Providing problem solving and educational information for topics related to industrial steam, hot water systems, industrial valves, valve automation, HVAC, and process automation. Have a question? Give us a call at (800) 892-2769 | www.meadobrien.com
Showing posts with label Southern Illinois. Show all posts
Showing posts with label Southern Illinois. Show all posts
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 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.
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 (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.
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.
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.
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.
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
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.
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.
Metso’s NelesNDX 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.
Pressure gauges rely on precise and responsive mechanisms to display changes in system pressure as rotational needle movement. By their very nature, these mechanisms are responsive to pulsations within the pressurized system and vibrations that may be evident in the connected piping and structures. The effect of vibration and pulsation is seen as an indicating pointer oscillating rapidly, making a definitive or even useful reading impossible. One solution, applied traditionally, was to fill the gauge with a viscous liquid that would dampen the rapid oscillation of the indicating needle.
While a liquid filled gauge does solve the oscillation problem, it does have a drawback. The liquid in the gauge presents its own set of operational issues requiring consideration in any application.
Provision should be made to check and maintain the liquid level in the gauge
A liquid filled gauge is an additional source of potential leakage in a facility
Ashcroft, a globally recognized manufacturer of gauges for commercial, industrial, and laboratory use, offers a different solution that provides the deflection dampening of a liquid gauge without liquid fill. Available on many of their gauges, the "Plus" option enables stable gauge face display in a dry gauge.
The video below provides a side by side demonstration of a liquid filled and a Plus gauge, so you can see the performance of both types. Share your process gauge requirements and challenges with instrumentation experts, combining your process knowledge with their product application expertise to develop effective solutions.
From sanitization to pasteurization, steam heating is critical in the brewing process and steam boilers are one of the most important investments a brewery will ever make. Understanding boiler components and safe boiler operation is crucial to ensuring the protection of people and property, as well as for maximum operating efficiency and optimal energy savings.
This video contains The Master Brewers Association of the Americas (MBAA.com) recent podcast with Mead O'Brien's Steve Huffman about steam boiler safety, operation, and performance.
Mead O’Brien is recognized as leading experts the industrial and commercial use of steam including industrial and commercial boilers, traps, condensate pumps, temperature and pressure controls, heating coils, and heat exchangers.
A centrifugal separator is a piece of equipment that uses centrifugal force, the force of gravity, and inertia to separate two or more materials. Centrifugal separators work by spinning the material in a chamber at high speed which causes the heavier materials to settle out separately from the lighter materials.
Upon entering the spinning chamber of a centrifugal separator, the spinning force affect materials differently. Heavier materials are more affected by gravity, while lighter materials are affected by inertia. As the materials separate, they are collected in various mechanical or physical ways, such as filtering and screening.
Gases can be purified through the spinning process to remove particulate matter and moisture. The pure gas gas is then be collected as it escapes through the top of the centrifugal separator. Similarly liquids of different weights and viscosities are divided into various chambers in the separator as it moves along.
The Anderson Hi-eF™ Centrifugal Separators operate on a patented two-stage principle of separation that employs carefully controlled flow guiding the entrainment laden vapor through a series of vanes and baffles. Each component of the separating element is designed to obtain maximum separating efficiency. Briefly, in the first stage of the separation, impingement against a baffle removes the larger droplets of entrainment. In the second stage of separation, the separator removes the fine mist entrainment by utilizing centrifugal scrubbing action through a uniquely designed contact element. In each stage, the gas medium and the separated liquid are carefully and continuously guided for maximum efficiency. The separators are designed to handle large volume flow of a broad range of fluids. Self-cleaning and engineered without filters or moving parts, the separators are free from maintenance and repair. For more information visit http://www.meadobrien.com or call (800) 892-2769.
Watch this video to see an animation of what happens inside the centrifugal separator.
