Direct Acting and Pilot Operated Pressure Relief Valve Operation

Here is a clear and well illustrated tutorial video demonstrating the operational principals of pilot and direct acting pressure relief valves.

There are many available configurations of pressure relief and safety valves, each tailored to accommodate a particular set of application criteria. Understanding how these valves work is important to their proper selection and application to industrial processes and their control.

Safety mindedness is critical for these applications, and you should always talk to an experienced applications expert before specifying or installing these products. Product performance and selection information, as well as application assistance, is available from your local product specialists.

Piping Specialties, Inc.
https://psi-team.com
800-223-1468

Problems with Measuring Level of High Density Pulp Stock

Level Measurement in Pulp Stock has posed problems for a wide range of level measurement technologies. In most pulp mills this is the most challenging application on site.

The environment in the high-density pulp tank is very corrosive to most common metals and the clouds of dense steam vapors that rise from the stock and foaming surface of the level are a constant source of signal loss for many non-contact technologies.

Due to the size of the vessel and density of the stock, mechanical devices are typically short  lived.Stock coatings that form on all interior surfaces add additional mechanical stress and the pulp coating deposits can adversely affect accurate level measurement performance.

One of the challenges of a level measurement device is to control the level in the stock tank, thereby helping to control the average pulp density by controlling the speed of the pump.The response time of the level measurement system is critical in controlling the pump speed and reducing pump oscillations and surges that will eventually reduce the life of the pump.Too slow of a response from the level instrument will allow the level to rise above it ’s optimum density level and cause excessive loading and wear on the pump.

DOWNLOAD THE FULL APPLICATION NOTE HERE

Piping Specialties, Inc.
PSI Controls
https://psi-team.com
800-223-1468

Problems with Measuring Level of High Density Pulp Stock from Piping Specialties, Inc and PSI Controls

Types of Pneumatic Valve Actuators

Scotch-yoke actuators (Morin)

Pneumatic valve actuators all provide the same function:  They convert air pressure to rotational

movement and are designed to open, close, or position a quarter-turn valve.  These include ball valves, plug valves, butterfly valves, or other types of 90 degree rotational valves.

The basic design variations of pneumatic valve actuators are as follows:

• Rack and pinion
• Scotch-yoke
• Rotary vane

Let's review each of these in detail:

Rack and Pinion Actuators

Rack and pinion actuator (Unitorq)

These actuators are sometimes referred to as, “lunch box,” because they, well, look like a lunch box. This actuator uses opposing pistons with integral gears to engage a pinion gear shaft to produce rotation. They are usually more compressed than a scotch yoke, have standardized mounting patterns, and produce output torques suitable for small-to-medium sized valves.  Rack and pinion nearly always include standard bolting and coupling patterns to directly attach a valve, solenoid, limit switch or positioner.  One of their features include several smaller coil springs mounted internally, which provide the torque to return the valve to its starting position.

Scotch-yoke Actuators 

Scotch-yoke actuators internal view.

These actuators come in a multitude of sizes, but are usually used on larger valves because they can produce a very high torque output.  They employ a pneumatic piston mechanism to transfer movement to a linear push rod.  That rod, in turn, engages a pivoting lever arm to provide rotation. Spring return units have a large return spring module mounted on the opposite end of the piston mechanism working directly against the pressurized cylinder.

Rotary Vane Actuators 

Rotary vane actuator animation.

These actuators are usually used when the application requires a significant space savings.  They take up less space when comparing size-to-torque with rack and pinion and scotch yoke. Rotary van actuators also benefit from a reputation of longevity.  They contain fewer moving parts than other types of pneumatic valve actuators.  Rotary vane actuators use externally mounted, helically wound "clock springs" for their spring return mechanism.

These style of valve actuators can all be secured with direct acting or spring return versions. Direct acting actuators use the air supply to move the actuator in both directs (open and close). Spring return actuators, as the name describes, uses springs to move the actuator back to its "resting" state. Converting a version from direct acting to spring return is done through simple modifications, typically just adding an external spring module, or removing the end caps from rack and pinion actuators and installing several coil springs.

