selection guide

SELECTION GUIDEFOR

CHECK VALVES
VD 500-600 E

SELECTION GUIDEFOR

CHECK VALVESVD 500-600 E

Adams Armaturen GmbHBaukauer Str. 55 - D.44653 Herne Page 1 / 11

TABLE OF CONTENTS

INTRODUCTION PAGE 2

SELECTION GUIDELINES PAGE 2

SELECTION DIAGRAM PAGE 3

LIQUIDS OR GAS AND STEAM FLOW PAGE 4

LIQUIDS PAGE 4

DAMPER CONTROLLED CLOSINGOR UNCONTROLLED CLOSING PAGE 4

FREE-ACTING ORPOSITIVE VALVE ACTION PAGE 5

TYPE GZA PAGE 5NO FLOW CONTROL CAPABILITYOR FLOW CONTROL CAPABILITY PAGE 5

TYPE RZN PAGE 6TYPE RZI PAGE 6TYPE GBZ (COMBINED FUNCTION VALVE) PAGE 6TYPE AZI (COMBINED FUNCTION VALVE) PAGE 7

FULL BORE TYPE PAGE 7TYPE MFK PAGE 7

GASES, STEAM PAGE 7

GRAVITY CLOSINGOR ASSISTED CLOSING PAGE 7

TYPE GMZ PAGE 8TYPE FCV WITH GRAVITY CLOSING PAGE 8TYPE FCV WITH ASSISTED CLOSING PAGE 9TYPE MAG WITH GRAVITY CLOSING PAGE 9TYPE MAG WITH ASSISTED CLOSING PAGE 10

CONCLUSION PAGE 10

SELECTION GUIDEFOR



INTRODUCTION

The purpose of check valves or non-returnvalves is to allow fluid flow in one preferreddirection and to prevent backflow or flow in theopposite direction. As pressure drops in a pipeand the fluid momentum slows, a check valveideally begins to close. As the flow directionreverses, the check valve closes completely.Based on this simple requirement it appearsthat a single check valve design would besufficient for use in any application. In additionto this basic non-return function, however,there are other service requirements whichmust be met by a check valve design whichcan vary extensively with different applications.

The following examples will illustrate thedifferent requirements imposed on checkvalves. Consider a check valve used on apump discharge where the pump supplieswater to a long discharge line and also a checkvalve utilized on a steam extraction line from aturbine to a heater. A pump discharge linecheck valve in a liquid requires a dampingdevice so the valve can close after the pumptrips to ensure controlled closure for maximumattenuation of pressure surge. In a steamextraction line, flow reversal can occur within0.2 seconds on loss of turbine pressure. Thisrequires a check valve with very fast closingcapabilities, low inertia of the valve disc andminimal inherent friction of all movingcomponents so that the impact of delayedvalve closure is reduced to a minimum.

The ADAMS range of check valves is probablythe most comprehensive and sophisticatedproduct line produced by any manufacturer.Types available range from gravity closed fastacting tilting disc valves to ultra fast closingpower assisted check valves for high pressure,high temperature applications and ultimately tohydraulically damped combined function checkvalves for severe pump applications.

The majority of our check valve designs arefurnished with the exclusive ADAMS inclinedconical seal system. This sealing system,utilized to seat the disc properly in the closedposition, has been used in thousands ofvalves over the past 30 years. During our

history we have continually improved anddeveloped our seat technology to the forefrontof valve technology. This sealing systemprovides tight shut-off over a wide range ofservice temperatures, freedom from jamming,and low trim inertia for faster valve response toflow changes.

The present ADAMS range of check valvesrepresents the result of our 30 years ofexperience with manufacturing, developmentand testing of check

valves for a wide range of applications. Resultsof ongoing development and extensive testingwill be used for continuous improvement of thecurrent check valve designs to maintain ourposition of leading check valve technology.

SELECTION GUIDELINES

The Selection Diagram (Figure 1) lists allADAMS check valve types together withselection criteria which should provide someassistance in finding the proper check valvetype for a specific application.

