Flowserve Gaseous Noise Control - PRO-QUIP

flowserve.comFlowserve Gaseous Noise ControlExperience In Motion

IndexSectionPage1 Introduction to Noise........................................... 31.1 Pressure Profiles Through Control Valves........ 31.2 Gaseous Severe Service................................... 31.3 Factors Impacting Noise................................... 31.4 Prediction Techniques...................................... 71.5 Additional Selection Factors............................. 72 Product Comparison............................................ 83 Stealth................................................................. 104 TigerTooth........................................................... 125 MegaStream........................................................ 136 Type III................................................................ 147 Type II.................................................................. 148 Type I................................................................... 159 RLS-System........................................................ 1610 XStream............................................................... 1611 Multi-Hole............................................................ 1712 SilentPac............................................................. 1713 Z-Trim.................................................................. 1814 Downstream Plates.............................................. 19

flowserve.comThe Bernoulliprinciple:When the fluidpressure in thevalve drops, thefluid velocityrises.1. Introduction to Noise1.1 Pressure Profiles Through Control ValvesAs a fluid travels through a conventional single-seatedglobe-style control valve, a vena contracta (point of narrowestflow restriction) develops directly downstream ofthe narrowest throttling point. At the point of vena contractathe fluid reaches a minimum pressure and maximumvelocity which rapidly recovers to a lower pressure thanthe inlet pressure (see Figure 1.1: Pressure Drop througha Control Valve). Due to the Bernoulli principle, when thefluid pressure in the valve drops, the fluid velocity rises(see Figures 1.2: Velocity through a Control Valve). Asthe velocity of the fluid increases, the noise generated byturbulence in the fluid also increases. A significant rise invelocity can produce noise beyond safe limits.1.2 Gaseous Severe ServiceHigh pressure drops in gas services will generate turbulencein the fluid flow downstream of the pressure drop.As a direct result of the turbulence, noise is radiated tothe surrounding area by the downstream piping system(Figure 1.3: Noise Radiating from Downstream Piping).In situations where equipment damage or personal injurycould be caused by a noise source, attenuation is mandatory.Tests have demonstrated that control valve noise increasesproportional to the velocity cubed (SPL ~ V3). Moderatelyhigher velocities can produce significantly loudernoise. Substantial noise can be generated even when velocitiesare significantly less than sonic.Mechanical vibration accompanies high acoustic noiselevels. Acoustic noise and mechanical vibration levels aregreatly compounded (up to 50 times) when the frequencyof the excitation matches acoustic and/or mechanicalnatural frequencies of the system.Noise suppression solutions should always be consideredin high pressure drop, high flow rate or resonant noiseapplications.Control Valve noise is measured in decibels (dBa). Decibelsuse a logarithmic scale, doubling the energy level ofsound pressure wave will cause the noise level to increaseby about 6 dBa. The dBa scale is structured to the humanear, the lowest noise a human can hear is around 0 dBaand a rivet gun is around 100 dBa. Ear protection shouldbe considered when noise levels are above 85 dBa.Uncontrolled noise is a significant problem that can leadto serious health problems, vibration and in the mostextreme cases can cause damage to equipment. Noisecalculations should be performed on all control valveflowing gasses to verify the suitability of the equipment1.3 Factors Impacting NoiseFluid VelocityThe most frequently used solution to high levels of controlvalve noise is to reduce the pressure from the valve inlet tooutlet gradually, eliminating pressure and velocity spikesthroughout the trim (Figure 1.4: Pressure through a Multi-Stage Valve). By lowering the pressure gradually, lowervelocities are created. The lower velocities generate lowernoise levels. Successfully applying this technique requirescontrolling the gas velocity through the valve trim and atall points from the inlet to the outlet of the valve.Occasionally fluid velocities at the valve outlet or even inthe downstream pipe can cause excessive noise. In thesecases, simple trim solutions will not provide the needednoise attenuation.