When considering the choice of pneumatic valve actuators, your decision comes down to size, power, torque curve and the ease of adding peripherals. To ensure that your valve actuation package will be optimized for safety, longevity, and performance, the advice of a qualified valve automation expert should be sought out. That expert will be able to help you with the best selection of the appropriate valve actuator for any quarter turn valve application.

For more information on valve actuation, contact Piping Specialties, Inc.
https://psi-team.com
800-223-1468

Understanding Differential Flow Measurement

The differential flow meter is the most common device for measuring fluid flow through pipes. Flow rates and pressure differential of fluids, such as gases vapors and liquids, are explored using the orifice plate flow meter in the video below.

The differential flow meter, whether Venturi tube, flow nozzle, or orifice plate style, is an in line instrument that is installed between two pipe flanges.

The orifice plate flow meter is comprised the circular metal disc with a specific hole diameter that reduces the fluid flow in the pipe. Pressure taps are added on each side at the orifice plate to measure the pressure differential.

According to the Laws of Conservation of Energy, the fluid entering the pipe must equal the mass leaving the pipe during the same period of time. The velocity of the fluid leaving the orifice is greater than the velocity of the fluid entering the orifice. Applying Bernoulli's Principle, the increased fluid velocity results in a decrease in pressure.

As the fluid flow rate increases through the pipe, back pressure on the incoming side increases due to the restriction of flow created by the orifice plate.

The pressure of the fluid at the downstream side at the orifice plate is less than the incoming side due to the accelerated flow.

With a known differential pressure and velocity of the fluid, the volume metric flow rate can be determined. The flow rate “Q”, of a fluid through an orifice plate increases in proportion to the square root the pressure difference on each side multiplied by the K factor. For example if the differential pressure increases by 14 PSI with the K factor of one, the flow rate is increased by 3.74.

Piping Specialties, Inc. / PSI Controls
800-223-1468
https://psi-team.com

The Azbil AX Series of Vortex Inline Flow Meters

The AX Series of Vortex inline flowmeters measure flows of liquid, gas, and steam by measuring the rate at which vortices are alternately shed from a bluff body; this rate has been shown to be directly proportional to the flow velocity.

As flow passes a bluff body in the stream, vortices create pressure differentials which are measured by a piezoelectric crystal sensor, which converts these pulses into electrical signals. The meter uses an all-welded sensor design to create a strong unit and minimize potential leakage.

The Azbil AX Series can be configured to measure anything from simple volumetric flow of liquids and saturated steam up through multivariable measurements, including mass flow rate, pressure, temperature and density of liquids and steam.

Insertion style vortex meters measure fl ow by detecting the local velocity at a strategically located position within the pipe. Using local velocity, calculated by measuring the rate at which vortices are alternately shed from a bluff body within the sensor, the Azbil AX2300 uses parameters such as fluid type, pipe size, and Reynolds number to calculate accurate measurements.

Download the Azbil AX Series Vortex Flow Meter brochure here.

Azbil AX Series Vortex Flow Meters from Piping Specialties, Inc and PSI Controls

Using Link-Seal in Combination with Century-Line Sleeves or Cell-Cast Disks for Sealing Pipe Penetrations when Pouring Walls, Floors or Ceilings

Sealing pipes passing through concrete barriers can be one of the really tough challenges confronted by designers and installers of any piping system. But there's a way to simplify the whole process. All it takes is the system approach.  Link-Seal in combination with Century Line sleeves makes for a dynamic combination.  Just what you need to quickly and easily seal any cylindrical object passing through concrete poured walls, floors, and ceilings.