Limit switches are devices which respond to the occurrence of a process condition by changing their contact state. In the industrial control field, their applications and product variations are almost countless. Essentially, the purpose of a limit switch is to serve as a trigger, indicating that some design condition has been achieved. The device provides only an indication of the transition from one condition to another, with no additional information. For example, a limit switch triggered by the opening of a window can only deliver an indication that the window is open, not the degree to which it is open. Most often, the device will have an actuator that is positively activated only by the design condition and mechanically linked to a set of electrical contacts. It is uncommon, but not unknown, for limit switches to be electronic. Some are magnetically actuated, though most are electromechanical. This article will focus on limit switch designs and variants used in the control and actuation of industrial process valves.
Employed in a wide range of industrial applications and operating conditions, limit switches
are known for their ease of installation, simple design, ruggedness, and reliability.
Valves, devices used for controlling flow, are motion based. The movable portions of valve trim create some degree of obstruction to media flow, providing regulation of the passage of the media through the valve. It is the movement of critical valve trim elements that limit switches are used to indicate or control. The movable valve trim elements commonly connect to a shaft or other linkage extending to the exterior of the valve body. Mounting electric, hydraulic, or pneumatic actuators to the shaft or linkage provides the operator a means to drive the mechanical connection, changing the orientation or position of the valve trim and regulating the media flow. Because of its positive connection to the valve trim, the position of the shaft or linkage is analogous to the trim position and can be used to indicate what is commonly referred to as “valve position”. Limit switches are easily applied to the valve shaft or linkage in a manner that can provide information or direct functional response to certain changes in valve position.
In industrial valve terms, a limit switch is a device containing one or more magnetic or electrical switches, operated by the rotational or linear movement of the valve.
What are basic informational elements that can be relayed to the control system by limit switches? Operators of an industrial process, for reasons of efficiency, safety, or coordination with other process steps, may need answers to the following basic questions about a process control valve:
Is the valve open?
Is the valve closed?
Is the valve opening position greater than “X”?
Has the valve actuator properly positioned the valve at or beyond a certain position?
Has the valve actuator driven the valve mechanism beyond its normal travel limits?
Is the actuator functioning or failing?
Partial or complete answers to these and other questions, in the form of electrical signals relayed by the limit switch, can serve as confirmation that a control system command has been executed. Such a confirmation signal can be used to trigger the start of the next action in a sequence of process steps or any of countless other useful monitoring and control operations.
Applying limit switches to industrial valve applications should include consideration of:
Information Points – Determine what indications are necessary or useful for the effective control and monitoring of valve operation. What, as an actual or virtual operator, do you want to know about the real time operational status of a valve that is remotely located. Schedule the information points in operational terms, not electrical switch terms.
Contacts – Plan and layout a schedule of logical switches that will provide the information the operator needs. You may not need a separate switch for each information point. In some cases, it may be possible to derive needed information by using logical combinations of switches utilized for other discrete functions.
Environment – Accommodate the local conditions and hazards where the switch is installed with a properly rated enclosure.
Signal – The switch rating for current and voltage must meet or exceed those of the signal being transmitted.
Duty Cycle – The cycling frequency must be considered when specifying the type of switch employed. Every switch design has a limited cycle life. Make sure your selection matches the intended operating frequency for the process.
Auxiliary Outputs – These are additional contact sets that share the actuation of the primary switch. They are used to transmit additional signals with specifications differing from the primary signal.
Other Actuator Accessories – Limit switches are often integrated into an accessory unit with other actuator accessories, most of which are related to valve position. A visual local indication of valve position is a common example.
Switches and indicators of valve position can usually be provided as part of a complete valve actuation package, provided by the valve manufacturer or a third party. It is recommended that spare contacts be put in place for future use, as incorporating additional contacts as part of the original actuation package incurs comparatively little additional cost.
Employing a properly configured valve automation package, with limit switches delivering valve status or position information to your control system, can yield operational and safety benefits for the life of the unit. Good advice is to consult with a valve automation specialist for effective recommendations on configuring your valve automation accessories to maximize the level of information and control.
The safety relief valve
is used to control or limit the buildup of pressure in a piping system,
tank or vessel. Uncontrolled pressure can occur because of valve
malfunction, process system upset, instrument failure, or fire.
