Industrial Valve Actuator Basics

Electric actuator (Limitorque)

Actuators are devices which supply the force and motion to open and close valves. They can be manually, pneumatically, hydraulically, or electrically operated. In common industrial usage, the term actuator generally refers to a device which employs a non-human power source and can respond to a controlling signal. Handles and wheels, technically manual actuators, are not usually referred to as actuators. They do not provide the automation component characteristic of powered units.

The primary function of a valve actuator is to set and hold the valve position in response to a process control signal. Actuator operation is related to the valve on which it is installed, not the process regulated by the valve. Thus a general purpose actuator may be used across a broad range of applications.

Pneumatic actuator (Metso Neles)

In a control loop, the controller has an input signal parameter, registered from the process, and compares it to a desired setpoint parameter. The controller adjusts its output to eliminate the difference between the process setpoint and process measured condition. The output signal then drives some control element, in this case the actuator, so that the error between setpoint and actual conditions is reduced. The output signal from the controller serves as the input signal to the actuator, resulting in a repositioning of the valve trim to increase or decrease the fluid flow through the valve.

An actuator must provide sufficient force to open and close its companion valve. The size or power of the actuator must match the operating and torque requirements of the companion valve. After an evaluation is done for the specific application, it may be found that other things must be accommodated by the actuator, such as dynamic fluid properties of the process or the seating and unseating properties of the valve. It is important that each specific application be evaluated to develop a carefully matched valve and actuator for the process.

Hydraulic and electric actuators are readily available in multi-turn and quarter-turn configurations. Pneumatic actuators are generally one of two types applied to quarter-turn valves: scotch-yoke and rack and pinion. A third type of pneumatic actuator, the vane actuator, is also available.

For converting input power into torque, electric actuators use motors and gear boxes while pneumatic actuators use air cylinders. Depending on torque and force required by the valve, the motor horsepower, gearing, and size of pneumatic cylinder may change.

Linear pneumatic actuator (Neles)

There are almost countless valve actuator variants available in the industrial marketplace. Many are tailored for very narrow application ranges, while others are more generally applied. Special designs can offer more complex operating characteristics. Ultimately, when applying actuators to any type of device, consultation with an application specialist is recommended to help establish and attain proper performance, safety and cost goals, as well as evaluation and matching of the proper actuator to the valve operation requirements. Share your fluid process control requirements with a specialist in valve automation, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Segmented or V Ported Ball Valves

Metso Neles segment ball valve

Ball, plug and butterfly valves all belong to a class of valves commonly referred to as "quarter-turn" valves. This refers the 90 deg (angular) rotation required to go from full closed, to full open position.

In most cases standard ball, plug, or butterfly valves are not the best choice as control valves (where the process media has to be modulated or throttled). Standard ball, plug and butterfly valves usually introduce very non-linear, dynamic flow coefficients. Furthermore, they can introduce undesirable turbulence to your piping system.

As a means to linearize flow coefficients and reduce turbulent flow, the machining, or characterization, of the valve disk is done so that the machined shape allows for more optimized flow.

For ball valves in particular, machining the ball's flow port with a "V", or even by machining the ball more radically, can deliver excellent flow curves. A term for a more radically machined ball is the "segment ball" (sometimes called "segmented").  In the following video you can see how a Metso Neles segment ball valve is designed to provide excellent control.

For more information about Metso Neles valves, contact Mead O'Brien at  (800) 892-2769 or visit http://meadobrien.com.

Common Ways to Measure Steam Flow

For steam, energy is primarily contained in the latent heat and, to a lesser extent, the sensible heat of the fluid. The latent heat energy is released as the steam condenses to water. Additional sensible heat energy may be released if the condensate is further lowered in temperature. In steam measuring, the energy content of the steam is a function of the steam mass, temperature and pressure. Even after the steam releases its latent energy, the hot condensate still retains considerable heat energy, which may or may not be recovered (and used) in a constructive manner. The energy manager should become familiar with the entire steam cycle, including both the steam supply and the condensate return.

When compared to other liquid flow measuring, the measuring of steam flow presents one of the most challenging measuring scenarios. Most steam flowmeters measure a velocity or volumetric flow of the steam and, unless this is done carefully, the physical properties of steam will impair the ability to measure and define a mass flow rate accurately.

Steam is a compressible fluid; therefore, a reduction in pressure results in a reduction in density. Temperature and pressure in steam lines are dynamic. Changes in the system’s dynamics, control system operation and instrument calibration can result in considerable differences between actual pressure/temperature and a meter’s design parameters. Accurate steam flow measurement generally requires the measurement of the fluid’s temperature, pressure, and flow. This information is transmitted to an electronic device or flow computer (either internal or external to the flow meter electronics) and the flow rate is corrected (or compensated) based on actual fluid conditions.

