Courtesy Emerson - Hytork
Automating industrial valve operation requires numerous considerations in selecting the correct power source, drive type, torque range, and much more. The widest range of possible operation conditions should be anticipated and accommodated by the actuator selection to assure safe and effective valve operation under normal and adverse conditions.

The use of compressed air or gas as the energy source for valve positioning has been in use for many years and remains popular to this day. Among the perceived advantages of this energy source are the ability to store it in pressurized vessels for emergency short term use and the absence of any potential ignition source, as may be the case with electric powered actuators.

A rack and pinion valve actuator delivers a linear torque output throughout its full range of travel. The movement of a piston causes movement of the rack. The rack is toothed, and drives the pinion, converting linear movement of the rack into rotational movement of the pinion. The pinion is connected to the valve shaft, providing re-positioning of the valve. Adjustable stops, part of the actuator, limit the travel of the valve trim.

spring return and double acting valve actuator diagrams
Double acting pneumatic rack and pinion actuator (left) on its inward stroke. Spring return actuator (right) on its
outward or air powered stroke  (Illustrations courtesy of Emerson - Hytork) 

There are two common configurations of rack and pneumatic pinion actuators. A double acting actuator has provisions for delivering or exhausting air from both sides of the piston. Small control valves coordinate the delivery and removal of pressurized air or gas to drive the pistons inward or outward, producing torque in a clockwise or counterclockwise direction. Its operation could also be described as "air to open, air to close".

The single acting version of the pneumatic rack and pinion actuator provides air driven movement in only one direction. In this case, reversing the direction of travel is accomplished with a spring installed within the chamber on one side of the pistons. The spring powered movement provides a fail safe positioning of the valve in the case of control air pressure loss. This actuator provides "air to open, spring to close" operation, although, in some cases the fail safe position can be changed.

This is the simple version. Share your process control challenges with a valve expert, combining your own process knowledge and experience with their product application expertise to develop effective solutions.



Thursday, March 9, 2017

Metal Seated Ball Valves Offer Potential for Long Term Cost Savings

3 piece ball valve with handle
Adding metal seats to a ball valve can extend its service life
Photo courtesy of Flo Tite
The majority of ball valves are provided with one of several elastomeric materials forming a soft seat between the trim, or ball, and the valve body. With the balance of the valve assembly in contact with the media likely to be metal (unless, of  course, it is a plastic valve), the soft seat, because of its properties and location, tends to experience wear and tear and be a common cause for repair or valve performance deterioration.

In fluid process control applications where the media conditions may not, at first glance, warrant the use of a metal seated valve, there may be long term returns to be gained from the added cost of metal seats. The factors that create wear and degradation of soft seats are generally better tolerated by metal seats. Process downtime or man-hours for repair have a cost, so avoiding or reducing the occurrences of repair or maintenance provide a return on the additional expenditure for a metal seated valve that can provide a longer service life.

Many commonly available ball valves are also available with metal seats as an option, or metal seated variants are offered as uniquely identified products. Whatever the case, consider hardening your valve selections with metal seated valves. There are instances where they are well suited to the application and will offer a return on the additional cost.

Share your fluid process control challenges with a valve specialist, combining your own process knowledge with their product application expertise to develop effective solutions.



Thursday, March 2, 2017

New Electric Linear Actuators for Industrial Valves

electric linear valve actuators
Electric linear actuators for industrial valves
ILEA Series
Courtesy Warren Controls
There are uncountable choices for industrial process control valves and actuators. With applications so diverse and requirements so specific, each product seems to enjoy a placement within a particular niche or range of usage where it provides the perfect combination of construction, performance, and cost attributes.

Warren Controls, manufacturer of a wide range of industrial control valves and actuators that include both linear and rotary designs, has released an electrically powered linear actuator that provides some application advantages.

The ILEA series of industrial linear electric actuators provides failsafe features, fast operation, robust environmental performance, and extended output force ranges. This all is delivered at a cost point making the ILEA series a contender for any modulating valve service application.