Link-Seal is a flexible belt of interconnected rubber links used to seal the void area or annular space between a cylindrical pipe and round wall opening. Be it a steel sleeve, plastic sleeve, or poured hole, installation is easy. The belt is simply wrapped around the pipe connected and secured by tightening the bolt heads moving clockwise around the seal. Pressure plates on each side of the link applied the compression necessary to expand the rubber. As the bolts are tightened, the links enlarge from a free to an expanded state, transforming the belt of separate links into a hydrostatic seal capable of holding in excess of 20 PSIG with a safety factor of 5 to 1. In the laboratory under controlled conditions, Link-Seal has been successfully tested to 100 PSIG and above.  In addition, accelerated aging tests have shown Link-Seal to be capable of providing maintenance-free service over performance life cycles estimated at 40 years or more.

In the real world, Link-Seal improves overall system reliability by effectively dampening the damaging effects of vibration.  Link-Seals reduce fatigue on pipe welds, flanges and threaded connections. As an added bonus, they may also be used to isolate stray electric current passing through pipes and casings. Applications for Link-Seal are almost infinite. In fact, any cylindrical object may be quickly easily and permanently sealed as they pass through barriers of all kinds.

For more information on Link-Seal, contact:
Piping Specialties, Inc.
https://psi-team.com
800-223-1468

What Are Trunnion Mount Ball Valves?

Trunnion ball valve design. Trunnions highlighted.

Ball valves are well understood in process control and industrial piping systems. Their simple 1/4 turn operation, compact form factor, bidirectional sealing, and tight shutoff make them a very popular choice for a wide range of applications.

Although there are many varieties of seat designs, body styles, and flow patterns, ball valves can be separated in to two main groups, distinguished by a primary design element - the mounting method of the valve ball.

The two groups are:

• Floating ball
• Trunnion mounted ball

Floating ball valves use the body and valve seats to position and hold the ball in the media flow path, allowing the flow force to lodge the "floating" ball firmly against the downstream seat. In this style, the ball is not mechanically held in place, thus the term "floating". Floating ball valves are, in general, limited to applications with smaller sizes and lower pressure ranges because, at some point, the fluid pressure on the ball may exceed the seat and trim's ability to hold the ball properly in place.

Trunnion mount valves, on the other hand, employ a "trunnion" in their design. A trunnion is a pin, or a pivot, forming one of a pair on which ball is mechanically connected and supported. The valve shaft and the trunnion connect at the top and bottom of the valve and create the vertical axis of rotation for the ball. The trunnion also prevents the ball from moving or shifting with changing pressures.

Due to their structural integrity, trunnion mount ball valves are generally well suited for all pressure ranges and valve sizes. Their design is used by many manufacturers for severe service. They provide excellent sealing properties over an extensive range of temperatures and pressures. Trunnion mount valves are available in both full and reduced bore designs with a wide range of materials, sizes, and pressure classes offered. The vast range of sizes, styles, pressure classes, and materials together with conformance to ANSI, API, and NACE specifications make these valves suitable for virtually all industrial, petrochemical, refinery, and oil and gas services. Finally, there may be an advantage to actuate trunnion ball valves due to lower torque requirements compared to similar floating ball valves whose torque increases with increasing flow pressure.

For more information on floating ball or trunnion mount ball valves, contact Piping Specialties, Inc. at 800-223-1468 or visit https://psi-team.com.

Process Refractometers Used in Black Liquor Recovery Boilers

The recovery boiler plays a central role in the chemical cycle of a modern pulp mill. The recovery boiler is a chemical reactor, which is used for recovering chemicals from spent kraft liquor and generating energy at the same time.

In the recovery boiler, the organic matter is burned. The dry solids liquor content required for firing is at least 60 %, but preferably more than 65 %. Black liquor is concentrated by evaporating water from the liquor. When the concentration of black liquor is maximized, so is the energy production. Before entering the burners, sodium sulfate decahydrate, or glauber salt, is added to cover chemical losses.

Application

Chemical curve: R.I. per Black
liquor Conc% at Ref. Temp. of 20 ̊C

The liquor should have a high content of combustible dry solids in order to minimize flue gas emissions and maximize boiler efficiency.

