Introduction: Introduction: Va
Valvlves es arare e inintetegragral l cocompmpononentents s in in pipipiping ng sysyststemems s ththey ey arare e ththe e prprimimarary y memeththod od of of controlling the flow, pressure and di
controlling the flow, pressure and direction of the fluid. rection of the fluid. Valves may be required to operateValves may be required to operate con
contintinuouuously sly e.ge.g. . concontrol trol valvalvesves, , or or thethey y may may be be opeoperatrated ed intintermiermittettentlntly y e.ge.g. . isoisolatlationion valves, or
valves, or they may they may be installed be installed to operate rarely to operate rarely if ever e.g. if ever e.g. safety valvsafety valves. es. A valve caA valve can ben be an extremely simple, low cost item or it may be and extremely complicated, expensive an extremely simple, low cost item or it may be and extremely complicated, expensive item.
item. In piping In piping design the design the valves probably valves probably require more engineering require more engineering effort than effort than any otherany other piping component. piping component. Valve Classifications: Valve Classifications: Isolation/Stop valve: Isolation/Stop valve: Th
The e isisololatatioion n of of ththe e dowdownsnstrtreaeam m sysyststem em frfrom om ththe e upupststreaream m sysyststem em by by ususe e of of anandd isolation /stop valve is a critically important function. The prime requirements of this valve isolation /stop valve is a critically important function. The prime requirements of this valve are tight shut off when closed and minimum restriction to flow when opens.
are tight shut off when closed and minimum restriction to flow when opens.
Valves used for this function include gate valves, globe valves, ball valves, plug valves, Valves used for this function include gate valves, globe valves, ball valves, plug valves, butterfly valves, diaphragm valves and pinch valves
butterfly valves, diaphragm valves and pinch valves
Regulation of flow: Regulation of flow:
Many applications require the flow of the fluid be regulated (throttled) at some fixed or Many applications require the flow of the fluid be regulated (throttled) at some fixed or variable level between fully zero and maximum flow
variable level between fully zero and maximum flow limits. limits. This is achieved by introducingThis is achieved by introducing res
resististancance e to flow, or to flow, or by by bypbypassassing flow or ing flow or by changby changing the ing the dirdirectection of ion of the flowthe flow. . AnAn important feature for control valves is that the output variable (flow) is related to the input important feature for control valves is that the output variable (flow) is related to the input variable (
variable (valve position)valve position). . An ideal An ideal operating charactoperating characteristic of eristic of a hand a hand operated flow operated flow controlcontrol va
valvlve e is is ththat at ththe e flflow ow is is didirerectctly ly prpropoporortitiononal al to to ththe e poposisitition on of of ththe e hahandndwhwheeeell Valv
Valve types for this fune types for this functioction includes gln includes globe, needlobe, needle, ball, and bute, ball, and butterflyterfly. . Globe and needGlobe and needlele valves are best suited for this duty but ball valves are also easily adapted to give reliable valves are best suited for this duty but ball valves are also easily adapted to give reliable flow control.
flow control.
Back flow prevention: Back flow prevention: In some
In some circumstances circumstances it is it is important to important to prevent reversed fprevent reversed fluid flow. luid flow. The type The type of valve of valve forfor thi
this s dutduty y is a is a nonnon-re-returturn-vn-valvalve e (NR(NRV) or V) or checheck valveck valve. . The impoThe importartant critent criteria whenria when selecting these valves are tight shut off against reverse flow, low resistance to flow for selecting these valves are tight shut off against reverse flow, low resistance to flow for forwa
forward flow, fast response. rd flow, fast response. The valve can be The valve can be operatoperated to ed to close by gravityclose by gravity, fluid flow, or, fluid flow, or spring.
spring.
Two main valve types are available for this function lift check valves or swing check valves. Two main valve types are available for this function lift check valves or swing check valves.