ConceptionDevelopmentManufactureOutlet velocities below 0.33 Mach are desirable. Highervelocities may be acceptable, but require an engineeringreview for each application. Velocities must be assessedfor the most difficult flowing conditions at the followingcritical points (as shown in Figure 1.5: Critical VelocityZones on page 6):• The inlet passageway to the valve• The internal flow area of the seat retainer at all plugpositions• The gallery flow area formed between the outsidediameter of the seat retainer and the inside diameter ofthe valve body• Outlet passage flow areaP 1 /P 2 , the Pressure RatioThe driving force behind velocity and noise is containedin the P 1 /P 2 ratio, which represents the energy availableto generate noise. When this ratio is low, the energy containedin the fluid stream will be low and the noise generatedwill typically be low as well. Each noise solution willhave a range of pressure ratios where the design is mosteffective. Noise control trim is most effective when pressureratio of the service is below the trim design limits.Reducing Pressure while Controlling VelocityThe most common method to reduce noise is to separatea large pressure drop into smaller pressure steps whichwill produce far lower velocities at each step. A numberof mechanisms are available to reduce the pressure withoutcreating excessive velocity. Designs which make efficientuse of these mechanisms will create the lowestnoise possible.Sudden Expansion and ContractionA fluid that experiences a sudden expansion or contractioncreates turbulent zones in the fluid flow. These turbulentzones takes energy out of the fluid in the form ofpressure. This is the primary effect used by orifice platesto create a pressure drop.Figure 1.1: Pressure Drop Through a Control ValveFigure 1.2: Velocity Through a Control Valve

flowserve.comOSFigure 1.3: Noise Radiating from Downstream PipingSmall Flow PassagesSmall flow passages accentuate the friction formed bythe passage walls. As the passage grows smaller, morepressure is required to force the fluid to flow. Many valvedesigns use small passages to create frictional losses toreduce the pressure.Mutual ImpingementBy directing two flows to impact each other at 180 degrees,a highly turbulent zone is created. This turbulentzone dissipates energy. With one flow working againstthe opposing flow, the pressure is reduced without addingvelocity to the flow.Increasing PressureTurnsEach sudden turn in the fluid flow path will cause thepressure in a fluid to drop. A small velocity increase occursas the fluid makes the turn. The angle of the turn canhave a dramatic effect on the energy loss from the fluidas it makes the turn. Angles sharper than 90 degrees aredifficult to manufacture, but have more of an effect onreducing pressure.Peak Frequency EffectMost noise in a control valve produces a range of frequencieswhich have a bell-curve type distribution anda peak frequency. Changes in the geometry of the valvedesign will shift this peak frequency.Figure 1.4: Pressure Through a Multi-Stage ValveShifting the peak frequency higher is very desirable fortwo primary reasons. First, it can shift the frequency outof the range of human hearing. This lowers the perceivednoise and reduces the damage to human organs. Second,it reduces the level of noise that can pass through thepipe. The natural frequency of pipe is low. When the frequencyof the noise matches the natural frequency of thepipe, the pipe will resonate in sympathy, easily passingthe noise from the inside to the outside of the pipe. Higherfrequencies don’t have this resonance and will passless noise out of a pipe. Higher peak frequencies will becontained inside the pipe better than lower frequencies.

Gallery Flow AreaInlet PassagewayOutlet PassageInternal Trim Flow AreaFigure 1.5: Critical Velocity ZonesA common method to raise the peak frequency is to makesmaller outlet holes in the noise control device. Cutting ahole diameter in half can lower the overall noise level byup to five decibels.WaveCracker TechnologyWaveCracker is a patented technology that reduces noiseas flow passes through passages with irregularly shapedcross sections. Tests have shown this technology effectivelycan reduce noise by more than ten decibels.WaveCracker works by forming an irregular cross sectionshape (see Figure 1.6: WaveCracker Passages). Soundwaves reflecting off the walls of the passage have irregularpatterns. These irregular patterns cause the soundpressure wave to lose intensity as it moves down thepassage.Mass FlowLower pressure drops across control valves will producesignificant noise if the mass flow rate is high. This happensmost often in large valves when many small noisegeneration sites combine to produce a loud cumulativenoise level. Combating this problem is more difficultsince taking the pressure drop in small stages may notbe effective.Acoustical AttenuationAcoustical attenuation can provide a barrier which blocksnoise. This can be done in many ways, from insulatingthe pipe to increasing the distance to the noise source.Careful engineering of a noise solution includes evaluatingany existing or potential attenuation.Harmonic VibrationHarmonic vibration occurs when the natural frequency ofthe pipe and valve approach a common frequency. Thiscauses a noise with a single frequency and a characteristicsound that is often called screech. Since screech occurswhen the frequency of the valve and pipe match, itis not easily predicted. However, simple changes in thevalve geometry can usually solve the problem.