Too low concentration of dry solids fed to the burners may result in a steam explosion with consequent damage or destruction to the boiler. Therefore, it is essential to utilize a refractometer to monitor the black liquor feed to the recovery boiler to ensure a safe operation.

Instrumentation and installation

The K-Patents Digital Divert Control System DD-23 complies strictly with all recommendations of the Black Liquor Recovery Boiler Advisory Committee (BLRBAC).

The DD-23 system includes two SAFE-DRIVE Process Refractometer sensors in the main black liquor line, two indicating transmitters and a divert control unit in an integrated panel.

The sensors are installed using K-Patents patented SAFE-DRIVE Isolation valve. This allows for safe and easy insertion and retraction of the refractometers under full operating pressure, without having to valve off the liquor piping or having to shut down the process. The SAFE-DRIVE Isolation valve contains a steam wash system for automatic prism cleaning. The system contains a SAFE-DRIVE Retractor Tool SDR-23 for safe sensor insertion and retraction.

For more information about refractometers used on blacl liquor recovery boilers, contact Piping Specialties by calling 800-223-1468 or visit https://psi-team.com.

The Drexelbrook USonic Non-contact Level Transmitter

The Drexelbrook USonic level transmitter provides a level measurement utilizing a non-contact ultrasonic sensor. Measurements of level, distance, volume and open channel flow is easily configured through the menu driven display. The Usonic level transmitter is offered with a two wire 4-20 mA, Hart output signal and is suitable for all Class I Div. 1, Zone 0, I.S. or XP locations.

For more information contact PSI Controls / Piping Specialties by calling 800-223-1468 or visit https://psi-team.com.

Level and Pressure Instrumentation for Pulp & Paper Production

Pulp and paper applications create a notoriously harsh, high moisture and chemical-laden environment; coupled with extreme vibration in many of the processes. The following document outlines an array of level, pressure, and position applications and solutions for the pulp & paper industry.

Download a copy of the Measurement Solutions for the Pulp & Paper Industry here.


Piping Specialties, Inc / PSI Controls
800 223-1468
https://psi-team.com

Level and Pressure Instrumentation for Pulp & Paper Production from Piping Specialties, Inc and PSI Controls

Process Flow and Process Instrument Diagrams

To show a practical process example, let’s examine three diagrams for a compressor control system, beginning with a Process Flow Diagram, or PFD. In this fictitious process, water is being evaporated from a process solution under partial vacuum (provided by the compressor). The compressor then transports the vapors to a “knockout drum” where they condense into liquid form. As a typical PFD, this diagram shows the major interconnections of process vessels and equipment, but omits details such as instrument signal lines and auxiliary instruments:

One might guess the instrument interconnections based on the instruments’ labels. For instance, a good guess would be that the level transmitter (LT) on the bottom of the knockout drum might send the signal that eventually controls the level valve (LV) on the bottom of that same vessel. One might also guess that the temperature transmitter (TT) on the top of the evaporator might be part of the temperature control system that lets steam into the heating jacket of that vessel.

Based on this diagram alone, one would be hard-pressed to determine what control system, if any, controls the compressor itself. All the PFD shows relating directly to the compressor is a flow transmitter (FT) on the suction line. This level of uncertainty is perfectly acceptable for a PFD, because its purpose is merely to show the general flow of the process itself, and only a bare minimum of control instrumentation.

Process and Instrument Diagrams

The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming in” of scope from the whole evaporator process to the compressor as a unit. The evaporator and knockout vessels almost fade into the background, with their associated instruments absent from view:

Now we see there is more instrumentation associated with the compressor than just a flow transmitter. There is also a differential pressure transmitter (PDT), a flow indicating controller (FIC), and a “recycle” control valve allowing some of the vapor coming out of the compressor’s discharge line to go back around into the compressor’s suction line. Additionally, we have a pair of temperature transmitters reporting suction and discharge line temperatures to an indicating recorder.