Pressure Regulation: Pressure Regulation:
In many applications, more generally associated with gases, there is a need to reduce the In many applications, more generally associated with gases, there is a need to reduce the suppl
supply y press to a press to a set fixed value. set fixed value. It is It is also necessalso necessary to maintain this reduced pressuary to maintain this reduced pressurere over a range of
over a range of fluifluid flow d flow condiconditionstions. . The pressurThe pressure regulator valve is engineered for thise regulator valve is engineered for this application.
application. The valve is basicThe valve is basically a globe valve biasally a globe valve biased open by an adjustable spring forceed open by an adjustable spring force with the feedback pressure tending to move the valve to a closed position such that at the with the feedback pressure tending to move the valve to a closed position such that at the set pressure the feedback pressure force just exceeds the spring force.
set pressure the feedback pressure force just exceeds the spring force. The pressure regulator valve
The pressure regulator valve operatoperates es using the using the downsdownstream fluid tream fluid presspressure ure as feedback.as feedback. Thi
This s is is mosmostly taken from tly taken from witwithin the hin the valvalve ve (se(self lf actactinging). ). For more For more accaccuraurate te concontrol atrol a feedback connection can be taken from the downstream piping.
feedback connection can be taken from the downstream piping.
The pressure regulation at low near zero flows is difficult and it is often necessary to include The pressure regulation at low near zero flows is difficult and it is often necessary to include internal or external relief valve functions to ensure no high pressures in the downstream internal or external relief valve functions to ensure no high pressures in the downstream system.
system.
Pressure Relief Valves- Safety valves: Pressure Relief Valves- Safety valves: A
A vevery ry imimpoportartant nt vavalvlve e fofor r sasafefety ty is is ththe e prepressssurure e relrelieief f vavalvlve. e. ThThis is vavalvlve e is is usused ed inin applications where excessive pressure in the system can cause damage or failure or can applications where excessive pressure in the system can cause damage or failure or can introduce a safety risk.
introduce a safety risk. Uncontrolled excessive pressures caUncontrolled excessive pressures can result in disastrous accn result in disastrous accidentsidents e.g. when
e.g. when potentially explospotentially explosive gases ive gases are being are being controlled. controlled. Relief valves Relief valves are mainly are mainly springspring loa
loaded ded but but thethey y can also can also be be gragravitvity y opeoperatrated ed and other and other mormore e spespeciacializlized ed desdesignigns s areare available.
available. Th
The e bubursrstiting ng /r/rupuptuture re didisc sc mumust st be be ininclclududed ed unundeder r ththe e gegeneneraral l heheadadining g of of sasafefetyty valv
valves. es. This iThis is simps simply a disc wly a disc which ruphich ruptures whtures when a set pren a set pressure iessure is excees exceeded. ded. The fluThe fluidid then escape
then escapes through the ruptured disc. s through the ruptured disc. If the If the burstbursting disc operates the system has being disc operates the system has be closed down and vented and the bursting disc is then replaced.
closed down and vented and the bursting disc is then replaced. Re
Relilief ef vavalvlves es whwhen en usused ed fofor r sasafefety ty apapplplicicatatioions ns arare e engenginineereered ed in in liline ne wiwith th sasafefetyty regulations and require regular inspections to confirm the settings and the operation. An regulations and require regular inspections to confirm the settings and the operation. An important part
important part of the of the relief valve relief valve installation installation is the is the routing of trouting of the relieved fluihe relieved fluid. d. This pipeThis pipe route must be to a safe location and must be engineered such that it is always fully open. route must be to a safe location and must be engineered such that it is always fully open.
Special and miscellaneous valves: Special and miscellaneous valves:
There are a wide variety of special valves developed for specific industries. There are a wide variety of special valves developed for specific industries.
Fluid Properties and operating conditions: Fluid Properties and operating conditions:
The properties of the fluid be controlled have a major impact on the design and materials of The properties of the fluid be controlled have a major impact on the design and materials of construction of the val
construction of the valve. ve. The piping industry, over the years, The piping industry, over the years, had developed a wide rangehad developed a wide range of val
of valve desve designigns and mats and materiaerial to hanl to handle vidle virturtuallally all of the fly all of the fluiduids beins being handg handledled. . TheThe selection of the valve should take into account fluid viscosity, temperature, density and flow selection of the valve should take into account fluid viscosity, temperature, density and flow rat
rate. e. The valvThe valve e musmust t be suitabe suitable to ble to witwithsthstand resuland resultinting g corcorrosrosion and erosiion and erosion and on and if if n
nececesessasary ry ththe e vavalvlve e mmay ay hahave ve tto o be be dedesisign gn ffor or no no ininteternrnaal l hholold d up up of of flfluiuidsds.. Important considerations include for absolute internal and external leak tightness when Important considerations include for absolute internal and external leak tightness when handling toxic or explosive flui
valve to maintain its internal and external integrity when the valve surrounded by flames valve to maintain its internal and external integrity when the valve surrounded by flames from a fire.
from a fire.