The following information is intended to providesome explanation of the selection criteriafollowed by a brief description of the checkvalve designs indicated in the SelectionDiagram.

SELECTION GUIDEFOR


Adams Armaturen GmbHBaukauer Str. 55 - D.44653 Herne

Figure 1Selection Diagram for the ADAMS range of Check Valves

CHECK VALVES

LIQUIDS GASES, STEAM

DASHPOTCONTROLLED

CLOSING

UNCONTROLLEDCLOSING

ASSISTEDCLOSING

FREE-ACTINGPOSITIVE VALVE

ACTION

TYPE GZA

NO FLOW CONTROLCAPABILITY

WITH FLOW CONTROLCAPABILITY

TYPE RZN TYPE GBZ

TYP RZI TYP AZI

FULL BORE TYPE

TYPE MFK

GRAVITYCLOSING

P

COMPRESSORBLOWER TURBINE

TYPE GMZWIT

WIT

COMPRESSORBLOWER

WIT WIT

WIT

TYPE FCVH ASSISTED CLOSING

TYPE MAGH ASSISTED CLOSING

TURBINE

TYPE MAGH GRAVITY CLOSING

TYPE FCVH GRAVITY CLOSING

TYPE MAGH GRAVITY CLOSING

age 3 / 11

SELECTION GUIDEFOR



LIQUIDS OR GAS AND STEAM FLOW

As shown in the Selection Diagram adistinction has been made between liquid andgas or steam flows. The reason for thisdistinction is as follows:

- The difference in inertia and elasticity ofthe different fluid types

- The time it takes for the flow velocity tobecome zero after a pump, compressor orturbine trip. The time until flow reversalcan take several seconds with liquid flows,while gas or steam flows can go to zero inless than 0.2 seconds in someapplications.

These variables call for specific check valvedesigns and possible accessories which mustprovide the basic inherent dynamic characte-ristics to ensure successful performance inservice.

LIQUIDS

DAMPER CONTROLLED CLOSINGOR UNCONTROLLED CLOSING

The ideal check valve should begin closing withdecreasing flow and close completely at thezero flow condition. In practice the check valveclosure is normally delayed to some extent,and the partially opened check valve is thensubjected to backflow.

Figure 2Multi-pump installation. 1 pump in service, 1 pump tripped out.Pressure rise on downstream side after closure of undamped checkvalve of size DN 400 (16")

A check valve without a damping device will beaccelerated in the closing direction whensubjected to backflow and will slam shut, givingrise to high pressures on the downstream side(see Figure 2). These pressure changes arefrequently called waterhammer because of thesound which often accompanies the pressuresurge. The rapid and uncontrolled closure of anundamped check valve due to flow reversal

produces a dynamic impact load on the discand body seat. Stresses caused by the impactload can lead to serious damage of valveinternals or, in the worst case, those internalsare broken off depending on the magnitude ofthe impact load and the adequacy of the valvedesign. The magnitude of the dynamic impactload depends solely on the velocity of the discat impact and the inertia of the moving valveparts.

Figure 3Same installation and service conditions as for Figure 2 above.Downstream pressure after closure of ADAMS RZN DN 400 (16")with damping device.

Unlike the performance of undamped checkvalves, the ADAMS range of damped checkvalves provides the feature of a controlledclosing action on the cessation of forward flowdue to the use of a hydraulic damper. TheADAMS damped check valve can initially closeundamped rapidly with decreasing forward flowand will gradually slow the disc closing speedto slowly reduce the backflow. This controlledclosing action of the damped check valveattenuates significantly the magnitude ofpressure surge (see Figure 3). In addition, thedynamic impact load on the check valve isreduced to negligible value.