The datasheet included below provides additional detail. Share your fluid process control valve challenges with valve application experts, combining your own process knowledge with their product application expertise to develop effective solutions.


Wednesday, February 8, 2017

Floating Ball Valves

exploded view of floating ball valve
Exploded view of floating ball valve
Courtesy HS Valve
Ball valves are used throughout fluid based applications, from residential to heavy industrial. The compact and rugged design of this valve type provides superior service when properly applied. There are many variants of the basic design, with manufacturers providing builds that meet very specific and stringent requirements posed by certain types of industrial process control applications.

Ball valves are named for the spherically shaped element encased in the valve body directly in the fluid flow path. The ball has a hole, or port, through it’s center, permitting fluid to pass when the port is aligned with the direction of flow. A stem is attached to the ball and extends to the exterior of the valve body, providing a mechanical means of rotating the ball between open and closed positions. Ninety degrees of rotation moves the ball from the fully open to fully closed position. Ball valves are generally suitable for manual or automated operation.

In the basic design of ball valves, there are two groups which exhibit an essential structural difference that is worth mentioning. There are two ways in which the ball in a ball valve is held in place. A floating ball valve has its main trim element held in place by the shape of the valve body and the seats. It is essentially suspended in the flow path by its surrounding parts. A very small amount of lateral movement of the ball is imparted by the fluid flow, pushing the ball tightly against the seat on the downstream side. This attribute enables a floating ball valve to provide tight shutoff of bidirectional flow. The floating ball design proves less effective as the nominal bore size increases. The added weight of the larger ball, coupled with the larger surface area exposed to fluid forces, can overcome the ability of the seals to properly support the ball and maintain good performance. The maximum size can vary among manufacturers.

Enjoying all the benefits of ball valve design, plus being comparatively simple to disassemble and service, floating ball valves are a solid choice for many industrial applications. Selecting the right valve design or type is an important step toward effective control of fluid operations. Share your fluid process control challenges with a valve expert, combining your process knowledge with their product application expertise to develop effective solutions.



Friday, December 2, 2016

Diaphragm Valves For Heavy Duty Industrial Applications

industrial diaphragm valve with handle metal body and metal diaphragm
Series 611 Industrial Diaphragm Valve
Courtesy Gemü
Diaphragm valves are suitably used for applications requiring hermetic isolation of the valve bonnet and stem from the flowing media. They also are capable of throttling flow and are generally tolerant of particulate matter entrained in the media. Selecting body and diaphragm materials that are compatible with the media are primary elements of achieving a successful application.

Gemü, a globally recognized manufacturer of diaphragm valves and other control components, offers a line of industrial metal diaphragm valves available in a range of materials and sizes to accommodate heavy duty applications.
  • Suitable for inert and corrosive liquid and gaseous media
  • Chemical resistant bonnet
  • Insensitive to particulate media
  • Valve body and diaphragm available in various materials and designs
  • Compact design
Share your fluid process control challenges with application specialists, combining your process knowledge with their product expertise to develop effective solutions.

Tuesday, August 30, 2016

Applications For Metal Seated Ball Valve

metal seated ball valve with handle and flange connections
Metal Seated Ball Valve
Crane - Krombach
Fluid process control employs valves of various types to start, stop, throttle, or divert flow of a fluid. Ball valves are a common selection for process application when their inherent advantages provide the greatest benefit.
  • Leak-proof service
  • Well suited for processes requiring only full flow or no flow operation.
  • Rapid open and close action, requiring only 90 degrees of rotation from fully open to fully closed.
  • Comparatively light weight and compact size.
  • Wide range of construction material options for body, ball, and seals make them suitable for many applications.
  • Require only moderate force to control valve position.
  • Flow path opening in the ball will often be “full port”, providing same cross section as the connected pipe and adding very little restriction or pressure drop to the flow.
  • Low maintenance, with no lubrication required.
There are numerous ball valve variants that provide modified features and performance, but let's focus on what is generally considered severe service applications.