Valve Connections: Valve Connections:
There are a number of methods of connecting valves into the piping systems are as follows: There are a number of methods of connecting valves into the piping systems are as follows:
•
• Flanges: The valve is provided with suitable rated flanges.Flanges: The valve is provided with suitable rated flanges. •
• Wafer: The valve is provided with suitable sealing faces and is trapped between lineWafer: The valve is provided with suitable sealing faces and is trapped between line
flanges. flanges.
•
• Butt Welded: The valve is provided with butt weld end and welded into the pipingButt Welded: The valve is provided with butt weld end and welded into the piping
system using high integrity joints. system using high integrity joints.
•
• Socket Welded: Socket welds allow and welded into the piping system using filletSocket Welded: Socket welds allow and welded into the piping system using fillet
welds. welds.
•
• Screwed Ends: Ends can be provided with female or male screwed ends. The threadsScrewed Ends: Ends can be provided with female or male screwed ends. The threads
can be taper or parallel can be taper or parallel
•
• Compression Fittings: Compression Fittings: Ends can Ends can be provided with be provided with compression fittingscompression fittings
Valve Containment: Valve Containment:
An important requirement in valve design is to minimize the leakage of fluids into the An important requirement in valve design is to minimize the leakage of fluids into the su
surrorrounundiding ng enenvivironronmementnt. . ThThis is is is ververy y imimpoportrtanant t in in ththe e nunuclcleaear r ininduduststry ry anand d whwhenen trans
transferring ferring toxic toxic or flaor flammablmmable fluie fluids. ds. The possiblThe possible leakae leakage poige points on nts on valvevalves are lis are listedsted below
below
•
• The end connections with the piping.-The end connections with the piping.-•
• The spindle gland seals -allowing axial and The spindle gland seals -allowing axial and rotary motion.rotary motion. •
• For top entry valves the sealed top closure jointFor top entry valves the sealed top closure joint •
• For three piece ball valves - the two split jointsFor three piece ball valves - the two split joints •
• Valve drain connections and vent connectionsValve drain connections and vent connections
The best option for minimizing risk of leakage from the pipe connections is to use butt The best option for minimizing risk of leakage from the pipe connections is to use butt welded joints which c
welded joints which can be verified by non-destrucan be verified by non-destructive-testing (NDT). tive-testing (NDT). This option obviouslyThis option obviously e
elliimmiinnaattees s tthhe e vvaallvve e ttyyppees s wwhhiicch h hhaavve e tto o bbe e rrememoovveed d ffoor r mmaaiinntteennaancnce.e. The options f
The options for eliminating risor eliminating risk of glak of gland leakage are nd leakage are to use to use bellows sealed vabellows sealed valves. lves. The riskThe risk can als
can also be reduced by incoo be reduced by incorporatrporating dual seaing dual seals with a test poils with a test point betweennt between. . Pinch vaPinch valveslves and diaphragm valves do not include gland sealing and are therefore not at risk of gland and diaphragm valves do not include gland sealing and are therefore not at risk of gland leakage.
leakage.
Flow Factors: Flow Factors: It
It is is cleclear ar thathat t difdifferferent ent sizsized ed valvalves have ves have difdiffereferent nt floflow w ratrate e capcapacacitiities es and it and it is is ververyy important to be able to assess the flow through a valve for a fluid at certain conditions. important to be able to assess the flow through a valve for a fluid at certain conditions. The flow characteristics for an on-off valve are fixed and can be evaluated directly using the The flow characteristics for an on-off valve are fixed and can be evaluated directly using the relevant flow factor.
relevant flow factor. The flow through flow control The flow through flow control valves, relief valves, valves, relief valves, pressure reducingpressure reducing valves and check valves depend on the operating condition for the valve and require a more valves and check valves depend on the operating condition for the valve and require a more detailed evaluation.
detailed evaluation.
The most general method of identifying the flow capacity of a valve is the C
The most general method of identifying the flow capacity of a valve is the C vv Factor.Factor.