flowserve.comWave Cracker PassageFigure 1.6: WaveCracker PassagesReflective SurfacesNoise coming from a pipe can be amplified by reflectivesurfaces. Noise predictions assume a free field, whichis defined as no reflective surfaces. A single flat surfacenear the control valve, like a concrete floor, can add threedecibels to the noise. Each flat hard surface can add anotherthree decibels. Two hard flat surfaces that are parallelto each other will add substantially more than six decibels.Adding walls, a ceiling and a floor can add thirty to fortydecibels.1.4 Prediction TechniquesA number of prediction techniques exist with varying levelsof accuracy for different applications. Using differentprediction techniques to predict the noise of an applicationwill often result is widely varying results. Unfortunately, nostandard exists which is the most accurate for all possibleconditions. Therefore, when noise is a critical factor a studyof the flow conditions, valve design, and the available noiseprediction methods should be undertaken.Valve Manufacturer StandardsMost manufacturer have proprietary techniques which willproduce acceptable predictions under a certain range ofconditions and with equipment the manufacturer is familiarwith. When used outside of the acceptable range or withother equipment, predicted noise calculations can be significantlydifferent than actual noise produced.IEC 60543-8-2In an effort to provide an accurate standard that can be usedto compare different manufacturers, the IEC committeehas developed the IEC standard 60543-8-2. Although thisprediction method is not perfect for all conditions or valvestyles, this method does create a clear baseline to comparedifferent valve models1.5 Additional Selection FactorsThe following factors should be considered before applyingexpensive noise suppression equipment:• How much noise attenuation is actually required?• What are the low-cost alternatives to noise attenuation?• If noise attenuation devices are necessary, what lowercostequipment can be specified? If the predicted soundpressure level (SPL) exceeds 85 or 90 dBA, noise suppressiondevices should be considered. However, highernoise levels may be acceptable if the noise is not associatedwith equip-ment damage and is located in a remotelocation away from people. Other possible low-cost alternativesto noise suppression equipment are:• Piping insulation• Discharging the valve directly into a vessel (allowingthe noise to be absorbed by the vessel)• Relocating the noise source (such as the downstreampiping) outside an enclosed area• Reversing the flow direction through the valve• Reducing the pressure drop across the valve.

2. Product ComparisonDesign Globe, Multi-Stage Noise Control Globe, Multi-Stage Noise Control Globe, Multi-Stage Noise ControlType Stealth TigerTooth MegaStreamBase Valve Mark Series Mark Series Mark SeriesSize Range 3˝ to 36˝ 1½˝ to 36˝ 1˝ to 36˝Cv Range to 4000 4 to 4000 5 to 10100Flow Direction Flow under the plug Flow under the plug Flow under the plugPressure Stages 6 to 20 2 to 8 1 to 7Features• Attenuation of up to 40 dBa• WaveCracker• Stealth is the most efficient high pressuredrop noise attenuation trim everdeveloped• Stealth uses laser-cut discs to createstacked disc seat retainers. The cutsin the discs form channels for thefluid to pass through.• Attenuation of up to 30 dBa• Can be taken apart for cleaning orrepair• TigerTooth uses stacked discs withgrooves, or teeth, to take multiplestaged pressure drops• Self-cleaning design with large passages• Attenuation of up to 20 dBa• MegaStream uses nested cylinders inplace of the seat retainer. Each drilledcylinder represents a stage of pressurereductionDesign Globe, Multi-Stage Noise Control Globe, Multi-Stage Noise Control Globe, Multi-Stage Noise ControlType RLS-System XStream Multi-hole plugBase Valve FlowTop, FlowPro FlowTop, FlowPro FlowTop, FlowProSize Range 1˝ to 12˝ ½˝ to 12˝ ½˝ to 12˝Cv Range Engineered up to 820 4.6 to 1040 2.9 to 1040Flow DirectionBidirectional Flow, Liquid flow to closeGas flow to openFlow under the plugBidirectional FlowPressure Stages 2 to 6 1 to 4 1Features• Attenuation of up to 30 dBa dependingon the operating conditions• Efficient, modular design• Every stage is controlled, whichresults in a high efficiency even atpartial load• For gas, steam and liquid service toreduce noise• Attenuation of up to 20 dBa dependingon the operating conditions• Efficient, modular design• Easy upgrade from standard, no trimset changes• For gas, steam and liquid service toreduce noise• Attenuation of up to 15 dBa dependingon the operating conditions• Efficient, modular design• For gas, steam and liquid service toreduce noise