The temperatures associated with steam flow measurement are often quite high. These temperatures can affect the accuracy and longevity of measuring electronics. Some measuring technologies use close-tolerance moving parts that can be affected by moisture or impurities in the steam. Improperly designed or installed components can result in steam system leakage and impact plant safety. The erosive nature of poor-quality steam can damage steam flow sensing elements and lead to inaccuracies and/or device failure.

The challenges of measuring steam can be simplified measuring the condensed steam, or condensate. The measuring of condensate (i.e., high-temperature hot water) is an accepted practice, often less expensive and more reliable than steam measuring. Depending on the application, inherent inaccuracies in condensate measuring stem from unaccounted for system steam losses. These losses are often difficult to find and quantify and thus affect condensate measurement accuracy.

Volumetric measuring approaches used in steam measuring can be broken down into two operating designs:

1. Differential pressure
2. Velocity measuring technologies.

DIFFERENTIAL

For steam three differential pressure flowmeters are highlighted: orifice flow meter, annubar flow meter, and spring-loaded variable area flow meter. All differential pressure flowmeters rely on the velocity-pressure relationship of flowing fluids for operation.

Orifice Flow Meter
(courtesy of Foxboro)

Differential Pressure – Orifice Flow Meter

Historically, the orifice flow meter is one of the most commonly used flowmeters to measure steam flow. The orifice flow meter for steam functions identically to that for natural gas flow. For steam measuring, orifice flow flowmeters are commonly used to monitor boiler steam production, amounts of steam delivered to a process or tenant, or in mass balance activities for efficiency calculation or trending.

Differential Pressure – Annubar Flow Meter

The annubar flow meter (a variation of the simple pitot tube) also takes advantage of the velocity-pressure relationship of flowing fluids. The device causing the change in pressure is a pipe inserted into the steam flow.

Differential Pressure – Spring-Loaded Variable Area Flow Meter

The spring-loaded variable area flow meter is a variation of the rotameter. There are alternative configurations but in general, the flow acts against a spring-mounted float or plug. The float can be shaped to give a linear relationship between differential pressure and flow rate. Another variation of the spring-loaded variable area flow meter is the direct in-line variable area flow meter, which uses a strain gage sensor on the spring rather than using a differential pressure sensor.

VELOCITY

The two main type of velocity flowmeters for steam flow, turbine and vortex shedding, both sense some flow characteristic directly proportional to the fluid’s velocity.

Velocity –  Turbine Flow Meter

A multi-blade impellor-like device is located in, and horizontal to, the fluid stream in a turbine flow meter. As the fluid passes through the turbine blades, the impellor rotates at a speed related to the fluid’s velocity. Blade speed can be sensed by a number of techniques including magnetic pick-up, mechanical gears, and photocell. The pulses generated as a result of blade rotation are directly proportional to fluid velocity, and hence flow rate.

Vortex Flowmeter
(courtesy of Foxboro)

Velocity – Vortex-Shedding Flow Meter

A vortex-shedding flow meter senses flow disturbances around a stationary body (called a bluff body) positioned in the middle of the fluid stream. As fluid flows around the bluff body, eddies or vortices are created downstream; the frequencies of these vortices are directly proportional to the fluid velocity.

For more information on process steam management, contact Mead O'Brien by visiting http://www.meadobrien.com or call (800) 892-2769,

Limitorque QX Electronic Actuator User Instructions

Limitorque QX

The Flowserve Limitorque QX quarter-turn smart electronic valve actuator continues the legacy of the industry’s state-of-the-art, non-intrusive, multi-turn MX actuator by including an absolute encoder for tracking position without the use of troublesome batteries. The QX design provides enhanced safety and reduced downtime through improved diagnostics, built-in self-test (BIST) features and LimiGard™ fault protection.

The QX design builds on more than 10 years of experience with proven Limitorque MX technology - the first generation double-sealed electronic valve actuator from Flowserve designed to provide control, ease of use and  accuracy. The QX includes all the user-preferred features of the MX in a quarter-turn smart actuator package. It is the only non-intrusive, double-sealed quarter-turn actuator to display the Limitorque brand.

For more information on any Limitorque actuator, visit Mead O'Brien at http://www.meadobrien.com or call (800) 892-2769.

Limitorque QX Electronic Actuator User Instructions from Mead O'Brien, Inc.

Common Industrial and Commercial Process Heating Methodologies

Fuel boiler producing steam.

Process heating methodologies can be grouped into four general categories based on the type of fuel consumed:

1. Steam
2. Fuel
3. Electric
4. Hybrid systems

These technologies are based upon conduction, convection, or radiative heat transfer mechanisms - or some combination of these. In practice, lower-temperature processes tend to use conduction or convection, whereas high-temperature processes rely primarily on radiative heat transfer. Systems using each of the four energy types can be characterized as follows:

STEAM

Tube heat exchanger.

