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®T H E V A L V E D O C T O R®S O L U T I O NThe World Leader in Severe Service Control Valves CCI designed, built and patented the fi rst DRAG ® control valve in 1967, answering the need for a valve capable of handling high-pressure liquids and gases such as water, oil, steam, natural gas, petroleum products and chemicals. DRAG ® technology is considered one of the landmark innovations in the history of the severe service control valve industry. Following that invention, CCI has continued to develop and introduce advanced product technology that has revolutionized the I’s industry leadership is the result of a proven record that focuses on performance. The knowledge gained from solving customer control valve performance problems generates high standards for quality that infl uence every step of the production process and extend into lifetime support of the valves installed in your plant.Many valve manufacturers claim to offer control valves for all service conditions, but few can provide the complete performance compatibility needed for severe service applications. CCI DRAG ® control valves are designed specifi cally to meet your individual application needs. Whatever your severe service application, there is only one intelligent choice: CCI’s DRAG ® control I’s Proven Experience CCI DRAG ® control valves have been used for more than 40 years to solve severe service control problems, continually serving the needs of the fossil power, nuclear power, oil and gas, petrochemical, combined heat and power, and pulp and paper industries.The Valve Doctor ® Approach CCI’s dedicated team of technology specialists focuses on solving control valve problems around the globe. CCI’s expertise extends beyond control valve design to actuation, noise reduction, system piping and system operation. The Valve Doctor ® utilizes his expertise to provide comprehensive solutions that enhance plant operation and result in signifi cant operational and maintenance savings. DRAG ® technology continues to play a pivotal role in providing these solutions!D R A G ®CCI severe service control valves featurepremium DRAG ® velocity control for precise, measurable performance.Since 1961, CCI has provided a uniquecombination of engineering experience andglobal resources with one goal: to exceedcustomer expectations.A typical CCI DRAG ® disk stack featuresvarying numbers of pressure-reducing stagesto ensure superior control.Improved plant performance Increased MW output and reduce leakage costs Higher reliability Lower noise.Better control.Longer intervals between maintenance Decreased maintenance costsReduced system costs DRAG®Improved plant performancencreased MW output and reduced leakag Increased MW output and reduced leakage afer plant operating conditions.Safer plant operating conditions.Safer plant operating co r plant operating conditions.ns.Safer plant operating conditions.Higher reliabHigher reliability Lower noise. control.Better control.intervals between mainten Longer intervals between maintenance Decreased maintenance costs Reduced system costs.Lower cost of ownership Lower cost of owne ower cost of ownership er co wer c Lower cost of ownership Improved plant performanceIncreased MW output and reduced leakage costs Safer plant operating conditions Higher reliability Lower noiseBetter control Longer intervals between maintenance Decreased maintenance costs Reduced system costs Lower cost of ownershipOil, Gas and Petrochemical Production, transmission and processing, including LNG and petrochemicals: Production chokes Separator-level control Gas lift/injection Injection pump recycle Overboard dump Gas regulator Surge relief Gas injection/withdrawal Metering stations (active/monitor) Compressor recycle/anti-surge Hot gas bypass Emergency depressuring/gas to fl are Amine letdown Expander bypass (JT valve) Vent to atmoshphere Feedwater regulator Feedwater pump recirculation Spraywater Steam header pressure controlPower GenerationFossil and nuclear power plants, cogeneration(CHP) facilities and other industries handling high-pressure water or steam:Reheat and superheat attemperator sprayMain and booster feedpump recirculationStartup and main feedwater regulationDeaerator-level controlCondensate booster pump recirculationAtmospheric steam dump and steam ventingTurbine bypassTurbine bypass spraySootblower controlOnce-through boiler startup (base-loaded and cycling units)System startup: B&W, CE, FW and licenseesAuxiliary steamTurbine seal pressure controlHigh-level heater drainsHP coolant injection (HPCI)Reactor core isolation cooling (RCIC)Core sprayResidual heat removal (RHR)Steam generator blowdownPressurizer PORVCVCS