The C
The C vv factor based on American imperial units and is defined as follows:factor based on American imperial units and is defined as follows:
C
C vv = The flow of water through a valve at 60= The flow of water through a valve at 60ooF in US gallon/minute at a pressure dropF in US gallon/minute at a pressure drop
of 1 lb/in of 1 lb/in22
The metric flow factor (K
The metric flow factor (K vv) is used throughout outside of America and is defined as follows:) is used throughout outside of America and is defined as follows:
K
K vv = the flow of water through a valve at 20= the flow of water through a valve at 20 ooC in mC in m33 /hr with a pressure drop of (1 bar) /hr with a pressure drop of (1 bar)
The conversion between the two factors is K
The conversion between the two factors is K vv = 0.865 C= 0.865 C vv
Also kv is defined as follows: Also kv is defined as follows: k
k vv = the flow of water through a valve at 20= the flow of water through a valve at 20 ooC in litres/min with a pressure drop of (1 bar)C in litres/min with a pressure drop of (1 bar)
The conversion between k
The conversion between k vv and Cand C vv is kis k vv = 14.42 C= 14.42 C vv
Liquid Flow: Liquid Flow:
To establish the flow (Q) in litres /m at a differential pressure (Dp) in bar for a liquid with a To establish the flow (Q) in litres /m at a differential pressure (Dp) in bar for a liquid with a specific gravity relative to water (γw).
specific gravity relative to water (γw).
Note: This relationship only applies for liquids similar to water at reasonable flows Note: This relationship only applies for liquids similar to water at reasonable flows (sub-sonic).
sonic). Gas Flow: Gas Flow:
For gases and supersonic flows more complicated formulae are required. For gases and supersonic flows more complicated formulae are required.
The formulae
The formulae below must below must be used only be used only for rule of for rule of thumb estimatthumb estimates. es. The assumptiThe assumption thaton that the critical Dp is at P
the critical Dp is at P11 /2 does not h/2 does not hold for all vaold for all valves. lves. For accFor accurate flurate flow calcow calculatulations theions the
valve manufacturer’s data sheets must be used. valve manufacturer’s data sheets must be used.
For gases flowing at sub-sonic velocities the following
For gases flowing at sub-sonic velocities the following relationship holds.relationship holds.
T
T11 = Inlet gas temperature deg K = Deg C = Inlet gas temperature deg K = Deg C + 273+ 273
γ
γaa =Gas specific gravity relative to air=Gas specific gravity relative to air
q
q nn = gas flow at normal = gas flow at normal conditionsconditions
P
P11 = Inlet Pressure (absolute)= Inlet Pressure (absolute)
For gases flowing at super-sonic velocities the
Gas Reference conditions Gas Reference conditions No
Normrmal al cocondndititioionsns: : P=P=101013.13.25m25mbb a
annd d TT==227733..1155KK Stand
Standard ard condiconditionstions: : P=1013.P=1013.25mb25mb and T=288.75K. and T=288.75K. VALVE DESCRIPTIONS: VALVE DESCRIPTIONS: Gate Valves: Gate Valves: Gate valves
Gate valves are generally are generally used in tused in the process ihe process industry for on-ndustry for on-off service. off service. The design The design is notis not suitable for throttling duty because the sealing surfaces can easily suffer from wire drawing suitable for throttling duty because the sealing surfaces can easily suffer from wire drawing (erosion) when low flows are being maintained against high differential pressures and the (erosion) when low flows are being maintained against high differential pressures and the design give very poor
design give very poor flow control characteristics.flow control characteristics.
The gate valve can be manufactured in a wide range of sizes from 5mm to above 2000mm The gate valve can be manufactured in a wide range of sizes from 5mm to above 2000mm dia.
dia. The The designdesigns are s are proven proven and wand well tell tested. ested. There There is a is a tendentendency tcy to movo move to e to buttebutterflyrfly valves as a lower cost option.
valves as a lower cost option.
The valve can be based on a solid wedge, a wedge which can adjust to suit the seal faces, The valve can be based on a solid wedge, a wedge which can adjust to suit the seal faces, or a parallel faced based on two discs which slide between parallel sealing faces with a or a parallel faced based on two discs which slide between parallel sealing faces with a mechanism form forcing the dis
mechanism form forcing the discs out on the last part of cs out on the last part of the spindle travel. the spindle travel. The valve canThe valve can be based on a simple rising spindle design or a fixed spindle which screws into the gate. be based on a simple rising spindle design or a fixed spindle which screws into the gate.
There are a large number of gate valve variations including slide valves, knife valves, There are a large number of gate valve variations including slide valves, knife valves, penstock valves, sluice valves, and venturi valves.