The hydraulic dampers as used on ADAMScheck valves provide a number of features:

- Closing spring to initiate disc closingacceleration at the start of flow transient

- Up to three-stage damping to meet themost complex system requirements

- Adjustable damping rates to control thedisc closing speed

All of these features are conveniently acces-sible from the outside for adjustment to tunethe check valve performance during start-up(see Figure 4).

SELECTION GUIDEFOR



It is frequently assumed that the magnitude ofpressure surge resulting from a rapid checkvalve closure under reverse flow conditionsmay present a problem for low pressure pipingsystems only. However, the pressure surgecan easily rise to values that are 10 times thesteady state system pressure. With water asthe flowing media in steel piping the maximumsurge pressure is approximately 10 bar (45 psi)for every 1 m/s (1 ft/s) change in the flowingvelocity. The pressure surge travels from thesource of velocity change (the slamming checkvalve) at the speed of sound through the pipingsystem. As a result, not only the check valve issubjected to the pressure surge but also theentire piping system.

Surge does not originate with the check valve,but it can be magnified by incorrect valveselection or attenuated by the correct one.Rapid uncontrolled closure of a check valve outof tune with the fluid system can becatastrophic.

Figure 4Schematic design of multi-rate adjustable damping system (RZN,GBZ) and closing characteristics.

FREE-ACTINGOR POSITIVE VALVE ACTION

In many applications it is commonly requiredthat a check valve automatically opens onforward flow and closes on cessation of flowwithout any external signal or energy supply.The automatic or free-acting performance ofthe ADAMS check valve ensures extremelyreliable system protection.During the past 15 years, however, the de-mand for positively operated valves has

increased particularly in sizes ranging from1200 mm (48") to 3000 mm (120"). Thesevalves are usually used on pump dischargelines to function as a check valve. On pumpstart-up the valve is positively moved to fullopen and on pump trip due to receipt of a tripsignal, the valve will close.

The advantage of a positively operated valveover a free-acting check valve is the reducedpressure loss across the valve due to its fullopen position regardless of flow rate and thestreamlined design of the valve interior. Theadvantage of a free-acting check valve is theautomatic response to flow changes withoutrequiring an external signal or energy supply.

TYPE GZA

The design of the GZAvalves utilizes the TypeOSK tight shut-offvalve as the basis,and an external leverwith closing weightwith a hydraulic cy-linder. The valves areusually supplied with ahydraulic power unitwhich can be fitted to the valve as a compactself-contained unit. On pump start-up the valveis positively opened and remains in the fullopen position during normal service due tohydraulic pressure applied to the externalhydraulic cylinder. On pump trip the valve isalso tripped to close due to receipt of a signal.The valve closes on its own accord by meansof the lever and closing weight. As the valvecloses, the hydraulic cylinder is used as adamping device providing two- or three-stagemulti-rate adjustable and controlled closingaction.

Use of multiple control valves and sensorswhich initiate the trip action can increase thesystem redundancy to ensure the safetyaspects of the valve performance. The tripsignal can be either hydraulic or electric.

GZA valves are frequently used in power plantapplications to reliably protect large pumps inthe cooling water system against reverse flow.

SELECTION GUIDEFOR



NO FLOW CONTROL CAPABILITYOR FLOW CONTROL CAPABILITY

The conventional check valve generally pro-vides no capability for flow control and is solelyutilized for the check valve function.

In many applications, however, the check valveis installed in the piping system in series with ashut-off valve. It is a reasonable idea tocombine the functions of the two valves in asingle valve. A combination shut-off and checkvalve provides a number of features:

- Installation space and costs savings- Reduction in pressure loss- Flow control capability together with the

priority check valve function- Possible use as drain valve

TYPE RZN

This fast actingtilting disc checkvalve with low inertiaensures quick valvere-sponse to liquidflow changes. Thedual eccentricallymount-ed disc pro-vides maximum hy-drodynamic perfor-mance for low pressure loss and freedom fromjamming and flutter.

The ADAMS inclined conical seal systemensures that shut-off against reverse flow istight and progressive. The RZN Type checkvalve with its multi-rate adjustable dampingsystem offers complete primary protection ineven the most adverse applications. Thecompact design allows installation in veryconfined spaces.