letdownSamplingPump test loopsThe Choice is SimpleWhen you need a complete solution to thedemanding conditions of severe service control,there’s only one choice: a custom-engineeredDRAG ® application I DRAG ® valves have been used in severe service applications worldwide. Years of research and experience in numerous applications have proven the superiority of the DRAG ® valve in critical applications.D R A G®The Need for Velocity Control High fl uid velocity through valve trim is a principal source of system control problems. System control is lost due to valves damaged by the effects of cavitation, erosion, abrasion and vibration, which can quickly destroy a valve and disrupt system operation.Even before damaging the valve, excessive noise, severe vibration, poor process control and product degradation can limit a facility’s ability to operate at maximum capacity and thereby reduce I has pioneered the effort to develop and apply the velocity control principle in control valves to offer total system control solutions for many different applications. Thousands of satisfi ed customers worldwide have benefi ted from CCI’s solutions. Velocity control criteria as published by ISA has become the industry standard in solving control valve problems.Since all plants must start up and shut down, good plant control must be available for a wide range of plant loads. CCI provides control over a full range of valve capacity by ensuring that velocity control features are in place for the entire valve travel. By designing DRAG ® disks throughout the travel to meet the unique requirements imposed by the plant transients, CCI’s solutions allow the automatic control systems to function without manual control stops to work around sensitive plantconditions.A single-stage pressure drop valve with poorcontrol presents problems like cavitation,erosion, noise and vibration.The velocity control principle: multi-stagepressure drop provides control andeliminates cavitation, erosion, noise andvibration problems. DRAG®D R A G ®The Velocity Control Challenge Until CCI introduced the DRAG ® valve, the design of control valves for handling high pressure drop liquids, gases or steam had changed little.Even today, despite other makers’ widespread attempts to copy the CCI DRAG ® solution in their modifi ed trim valves, process fl uids still fl ow through some version of a single orifi ce or multiple area orifi ces. Fluid velocity through each orifi ce is a function of the valve pressure drop or required process differential head.Fluid in the valve reaches its maximum velocity just slightly downstream of the valve trim’s orifi ce in the vena contracta or minimum fl owing area (see Figure 1). These high velocities produce cavitation, erosion and abrasion, which can quickly destroy the valve. Even before damaging the valve, excessive noise, severe vibration, poor process control and product degradation are observed in many applications without velocity control. Interestingly, these high velocities are unwanted side effects of pressure reduction through the valve and are not treated as a design criteria by other valve manufacturers until it’s too late. Many attempts to resolve the side effects simply treat the symptoms rather than the real cause of the problem.In general, poor valve performance in severe service applications is primarily due to excessive fl uid velocity. Even using harder materials in the valves to offset erosion from cavitation, or using pipe-lagging or downstream diffusers, can only marginally offset valve failure from uncontrolled velocity. Velocity must be controlled at all valve settings to maintain valve performance and reliability. Problems resulting from high velocity affect plant performance and output, resulting in effi ciency loss, unit load limitations, unscheduled plant shutdowns anddamage to other equipment.2V 1V 2V 2V 1=2gh>Figure 1: Single-stage pressure drop The evidence: high-velocity erosion damageon a single- stage cage and valve internals isobvious.DRAG ®Solution to High Velocities DRAG ® velocity control valves from CCI addressed the problems created by high velocity a generation ago. DRAG ® valves prevent the development of high fl uid velocities at all valve settings. At the same time, they satisfy the true purpose of a fi nal control element: to effectively control system pressure and fl ow rate over the valve’s full stroke. Here’s how the DRAG ® valve accomplishes what the others can only approach:The DRAG ® trim divides fl ow into many streams to minimize the mass and energy levels (Figure 2). Each fl ow passage consists of a specifi c number of right-angle turns to form a tortuous path (Figure 3) in which each turn reduces the pressure of the fl owing