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 Texas Panhandle. Show all posts
Showing posts with label Texas Panhandle. Show all posts
The gas-powered scotch yoke actuator is a mechanical device designed to convert linear motion into rotary motion, primarily used for valve actuation in the oil and gas industry and other industrial applications requiring precision control of fluid flow. This actuator is particularly advantageous for heavy-duty and high-torque applications, offering reliable and efficient operation with minimal maintenance. Here's a detailed overview of how it operates and its primary application:
Operation:
Gas supply: The gas-powered scotch yoke actuator uses pressurized gas as the driving force, which, depending on the specific application and site requirements, the gas source is a natural gas pipeline, an onsite compressor, or bottled gas.
Pneumatic cylinder: The gas enters the pneumatic cylinder, which is the core component of the actuator. The cylinder contains a piston that moves linearly when pressurized gas is applied.
Scotch yoke mechanism: The linear motion of the piston is converted into rotary motion using the scotch yoke mechanism. The scotch yoke consists of a yoke (a slotted, U-shaped component) attached to the piston rod and a pin mounted on the rotating output shaft. The yoke slides along the pin as the piston moves linearly, causing the output shaft to rotate.
Output shaft: The output shaft's rotation is transferred to the valve stem, causing the valve to open or close, depending on the direction of the rotation. The shaft is connected to the valve using a coupling, which ensures proper alignment and torque transmission.
Spring return mechanism: Some gas-powered scotch yoke actuators have a spring return mechanism, which enables the valve to return to a predetermined fail-safe position in the event of a loss of gas supply or system failure.
Primary application: The primary application of the gas-powered Scotch yoke actuator is in the oil and gas industry, where it controls various types of valves, such as ball valves, butterfly valves, and plug valves. These valves are essential for regulating the flow of oil, gas, or other fluids in pipelines, processing plants, and other facilities.
The actuator's high torque capabilities make it suitable for heavy-duty applications, such as large-diameter or high-pressure valves. Additionally, the gas-powered design offers several advantages over electric or hydraulic actuators, including lower operating costs, reduced environmental impact, and compatibility with remote or hazardous locations where electricity or hydraulic power may not be readily available.
Limitorque has established a dominant position in the gas-powered scotch yoke actuator market, owing to its reputation for delivering high-quality, reliable, and efficient products. Their actuators are known for their durability and low maintenance requirements, making them a preferred choice for heavy-duty applications in the oil and gas industry. The company's commitment to continuous innovation and its extensive experience in the field has allowed them to develop customized solutions to address the unique challenges faced by its customers. Furthermore, Limitorque's strong global presence and extensive support network ensure they provide exceptional after-sales service, reinforcing their position as a trusted leader in the market.
OmniSeal expanding plug valves are intended for applications requiring positive shut-off, verifiable zero leakage, double block and bleed (DB&B), and/or double isolation and bleed (DIB).
OmniSeal is perfect for great leased automated custody transfer (LACT), product metering, aviation fueling, product isolation, blending, lockout/tagout (LOTO), multi-product manifolds, tank storage, and other DB&B applications.
The OmniSeal is a single valve solution that blocks both upstream and downstream flow while allowing the user to test seal integrity with a manual or automatic body bleed system. OmniSeal valves have exclusive features designed to improve performance over the valve's life.
All OmniSeal DB&B expanding plug valves are manufactured and monogrammed per API 6D and ISO 9001, fire tested under API 607 and API 6FA, and have specific certifications such as CE/PED, CRN (Canadian Registration), TA-Luft, or other similar design or regional certifications where applicable.
For more information about OmniSeal valves contact Mead O'Brien. Call (800) 874-9655 or visit https://meadobrien.com.
Radar is the preferred technology for level measurement in many of today’s industrial applications. Selecting the best microwave frequency transmitted by the device for your application is crucial, and understanding the relationship between frequency and beam angle is very important.
In this video, Jeff Blair, Offer Manager for level products at Schneider Electric, presents the difference in beam angle at various frequencies and how to use Beam Angle Calculators to determine beam width at various levels in a tank.
For more information about radar level instrumentation, contact Mead O'Brien. Call them at (800) 892-2769 or visit their website at https://meadobrien.com.
Ulmer Equipment Company is a well known and well respected manufacturer’s representative and distributor of AWWA and industrial valves and accessories.
The acquisition expands Mead O'Brien’s offering in valves and related equipment to the Water and Wastewater industry sector in the Midwest region.
Mead O’Brien, Inc. headquartered in North Kansas City, is a midwestern regional manufacturer’s representative and distributor with branches and warehouses in St. Louis, MO; Calvert City, KY; and Tulsa, OK. Sister companies include H*E Engineered Equipment Co., J&M Engineered Products Inc., and Pinnacle Controls LLC.
As experts in valve automation, process instrumentation, steam systems and hot water systems, Mead O'Brien provides solutions to industrial companies in Missouri, Kansas, Nebraska, Iowa, Oklahoma, Arkansas, Texas Panhandle, Southern Illinois, Western Kentucky, and Southwest Indiana.
Specializing in Power, Refining, Chemical, Food & Beverage, Oil & Gas, Heavy Industrial, Water & Wastewater, and HVAC, Mead O’Brien provides it's customers outstanding products, superior customer service, a team of highly skilled technicians, and decades of application experience.
These assets, in combination with their track record of successful outcomes and loyal customer base, positions Mead O'Brien as the perfect partner for all your process control equipment needs.
Mead O’Brien specializes in valves & valve automation, steam & hot water products and systems, instrumentation products, skid designs, field services, surveys, assessments, and consulting.
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.
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.
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 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.
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.
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.
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:
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.
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.
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.