Some other noteworthy details emerge in the P&ID as well. We see that the flow transmitter, flow controller, pressure transmitter, and flow valve all bear a common number: 42. This common “loop number” indicates these four instruments are all part of the same control system. An instrument with any other loop number is part of a different control system, measuring and/or controlling some other function in the process. Examples of this include the two temperature transmitters and their respective recorders, bearing the loop numbers 41 and 43.

lease note the differences in the instrument “bubbles” as shown on this P&ID. Some of the bubbles are just open circles, where others have lines going through the middle. Each of these symbols has meaning according to the ISA (Instrumentation, Systems, and Automation society) standard:

The type of “bubble” used for each instrument tells us something about its location. This, obviously, is quite important when working in a facility with many thousands of instruments scattered over acres of facility area, structures, and buildings.

The rectangular box enclosing both temperature recorders shows they are part of the same physical instrument. In other words, this indicates there is really only one temperature recorder instrument, and that it plots both suction and discharge temperatures (most likely on the same trend graph). This suggests that each bubble may not necessarily represent a discrete, physical instrument, but rather an instrument function that may reside in a multi-function device.

Details we do not see on this P&ID include cable types, wire numbers, terminal blocks, junction boxes, instrument calibration ranges, failure modes, power sources, and the like. To examine this level of detail, we must turn to another document called a loop diagram (not in this post).

Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

Drexelbrook’s ThePoint™ Series Point Level Switch: Settings, Adjustments, and Changing Calibration Modes

The AMETEK Drexelbrook ThePoint™ Series uses No-Cal™ technology to detect the presence or absence of material without calibration or initiation via setpoint adjustments, push-buttons or magnets.

ThePoint™ level measurement switch features both Auto-Cal and manual calibration. The standard Auto-Calibration mode is applicable to most liquid and slurry point level measurements. If preferred, the manual calibration can be used and is recommended for some application. ThePoint electronic unit has auto and manual calibration modes built into the standard unit and can be accessed through the simple routine shown in the video below. The inclusion of these calibration modes allows the Drexelbrook RF Point Level Products application flexibility that is far greater than any other point level product on the market. ThePoint™ level switch can be used in Liquids, Solids, Slurries, and Interface applications.

To learn more specific instructions on the (8) calibration modes ThePoint™ has available, download the "Drexelbrook ThePoint Series Point Level Switch Installation and Operating Instructions" from this link.

Piping Specialties / PSI Controls: New England's Preferred Source for Industrial Valves, Valve Automation, and Process Instrumentation

Founded in 1975, with offices in Portland, Maine and Danvers, Massachusetts, PSI has earned their reputation as New England's premier supplier of industrial valves, valve automation, process instrumentation and specialty process equipment.

PSI specializes in engineered products for these industries:

• Power Generation
• Pulp & Paper
• LNG / LPG / Natural Gas / Gas Storage & Distribution
• Pharmaceutical / BioTech
• Food and Beverage
• HVAC
• Water & Wastewater

Piping Specialties, Inc / PSI Controls
https://psi-team.com
800-223-1468

Top 5 Considerations in Selecting Pressure Gauges

Pressure gauges are ubiquitous in industry and installed on machinery around the world. While there are millions of possible combinations of shapes, sizes, options and materials, careful attention needs to be given to the following five criteria for safe use and long product life.

1) Process Media
Direct exposure of the sensing element to the process media is a possibility, so attention must be given to any corrosive media, media with particulate, or media that can solidify and clog the pressure gauge element. For non-clogging media, a direct connection and Bourdon tube sensor can be applied. For process media that could potentially cause clogging, a diaphragm seal should be used.

2) Process Media Temperature

Gauge with
diaphragm seal.
(AMETEKUS Gauge)

Very hot media, such as steam or hot water, can elevate the gauge's internal temperature leading to failure or an unsafe condition. For high temperature application, the use of a gauge "siphon" or diaphragm seal be applied.