Rising Spindle Gate Valve Rising Spindle Gate Valve
Fixed spindle Gate Valve Fixed spindle Gate Valve </TD< tr>
</TD< tr>
Globe Valves: Globe Valves: The globe
The globe valve includes valve includes an orifice an orifice set into set into the body tthe body through which through which the fluid flhe fluid flows. ows. A discA disc located on the end of the spindle is engineered to move in and out along the axis of the located on the end of the spindle is engineered to move in and out along the axis of the orifice.
orifice. When the When the disc is disc is moved to moved to sit in sit in the orificthe orifice the e the flow path flow path is shut-ofis shut-off. f. The flow The flow pathpath is progressively increased as the disc
is progressively increased as the disc is moved away from the is moved away from the orifice.orifice.
The surface of
The surface of the orifice (seat) is the orifice (seat) is generagenerally engineerinlly engineering g as a as a replareplaceablceable e item made fromitem made from erosion resistant material with a polished surface f
erosion resistant material with a polished surface finish. inish. The disc can be fitted with a softThe disc can be fitted with a soft sea
seat t if a if a tigtight ht shushut-ot-off is ff is reqrequiruired. ed. For flow contrFor flow control ol dutduties the ies the disdisc c is supplis supplied with anied with an engineered shape often with a contoured skirt.
engineered shape often with a contoured skirt.
For manually operated valves the spindle screwed so that rotation of the handle moves the For manually operated valves the spindle screwed so that rotation of the handle moves the disc in and out.
disc in and out. For actuated control valves the sFor actuated control valves the spindle is moved in and out using a pindle is moved in and out using a linearlinear actuator which can be pneumatic, hydraulic or
actuator which can be pneumatic, hydraulic or electric.electric.
The fluid flow path through globe
The fluid flow path through globe valves is such that there is normally a high valves is such that there is normally a high fluid head lossfluid head loss throu
through the valve. gh the valve. The inliThe inline body design hane body design has the highess the highest head loss; tht head loss; the angle patte angle patternern body design h
body design has a as a lower head llower head loss. oss. There are cThere are certain designs ertain designs of globe vaof globe valves which lves which havehave been engineered to have low head loss characteristics. (Ref Dynamic Controls cartridge been engineered to have low head loss characteristics. (Ref Dynamic Controls cartridge valv
valves). es). Globe valGlobe valves are supplves are supplied in sizes from 3mm boried in sizes from 3mm bore through 400mm ane through 400mm and can bed can be used, s
used, size limize limiting at priting at pressureessures up to 450 bargs up to 450 barg. . DependiDepending on the sealng on the sealing sysing systems thetems the valves can be used at temperatures the 600
Small Size Screwed Globe Valve Small Size Screwed Globe Valve Needle Valves:
Needle Valves: The
The neeneedle dle valvalve ve is is useused d spespecifcificaically lly for for accaccuraurateltely y concontroltrollinling g the the floflow w of of flufluids ids at at lowlow flows.
flows. The valve iThe valve is basically s basically a globe valva globe valve without the e without the disc. disc. It is generally It is generally used provided inused provided in small sizes of up to 20mm bore.
small sizes of up to 20mm bore.
Needle Valve Needle Valve Plug Valves: Plug Valves: The plug val
The plug valve is ve is the oldethe oldest of st of the valthe valvesves. . PluPlug g valvalves have been in ves have been in use for over 2000use for over 2000 years. This valve has been in continuous development over recent years. The plug valve is years. This valve has been in continuous development over recent years. The plug valve is basi
basically and on-off valve based on cally and on-off valve based on a plug a plug with a with a rectanrectangular hole through which the gular hole through which the fluifluidd flows.
flows. The plug is The plug is either tapered or either tapered or cylindrical and cylindrical and is located is located in the vin the valve body aalve body and can nd can bebe rotated through a quarter turn to line the hole up with the pipe when open or across the rotated through a quarter turn to line the hole up with the pipe when open or across the pipe when closed.
The plug can be adapted for multi-port use allows the valve to be used for diverting flow. The plug can be adapted for multi-port use allows the valve to be used for diverting flow. The valve can be engineered with a lubricated plug which uses the lubricant to enable The valve can be engineered with a lubricated plug which uses the lubricant to enable convenient operation
convenient operation over a over a wide range wide range of pressures. of pressures. The lubricaThe lubrication film tion film also provides also provides aa seal.
seal.