In
generally accepted practices, pressure build-up is relieved by allowing
the fluid to flow from an alternate path in the piping system. A safety
relief valve is engineered so that it opens at a predetermined pressure
setpoint to protect vessel, piping or ancillary equipment equipment
from being subjected to pressures that exceed their design limits.
When
process pressure is exceeded, a safety relief valve becomes the “weak
link”, and the valve opens to divert a portion of the fluid to another
path. The diverted liquid, gas or liquid–gas mix is usually routed
through a piping system to a process where it is safely contained or
burned off via a flaring system. Once the liquid or gas is diverted, the
pressure inside the vessel drops below the safety relief valves'
re-seating pressure, and the valve closes.
The Data Supplement below presents a wealth of technical information on Kunkle relief valves.
The use of hot water systems for process heating pre-dates World War II, and initiated an ongoing effort for engineered materials to accommodate higher pressures and temperatures. After WWII the need for instantaneous hot water generation, distribution and precise temperature control for industrial applications continued to rise. High temperature hot water systems became increasingly popular because they were relatively inexpensive to install, provided long operating life, and were inexpensive to operate and maintain. Their closed system design made these systems more tolerant to corrosion and scale, while the use of pumps eliminated the need for complex piping for managing condensate.
By developing a comprehensive strategy that includes state-of-the-art water heaters, water temperature controls, hose stations, variable frequency drive (VFD) pump assemblies and ancillary accessories such as storage tanks, and pressure-reducing valves, processing plants can improve efficiency and safety, and increase production and yield.
Advanced hot water heating systems typically include:
Steam/water hot water systems with digital control technology and instantaneous heat exchanger design—shell and tube or plate and frame.
Industrial mixing center with digital control valves, pre-piped as an IMC with requisite installation components for compact design and ease of installation.
Digital control valves for delivering hot water immediately on demand, and maintained at precision temperatures (+/-1°F, +/-0.5°C).
VFD pump assemblies application-engineered and configured for your site.
Hot & cold water hose stations with thermostatic mixing valves that replaces the old, basic Y as the temperature controller.
The brochure below, courtesy of Armstrong International, provides more insight where specific components are used.
Neles Triple Eccentric Disc Valve, Metal Seated with Flow Balancing Trim
TRIPLE ECCENTRIC SEATING PRINCIPLE
The disc of the valve is machined to close tolerances to create an elliptical shape similar to an oblique slice taken from a solid metal cone. When the valve is closed, the elliptical disc at the major axis displaces the seat ring out- ward, causing it ring to contact the disc at the minor axis. When the valve is opened, the contact is released and the seat ring returns to its original circular shape.
CONTROL STABILITY AND SUPERIOR TIGHTNESS
The S-DISC® control valve unit provides outstanding control performance and excellent long-lasting tightness in the same valve. The very simple and robust construction guarantees long trouble-free operation and maximum reliability.
The S-DISC design consists of a standard NELDISC® triple eccentric disc valve equipped with a flow-balancing trim. The trim has been located on the downstream side of the valve body. The ingenious idea of this design is to transfer fluid forces out of the disc to the body.
Figures 2 and 3 illustrate the flow treatments with a concentric-type conventional butterfly valve compared to the S-DISC-design. The S-DlSC design offers stable flow control and reduced dynamic torque, noise level and vibrations. The dynamic behavior of the valve is very smooth and stable, which means less load on the shaft bearings, less required torque, smaller actuators and more economical control unit total costs. All of the excellent features of the standard NELDISC are available.
The most standard NELDISC can be easily modified to the S-DISC design, just by changing the flange ring.
FEATURES
Excellent flow and control performance.
Wide temperature range from -200 ... +600 °C /-330 ... +1110 °F.
Reduced dynamic torque and noise.
Mechanical and flow dynamic stability allows higher pressure drop service than a conventional disc.
Commonly, filters and strainers are positioned to capture solids and particulate. The filter will obstruct the flow through the pipe lowering the pressure on the downstream side. These effects may vary depending on the filters construction. Filter media is the material that removes impurities. The smaller the pores the larger the friction. Higher friction means greater pressure drop. Contaminants for particulates that buildup in the filter will reduce media flow. As the filter becomes clogged the downstream pressure drops. This results in an increased differential pressure, also referred to as the Delta-P. Saturated filters may also begin to shed captured particles.