3) Ambient Operating Temperature and Environment
It is important to know the rated ambient environment for any instrument. Elevated ambient temperatures, moisture, vibration, and corrosive atmospheres can all affect accuracy, calibration, and safety. Choose the proper case and mechanism materials if oxidizing or reducing atmospheres exist, and consider the addition of ancillary devices, such as remote diaphragm seals, to relocate the gauge.

4) Possibility of Severe Pressure Fluctuations

In applications where dramatic line pulsations or strong over-pressure conditions are a possibility the use of pressure restrictors, snubbers, or liquid-filling will extend the service life of the pressure gauge.

5) Mounting

Snubbers & restrictors

Pressure gauges are standardly available with bottom (radial) and back connections. NPT (National Pipe Thread Taper) threaded connections are generally the standard. Many other process connections are available though, such as straight threads, metric threads, and specialized fittings. Make sure you know how the gauge is being connected. When mounting, pressure gauges should be almost always be mounted upright.

For more information about pressure gauges, contact PSI Controls by visiting https://psi-team.com or by calling 800-223-1468.

What is an External Spring, Lever & Weight Single Disc Check Valve

Single disk check valve animation.

According to Wikipedia, "Check valves are used in many fluid systems such as those in chemical and power plants, and in many other industrial processes."

Check valve symbol

As shown in the animation to the left, the single disc (swing) check valve use the directional flow to push open a swinging disk. As long as flow continues, the disk stays raised. But as flow stops, gravity allows the disk to re-seat itself and any reverse flow is prevented by the closed disk. As reverse flow pressure increases, the swing check valves seating increases as well.

Single disc check valves also use springs, levers and/or weights mounted on the valve to allow for better control of surge and to prevent the valve from slamming closed. These assemblies are used to vary the valve’s closing operation in order to reduce the severity of the closing water hammer.

External spring, external spring & lever, and external spring, level & weight designs (left to right).
Courtesy of Champion Valve.

For more information on any industrial check valve, contact Piping Specialties, Inc. by visiting https://psi-team.com or calling 800-223-1468.

An Introduction to Triple Offset Butterfly Valves

Triple Offset Butterfly Valve
(Pratt Industrial)

Triple offset butterfly valves are designed to fill the demand for an alternate solution to gate valves and ball valves. They are preferred when weight, space, performance, and the ability to modulate to the process flow are an issue. Typically available in sizes 3" through 48", and in 150, 300 and 600 pressure classes, they're rated for operation from -50 deg. F. through 750 deg. F.

Designed with metal-to metal seats, triple offset butterfly valves provide distinct advantages over traditional gate valves, namely lower weight, zero-leakage, ease in automation, and capable of being used for modulating service.

Industries Using 

• Chemical
• Refinery
• Power
• Steam Generation
• Petrochemical
• Water/Waste Water Treatment

Click on image for larger view.

Triple Eccentric Disc-Shaft Design (diagram above)

• Offset 1: It is accomplished by moving the centerline of the shaft away from the seating plane.
• Offset 2: It is accomplished by moving the centerline of the shaft offset from the centerline bore of the valve.
• These two design features cause the disc to open and close relative to the body seat in a “camming” action and effectuate the position seated valve design which is typical of the High Performance Butterfly Valve, however there is still contact between the disc and the seat in the first several degrees of opening and closing which can cause premature wear of the seat in the general areas.
• In order to achieve an API 598 Shut Off classification a 3rd offset needed to be introduced to make the valve a “torque seated” design with graphite and metal seating surfaces.
• Offset 3: It is accomplished by adjusting the cone angle created by the 1st and 2nd offset angles at some point downstream of the valve in the center of the piping to the adjacent piping wall as depicted in the illustration below “Sticking tendency”. By incorporating the 3 offsets into one design typical of gate valves is eliminated with seat contact throughout the entire stroke reducing run torques and improving actuator modulating performance at the same time.

For more information, contact Piping Specialties by visiting https://psi-team.com or by calling 800-223-1468.