Severe service, while not currently defined by an international standard, generally can be characterized by one or more operating conditions that put great levels of stress or wear on valves.
  • Very extreme media or environmental temperature
  • High pressure drop operation that may cause cavitation
  • Rapid and extreme changes to inlet pressure
  • Certain types or amounts of solids contained in the fluid
  • Corrosive media
Some of these conditions will greatly impact the valve seat. Many valves are provided with thermoplastic seats that, while providing suitable performance throughout a wide range of media conditions, will deteriorate quickly under conditions prevailing in severe service. An alternative to the soft thermoplastic seats is a metal seat design. 
  • Greater temperature tolerance
  • Self cleaning seat
  • Improved resistance to effects of particulate laden media or slurries
  • Corrosion resistance, enhanced by special coatings applied to metal construction
The document below provides an in depth view of a metal seated ball valve. Operating conditions, specifications, and illustrations (including my favorite, the cutaway view) are provided. Share your fluid control requirements with product and application specialists, combining your process expertise with their product application knowledge to develop effective solutions.


Friday, April 1, 2016

Video Demonstration of Weir Diaphragm Valve Operation

industrial diaphragm valve sectional view for process control
GEMU 620 Industrial Diaphragm Valve
Diaphragm valves comprise one of many different process control valve designs, each with specific attributes making them better suited for certain applications. Selecting the right valve type for an application is a critical early step toward successful control implementation.

Familiarity and understanding of how a particular valve type functions is necessary when equipping a fluid control system. Here are some considerations for valve operation that come into play.

  • Media Compatibility:
    Industrial process control applications cover an immense range of viscosity, velocity, solids content, and other physical media characteristics that may, or may not, be acceptably addressed by some valve types.
  • Cycle Frequency:
    Some valve types are more suitable for a high frequency of on/off cycles, others are better suited to slower rates.
  • Compatibility With Sanitary or Similar Operations:
    Some industries have requirements for special cleaning, sanitizing, or sterilizing of the process flow path. A valve design that does not trap the media within the valve body and allows for full exposure of the fluid path to whatever cleaning agent is applied has certain advantages for these applications. Some cleaning operations also require a full bore or straight through flow path to allow for proper cleaning.
  • Operating Speed:
    Different valve types may have varying capabilities to provide rapid change of valve position. Valve operating speed must be compatible with process requirements that may call for either rapid or slow opening or closing.
  • Throttling Ability:
    Each valve type, through the characteristics of its closure mechanism, offers comparatively different capacity for regulate fluid flow across an extended range between completely closed and fully open.
  • Space Requirements:
    Different valve trim arrangements can predicate how much installation space a valve may require for proper operation and maintenance. For example, a valve with a rising stem will generally require more clearance than a similar capacity valve with a rotating stem.
Industrial process control diaphragm valve Gemu
GEMU Model 620 Industrial Diaphragm Valve
Certainly, there are more aspects of valve operation that will be taken into account in the selection process. 

Diaphragm valves defend their niche of applications with their ability to:
  • Provide on/off or throttling service
  • Eliminate stem leakage
  • Provide bubble tight service
  • Eliminate pockets that may trap media
  • Isolate valve mechanism from media
  • Prevent contamination of media by valve parts or operation
Below is a short video that provides an animated look inside a weir diaphragm valve. The video provides a clear illustration of how the fluid flows through the valve and how the valve controls flow. There are variants of the diaphragm valve that do not use a weir, providing a straight through or full bore flow path. Their operation is similar.
Watch the video. It's short and to the point. Get the help you need solving your process control valve challenges from the seasoned experts at Mountain States Engineering.
"

Tuesday, February 16, 2016

Specialized Gate Valve For Control Applications

Sliding gate process control valve
Sliding Gate
Process Control Valve
Schubert & Salzer
Gate valves are widely employed throughout the industrial process control field to start and stop the flow of a wide range of fluids and slurries. The common construction of a gate valve, with a solid wedge or disc that moves perpendicularly to the direction of fluid flow, tends to limit the application of this valve type to processes where fully open or fully closed are the desired valve positions. The comparatively large travel range of the wedge from open to closed, combined with a need to close the valve slowly to avoid hammering, saddles the common gate valve with a slow operating speed. Holding the gate at a partially open position has potential to induce vibration in the fluid, resulting in noise and possible negative impact on the fluid transport system. For this reason, common gate valves are generally not used in control applications requiring flow modulation .