With the filter no longer functioning properly, the contaminants can escape into the process. This is why proper monitoring of pressure drop is crucial. So how can we measure the DP? Placing taps both before and after the filter, a differential pressure measuring instrument can be connected to detect the high side and close side pressures. the instrument will report the difference between the two sides. The saturation point will be indicated when the Delta-P value reaches a predetermined threshold. This value is derived from a calculation that factors in the flow rate, fluid viscosity, and filter characteristics.
When specifying a differential pressure instrument there are two important factors to consider. The first is the DP range, which is based upon the most difference in pressure that the restriction is likely to produce. The second is the instruments ability to contain the line or static pressure level.
For more information on pressure measurement, call Mead O-Brien at (800) 892-2769 or visit www.meadobrien.com.
Here is a great video, courtesy of Ashcroft, that provides an excellent visual understanding of differential pressure.
Cyber attacks against Industrial Control Systems (ICS) are on the rise, putting nations’ critical infrastructure at risk. In a paradigm shift from the traditional network security systems, a new approach — Dynamic Endpoint Modeling — learns and models the behavior of all devices on the network and triggers alerts when algorithms detect changes in learned behavior.
Here is a partial listing of typical applications in a power plant where ASCO products provide reliable solutions.
ASCO Solenoid Valves
Ideal for steam, air, or liquid flows. Throughout the power plant, our solenoid valves provide superior service in areas such as SO2 scrubbing, turbine lubrication systems, and igniter burner No. 2 fuel lines to name a few.
Numatics FRLs
Filters, regulators, and lubricators treat air quality and pressure in your plant’s pneumatic system. Apply them to control pressure or meet filtration requirements for your pneumatic equipment. These high-performance products are available in multiple configurations, including electronic regulators.
ASCO Angle-Body Piston Valves
Well suited to replace ball valves in air, water, and steam applications with pipe sizes 2 1/2" or smaller and up to 150 psi. This compact solution reduces cost of ownership, eliminates water ham- mer, and creates tight shutoff in both directions. Available with limit switches, AS-interface®, and DeviceNetTM protocols, Class I, Div. 2 HS Series position indicators, and low power solenoids.
ASCO Dust Collector Valves
ASCO integral or remote pilot valves are especially designed for dust collector applications, combining high flow, long life, and extremely fast opening and closing to produce reliable and economical operation. Valves with quick mount connections eliminate time consuming thread cutting and sealing.
ASCO Pressure Sensors
A range of high-quality sensors with long-life designs and ensured repeatability, these signal when process media reach pressure set points. They play a vital part throughout the entire power generation process.
ASCO Redundant Control System
The ASCO RCS is a redundant pilot valve system that acts as a single 3-way valve. Features include the ability to perform automatic online testing of the redundant solenoid valves, automatic partial stroke testing of the process valve, and online maintenance capabilities. Use this product in high reliability or critical applications. Certified per IEC 61508 Parts 1 and 2 and are SIL 3 capable.
ASCO Solenoid Pilot Valves
Designed to operate at high cycles or for long periods of dormancy, these 3 and 4-way models provide ensured action in demanding applications. Features include, manual operators, high flows, and explosion-proof options. Plus new 0.55 W models are perfect for networks with low power limitations. Brass and stainless steel versions available.
Numatics Cylinders
A large range of high quality Numatics cylinders that can withstand the harsh environment of power generation systems. Whether you are operating a scrubber, bag house, or damper controls, Numatics cylinders are used to open and close large orifices in these systems. Available in 17 bore sizes from 1 1/2" to 24".
For more information about any ASCO product, contact:
Water hammer. It's a familiar sound nearly everyone has heard in their own home when someone slams a faucet closed. You have probably also heard it coming from radiators during the winter heating season. In industrial situations, though, water hammer is more than just a noisy annoyance. Water hammer that results from localized abrupt pressure drops may never be heard. Yet water hammer can acquire great force, damaging equipment, ruining product, and potentially putting personnel at risk.