Steam-based process heating systems introduce steam to the process either directly (e.g., steam sparging) or indirectly through a heat transfer mechanism. Large quantities of latent heat from steam can be transferred efficiently at a constant temperature, useful for many process heating applications. Steam-based systems are predominantly used by industries that have a heat supply at or below about 400°F and access to low-cost fuel or byproducts for use in generating the steam. Cogeneration (simultaneous production of steam and electrical power) systems also commonly use steam-based heating systems. Examples of steam-based process heating technologies include boilers, steam spargers, steam-heated dryers, water or slurry heaters, and fluid heating systems.

FUEL

Fuel-based process heating systems generate heat by combusting solid, liquid, or gaseous fuels, then transferring the heat directly or indirectly to the material. Hot combustion gases are either placed in direct contact with the material (i.e., direct heating via convection) or routed through radiant burner tubes or panels that rely on radiant heat transfer to keep the gases separate from the material (i.e., indirect heating).  Examples of fuel-based process heating equipment include furnaces, ovens, red heaters, kilns, melters, and high-temperature generators.

ELECTRICITY

Electricity-based process heating systems also transform materials through direct and indirect processes. For example, electric current is applied directly to suitable materials to achieve direct resistance heating; alternatively, high-frequency energy can be inductively coupled to suitable materials to achieve indirect heating. Electricity-based process heating systems are used for heating, drying, curing, melting, and forming. Examples of electricity-based process heating technologies include electric arc furnace technology, infrared radiation, induction heating, radio frequency drying, laser heating, and microwave processing.

HYBRID

Hybrid process heating systems utilize a combination of process heating technologies based on different energy sources and/or heating principles to optimize energy performance and increase overall thermal efficiency. For example, a hybrid boiler system may combine a fuel-based boiler with an electric boiler to take advantage of access to lower off-peak electricity prices. In an example of a hybrid drying system, electromagnetic energy (e.g., microwave or radio frequency) may be combined with convective hot air to accelerate drying processes; selectively targeting moisture with the penetrating electromagnetic energy can improve the speed, efficiency, and product quality as compared to a drying process based solely on convection, which can be rate-limited by the thermal conductivity of the material. Optimizing the heat transfer mechanisms in hybrid systems offers a significant opportunity to reduce energy consumption, increase speed/throughput, and improve product quality.

The experts at Mead O'Brien are always available to assist you with any process heating application. Visit http://meadobrien.com or call (800) 892-2769 for more information.

The Basics of a Fieldbus Control Network

Computer systems used within the industrial sector are connected by networks known generally as Fieldbus. Fieldbus systems are a way to connect computers and instruments to a single network in a manufacturing plant and allow for real-time control and monitoring. Fieldbus industrial networks can be broken down into four levels each with increasing levels of complexity.

The most basic level is the sensor bus networks. Sensor bus networks are the least complex of networks developed for industrial application. In these networks, multiple basic field devices like limits witches or level optical sensors are connected to one network cable. The sensor bus network is also capable of transmitting output signals from the controller over one cable to indicator lamps, alarms, or other actuator devices.

The next increasingly complex level of industrial Fieldbus networking is the device bus network. The device bus network is similar in function to the sensor bus network but works on a larger scale connecting many sensors and actuators together. The device bus network also connects equipment to variable speed drives and motor control centers that allow for control of individual elements in the network.

Moving up the pyramid, the next increasing complex level of Fieldbus networking is the control bus network. Control bus networks are the most advanced networks used on the factory floor and data communication happens at a high level. PLC's, or programmable logic controllers, are connected to each other alongside HMI's or human machine interface panels to allow for complete configuration and control of every instrument on the network. Smart instruments, capable of performing complex operations, can also be connected at this network level. For instance, there might be a smart instrument that measures wear and tear on a valve. When the wear reaches a dangerous level it will signal the controller that the valve needs to be replaced.

The enterprise or information level network in a company connects all computers and departments together it is the most overarching and complex of all the various network levels. This level of networking is primarily computer driven which allows for data collection, data monitoring, file transfers, and email exchange on a large scale. The various levels of interconnected Fieldbus networking help to keep industry functioning smoothly and successfully.

Process Instrument Calibration and Repair

The Mead O’Brien Instrument Shop is fully equipped to handle your instrument calibration and repair needs. Whether its repair, calibration or certification services, Mead O’Brien can handle the job. Our technicians are factory trained and certified and can repair and re-calibrate virtually any pressure and temperature transmitter, pressure gauge, pressure switch, thermometer, RTD, or thermocouple.