The unlubricated design includes seals in the plug and requires plastic bearing systems. The unlubricated design includes seals in the plug and requires plastic bearing systems. The valve can include a cage between the plug and the body which includes the bearing The valve can include a cage between the plug and the body which includes the bearing seal
sealing ing systesystems and ms and alloallow w convenconvenient maintenaient maintenance. These nce. These valvvalves es have been have been specispeciallyally dev
develoeloped ped for for use use in in indindustustrieries s reqrequiruiring ing highigh h perfperformormancance e opeoperatration ion undunder er arduarduousous c
coonnddiittiioonns s aannd d aalllloowwiinng g rreemmootte e mmaaiinntteennaanncce e ee..gg. . tthhe e nnuucclleeaar r iinndduussttrryy.. The valve is a full bore
The valve is a full bore and has virtually no internal cavities.and has virtually no internal cavities.
Lubricated Plug Valve Lubricated Plug Valve Ball Valves:
Ball Valves: The ball va
The ball valve is basiclve is basically a plug ally a plug valve with a valve with a spherical plug and spherical plug and a round hole. a round hole. Over recentOver recent years the materials of construction of the ball valve have been developed such that the ball years the materials of construction of the ball valve have been developed such that the ball valv
valve is becomie is becoming the most pong the most popular vapular valve for moslve for most procest process applis applicatications. ons. There are twoThere are two primary options for the ball valve design
primary options for the ball valve design
•
• Floating Ball Design- This is low cost option for the lower dutiesFloating Ball Design- This is low cost option for the lower duties •
• Trunnion Ball Design- This is a more costly option for the higher dutiesTrunnion Ball Design- This is a more costly option for the higher duties
The ball valve is generally provided as a reduced bore design allowing a smaller body but The ball valve is generally provided as a reduced bore design allowing a smaller body but still with relatively low head loss compared to most other valve options e.g. 25nb valve has still with relatively low head loss compared to most other valve options e.g. 25nb valve has a 20mm reduced bore,.
a 20mm reduced bore,. The full bore option has The full bore option has a larger body but provides zero a larger body but provides zero restrictionrestriction to flow.
to flow. The valvThe valve can be supplie can be supplies as a multies as a multi-port desi-port design for flow divegn for flow diverting but onlrting but only withy with the reduced bore option.
the reduced bore option.
The engineering of the ball valve has to include for fitting and removing the ball and seat The engineering of the ball valve has to include for fitting and removing the ball and seat
system.
system. Ideally this Ideally this has to has to be engineered be engineered to enablto enable the e the valve tvalve to be o be maintained maintained inline. inline. OneOne method of achieving this is to use the top-entry version - all of the internals are accessible method of achieving this is to use the top-entry version - all of the internals are accessible by remo
by removinving the top flang the top flange. ge. AnoAnothether methor method is to d is to use a threuse a three piece bode piece body basey based on d on aa centr
central piece sandwial piece sandwiched between two pieces conneched between two pieces connectincting the g the valvvalve to e to the pipe work. the pipe work. TheThe central piece can be released and pivoted away from the two outer pieces allowing access central piece can be released and pivoted away from the two outer pieces allowing access to all of the valve
to all of the valve components.components.
The ball valve can be engineered as a multi-port valve for flow diverting duties. The ball valve can be engineered as a multi-port valve for flow diverting duties.
An important advantage of all full bore valves is that the valve allows certain pipe cleaning An important advantage of all full bore valves is that the valve allows certain pipe cleaning operations e.g. ridding.
operations e.g. ridding. Ball valves can also be usBall valves can also be used on branches to enable instruments toed on branches to enable instruments to be fed into pipe systems during operating periods.
be fed into pipe systems during operating periods.
Ball va
Ball valves are avlves are availaailable in all mable in all materialterials in sizes frs in sizes from 5mm to over 600om 5mm to over 600mm. mm. The valvThe valveses can be used at
can be used at pressupressures up to res up to 700 bars. 700 bars. The main componThe main components limitients limiting the ng the perforperformancemance of ball valves are the
of ball valves are the ball seals and valves are available with metallic seals.ball seals and valves are available with metallic seals.