The RZN is the ideal choice for everyinstallation which demands an ultra-reliablenon-slam check valve.

TYPE RZI

The RZI is essen-tially the same basicdesign configurationas the RZN exceptfor its more advan-ced damping systemwhich is setting newstandards in surgecontrol. UsingADAMS exclusivemulti-rate adjustable interval damping system,the RZI provides the optimum control oversurge in liquid transmission lines. In addition toproviding adjustment for each of three separatedamping rate increments, the point during thecheck valve closing travel at which each ratechange occurs is completely adjustable. Thismeans that the RZI can be tuned to exactlymatch the closing characteristics required in apump installation to prevent excessivepressure surge.

TYPE GBZ(COMBINED FUNCTION VALVE)

This combination stop and check valvecombines tight shut-off, flow control andcheck valve func-tions in a singlecompact unit. Likethe Type MAG, RZNand RZI designs, afast acting tilting disccheck valve is usedas the basis for theGBZ design. The GBZ is fitted with a compactgearbox which contains the reduction gear, lostmotion coupling and a hydraulic damping unit.The lost motion coupling ensures priorityfunction as a check valve so that the valve canauto-close from any partial or full open position.Throttling of the valve, which can be achievedby turning the handwheel, can be quite usefulfor filling a piping system during start-up orafter an outage. Additionally, the valve disc canbe locked in full open position by turning thehandwheel to drain a piping system. Thehandwheel can even be replaced in the fieldwith an electric actuator for automated remoteoperation.

SELECTION GUIDEFOR



The integral, hydraulic damping cylinderprovides multi-rate adjustable damping forcontrolled and non-slam closure to cope witharduous system requirements.

Figure 5Outlines of swing check/gate valve and GBZ installation

Since the GBZ can replace two (2)conventional valves, there are a number ofsavings such as less weight, less space, lowerinstallation costs and low pressure loss (Figure5).

These features make the GBZ ideally suited forinstallation on pump discharge lines.

TYPE AZI(COMBINED FUNCTION VALVE)

The function of theAZI is identical tothat of the Type GBZcombination stopand check valve.The AZI, however,extends the range ofapplications be-cause of itsavailability in largersizes and higher pressure ratings. Instead of asingle gearbox used on the GBZ, the AZI isfitted with a hydraulic damping unit on one sideand a gearbox with an integral lost motioncoupling on the other. The hydraulic dampingunit provides optimum control over surgepressure in liquid piping systems. Fullyadjustable damping increments in conjunctionwith adjustable damping strokes ensure a fullycontrolled and non-slam closing action.

The gearbox, including a lost motion coupling,provides flow control and automatic checkvalve function which can be very beneficial forfilling a piping system. The handwheel at thegearbox can be easily replaced with an electricactuator for remote operation. As an alternativethe AZI gearbox can be replaced with a

hydraulic power unit which permits the use ofthe hydraulic damping cylinder for positivevalve operation.

The AZI is a beneficial choice for everyinstallation calling for the application of a shut-off valve and a non-slam check valve in largersizes or higher pressures than the GBZ wasdesigned for.

FULL BORE TYPE

The full bore check valve provides unrestrictedflow passage in the normal flow direction withthe valve disc lifting clear of the fluid stream.The interior of valve body is shaped withoutany major change in cross sectional area togive smooth flow passage. These featuresmake the full bore check valve particularlysuitable for contaminated fluids such assewage, preventing material build-up in thevalve to eliminate blockage.

TYPE MFK

The MFK is a full borecheck valve providingunrestricted flow pas-sage in the normalflow direction. Thevalve is fitted with amulti-rate adjustablehydraulic damping unitfor non-slam closure.Developed as amodular design with a variety of accessories,this valve covers a range of applications inliquid waste handling.

The basic design concept of this check valvemakes the MFK particularly suitable forapplication in piping systems with sewage orother contaminated media.