Industrial Pressure Switches

Industrial Pressure Switch (Ashcroft)

A pressure switch is a device that detects the presence of fluid pressure. Pressure switches use a variety of sensing elements such as diaphragms, bellows, bourdon tubes, or pistons. The movement of these sensors, caused by pressure fluctuation, is transferred to a set of electrical contacts to open or close a circuit.

Normal status of a switch is the resting state with stimulation. A pressure switch will be in its “normal” status when it senses low or minimum pressure. For a pressure switch, “normal” status is any fluid pressure below the trip threshold of the switch.

One of the earliest and most common designs of pressure switch was the bourdon tube pressure sensor with mercury switch. When pressure is applied, the bourdon tube flex's enough to tilt the glass bulb of the mercury switch so that the mercury flows over the electrical contacts, thus completing the circuit. the glass bulb tilts far enough to cause the mercury to fall against a pair of electrodes, thus completing an electrical circuit. Many of these pressure switches were sold on steam boilers. While they became a de facto standard, they were sensitive to vibration and breakage of the mercury bulb.

Pressure Switch Symbols

Pressure switches using micro type electrical switches and force-balanced pressure sensors is another common design.  The force provided by the pressure-sensing element against a mechanical spring is balanced until one overcomes the other. The tension on the spring may be adjusted to set the tripping point, thus providing an adjustable setpoint.

One of the criteria of any pressure switch is the deadband or (reset pressure differential). This setting determines the amount of pressure change required to re-set the switch to its normal state after it has tripped.  The “differential” pressure of a pressure switch should not to be confused with differential pressure switch, which actually measures the difference in pressure between two separate pressure ports.

When selecting pressure switches you must consider the electrical requirements (volts, amps, AC or DC), the area classification (hazardous, non-hazardous, general purpose, water-tight), pressure sensing range, body materials that will be exposed to ambient contaminants, and wetted materials (parts that are exposed to the process media).

Steam Conservation Guidelines for Condensate Drainage

Any company that is energy conscious is also environmentally conscious. Less energy consumed means less waste, fewer emissions and a healthier environment.

In short, bringing energy and environment together lowers the cost industry must pay for both. By helping companies manage energy, Armstrong and Mead O'Brien products and services are also help protect the environment.

Steam is an invisible gas generated by adding heat energy to water in a boiler. Enough energy must be added to raise the temperature of the water to the boiling point. Then additional energy—without any further increase in temperature—changes the water to steam.

Steam is a very efficient and easily controlled heat transfer medium. It is most often used for transporting energy from a central location (the boiler) to any number of locations in the plant where it is used to heat air, water or process applications.

As noted, additional Btu are required to make boiling water change to steam. These Btu are not lost but stored in the steam ready to be released to heat air, cook tomatoes, press pants or dry a roll of paper.

The heat required to change boiling water into steam is called the heat of vaporization or latent heat. The quantity is different for every pressure/temperature combination, as shown in the steam tables.

Heat flows from a higher temperature level to a lower temperature level in a process known as heat transfer. Starting in the combustion chamber of the boiler, heat flows through the boiler tubes to the water. When the higher pressure in the boiler pushes steam out, it heats the pipes of the distribution system. Heat flows from the steam through the walls of the pipes into the cooler surrounding air. This heat transfer changes some of the steam back into water. That’s why distribution lines are usually insulated to minimize this wasteful and undesirable heat transfer.

When steam reaches the heat exchangers in the system, the story is different. Here the transfer of heat from the steam is desirable. Heat flows to the air in an air heater, to the water in a water heater or to food in a cooking kettle. Nothing should interfere with this heat transfer.

Condensate Drainage - Why It’s Necessary

Condensate is the by-product of heat transfer in a steam system. It forms in the distribution system due to unavoidable radiation. It also forms in heating and process equipment as a result of desirable heat transfer from the steam to the substance heated. Once the steam has condensed and given up its valuable latent heat, the hot condensate must be removed immediately. Although the available heat in a pound of condensate is negligible as compared to a pound of steam, condensate is still valuable hot water and should be returned to the boiler.

The document below provides and excellent reference for understanding the properties of steam and the importance of condensate drainage for an efficient system. You may also download your own copy of the Steam Conservation Guidelines for Condensate Drainage here.

Steam Conservation Guidelines for Condensate Drainage from Mead O'Brien, Inc.

Condensate Drainage ... Why It’s Necessary in Industrial Steam Systems

Condensate drain
(Armstrong).

Abstracted with permission from Armstrong International

Condensate is the by-product of heat transfer in a steam system. It forms in the distribution system due to unavoidable radiation. It also forms in heating and process equipment as a result of desirable heat transfer from the steam to the substance heated. Once the steam has condensed and given up its valuable latent heat, the hot condensate must be removed immediately. Although the available heat in a pound of condensate is negligible as compared to a pound of steam, condensate is still valuable hot water and should be returned to the boiler.