flowserve.comGlobe, Multi-Stage Noise Control Globe, Multi-Stage Noise Control Globe, Multi-Stage Noise Control DesignType III Type II Type I TypeKämmer Series Kämmer Series Kämmer Series Base Valve½˝ to 4˝ ½˝ to 4˝ ½˝ to 4˝ Size Range1.8 to 228 1.8 to 466 Cv RangeFlow under the plug Flow under the plug Flow under the plug Flow Direction2 1 1 Pressure Stages• Attenuation of up to 26 dBa• Both plug characterized or cage characterizeddesigns available• Custom engineered to match theservice conditions• As the plug opens in the seat, it simultaneouslyopens the cage for effectivenoise control over the entire strokelengthGlobe, Multi-Stage Noise Control• Attenuation of up to 22 dBa• Customizable trim characteristicsavailable• Combination with Type I possible (upto 29dBA)Ball Valve, Multi-Stage Noise Control• Attenuation of up to 23 dBa• 3 designs (single cage, double cage,double cage with silencer)• Easy retrofit• Standard PlugDownstream Orifice Plate, Multi-StageNoise ControlFeaturesDesignSilentPack Z-Trim DownStream Plates TypeFlowTop, FlowPro Setball, Duball, ShearStream SB Downstream of any valve Base Valve½˝ to 12˝ 2˝ to 20˝ 1 ½˝ to 24˝ Size Range0.73 to 925 90 to 15950 6 to 3340 Cv RangeFlow under the plugDuball; Bidirectional FlowSetball; Shaft DownstreamDownstream of control valve Flow Direction1 1 to 5 1 to 3 Pressure Stages• Attenuation of up to 18 dBa depending • Attenuation of up to 17 dBa• Attenuation of up to 25 dBaFeatureson the operating conditions• Pressure drops up to the valve limits • Downstream plates are installed• Efficient, modular design• Tight Shutoffdownstream of a valve providing• Easy upgrade from standard, no trim • The unique patented Z-trim design reducesnoise by taking pressure drops • Noise control plates have multiplebackpressure and noise attenuationset changes• For gas and steam service to reduce in up to five stepsdrilled holes to attenuate noise whilenoise• The design makes it possible to managehigh pressure drops at low flows trol valvetaking the pressure load off the con-and small opening angles and stillhave high capacities (Cv) at largeropening angles• The Z-Trim is self cleaning for applicationswith entrained media

3. StealthIntroductionThe most sophisticated noise attenuation design, Stealth trimeffectively reduces sound pressure levels in the most demandingapplications (Figure 3.1: Control Valve with Stealth Trim).The advanced Stealth design combines the most effective noiseand pressure control mechanisms to produce the most efficientnoise reduction trim ever created.DesignStealth is produced by laser cutting circular discs to form fluidpassageways and then braising the discs together to form aseat retainer (Figure 3.2: Stealth Stack). Three different discsare cut and matched together to form a flow path set (Figure3.3: Stealth Discs) (Figure 3.4: Stealth Flow Passage). A numberof disc sets are then stacked together and the whole assembly isbraised together to form a stack.Similar to TigerTooth an important mechanism reducing thepressure in Stealth trim is the sudden expansion and contractionphenomenon that takes place as the flow passes over theteeth. The Stealth trim’s ability to gradually reduce pressurewithout generating high velocities is important for the reductionof noise in the process line.In addition to reducing the pressure gradually, Stealth takes advantageof frequency shifting by providing small outlet holeswhich raise the frequency and lower the noise.An important feature in the noise control capabilities of theStealth is the patented WaveCracker technology, patent numberWO 2006/093956 A1. WaveCracker technology provides extranoise attenuation without creating extra pressure drops in thevalve.Trim exit flow paths on the Stealth are angled to direct the flowto the valve exit. This feature increases the flow capacity of thevalve and lowers the noise by reducing exit turbulence.Combining the pressure reduction, and velocity control featureswith the noise elimination features of the Stealth produces themost advanced noise elimination technology available.Figure 3.1: Control Valve with Stealth Trim10

flowserve.comBase Valve DesignBase valves for the Stealth include the Mark One and Mark 100.Mechanisms at Work• Pressure Control• Velocity Control• Attenuation• Frequency Shifting• Noise Cancellation• WaveCrackerFigure 3.2: Stealth StackFigure 3.3: Stealth DiscsFigure 3.4: Stealth Flow Passage11