The limiting factors just described can be mitigated or eliminated with a modification to the gate configuration. Instead of a solid gate, two plates with matching orifice matrices are mounted in the fluid path. One plate is fixed and the other is moved by the valve actuator, sliding through a motion range that expands flow area by increasingly matching the orifice openings on the two plates. This gate valve design is often called a sliding gate valve and it is easily recognizable through its pattern of slotted openings on the gate.

Some notable features of the sliding gate valve:

  • Straight through flow path with little turbulence.
  • Flow is broken into multiple small streams by the orifice pattern, reducing the impact of the flow force on the valve trim.
  • Suitable for fluid control operation, not just fully open or closed.
  • Travel distance and time from fully open to fully closed is significantly reduced, when compared to common gate valve.
  • Quieter operation.
  • Long service life.
  • Suitable for lower viscosity, generally clean, fluids
Every valve design has applications where it will tower over others in terms of overall performance. The variable orifice control valve (sliding gate valve) will prove to be the best choice for certain applications. Share your fluid process control challenges with an industrial control specialist. Combining your process expertise with their product application knowledge is a sure way to produce positive outcomes. 


Wednesday, December 9, 2015

A Close Look at Butterfly Valve Seat

Butterfly valve soft seat cutaway view
Cutaway View of Butterfly Valve With Soft Seat
Courtesy Flowseal - Crane CPE
Butterfly valves are found throughout the fluid based applications in the process control field. They are one of many common and special types of industrial valves used to regulate fluid flow in ways that are compatible with the media being controlled and the degree of precision needed to produce the desired process outcome.

The industrial process control field benefits from a large array of valve manufacturers in pursuit of the favor and business of process operators. Operators continually seek better performance and lower life cycle costs. Manufacturers respond with increasingly improved designs.

A butterfly valve has a disc that is positioned in the fluid flow path. It rotates around a central axis, the stem, through a 90 degree arc from a position parallel to the flow direction (open) to perpendicular (closed). A critical element of a butterfly valve is the seat, where the disc seals to the body in the closed position. Seat design should provide these positive operating attributes:
  • Low friction to reduce valve operating torque
  • Resistance to wear
  • Arrangement that provides for easy replacement
  • Seal or shutoff tightness appropriate for the application
Flowseal, part of the Crane, CPE group of brands, utilizes their specially designed Soft Seat valve sealing arrangement on their resilient sealed butterfly valves. The Soft Seat feature provides beneficial fulfillment of process requirements for the attributes listed above. The valve is available in a range of sizes, with options and variants to meet a wide array of industrial process requirements.

Learn more about the Flowseal Soft Seat butterfly valves by watching the short video below. You can delve deeper with a browsing of the illustrative brochure that is also included below. It provides some detailed illustrations of how the seat functions under differing operating conditions. Contact a product specialist and share your process challenges. Your process knowledge and their product application expertise, when combined, will produce a useful solution.


Monday, September 14, 2015

No Compressed Air? Use Water to Power Your Valve Actuator.

Hytork XLW Water Powered Valve Actuator
XLW Water Powered Valve Actuator
Courtesy Hytork
Air is everywhere, but very little of it is compressed for our use in powering a valve actuator. Sometimes, possibly at sites located remotely, a reliable source of compressed air is unavailable for process control valve actuation. Installing an air compressor at the site may be an option, but one with impact on the reliability of the installation deemed undesirable. One possible solution is a water powered valve actuator. With mains water available, pressurized within the range of 60 to 100 psi (4-7 bar), actuator power can be derived and valve operation successfully achieved.