The need to drain the distribution system.

Figure 1: Condensate allowed to collect in pipes or tubes
is blown into waves by steam passing over it until it blocks
steam flow at point A. Condensate in area B causes a pressure
differential that allows steam pressure to push the slug
of condensate along like a battering ram.

Condensate lying in the bottom of steam lines can be the cause of one kind of water hammer. Steam traveling at up to 100 miles per hour makes “waves” as it passes over this condensate (Fig. 1). If enough condensate forms, high-speed steam pushes it along, creating a dangerous slug that grows larger and larger as it picks up liquid in front of it. Anything that changes the direction—pipe fittings, regulating valves, tees, elbows, blind flanges—can be destroyed. In addition to damage from this “battering ram,” high-velocity water may erode fittings by chipping away at metal surfaces.

The need to drain the heat transfer unit. 

Figure 2: Coil half full of condensate can’t
work at full capacity.

When steam comes in contact with condensate cooled below the temperature of steam, it can produce another kind of water hammer known as thermal shock. Steam occupies a much greater volume than condensate, and when it collapses suddenly, it can send shock waves throughout the system. This form of water hammer can damage equipment, and it signals that condensate is not being drained from the system. Obviously, condensate in the heat transfer unit takes up space and reduces the physical size and capacity of the equipment. Removing it quickly keeps the unit full of steam (Fig. 2). As steam condenses, it forms a film of water on the inside of the heat exchanger. Non-condensable gases do not change into liquid and flow away by gravity. Instead, they accumulate as a thin film on the surface of the heat exchanger—along with dirt and scale. All are potential barriers to heat transfer (Fig. 3).

The need to remove air and CO2. 

Air is always present during equipment start-up and in the boiler feedwater. Feedwater may also contain dissolved carbonates, which release carbon dioxide gas. The steam velocity pushes the gases to the walls of the heat exchangers, where they may block heat transfer. This compounds the condensate drainage problem, because these gases must be removed along with the condensate.

Fig 3: Potential barriers to heat transfer: steam heat and temperature
 must penetrate these potential barriers to do their work.

For more information about any industrial steam or hot water system, contact Mead O'Brien by visiting www.meadobrien.com or call (800) 892-2769.

Industrial Valve Automation, Service and Repair

From quarter-turn ball, butterfly, or plug valves, to linear gate and globe valves, Mead O'Brien can handle the most challenging actuation design. Options and accessories such as valve communications, limit switches, fail-safe devices, and solenoid valves are no problem.

With decades of expertise in rack and pinion and scotch-yoke actuators, as well as electric quarter-turn and linear actuators, Mead O'Brien has the experience and facilities to deliver a well engineered automated valve package. Visit www.meadobrien.com.

Understanding Industrial Valve Actuators

Automated Pneumatic
Ball Valve (Jamesbury)

Valves are essential to industries which constitute the backbone of the modern world. The prevalence of valves in engineering, mechanics, and science demands that each individual valve performs to a certain standard. Just as the valve itself is a key component of a larger system, the valve actuator is as important to the valve as the valve is to the industry in which it functions. Actuators are powered mechanisms that position valves between open and closed states; the actuators are controllable either by manual control or as part of an automated control loop, where the actuator responds to a remote control signal. Depending on the valve and actuator combination, valves of different types can be closed, fully open, or somewhere in-between. Current actuation technology allows for remote indication of valve position, as well as other diagnostic and operational information. Regardless of its source of power, be it electric, hydraulic, pneumatic, or another, all actuators produce either linear or rotary motion under the command of a control source.

Thanks to actuators, multiple valves can be controlled in a process system in a coordinated fashion; imagine if, in a large industrial environment, engineers had to physically adjust every valve via a hand wheel or lever! While that manual arrangement may create jobs, it is, unfortunately, completely impractical from a logistical and economic perspective. Actuators enable automation to be applied to valve operation.

Pneumatic actuator
(Jamesbury Quadra-Powr) 

Pneumatic actuators utilize air pressure as the motive force which changes the position of a valve. Pressurized-liquid reliant devices are known as hydraulic actuators. Electric actuators, either motor driven or solenoid operated, rely on electric power to drive the valve trim into position. With controllers constantly monitoring a process, evaluating inputs, changes in valve position can be remotely controlled to provide the needed response to maintain the desired process condition.

Manual operation and regulation of valves is becoming less prevalent as automation continues to gain traction throughout every industry. Valve actuators serve as the interface between the control intelligence and the physical movement of the valve. The timeliness and automation advantages of the valve actuators also serve as an immense help in risk mitigation, where, as long as the system is functioning correctly, critical calamities in either environmental conditions or to a facility can be pre-empted and quickly prevented. Generally speaking, manual actuators rely on hand operation of levers, gears, or wheels, but valves which are frequently changed (or which exist in remote areas) benefit from an automatic actuator with an external power source for a myriad of practical reasons, most pressingly being located in an area mostly impractical for manual operation or complicated by hazardous conditions.