SELECTION GUIDEFOR



GASES, STEAM

GRAVITY CLOSING OR ASSISTED CLOSING

For the protection of rotary equipment such ascompressors and turbines against reverse flowit is sometimes suitable to utilize check valveswhere closing is achieved just by gravity.These valves are usually identified as non-critical check valves.

When protection of valuable rotary equipmentagainst reverse flow is of importance, checkvalve designs are available as combinedfunction or assisted closing check valveswhere some method of positive actuation isadded to the basic auto-closing valve. Theseassisted closing actuators fitted to the checkvalves overcome increased inherent valvefriction caused by any deposits or wear due tofrequent cycling. They are providing a backupprotection for rotating equipment because theyare forcing valve closure in the event the checkvalve should fail to auto-close on cessation offlow.

Positively assisted closing action is frequentlyrequired for check valves utilized on largecompressor discharge lines and on steamextraction lines to heaters where a largeamount of energy is stored in the specificextraction system. Methods of actuationinclude double acting pneumatic or hydrauliccylinders with options of spring return oraccumulator stored energy systems.

Another feature of the assisted closingactuators is the optional provision for on-loadexercising, a test procedure which is widelyused with check valves installed in steamextraction lines from turbines. The actuator isperiodically tripped (sometimes daily), and asthe valve disc is momentarily forced far enoughclosed to demonstrate that the check valveoperates freely and returns to its initialoperating position after actuation force isremoved. On-load testing can be performedlocally or remotely.

TYPE GMZ

The ADAMS TypeGMZ assisted non-slam check valve isdesigned for gassystems where ultra-reliable high integrityoperation is required.The basic element is afast acting tilting disccheck valve withstable flow response. Disc movement is con-trolled by a lever, an adjustable closing weightand a light hydraulic damper to prevent slam ordisc oscillation. Assisted closing is provided bya single-acting pneumatic cylinder connectedto the lever arm by a clevis. The pneumaticactuator is controlled by a solenoid valve whichpermits tripping for positively assisted closurewith either a de-energized or energized state.The solenoid valve is normally operatedthrough a compressor start-up and shut-downsignal.

In normal GMZ operation the disc is opened byforward flow to a position where flow andgravity forces are balanced. With loss offorward flow the GMZ will auto-close as thehydraulic damper permits smooth non-slamclosure. In addition, normal shut-downprocedure is initiated by a signal to the solenoidvalve to start pneumatic assisted closure priorto cessation of the forward flow.

Special options and accessories availableinclude air open / spring close actuators, steamjacketing, limit switches and positiontransmitter for remote indication of discposition.

The Type GMZ check valve is particularlysuitable for installations in gas systems andwidely used on compressor discharge lines.

SELECTION GUIDEFOR



TYPE FCV WITH GRAVITY CLOSING

Developed as a resultof many years ex-perience on largesteam turbines andcompressors theADAMS Type FCV is avery robust check valvewith the lowest inertiamoving parts designedto with-stand very fastclosure with complete reliability. Suchcharacteristics are essential for valves designedto protect vital machinery and systems fromdamage following a trip-out or an emergencyshut-down.

Figure 6Opening characteristics of a 450 mm (18") FCV valve, class 300 versusturbine load

On loss of load, large steam turbines can rapidlyaccelerate to overspeed due to reverse steamflow caused by the energy contained in theextraction and feedwater heater system. Flowreversal can occur in less than 0.2 seconds andthis can cause very high impact loads on checkvalve closure if delayed. This necessitates thespecial design features of the Type FCV.

The Type FCV is designed to respond as rapidlyas possible by means of low inertia components,optimum closing moment and minimum friction.