medium by more than one velocity head.The number of turns, N, needed to dissipate the maximum expected differential head across the trim, as illustrated in Figure 4, is found by changing the equation from:V 2 (orifi ce) = to a new equation:V 2 (DRAG ®) element = The number of turns, N, is selected to ensure a specifi c fl uid energy level exiting the channel. Applying this principle to the DRAG ® valve’s disk stack and plug is shown in Figure 5. The disk has several fl ow channels, each channel comprising multiple right-angle turns (Figure 6). Thus DRAG ® technology fully controls velocity in each passage on every disk in the stack, and the valve can operate at a controlled, predetermined velocity over its full service range.To achieve enough capacity for the valve, CCI’s solutions add disks to provide the necessary fl ow cross-section. This technology is in stark contrast to valves using multiple-orifi ce-modifi ed trims. Each orifi ce converts potential energy to kinetic energy, but with a startling increase in velocity. Therefore, multiple-orifi ce solutions do not provide the protection that the DRAG ®-type trim provides.In the DRAG ® trim, the resistance, number and area of the individual fl ow passages are custom matched to your specifi c application, and exit velocities are managed to eliminate cavitation and erosion in liquid service and vibration and noise in gas service. DRAG®V 1V 2=V 1V 2V 2=2gh/NV 1V 2=V 1V 1V 2=V 1VV2=2ghFigure 2: Multi-path pressure reductionFigure 3: Right-angle tortuous pathFigure 4: Multi-stage pressure reductionFigure 6: Multi-path, multi-stage DRAG ® disk Figure 5: DRAG ® disk stack and plug2gh 2gh/NThe Cavitation ChallengeWhen liquid pressure is reduced to its vapor pressure or lower, fl ashing and bubble formation occur. In most control valves (Figure 7), fl uid enters at pressure P 1 and velocity V 1. As the fl uid moves through the reduced area of the valve trim, it accelerates to velocity V VC as its static pressure drops suddenly to P VC – a level at or below the liquid’s vapor pressure P V . At this point, the liquid boils. Any valve using a single or multiple-orifi ce trim will cause this problem because of its uncontrolled velocities in the areas of each “vena contracta,” the narrowest central fl ow region of a jet of fl uid fl ow.As the fl uid moves out of the throat of the valve, pressure recovery begins, converting kinetic energy back to potential energy. Full recovery to downstream pressure is indicated at P 2 and velocity V 2. When the recovery pressure exceeds the fl uid’s vapor pressure P V , collapse or implosion of the just-formed bubbles takes place, resulting in cavitation. The energy thus released causes local surface stresses greater than 200,000 psi (1400 MPa), which can consume even hardened trim rapidly.Symptoms of Cavitation n Noise when liquid-handling valves modulate or shut off n Valve components showing “pitting” damage n Poor process control with the valve Cavitation is the formation and subsequentcollapse of microscopic vapor bubbles thatcan destroy trim.D R A G®Figure 7: Inter-stage cavitation damage frominsuffi cient stagingSeat ring damage caused by cavitationresults in leakage that can harm downstreamequipment.The DRAG ® Solution to CavitationThe DRAG ® valve eliminates the destructive effects brought about by uncontrolled fl uids in today’s processes. DRAG ® technology does this by fi rst splitting the fl ow into many small channels so that, if a gas bubble is formed, it is very small and does not have the energy necessary to cause stresses that would result in material failure. Secondly, DRAG ® maintains the fl uid velocity at minimum levels so that local pressures are unlikely to drop below the vapor pressure of the fl uid. Thus none of the adverse effects of bubble collapse can harm the valve as in other valve designs. In addition to many years of successfully applying the DRAG ® design principles to control valve cavitation, CCI has conducted independent tests in accordance with ISA 75.23 and verifi ed the practice. In every possible combination of test conditions, the testing confi rmed the DRAG ® design principles and the technology’s ability to solve the most diffi cult industry problems of fl uid fl ow control.In general, the damaging effects of cavitation are a typical signal that fl uid velocities are not being controlled. As previously mentioned, using harder materials, pipe-lagging or downstream orifi ces can only marginally offset valve failure from cavitation damage. High fl uid velocity and insuffi cient staging (shown in Figure 7) will result in inter-stage cavitation damage, reducing the effectiveness of the valve as a fl ow modulating device and exposing the trim to damage, which leads to a leaking valve. The solution to cavitation, therefore, is the DRAG ® velocity control valve, as illustrated in Figure 8.Fluid velocity requirements, based on the vapor pressure of the fl uid (at design temperature), is governed by the following equation: English MetricDRAG®CCI’s multi-path, multi-stage trim designsare characterized to provide optimal valveperformance at all fl ow conditions across thefull stroke of the valve plug.V = 4637 (P 2 - Pv )/ or V = 1000 (P2 - P v )/Table 1: Recommendation for Fluid Velocity to Control Cavitation*Figure 8: The DRAG ® solution eliminatescavitation.