Electric Actuator
(Limitorque)

Thanks to their versatility and stratified uses, actuators serve as industrial keystones to, arguably, one of the most important control elements of industries around the world. Just as industries are the backbones of societies, valves are key building blocks to industrial processes, with actuators as an invaluable device ensuring both safe and precise operation.

Intelligent Transmitters Help Coal Plant Reduce Costs and Improve Performance

Effective, profitable power plant operation requires managing capital-expense turbine, boiler, and combustion equipment, along with many other assets that must be precisely balanced. Reliable readings of pressure, temperature, and other process variables are critical to success.

While analog transmitters are known for accuracy and reliability, maintenance costs increase with age, and flexibility for performance improvement is limited. To reduce long-term operating costs and maintain quality service to more than 300,000 customers, a Michigan power utility launched a program to replace its aging analog transmitters with modern digital models.

The utility uses transmitters for draft indications on the boiler and pulverized mill area. They read pressure on the boiler and the turbine as well as combustion and steam heating equipment. Some of the instruments send data to a centralized distributed control system (DCS), which manages the set points that control the sensitive interactions. Other instruments simply indicate various pressure states to operators and maintenance technicians.

When this power utility implemented its first DCS, all transmitters were analog. At the time, mixing and matching multiple brands of analog sensors was difficult, and in some cases impossible, due to proprietary mounting configurations. Managers at this Michigan power plant wanted to be certain that they selected a digital sensor that would not lock them into a single vendor.

To learn how this power company came up with a the solution and to learn the results, read the complete document below. For any process instrument requirement, visit Mead O'Brien at www.meadobrien.com or call (800) 892-2769.

Intelligent Transmitters Help Coal Plant Reduce Costs and Improve Performance from Mead O'Brien, Inc.

Train Your People for Better Plant Steam and Hot Water Systems

Do the people who maintain your plant’s steam system really understand how to save you money?

It's probably a good idea to have them attend a professional steam and hot water training seminar. These programs provide a window into elements of the plant steam cycle as they observe live steam and condensate behavior in glass piping and glass-bodied steam traps under differing conditions. They gain very useful knowledge regarding:

• Steam generation 
• Distribution 
• Control & Heat transfer 
• Heat Recovery opportunities 
• Condensate removal & return

Mead O'Brien, a company with decades of experience in industrial and commercial steam and hot water systems provides such training. See their video below:

The Application of Heat in Industrial Applications

Heat exchanger (courtesy of Armstrong)

The measurement and control of heat related to fluid processing is a vital industrial function, and relies on regulating the heat content of a fluid to achieve a desired temperature and outcome.

The manipulation of a substance's heat content is based on the central principle of specific heat, which is a measure of heat energy content per unit of mass. Heat is a quantified expression of a systems internal energy. Though heat is not considered a fluid, it behaves, and can be manipulated, in some similar respects. Heat flows from points of higher temperature to those of lower temperature, just as a fluid will flow from a point of higher pressure to one of lower pressure. 

A heat exchanger provides an example of how the temperature of two fluids can be manipulated to regulate the flow or transfer of heat. Despite the design differences in heat exchanger types, the basic rules and objectives are the same. Heat energy from one fluid is passed to another across a barrier that prevents contact and mixing of the two fluids. By regulating temperature and flow of one stream, an operator can exert control over the heat content, or temperature, of another. These flows can either be gases or liquids. Heat exchangers raise or lower the temperature of these streams by transferring heat between them. 

Recognizing the heat content of a fluid as a representation of energy helps with understanding how the moderation of energy content can be vital to process control. Controlling temperature in a process can also provide control of reactions among process components, or physical properties of fluids that can lead to desired or improved outcomes.

 

Heat can be added to a system in a number of familiar ways. Heat exchangers enable the use of steam, gas, hot water, oil, and other fluids to deliver heat energy. Other methods may employ direct contact between a heated object (such as an electric heating element) or medium and the process fluid. While these means sound different, they all achieve heat transfer by applying at least one of three core transfer mechanisms: conduction, convection, and radiation. Conduction involves the transfer of heat energy through physical contact among materials. Shell and tube heat exchangers rely on the conduction of heat by the tube walls to transfer energy between the fluid inside the tube and the fluid contained within the shell. Convection relates to heat transfer due to the movement of fluids, the mixing of fluids with differing temperature. Radiant heat transfer relies on electromagnetic waves and does not require a transfer medium, such as air or liquid. These central explanations are the foundation for the various processes used to regulate systems in industrial control environments.