Water hammer begins when some force accelerates a column of water along an enclosed path. The incompressible nature of water gives it the power of a steel sledge as it slams into elbows, tees, and valves. The resulting vibrations are transmitted along the water column and piping, damaging fittings and equipment far removed from the problem source.
Water hammer can occur in any water supply line, hot or cold, and its effects can be even more pronounced in bi-phase systems. Bi-phase systems contain both condensate and live or flash steam in the same space. Heat exchangers, tracer lines, steam mains, condensate return lines, and in some cases, pump discharge lines, may contain a bi-phase mix.
Three distinct conditions have been identified, which provide the force that initiates water hammer. These conditions, hydraulic shock, thermal shock, and differential shock, are common to many industrial fluid applications. However, following a few simple guidelines will help you minimize the occurrence of these shocks and diminish the chance of damaging water hammer.
Hydraulic shock occurs when a valve is closed too abruptly. When a water valve is open, a solid column of water moves from its source at the main to the valve outlet. This could be 100 pounds of water flowing at 10 feet per second, or about 7 miles per hour. Closing the valve suddenly is like trying to instantly stop a 100-pound hammer. A shockwave of about 6600 psi slams into the valve and rebounds in all directions, expanding the piping and reflecting back and forth along the length of the system until its momentum is dissipated. By closing the valve slowly, the velocity of the water is reduced before the column is stopped. Since the momentum of the water is decreased gradually, damaging water hammer will not be produced.
Sometimes, check valves can produce hydraulic shock. Swing check valves are often used to prevent liquid being drawn into spaces that are subject to intermittent vacuums. They are also applied to prevent back-flow from elevated systems when adequate pressure to raise the liquid cannot be guaranteed. In either case, the acceleration of the reversing column of liquid may be quite high. If the swing length of the check valve is sufficient, the column will build enough inertia to cause hydraulic shock in the time it takes the valve to slam shut. Substitute silent or non-slam check valves for swing checks to prevent water hammer in these situations. Silent check valves are center-guided to provide a much shorter stroke than swing checks. These valves also use a spring to help enclosing. The result is that silent check valves are closed by the loss of upstream pressure rather than the reversal of flow, preventing hydraulic shock.
Water hammer arresters, if correctly sized, placed, and maintained, will reduce water hammer. When the forward motion of the water column is stopped by the valve, part of the reversing column is forced into the water hammer arrester. The water chamber of the arrester expands at a rate controlled by the pressure chamber, gradually slowing the column, and preventing hydraulic shock. To prevent water hammer due to hydraulic shock, avoid suddenly stopping water columns. Ensure slow closure of valves, and install spring-loaded, center-guided, non-slam, or silent check valves that close before flow reversal when appropriate. Use water hammer arresters if necessary, but be sure they are sized and placed correctly, and are well-maintained.
Water hammer may also be initiated by thermal shock. In bi-phase systems, steam bubbles may become trapped in pools of condensate. Since the condensate temperature is usually below saturation, the steam will immediately collapse. Steam occupies hundreds of times the volume of an equal amount of water. When the steam collapses, water is accelerated into the resulting vacuum from all directions. When the void is filled, the water impacts at the center, sending shockwaves in all directions.
One likely place for thermal shock to occur is in steam utility corridors. In these areas, the drip traps from high-pressure steam mains often discharge directly into the pumped condensate return lines. The temperature of the condensate in these lines usually ranges from 140 to 180 degrees Fahrenheit. The condensate being discharged from the steam trap is at nearly steam temperature when it passes through the trap orifice. When the trap discharge enters the low-pressure condensate line, a great deal of it flashes back into steam. The flash steam immediately collapses again when it encounters the relatively cool pump discharge water. This thermal shock often causes damaging water hammer. The localized sudden reduction in pressure near the wall chips away piping and tube interiors. Oxide layers that otherwise would resist further corrosion are removed, resulting in accelerated deterioration of piping and equipment. To minimize such a disturbance, the drip trap should discharge in the direction of condensate flow by means of a special fitting.