* Based on information presented in the publication “Control Valves - Practical Guides for Measurement and Control” edited by Guy Broden , Jr. and Paul G. Friedman, 1998 edition, published by ISA and other sources.A competitor’s body and trim that failed towithstand severe service conditions show signsof damage that result in poor performance andcontrol.D R A G®With the expertise of a CCI Valve Doctor ®,our DRAG ® valves are designed to yourperformance specifi cations and offer theultimate solution to noise and vibrationproblems in severe service applications.The Noise and Vibration Challenge Modern plants are subject to many complex and strict regulations dictating the allowable noise level for either the worker or for the plant neighbors. Occasionally, a system will experience signifi cant piping vibration that may eventually lead to a failure. Such vibration can also cause component damage and, in many cases, the vibration is a safety concern for both plant personnel and expensive equipment essential to plant operation. Frequently, the cause of vibration is a valve that has not been properly selected for the application. The excessive fl uid velocities and energy levels force uncontrolled pipe motion, which results in failure of pipes and supports and damage to downstream components. Noise and vibration are pervasive in applications involving throttling or venting of compressible gases. For applications where noise is signifi cant, sonic vibrations not only create hazardous health areas, but may also pose a threat to the reliability of equipment and system operation. Even if lagging, dampening or enclosing the noisy valve successfully controls audible noise leaks, the potential for costly damage and valve failure still exists. A plant may meet hearing safety requirements by insulating the valve; however, unless the source of the noise is eliminated, the risk of signifi cant damage to the valve and process remains. In addition, noise propagates through the process piping and often contributes to problems with other components in the system. Eliminating the source and mechanism of noise is the only way to mitigate these risks.Even more signifi cant than audible noise are the problems associated with high vibration levels. Signifi cant vibration in a valve can quickly lead to failure of the valve components (cage, plug, stem and accessories) and process components, the eventual failure of pipes andsupports, and damage to downstream equipment. In extreme cases, many control valves with signifi cant vibration problems often cause system trips and result in costly effi ciency and production losses.The DRAG ® Solution to Noise and Vibration In an effort to eliminate the sources of system vibration, CCI encourages the process industries to adhere to ISA guidelines for valve trim exit kinetic energy levels. The right-angle tortuous path trim approach used in the DRAG ® technology achieves the required low energy levels. The right-angle turns drop the fl uid velocity to levels that provide the expected control. Figure 9 illustrates actual fi eld results of DRAG ® technology. This fi gure shows vibration before and after application of the DRAG ® design. There is usually a 90% reduction in the peak vibration level of the valve or piping component with the application of DRAG ®. CCI can provide control valve systems that will ensure the noise levels remain below the specifi ed requirements. The DRAG ® valve approach is to prevent the creation of noise as opposed to trying to muffl e it once it is produced. CCI uses the prediction technology that forms the basis of the IEC and ISA noise prediction standards. Noise is controlled by making sure that the trim exit jets leaving the disk stack do not induce excessive acoustic levels inside the pipe. Subsequently, the noise passing through the pipe wall and sensed in the vicinity of the valve is lower than the specifi ed levels. DRAG ® technology mitigates the excessive sonic vibrations created within the valve by controlling the source of the noise, as demonstrated in the following formula:DRAG ® valves like this 28-inch (700 mm) multi-stage, pneumatic-controlled device have beeninstalled in over 2,000 plants around the worldto solve vibration and noise problems. DRAG®W= sound power = fl uid density d = characteristic dimension U = fl uid velocity C = velocity of sound fi eld d 2 U 6 C 3W Figure 9: Stem vibration velocity for aconventional valve before retrofi t (blue line)and after retrofi t with DRAG ® trim (red line)*Table 2: Recommendation for Fluid Kinetic Energy (Velocity Head) at trim Exit **S temV i b ra ti o n V elocity(mm/s,-pk )Hertz50403020100100200300400500Conventional valveCCI DRAGvalvefull open* “Multi-Stage Valve Trim Retrofi ts Eliminate Damaging Vibration”, J. R. Arnold, H.L. Miller, and R. E. Katz, Power-Gen 96 International, Orlando, Florida, Book IV, pg. 102-110, PennWell Conferences & Exhibitions, Houston, Texas, December, 1996. ** Based on information presented in the publication “Control Valves - Practical Guides for Measurement and Control” edited by Guy Broden , Jr. and Paul G. Friedman, 1998 edition, published by ISA and other sources.Note:KE =V 22g CThe Erosion ChallengeErosion of the valve trim can be caused by the washing action of a fl uid or abrasion from particles entrained in the fl uid. The erosion effect is most severe at high pressures and high concentrations of entrained material. Even very pure water can be extremely erosive.While clean dry gases usually are not a cause for concern, throttling even clean superheated steam can cause severe problems, as illustrated in Figure 10. Consider the following example: superheated steam at P 1 (inlet pressure) of 600 psia (4 MPa) and T 1 of 600°F (300°C) entering a conventional or modifi ed-trim valve is let down to 50 psia (0.3 MPa). The low pressure and high velocity inherent in fl ow through these valve trims allow the steam to expand isentropically or polytropically to point P 2. At this point, with velocity at its peak, the steam develops a moisture content between 12% and 20%. The resulting water droplets, traveling at maximum velocity, will rapidly erode the trim and damage the valve body. Pressure recovery is completed in the outlet and the temperature reaches equilibrium, resulting in superheated steam leaving the valve at P 3 (outlet pressure) of 50 psia (0.3 MPa) and T 3 of 515°F (270°C). However, while the valve has achieved its pressure drop, continuous formation of wet, high-velocity steam will soon result in severe trim damage. The same holds true in a gas handling service where hydrate (ice crystals) formed under similar circumstances can clog the conventional trim in a short time.Erosion by solids/sand is particularly tough on control valves. Materials that are readily available are quickly consumed by the sand-blasting effect of entrained solids. Controlling the velocity and the use of erosion-resistant materials adds signifi cantly to the life of the valve components handling these fl uids.As trim erodes, the valve’s C V changes and fl ow becomes diffi cult to control, inducing other symptoms like increased vibration and related high noise levels. Any time control is compromised, the risks soar. Lack of control results in a shortened life for the valve that threatens plant performance and reliability. Moreover, it means increased expense forthe plant operator.Erosion by a fl uid can alter the landscape ofvalve components over time, affecting thequality of operation.Erosion damage to a competitor’s valve plugcaused by high fl uid velocity results in poorshutoff.D R A G®One damaged part can shut a plantdown; a CCI DRAG ® valve can prevent thisunnecessary downtime and give you peaceof mind.The DRAG ® Solution to ErosionThe traditional approach to problems such as erosion include continual maintenance, brute force or both. The brute force strategy involves using harder materials where erosion is a problem, which covers up the symptoms without addressing the root cause. The rate of erosion varies as a third to fi fth-power function of fl uid velocity (V 3 to V 5). For example, if the fl uid velocity can be reduced by a factor of two, then the erosion rate will be reduced by a factor ranging between 8 and 32. To eliminate erosion, it is essential that the fl uid velocity be maintained at manageable levels. The DRAG ® design controls velocities throughout the disk so that pressure recovery does not take place. For erosion problems that result from abrasion, the DRAG ® trim operates at a controlled velocity. The inlet/outlet and trim velocities are low, so the steam expansion through the valve is isenthalpic – going from point P 1-T 1 directly to point P 3-T 3 (see Figure 10). Steam through the DRAG ® valve never has a chance to develop destructive