The manner in which heat is to be applied or removed is an important consideration in the design of a process system. The ability to control temperature and rate at which heat is transferred in a process depends in large part on the methods, materials, and media used to accomplish the task. 

Don’t Overlook the Value of Valve Automation Professionals on Your Next Valve Project

Sales and Engineering Professionals are there to assist
and save you time and money.

Local distributors and representatives who sell industrial valves, actuators and controls also provide services and equipment that will save you time, money, and help you achieve a better outcome for the entire project.

Projects requiring engineered valve systems are best completed and accomplished through the proper selection and application of the valves, actuators, positioners, limit switches and other associated components. A great resource exists, ready to provide a high level of technical knowledge and assistance, that can be easily tapped to help you with your project - the valve automation sales professional.


Consider a few elements the valve automation professional brings to your project:

Product Knowledge: Valve automation professionals are current on product offerings, proper application technique, and product capabilities. They also posses  information on future product obsolescence and upcoming new designs. This type of information is not generally accessible to the public via the Internet.

Experience: As a project engineer, you may be treading on new ground regarding some aspects of your current valve system design assignment. There can be real benefit in connecting to an experienced and highly knowledgable source, with past exposure to your current challenges.

Access: Through a valve automation professional, you may be able to establish a connection to “behind the scenes” manufacturer contacts with essential information not publicly available. The rep knows people at the factories, a well as at other valve related companies, who can provide quick and accurate answers to your valve automation related questions.

Of course, any valve actuation or automation solution proposed are likely to be based upon the products sold by the representative. That is where considering and evaluating the benefits of any solution becomes part of achieving the best project outcome.

Develop a professional, mutually beneficial relationship with a local valve automation professional to make your design job go after, more efficiently, and more cost effective. Their success is tied to your success, and they are eager to help you.

For assistance with any industrial valve automation requirement, contact Mead O'Brien at (800) 892-2769 or visit http://www.meadobrien.com.

Pressure Reducing Valves and Temperature Regulators

Pressure reducing valves
(courtesy of Armstrong)

Pressure reducing valves (PRVs) and temperature regulators help you manage steam, air and liquid systems safely and efficiently. And they ensure uninterrupted productivity by maintaining constant pressure or temperature for process control.

Steam, liquids and gases usually flow at high pressure to the points of use. At these points, a pressure reducing valve lowers the pressure for safety and efficiency, and to match the requirements of the application. There are three types of PRVs.

1. Direct-Acting. The simplest of PRVs, the direct-acting type, operates with either a flat diaphragm or convoluted bellows. Since it is self-contained, it does not need an external sensing line downstream to operate. It is the smallest and most economical of the three types and is designed for low to moderate flows. Accuracy of direct-acting PRVs is typically +/- 10% of the downstream set point.
2. Internally Piloted Piston-Operated. This type of PRV incorporates two valves-a pilot and main valve-in one unit. The pilot valve has a design similar to that of the direct-acting valve. The discharge from the pilot valve acts on top of a piston, which opens the main valve. This design makes use of inlet pressure in opening a large main valve than could otherwise be opened directly. As a result, there is greater capacity per line size and greater accuracy (+/- 5%) than with the direct-acting valve. As with direct-acting valves, the pressure is sensed internally, eliminating the need for an external sensing line.
3. Externally Piloted. In this type, double diaphragms replace the piston operator of the internally piloted design. This increased diaphragm area can open a large main valve, allowing a greater capacity per line size than the internally piloted valve. In addition, the diaphragms are more sensitive to pressure changes, and that means accuracy of +/- 1%. This greater accuracy is due to the location, external to the valve, of the sensing line, where there is less turbulence. This valve also offers the flexibility to use different types of pilot valves (i.e., pressure, temperature, air- loaded, solenoid or combinations).

Designed for steam, water and non-corrosive liquid service, self-actuated temperature regulators are compact, high-performance units. They operate simply and are therefore suitable for a wide variety of applications. Flexible mounting positions for the sensor, interchangeable capillaries and varied temperature ranges make installation, adjustment and maintenance quick and easy.

For more information on pressure reducing valves, contact Mead O'Brien at (800) 892-2769 or visit http://www.meadobrien.com.

A Valve Controller Designed to Operate on All Control Valve Actuators in All Industries

Neles ND9000

Metso's Neles ND9000 is a top class intelligent valve controller designed to operate on all control valve actuators and in all industry areas. It guarantees end product quality in all operating conditions with unique diagnostics and incomparable performance features. ND9000 is a reliable and future-proof investment with Metso FieldCareTM life-time support.