What is a Piping and Instrumentation Diagram (P&ID)?

Piping and  instrumentation diagrams (P&ID's) are schematic representations of a process control system and used to illustrate the piping system, process flow, installed equipment, and process instrumentation and functional relationships therein. They are also known as "process and control flow diagrams".

They are intended to provide a “picture” of all the process piping, including the physical branches, valves, equipment, instrumentation and interlocks. By using a standard set of internationally recognized symbols, each component of the process system - instruments, piping, motors, pumps - is recognized on paper or computer screen.

P&ID’s may be very detailed and are generally the primary source from where instrument and equipment lists are generated. They are also used as a handy reference for maintenance planning and system upgrades. Furthermore, P&ID’s also play an important early role in plant safety planning by providing a thorough understanding of the operability and relationships of all components in the system.

Watch the short video below for more information.

For more information contact:
Piping Specialties / PSI
https://psi-team.com
800-223-1468

Continuous and Point Level Control Selection Guide

Drexelbrook Continuous and Point Level Control Products

Based on experience from of thousands of inquiries about level measurement, most questions boil down to "What is the best level measurement instrument for my application? That depends on quite a few application considerations, such as:

• Will the measured media add coating to the probe?
• Can the probe have contact with the media?
• Are there explosion hazards?
• What is the physical type of application, well, tank, open channel or floating roof tank?

This document can help deliver the perfect continuous level transmitter or level switches for your application.

Download a PDF version of the Drexelbrook Continuous and Point Level Control Selection Guide here, or view the embedded document below.

https://psi-team.com
800-223-1468

Drexelbrook Continuous & Point Level Selection Guide from Piping Specialties, Inc and PSI Controls

Considerations for Choosing Industrial Butterfly Valves

High Performance Butterfly Valve
(Pratt)

Industrial process control valves are available in uncountable combinations of materials, types, and configurations. An initial step of the selection procedure for a valve application should be choosing the valve type, thus narrowing the selection field to a more manageable level. Valve "types" can generally be classified by the closing mechanism of the valve.

A butterfly valve has a disc that is positioned in the fluid flow path. In the most common form of butterfly valve, the disc 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 variety of materials are used in the valve body construction, and it is common to line the valve with another material to provide special properties accommodating particular process media.

What attributes might make a butterfly valve a beneficial selection over another valve type?

Resilient Seated Butterfly Valve
(Pratt)

• The closure arrangement allows for a comparatively small size and weight. This can reduce the cost, space, and support requirements for the valve assembly.
• Generally low torque requirements for valve operation allow for manual operation, or automation with an array of electric, pneumatic, or hydraulic actuators.
• Low pressure drop associated with the closure mechanism. The disc in the flow path is generally thin. In the fully open position, the disc presents its narrow edge to the direction of flow.
• Quarter turn operation allows for fast valve operation.
• Some throttling capability is provided at partially open positions.
• Small parts count, low maintenance requirements.

What may be some reasons to consider alternate valve types?

• Butterfly valve throttling capability is generally limited to low pressure drop applications.
• Cavitation can be a concern.
• Some sources mention the possibility of choked flow as a concern under certain conditions.

Butterfly valves, like other valve types, have applications where they outperform. Careful consideration and consultation with a valve expert is a first step toward making a good selection. Combine your process know-how with the product application expertise of a professional sales engineer to produce the best solutions to your process control challenges.

For more information regarding an type of industrial valve, contact Piping Specialties, Inc. by visiting https://psi-team or by calling 800-223-1468.

MOGAS Severe Service Ball Valve "Mate Lap" Seal Demonstration

The video below demonstrates the effectiveness of the MOGAS "Mate Lap" seal provided on MOGAS severe service ball valves.

MOGAS valves have outperformed others worldwide in some of the most severe service conditions, including: Extreme temperatures; High pressures; Abrasive particulates; Acidic products; Heavy solids build-up; Critical plant safety; Large pressure differentials; Velocity control; Noise control.