moisture. In gas applications, controlled velocity minimizes the formation of hydrate, thus preventing the trim from clogging. CCI combines the velocity control principle and higher erosion-resistant material to solve erosion resulting from solids like sand. Choke valve applications use a multi-stage DRAG ® disk stack produced from tungsten carbide for substantially longer life compared to traditional solutions.DRAG®Figure 10: The low pressures and highfl uid velocities inherent in conventionalvalve trim (single-stage and multi-stage)result in erosion by abrasion, even in cleansuperheated steam, as water droplets areallowed to form.E n t h a l p yDRAG RTungsten carbide DRAG ® disks provide provenerosion prevention.The Leakage ChallengeLeakage through control valves can signifi cantly reduce plant effi ciency and result in higher overall operational and maintenance costs. This frequently means that millions of dollars are lost every year. This issue is overlooked by many operators who do not realize that a valve may still offer acceptable control while allowing signifi cant leakage when fully closed. In reality, the leakage past most control valves results in lost fuel, heat or system capacity, which directly impacts the economic viability of the process. In fact, the cost of leakage in a severe service control valve is always far greater than the price of the valve. In extreme cases, an entire plant may be shut down because of a single leaking valve. The costs of leakage through a control valve are signifi cant and are often manifested in the following ways:n Unscheduled plant shutdowns n Increased maintenance schedules to replace damaged valve and system components n System effi ciency losses resulting in increased fuel and power consumption n Heat rate losses and unit load limitations n Control system oscillations or outright loss of control Symptoms of Leakage n High temperature in the downstream pipe for a normally closed valve n Loss of process control, even when valve is fully closed n Steam or gas leaks through vents n Inability to hold the pressure inside the condenser nNoise produced by valve even when closed In the extreme case, a power plant shutdownmay be unavoidable because of a singleleaking valve.D R A G®Plant managers and engineers rely on CCI’sDRAG ® technology for reliable performanceto keep their facilities running trouble-free.The DRAG ® Solution to LeakageControlling leakage through a severe service control valve requires a combination of technologies and a dynamic understanding of the behavior of the fl uid as it passes through the valve. CCI customers place a premium on tight shutoff because it translates directly into operational cost savings. CCI engineers realize that tight valve shutoff is not only a function of operational closing forces, but also requires control of fl uid velocities through the valve seating area. DRAG ® technology limits the velocity of the fl uid as it enters the seating area and minimizes the erosive forces that would otherwise compromise the valve’s ability to effectively control leakage. In addition to controlling destructive fl uid velocities, CCI utilizes both high actuation forces and uniquely designed seals and seat to maintain repeatable tight shutoff. By combining the advantages of DRAG ® with CCI’s advanced actuation, sealing and seating technology, CCI severe service control valves provide repeatable tight shutoff and reliable operation to assure customers that the costs associated with system leakage are truly being controlled.Exceptional Shutoff — Repeatable Class V (or better)DRAG ® severe service control valves offer exceptional shutoff performance to withstand long periods of closure at high pressure differentials. CCI uses a uniquely designed seat that, when combined with CCI’s high actuator force, delivers tight shutoff each and every time. The high actuator force coins (leaves a circumferential impression into) the valve seat ring. The coining erases micro scratches caused by fi ne debris in the fl uid, providing reliable and repeatable long-term shutoff. In applications that need tight shutoff, CCI provides Class V or MSS-SP-61 (equivalent to a block valve) closure.DRAG®Table 3: Recommendation for Seat Load Requirements in Control Valves ** Based on information presented in the publication “Control Valves - Practical Guides for Measurement and Control” edited by Guy Broden , Jr. and Paul G. Friedman, 1998 edition, published by ISA and other sources.To ensure absolutely tight shutoff, CCIprovides a DRAG ® valve with pressurized seating as illustrated above.InletA CCI DRAG ® valve equipped withRHP ™seating technology establishes ahigher standard of valves for critical gasapplications.。