Features

• Benchmark control performance on rotary and linear valves
• Superior diagnostics and data storage capabilities
• Local and remote configuration
• Easy interpretation of diagnostics data
• Efficient mounting program for all types of actuators
• Low power consumption
• Available for HART, PROFIBUS-PA and FOUNDATION Fieldbus networks
• Reliable and robust design
• Device self diagnostics
• On-line, performance and communication diagnostics
• Hot swap support: possibility to install also on valves that are in process with 1-point calibration feature
• SIL 2 approved device

Benefits

• Minimize variability
• Open solution based on FDT technology
• Supports Electronic Device Description Language (EDDL) technology
• Total cost of ownership
• Easy to use
• Open solution
• Product relibilty
• Prevention and prediction

Applications

• ND9000 can be integrated with all major DCS systems
• Mounting kits for any 3rd party actuators
• Remote mounting
• SIL 2 approved
• Marine approved

What are Magnetic Flowmeters and How Do They Work?

Magnetic Flowmeter
(courtesy of Foxboro Schneider Electric)

Crucial aspects of process control include the ability to accurately determine qualities and quantities of materials. In terms of appraising and working with fluids (such as liquids, steam, and gases) the flowmeter is a staple tool, with the simple goal of expressing the delivery of a subject fluid in a quantified manner. Measurement of media flow velocity can be used, along with other conditions, to determine volumetric or mass flow. The magnetic flowmeter, also called a magmeter, is one of several technologies used to measure fluid flow.

In general, magnetic flowmeters are sturdy, reliable devices able to withstand hazardous environments while returning precise measurements to operators of a wide variety of processes. The magnetic flowmeter has no moving parts. The operational principle of the device is powered by Faraday's Law, a fundamental scientific understanding which states that a voltage will be induced across any conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure quality of a substance to be expressed via the magmeter. In a magmeter application, the meter produces the magnetic field referred to in Faraday's Law. The conductor is the fluid. The actual measurement of a magnetic flowmeter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with other measurements.  

The magnetic flowmeter technology is not impacted by temperature, pressure, or density of the subject fluid. It is however, necessary to fill the entire cross section of the pipe in order to derive useful volumetric flow measurements. Faraday's Law relies on conductivity, so the fluid being measured has to be electrically conductive. Many hydrocarbons are not sufficiently conductive for a flow measurement using this method, nor are gases.

Magnetic Flowmeter and controller.
(courtesy of Foxboro Schneider Electric)

Magmeters apply Faraday's law by using two charged magnetic coils; fluid passes through the magnetic field produced by the coils. A precise measurement of the voltage generated in the fluid will be proportional to fluid velocity. The relationship between voltage and flow is theoretically a linear expression, yet some outside factors may present barriers and complications in the interaction of the instrument with the subject fluid. These complications include a higher amount of voltage in the liquid being processed, and coupling issues between the signal circuit, power source, and/or connective leads of both an inductive and capacitive nature.

In addition to salient factors such as price, accuracy, ease of use, and the size-scale of the flowmeter in relation to the fluid system, there are multiple reasons why magmeters are the unit of choice for certain applications. They are resistant to corrosion, and can provide accurate measurement of dirty fluids ñ making them suitable for wastewater measurement. As mentioned, there are no moving parts in a magmeter, keeping maintenance to a minimum. Power requirements are also low. Instruments are available in a wide range of configurations, sizes, and construction materials to accommodate various process installation requirements. 

As with all process measurement instruments, proper selection, configuration, and installation are the real keys to a successful project. Share your flow measurement challenges of all types with a process measurement specialist, combining your process knowledge with their product application expertise to develop an effective solution.

A Look Inside the Neles NDX Intelligent Valve Controller

Neles intelligent valve controller 

Metso’s Neles NDX is the next generation intelligent valve controller working on all single acting control valves and in all industry areas. It guarantees end product quality in all operating conditions with incomparable performance, unique diagnostics, and years of reliable service.

Operating Principle:

The NDX is a 4–20 mA powered micro-controller based intelligent valve controller. The device contains a local user interface enabling configuration and operation without opening the device cover. Configuration and operation can also be made remotely by PC with asset management software connected to the control loop.

After connections of electric signal and pneumatic supply, the micro-controller (μC) continuously reads measurements:

Click for larger view

• Input signal 
• Valve position with contactless sensor (α), 
• Actuator pressure (I) 
• Supply pressure (S) 
• Device temperature

Advanced self­-diagnostics guarantee that all measurements operate correctly.

Powerful micro-controller calculates a control signal for I/P converter (prestage). I/P converter controls the operating pressure to the pneumatic relay (output stage). Pneumatic relay moves and actuator pressure changes accordingly. The changing actuator pressure moves the control valve. The position sensor measures the valve movement. The control algorithm modulates the I/P converter control signal until the control valve position matches the input signal.

The video below demonstrates the NDX's operation. Below the video is the complete installation, maintenance and operation manual for your convenience.

Neles NDX Intelligent Valve Positioner from Mead O'Brien, Inc.