Water always presents its own set of special considerations, not the least of which is that it tends to corrode most metals used in construction of actuator parts over time. Of additional concern are the particulates present in water systems which can cause premature deterioration of seals and scoring of cylinders in the actuator. Directional control solenoid valves will also function more reliably with a water supply free of larger particulates. While this is a concern, the solution is simply to place an inexpensive filter upstream of the devices, eliminating the contaminates from the water supply.

While it is possible to employ some "standard" actuators in a water powered setting, there are special adaptations that can be applied to common actuator design to better suit the use of water power. One manufacturer, Hytork, has done just that with their XLW Series of water operated actuators. The XLW Series is a water powered adaptation of the company's successful XL Series actuators. Special coatings are applied to critical parts to provide necessary protection for water applications. There are other differences between the compressed air and water versions of the actuator, detailed in the installation and operating instruction manual shown below. The manual is short enough to be read in a couple minutes (really, just a couple minutes) and provides useful and illustrative information about actuator construction, operating characteristics, and maintenance requirements.

Contact a valve application specialist for more information, or to discuss any of your fluid control application needs.


Monday, September 7, 2015

When is a Diaphragm Valve Your Best Choice?

Gemu Industrial Diaphragm Valve Metal Body Hand Operated
Hand Operated Metal Body Diaphragm Valve
Courtesy Gemu
Industrial process control, as a field of endeavor, covers an incredibly broad range of applications, all highly specialized in their own way. The control and handling of fluids is a prevalent activity in process control, leading to a wide variety of valves from which to choose for your application. Figuring out which flow control valve will best meet the needs of a particular application requires a detailed assessment of the physical elements to which the valve will be exposed, and under what conditions it will need to operate. In other words, know your process fluid, know your operating environment. A solid understanding of your process will make valve selection a simpler task, since there will likely be a small segment of your requirements able to be fulfilled by only one or two valve types.

When referring to valve types, common terminology generally describes the means utilized to control the flow. Some prevalent valve types, though certainly not an exhaustive list, include ball, plug, butterfly, diaphragm, gate, needle, and globe. Each of these basic designs have characteristics that make them more suitable than others for certain application conditions. Let's look at diaphragm valves.

A diaphragm valve controls fluid flow through the movement of a flexible membrane, unsurprisingly called a diaphragm. Numerous means can be employed to apply force to the diaphragm and a seal is created when the membrane compresses against a targeted portion of the valve body. A prominent feature of this valve type is the isolation, by the diaphragm, of the valve operation mechanism from the fluid. Two general body styles are available, referred to as weir and straight through. The weir design requires less extensive movement of the diaphragm than the straight through type, resulting in a longer expected life for the diaphragm. The straight through style, when open, provides little obstruction to the fluid flow and may be more suitable for some media.

Some diaphragm valve characteristics that might prove advantageous:

Pneumatically Operated Diaphram Valve, Plastic Body
Pneumatically Operated Diaphram
Valve, Plastic Body
Courtesy Gemu

  • Isolation of the valve operating mechanism from the fluid.
  • Design is easier to sanitize or sterilize in place than other valve types.
  • Throttling or shutoff service. Throttling generally limited to weir type.
  • Fast operation with powered actuators on weir type.
  • Valves can be lined with materials suitable for abrasive, corrosive, high purity, or other media.
  • Diaphragms available in wide variety of materials to suit application.
  • Leak tight shutoff.
  • Valves can be serviced in-line.
  • Suitable for many high purity applications with proper lining and membrane materials.

Diaphragm valve limitations that may be significant to your application:

  • Limited operating pressure range, when compared to many other valve types.
  • Flexing of diaphragm during operation limits usable life of the membrane and creates maintenance event.
  • Temperature range is limited to that of the membrane and liner material.
  • Range of available sizes is generally less than other valve types.
  • Manual operation is generally slow, requiring multiple turns of a handwheel.
Consider your process environment, consider your process fluid, consider if a diaphragm valve will provide the performance you need. I always recommend taking the time to discuss your application with a valve specialist. Their extensive knowledge base and application experience will enhance your solo valve selection performance.