4. TigerToothIntroductionDecades of field experience has proven the sophisticated designof the TigerTooth to be one of the most effective noisereduction trims available. Designed to be most effective at highpressure drops, the TigerTooth design effectively reduces thesound pressure levels in the most demanding applications(Figure 4.1: Control Valve with TigerTooth Trim).DesignThe TigerTooth design employs highly engineered concentricgrooves (or teeth) machined into the face and backside of aseries of circular stacked discs (called a stack), which form theseat retainer (Figure 4.2: Cross-Sectioned TigerTooth Seat Retainer).Legs separate one disc from another, providing a gapbetween individual discs, forming flow passages.Figure 4.2: Cross-Sectioned TigerTooth Seat RetainerAn important mechanism reducing the pressure inTigerToothtrim is the sudden expansion and contraction phenomenon thattakes place as the flow passes over the teeth. The TigerToothvalve’s ability to gradually reduce pressure without generatinghigh velocities is important for the reduction of noise in theprocess line.In addition to the standard linear and bi-linear designs, Tiger-Tooth can also be designed with a full-open area at the top of thestack to provide additional flow capacity. This design flexibilityallows the TigerTooth to take very high pressure drops whenthrottling low and still deliver high capacities when required,while generating exceptionally low noise levels.Passages in the TigerTooth design are self cleaning. Passagesgrow wider as the fluid passes from the inside to the outside.This allows large solids to easily pass through the trim.Base Valve DesignBase valves for the TigerTooth include the Mark One, Mark Two,Mark Eight, and Mark 100.Figure 4.1: Control Valve with TigerTooth TrimMechanisms at Work• Pressure Control• Velocity Control• Attenuation12

6. Type III 7. Type IIIntroductionUsing the same skirt guided drilled-hole plug as the Type II designand a heavy duty drilled-hole cage, the Type III design iscreated (Figure 6.1: Type III Trim). The Type III system is mosteffective at reducing noise generated by higher pressure drops.The Type III trim offers one or two stages of pressure reductionin a heavy duty design.DesignWhen using two stages of pressure drop, the Type III designhas a skirt guided drilled-hole plug, and a heavy duty drilledholecage. In the single stage style, the heavy duty drilled-holecage is used. Both styles use cage guiding to throttle each stagefor effective noise control over the complete range. Each stagetakes part of the pressure drop to produce the minimum noisewhile still attenuating noise generated upstream. Both designwork by attenuating upstream noise and shifting the noise frequencyhigher.Standardized designs allow for quicker deliveries and lowercosts.Base Valve DesignAvailable in a number of Kammer platforms, the most commonlyused is the 35000 series control valve.Mechanisms at Work• Pressure Control• Velocity Control• Attenuation• Frequency ShiftingFigure 6.1: Type III TrimIntroductionBy adding a skirt guided drilled-hole plug to the attenuators usedin the Type I design, the Type II design is created (Figure 7.1: TypeII Trim). The Type II system is most effective at reducing noisegenerated by moderate to high pressure drops. The Type II trimoffers up to four stages of pressure reduction.DesignWhen using all four stages of pressure drop, the Type II designhas a skirt guided drilled-hole plug, an inner perforated metalstage, a metal mesh silencer and an outer perforated metalstage. Each stage takes part of the pressure drop to produce theminimum noise while still attenuating noise generated upstream.When only a single stage is required, the skirt guided drilled-holeplug is used. The three stage design uses a skirt guided drilledholeplug along with both the inner and outer stages of the cage.Adding the baffle creates the four stage style. All three designswork by attenuating upstream noise and shifting the noise frequencyhigher.Standardized designs allow for quicker deliveries and lowercosts.Base Valve DesignAvailable in a number of Kammer platforms, the most commonlyused is the 35000 series control valve.Mechanisms at Work• Pressure Control• Velocity Control• Attenuation• Frequency ShiftingFigure 7.1: Type II Trim14

13. Z-TrimFigure 13.1: Setball Control Valve with Z-TrimIntroductionZ-Trim combines the benefits of an advanced control valve withthe simplicity of a ball valve. Most effective with low to mediumpressure drops, the Z-trim excels at eliminating noise in highflow services. Using the standard Setball (Figure 13.1: SetballControl Valve with Z-Trim) or Duball (Figure 13.2: Duball ControlValve Z-Trim) as a platform, adding the Z-Trim requires only onepart to be changed.Noise Control DesignThe simple design of the Z-Trim gets it’s effective noise reductionby passing the fluid through as many as five stages of pressurereduction. Increasing passage areas of each subsequent stageof the Z-Trim allows the gas to expand while maintaining lowvelocities for lower noise.Figure 13.2: Duball Control Valve with Z-TrimAs the valve opens, fewer stages are taken until the ball is openand the valve develops full capacity. This feature gives effectivenoise attenuation at the low end, where pressure drops are high,and still delivers the high capacity expected from a ball valve.Base Valve DesignThe Z-Trim is available in the Duball, Setball and ShearStreamSB control valves.Mechanisms at Work• Pressure Control• Velocity Control• Attenuation• Frequency ShiftingEach stage provides both attenuation of upstream noise and limitsthe velocity through the trim minimizing noise generation.18