Ball Valve - With Floating Ball Ball Valve - With Floating Ball
Ball Valve Trunnion Mounted Ball Valve Trunnion Mounted </TD< tr>
</TD< tr> Butterfly Valves:
Butterfly Valves: The butterfly
The butterfly valve has hvalve has head loss ead loss characteristics of characteristics of a full a full bore valve. bore valve. The design is The design is basedbased on use of an engineered disc of the same dia as the bore of the pipe arranged to pivot such on use of an engineered disc of the same dia as the bore of the pipe arranged to pivot such that when it is across the bore is closes of
that when it is across the bore is closes off the flow path. f the flow path. When turned throuWhen turned through 90gh 90oo thethe
disc provides minim
disc provides minimum resistance to thum resistance to the flow. e flow. The valve is The valve is a quarter turn valve.a quarter turn valve.
The main variations for this valve are the methods of sealing the perimeter of the disc in its The main variations for this valve are the methods of sealing the perimeter of the disc in its cl
closed pososed positiition. on. The simThe simpleplest variast variatiotion n is to is to use an elastuse an elastomeomer r linlined ed borbore which is ane which is an interference fit on the di
interference fit on the disc. sc. The other variations arThe other variations are based on offsetting the die based on offsetting the disc plane fromsc plane from the axis of rotation allow the disc to close against a circular face seal such that the fluid the axis of rotation allow the disc to close against a circular face seal such that the fluid pressure increases the seal eff
pressure increases the seal effect. ect. Metallic seals are aMetallic seals are available allowing the valve tvailable allowing the valve to be usedo be used for a wide range of fluids at high temperatures.
for a wide range of fluids at high temperatures. The butterfly valve has been developing
The butterfly valve has been developing such that for many duties it now such that for many duties it now provides optimumprovides optimum solution for a leak t
solution for a leak tight on-off valve supplanight on-off valve supplanting the gate valve. ting the gate valve. The butterfly valve can beThe butterfly valve can be engineered as a small valve of 25mm bore and can be made for extremely large sizes engineered as a small valve of 25mm bore and can be made for extremely large sizes above 5000m
above 5000mm bore. m bore. DependDepending on the valve size working pressing on the valve size working pressures up to 100 ures up to 100 bars canbars can be handled.
Butterfly Valve – Lined Butterfly Valve – Lined
Diaphragm Valves: Diaphragm Valves:
The diaphragm valve has a significant advantage over most of the other available designs, The diaphragm valve has a significant advantage over most of the other available designs, apart f
apart from the pinrom the pinch valvech valve, in that the, in that there is no glanre is no gland seal requid seal requirementrement. . The fluThe fluid flowsid flows str
straigaight throuht through the valve via a gh the valve via a chachambember r oveover r whiwhich is ch is an elasan elastomtomer diapher diaphragmragm. . ThiThiss diaphragm is normally arran
diaphragm is normally arranged to provide no resistance to thged to provide no resistance to the flow. e flow. The perimeter of theThe perimeter of the diaphragm is simply clamped to a
diaphragm is simply clamped to a seal face of the valve body seal face of the valve body as a static seal.as a static seal.
To close off the valve the diaphragm is simply forced down into the chamber to block off To close off the valve the diaphragm is simply forced down into the chamber to block off th
the e flflow. ow. ThThe e chchamambeber r cacan n ininclcludude e a a weweir acroir across the ss the flflow path agaow path againinst whicst which h ththee diaphragm can be pressed to affect a more efficient seal with r
diaphragm can be pressed to affect a more efficient seal with r educed diaphragm distortion.educed diaphragm distortion. The straight through variation is effectively a full bore valve design with all the associated The straight through variation is effectively a full bore valve design with all the associated benefi
benefits. ts. HowevHowever this optier this option resulon results in a much morts in a much more arduous due arduous duty on the diapty on the diaphragmhragm which has to be a
which has to be a softer material.softer material.
This type of valve is manufactured in sizes from 6mm to 400mm and is generally limited to This type of valve is manufactured in sizes from 6mm to 400mm and is generally limited to rel
relatiativelvely y low flulow fluid pressuid pressures (lesres (less than 7 s than 7 barbarg). g). HowHowever in the ever in the smasmalleller r sizsizes (up toes (up to 50m
50mm) valm) valves can be specves can be specialially engily engineerneered for use at pressed for use at pressures up to 30barures up to 30barg. g. TheThe di
diapaphrhragagm m mumust st be be chchososen en to to be be cocompmpatatibible le wiwith th ththe e flfluiuid. d. WhWhatatevever er ththe e flfluiuid d ththee diaphragms must be replaced at regular intervals and it is advisable to operate the valves diaphragms must be replaced at regular intervals and it is advisable to operate the valves frequently.
frequently.