Figure 7Closing time of an FCV of 450 mm (18") size, class 300 in free air

The basic design features of the FCV Typecheck valve are as follows:

- Low inertia of moving valve parts- Low inherent friction- Ultra-fast response to flow changes- Reduced distance disc travel- Optimum opening characteristics (Figure 6)- Ultra-fast valve closure (usually in 0.2 to

0.5 seconds in free air - depending onvalve size - Figure 7)

- Extremely reliable sealing system for tightshut-off and freedom from jamming

- Hard faced seat and disc tips to withstandhigh impact loads

- No bolting inside the valve for completereliability

The Type FCV has achieved an enviablerecord of reliability over long periods of servicewith very low maintenance, even in units withnumerous shut-downs. The Type FCV withgravity closing is particularly designed for useon steam extraction lines to protect turbinesagainst overspeed and partial water inductionon load rejection.

SELECTION GUIDEFOR



TYPE FCV WITH ASSISTED CLOSING

An air open/springreturn actuator isfitted on top of thevalve body toprovide assistedclosing action. Theclosing actuation isdirect acting via apad on the back ofthe valve disc thusavoiding the use of a shaft seal. With airpressure acting on the cylinder, the piston rodretracts and compresses the closing spring.The check valve is opened by steam flow andcloses automatically by gravity on cessation offlow. On receipt of a signal the actuator istripped, and the check valve is forced to closein the event the valve has failed to auto-close.

The FCV with assisted closing is the idealchoice as an extremely reliable and long lastingcheck valve for installation in steam extractionsystems where positive assist actuation isspecified by the turbine manufacturer.

TYPE MAG

The ADAMS Type MAG has been speciallydesigned and developed for low pressuregas/steam service to protect steam turbinesand compressors from the effects of reversalof gas/steam flow on trip or emergency shut-down. Its main features are ultra-reliable fastclosure, tight shut-off, low pressure loss andthe ability to withstand a large number of cycleswithout failure.

TYPE MAG WITH GRAVITY CLOSING

The MAG is a gravityclosing tilting disccheck valve openedby gas / steam flowand designed toclose rapidly justprior to flow reversal.The disc is profiledto improve aero-dynamic lift, and theclosing weight partially balances the discweight in any open position to minimizepressure loss. The weight is contained in a

pressurized chamber out of the flow stream toavoid the friction of a shaft seal and to furtherenhance reliability and reduce flow disturbance.The weight chamber is provided with adequatedrains to eliminate problems with condensateor dirt build-up and is accessible formaintenance.

TYPE MAG WITH ASSISTED CLOSING

The MAG is alsoavailable with anactuator for positivelyassisted closure. TheMAG is fitted with arotary Type actuatorwhich operates via alost motion couplingon the valve shaft.The coupling is contained in the weightchamber to ensure that shaft seal friction is notaffecting the valve performance. Actuation canbe either manual, electric, hydraulic orpneumatic.

The MAG is generally used on large, lowpressure steam extraction lines either with orwithout power assisted closure as specified.Another application of the MAG is for use onprocess gas lines to protect large crackingfurnaces against flow reversal during theswitch-over procedure or due to a tube rupturein the furnace.

CONCLUSION

The check valve Types as presented in thisdiscussion are available in a wide range ofsizes, pressure ratings and materials. Inaddition, many special construction featuresand various accessories can be supplied tomeet requirements for specific applications.

The foregoing discussion together with theSelection Diagram lists the most commoncheck valve applications. There are manyspecial options and designs which cannot becovered in a brief guide like this. ADAMSproduces many special valves (air admission,line break, emergency shut-down, etc.) someof which utilize check valve features. Leafletsgiving detailed data on special applications areavailable on request.

SELECTION GUIDEFOR



When specifying check valves for majorprojects it is advisable to consult your nearestADAMS sales office or representative forspecific information and advice.

Thank you for considering ADAMS.

HEAD OFFICE + WORKS

Adams Armaturen GmbHBaukauer Strasse 55

D-44653 Herne

Tel.: (0 23 23) 2 09-0Fax: (0 23 23) 2 09-2 86 / 2 87E-mail: [email protected]

www.adams-valves.com

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