This method of controlling thermal shock, called "sparging," reduces the concentration of collapsing steam bubbles, and keeps the action from occurring by the pipe wall. Thermal shock can also occur easily in steam coils if they are constructed as shown here. Since the steam is directed toward the center tube first, it can reach the return header before the top and bottom tubes are filled. Consequently, steam feeds the more remote tubes from both ends. With steam flowing into both ends of a tube, waves of condensate flow toward each other. These waves have the potential of trapping pockets of steam between them. If this happens, thermal shock will result when the pocket of steam collapses and water hammer will probably occur.
Prevent the thermal shock that is generated by such a design by substituting a constant-purge device, such as a differential condensate controller, for the steam trap. Condensate controllers maintain a positive differential pressure across the coil at all times. All the tubes will be fed from the supply end only, preventing the entrapment of steam and the resulting thermal shock. Malfunctioning steam traps may also contribute to thermal shock followed by water hammer. A steam trap that has failed open injects live steam directly into the condensate return line. If this steam is mixed with return line condensate of sufficiently low temperature, it will immediately collapse, and thermal shock will follow.
To prevent the occurrence of water hammer due to thermal shock, you must reduce the concentration of collapsing steam bubbles in the condensate. If flashing condensate must be discharged into a cool condensate line, it should be discharged in the direction of condensate flow and away from the pipe wall. Precautions must be taken that heat exchanger tubes are always filled from the supply end only.
Differential shock, like thermal shock, occurs in bi-phase systems. Differential shock can occur whenever steam and condensate flow in the same line, but at different velocities, such as in high-pressure condensate return lines. In bi-phase systems, the velocity of the steam is often ten times the velocity of the liquid. If this gas flow causes condensate waves to rise and fill the pipe, a seal is formed with the pressure of the steam behind it. Since the steam cannot flow through the condensate seal, pressure drops on the downstream side. The condensate seal now becomes a piston that is accelerated downstream by virtue of this pressure differential. As it is driven downstream, the piston picks up more liquid that is added to the existing mass of the slug, and velocity increases. This is differential shock. If the slug gains high enough momentum, and is then required to change direction at a tee or elbow, or is stopped by a valve, great damage can be done.
In the demo lab at Armstrong International, a fixture was assembled to illustrate the problem with a 20-foot, 2-inch-diameter glass pipe to act as a condensate return line. The pipe is pitched one-quarter inch in 10 feet to provide gravity flow. Flowing through the pipe, we have cold water. In addition to water, we can also have compressed air flowing in the system to simulate flash steam flowing across the top of the condensate by virtue of differential pressure. One flow meter constantly measures the flow rate of the water. Another flow meter continuously monitors the flow rate of the compressed air. As you can see, we now have 1500 pounds per hour of water flowing in our glass pipe, and no compressed air. Under this condition, our pipe is approximately half-filled with water.
As we increase the flow rate of water in our pipe to 2,000 pounds per hour, the depth of the water increases to five-eighths. We now introduce compressed air into the system to simulate flash steam with a flow rate of about 200 standard cubic feet per hour, and the depth of the water recedes. We are increasing the speed of the water flowing through the pipe by virtue of the velocity of the gas flowing across its surface. Observe now as the compressed air flow increases. The waves formed on the surface of the condensate become higher. Further increasing the air flow causes the waves to block off more of the cross section of the piping until a seal is formed, completely closing off the pipe. A slug of condensate is accelerated downstream by the pressure differential, becoming a piston that gains in mass and velocity as it travels. The proper sizing and pitching of condensate lines are the only means of guarding against this type of problem. The Armstrong Steam Conservation Handbook includes a chart that helps you in deciding the correct condensate return line size for your particular application.