These valves are often used for duties which require a high degree of cleanliness as they These valves are often used for duties which require a high degree of cleanliness as they can be supplied lined, and polished and can be very conveniently cleaned.
Diaphragm Valve - With weir Diaphragm Valve - With weir
Diaphragm Valve - straight Diaphragm Valve - straight </TD< tr>
</TD< tr> Pinch Valves:
Pinch Valves:
The pinch valve is a theoretically ideal solution for fluid on-off duties. The valve is simple a The pinch valve is a theoretically ideal solution for fluid on-off duties. The valve is simple a length of pipe made from an elastomeric material with a mechanical system for squeezing length of pipe made from an elastomeric material with a mechanical system for squeezing the tube clos
the tube closed when a shued when a shut off is t off is required. required. The valve iThe valve is a true fs a true full bore valve ull bore valve - there are- there are no mechanic
no mechanical parts al parts in contact with the in contact with the fluifluid- The d- The operatoperation of ion of the valve is the valve is idealideally simple-ly simple-The valve can be easily engineered as a tight-shut off valve.
The valve can be easily engineered as a tight-shut off valve.
The valve is often supplied with the pinch tube contained within a outer pipe between the The valve is often supplied with the pinch tube contained within a outer pipe between the end flanges
end flanges. . This optioThis option provides a method of n provides a method of monitmonitoring for tube leaks and provides aoring for tube leaks and provides a degree of secondary containment.
degree of secondary containment.
The valve has simil
The valve has similar limitatiar limitations to ons to the diaphrathe diaphragm valve. gm valve. The diaphraThe diaphragm valve is gm valve is reallreally ay a variation on the pinch valve principles. Pinch valves are supplied is for diameters 25 mm variation on the pinch valve principles. Pinch valves are supplied is for diameters 25 mm -1000 mm, temperatures -50 C - +160 C, and pressures 0 - 100 bar.
1000 mm, temperatures -50 C - +160 C, and pressures 0 - 100 bar.
Pinch Valve Pinch Valve
Check Valves: Check Valves:
Check valves are automatic in operation and designed to prevent reversal of flow in fluid Check valves are automatic in operation and designed to prevent reversal of flow in fluid pip
piping sysing systemtems. s. The valThe valves are maives are maintantaineined d opeopen by n by the flothe flow of w of flufluid in the id in the forforwarwardd direction and are closed by back pressure of the fluid or by the weight of the closing direction and are closed by back pressure of the fluid or by the weight of the closing mechanism or by
mechanism or by a spring force. a spring force. Various designs aVarious designs are available as lre available as listed below.isted below.
•
• Swing checkSwing check •
• Tilting discTilting disc •
• Ball lift typeBall lift type •
• Disc lift typeDisc lift type •
• Piston checkPiston check •
• Stop checkStop check
The range of check valve sizes range
The range of check valve sizes range from 6mm to massive units of 3000mm from 6mm to massive units of 3000mm dia and more.dia and more. The swing check variation is a l
The swing check variation is a low pressure drop unit based on a hinged disc. ow pressure drop unit based on a hinged disc. This type of This type of valve is suitable for low velocity appl
valve is suitable for low velocity applications with infrequent velocity reversals. ications with infrequent velocity reversals. The valveThe valve can be fitted with external weights
can be fitted with external weights to allow faster closure to reduce to allow faster closure to reduce water hammer or shockwater hammer or shock pressure on flow reversal.
pressure on flow reversal. External systems can alsExternal systems can also be included to force the valve closedo be included to force the valve closed in the event of a local fire.
in the event of a local fire.
The lift check val
The lift check valve and piston check variatve and piston check variations are used for higher duty applicaions are used for higher duty applications. tions. TheThe valve is forced open by the fluid flowing up through the valve and is closed on fluid reversal valve is forced open by the fluid flowing up through the valve and is closed on fluid reversal by gravity, back pressure or by spring force.
by gravity, back pressure or by spring force.
The tilting disc variation on the swing check valve provides improve speed of operation and The tilting disc variation on the swing check valve provides improve speed of operation and pressure performance and is probably the most popular design of check valve used in the pressure performance and is probably the most popular design of check valve used in the process industry.
process industry.
Lift Check Valve Lift Check Valve
Swing Check Valve Swing Check Valve </TD< tr>