Differential shock can also become a problem when elevated heat exchange equipment is drained with a substantial vertical drop ahead of the trap. Under normal conditions, condensate drains down the walls of the pipe. A sufficient volume of steam constantly flows down the center of the pipe to replace the steam that is condensed by radiation losses of the piping and the trap body itself. The steam flow rate increases if a thermostatic element, such as the bellows or wafer in an F & T trap, opens. If a slug of condensate seals off the pipe, steam collapses downstream of the seal. Again, a pressure differential forms, and this, along with gravity, accelerates the slug. When this piston strikes the trap, it can damage the float, the thermostatic element, or other parts of its mechanisms.
To avoid differential shock arising from this situation, use an F & T trap and back-vent it to the top of the vertical line to maintain near-equal pressure throughout the riser, even if a slug of condensate forms. In both of the two previous cases, the condensing of steam downstream of the seal produced the acceleration. It follows that the likelihood of differential shock arising, and causing water hammer, is greater in uninsulated pipes, especially on outdoor systems, than in insulated pipes. Long runs of any kind between the heat exchange equipment and the trap can produce this situation, and should be avoided. Damaging water hammer may also occur due to differential shock whenever there is an improperly-dripped pocket ahead of a control valve. Condensate builds up in front of the valve while it is closed. When the valve is opened, the slug of condensate is driven through the valve and into the piping and equipment by the live steam. The placement of a riser and a drip trap immediately upstream of the control valve will prevent this rampaging slug.
To control differential shock, you must prevent condensate seals from forming in bi-phase systems. Condensate lines must be sized correctly, and long vertical drops to the traps must be back-vented. The length of the lines to traps should be minimized, and the lines may have to be insulated to reduce condensing. The installation of a proper drip leg ahead of control valves will prevent differential shock from occurring when the control valve is opened after a period of closure.
Careful attention to these few guidelines will prevent most water hammer. Prevent the sudden stopping of water in pipelines by closing manual valves slowly, and by installing spring-loaded, center-guided, silent check valves where appropriate. Prevent thermal shock by using a sparging tube wherever flash steam is discharged into condensate at a lower temperature, and by ensuring that heat exchanger tubes are filled from one end. Prevent differential shock in bi-phase systems by providing return lines that are properly pitched and have adequate size. Avoid draining equipment with long lines to the trap, and insulate condensate lines whenever necessary. Following these guidelines for the proper design and operation of your system will minimize the likelihood of the shocks that cause water hammer. This, in turn, will greatly reduce the likelihood of damage to your system, to your product, and to your personnel.
Fill tanks and hoppers rapidly and accurately using the StoneL Axiom Expeditor valve monitor on a pneumatically operated valve.
You can set the Axiom Expeditor to partially close the valve to reduce flow as the full level approaches. You get fast, economical “topping off” of every batch with a single valve sized for high flow rates, which may be throttled back at the end of the fill cycle.
Simple operation and control system integration
Full open and closed cycling is performed by energizing and de-energizing the discrete 24 VDC output (DO) from the control system.
A preset intermediate position may be achieved by maintaining power from the discrete output (DO) and switching on the analog output (AO) at a preset level between 4 and 20 mA.
Intermediate control is achieved by maintaining power from the discrete output (DO) and energizing the control system’s analog output (AO). By changing the AO signal, the Axiom control output will toggle the solenoids to the desired position within ±4% of full scale.
The valve/actuator operates to the fail-safe position whenever the discrete output (DO) is de-energized.
Schematic for tank fill application showing control inputs/outputs.
Watch this short video illustrating how the tank fill feature works.
The development and implementation of safety related devices in plant systems is crucial for dependable operation, not to mention peace of mind. Safety and safe operation were once only high priorities for installations that involve hazardous environments. Expensive certification testing was, and still is, paramount to meeting the hazards of such environments, but a new level of plant-wide integrity is emerging — that of Safety Integrity Level (SIL) and SIS. SIL is a safety rating that can be derived by analyzing a system to determine the risk of a failure occurring and the severity of its consequences. Safety Instrumented Systems (SIS) are systems containing instrumentation or controls installed for the purpose of preventing or mitigating a failure either by emergency shut down (ESD) or diverting the hazard. New or replacement equipment must have the ability to be introduced into plant systems without jeopardizing either the SIL of the operation or negatively impacting the SIS.
