plumbing valve and their applications

8/3/2019 Plumbing Valve and Their Applications

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What is a Plumbing Valve and What areTheir Applications

Posted on August 14, 2010 by theplumbinginfo

The plumbing valve, its simplest definition is any valve used to regulate the flow of water in a potable or human waste water system. Pretty simple right? We suppose the the basic premise of a plumbing valve is simple but the types of valves and the broad range of applications are anything but simple. In the next few paragraphs we will give you each type of plumbing valve and itsapplications.

Angle Valve or Stop Angle stops are named because they are manufactured at a 90

degree angle, they are used as shut off valves atthe water intake of plumbing fixtures or appliances. They usually have an oval handle or canhave a removable handle when vandalism or theft is an issue.

In the past the angle stop needed to be rotated many times to ensure a complete water shut of,now most manufacturers make a 1/4 turn valve so the water can be shut off quickly in case of emergency.

Well give you one emergency everyone has experienced that will make the 1/4 turn valve

extremely valuable. Have you ever had a toilet backup and seen your toilet water level risingever so slowly maybe you notice a floater or two and you couldnt turn the angle valve fastenough to turn the water off? If you only had a 1/4 turn to close the valve off and that risingwater would stop.

The angle valve is not meant for high pressure applications. The type of connections used for angle stops are sweat, threaded and compression connections.
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Gate Valve The gate valve is a very old valve design. It is still used everyday on large

diameter piping, in high pressure applications andin application where a valve is needed for a complete shut down.

The gate valve is typically operated by a wheel handle and that handle lifts and lowers a metaldisc or wedge cutting off or opening the flow of water. A gate valve should not be used tothrottle or regulate the flow of water.

When a gate valve is left partially opened water tends to rattle the mechanism inside eventuallywearing out the seats and seals. Gate valves are usually described as rising stem sometimescalled an OS&Y (Outside Screw and Yoke) or non-rising stem.

An OS&Y valve allows you to see whether or not the gate valve is either open or closed becausethe stem rises outside the valve body. Non-rising stem gate valves are used in areas where spaceis an issue. The type of connections commonly used to connect a gate valve to the piping arethreaded, flanged and sweat connections.
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Check Valve A check valve is a one way valve in that is has one inlet and one outlet

that allows the a liquid to travel in one direction.It is used to halt the flow of the aforementioned liquid in case of a drop in pressure or reverse indirectional flow.

The majority of check valves used in the plumbing industry work automatically meaning whenthe pressure or direction changes the valve slams shut. One example of a check valve that is easyto understand is a backwater valve used on a sewer main as it leaves a residential or commercial

building. Its main function is to close of the sewer in case the city main cant handle stormwater. If the city sewer runs full the only place for the water to go are the buildings connected toit, the valve keeps the water from coming back into the building. These valve can have a manualhandle to close the valve, this is especially useful when leaving the residence or building

unattended. The only problem is you have to remember to open it back up, you can imagine themess if you use the toilets, lavatories etc. with no way for the waste to get out.
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Backwater Check Valve This valve works just like the above. It is a one way valve

that is used most often in residential applicationsThey are made by several manufacturers and they are basically heavy duty check valves. Theyare installed on the main sewer right at the foundation wall. They come in a check valve style inthat when water starts backing up into the sewer line the valve slams shut or in a manual style. If a home owner chooses a manual style back water valve they have to crank the valve shut duringheavy rains and remember to open it back up when the rain is over because if someone uses thefacilities while the valve is closed you will have some serious backups. Advantages of having a

backwater valve, they work and they work well. Disadvantages, they arent cheap to buy or install.

Ball Valve The ball valve is the most popular and widely used type of valve in the

plumbing industry. It is built using a sphericaldisc or ball with a hole in it.
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When the ball is turned to the open position the hole or port is lined up with the flow of liquidletting it pass through. When the ball is turned to the closed position the port is perpendicular to the flow of liquid cutting off the opening.

Its early history is a little vague but here are couple known facts, the first ball type valve was

patented by John Warren and issued to both Warren and John Chapman the founder of ChapmanValve Co.

It was a manufactured out of brass with a brass ball and seats. The valve became an

afterthought and was not mentioned in theChapman literature. The next mention of the ball valve and the first resilient seated ball valvewas developed and patented by Crane Company in 1945 (Resilient Seat this is a real basic

definition but youll get the idea, this is a non metallic seat that is resistant to oils, water andhydraulic fluids, has very good strength and works well in a broad spectrum of temperatureranges so it is resistant to expansion and contraction. Some examples of resilient seatingmaterials are Neoprene, Buna-N and EPDM.) but like their historical predecessor Crane couldnot find a use for the valve.

Wafer Check A wafer style check valve is obviously a check valve that is used when spaceconstraints wont allow traditional check valves to be used. Some of the other benefits of using awafer check is weight, this style of check doesnt need as much support as its traditional full

body counterpart.

A wafer valve is made using a thin disc that can be fastened in the center or the top or can bespring loaded in the center.

This valve is meant to placed between two flanged fittings and secured between the two fittingswith all thread rod. The valve is notched in the same positions as the bolt pattern of the flangesso the rod can pass by the valve. The valve is secured at both ends by the flanges.
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Butterfly Valve The butterfly valve has some similar features to that of the above

wafer check valve. It is very thin and lightweightso space and support are not issues. It is closed using a wafer or disc that is mounted on a rodthat is secured in the middle of the valve. The rod exits the valve at the top and ends with ahandle that incrementally controls the internal disc.

In the open position the disc is parallel to the pipe in the closed position the disc is perpendicular to the pipe closing off flow.

These types of valves can be used to control flow and are especially affective in tight spots. Mosttimes the handles are spring loaded and allow you to lock the valve into a certain position.

Circuit Setter This a very specialized valve used in the heating/cooling, HVAC and plumbingindustry. We will give you a basic description of the valve and its functions but for further explanation please see our article on System Balancing.It is complex enough to warrant its ownarticle and we would be doing the subject a disservice by not addressing it by itself.

A circuit setter is a balancing type valve used in an HVAC or plumbing system to regulate pressure in the whole system or within part of the system.

In a plumbing system it is used to regulated pressure between hot and cold water inside the potable water system. Many years ago a check valve and a ball valve where used, the check valve would shut down a hot or cold water supply if there was a sudden drop in pressure and the

ball valve with a memory stop was used to regulate flow. This prevented cold or hot water bleedover if the pressure was increased or decreased in either supply piping.

Here are some things you should look for when choosing a circuit setter

What is the adjustment range of valve. Is the valve only able to adjust in quarter turnincrements? If precision adjustment is needed look for a valve that has 360 degrees of adjustment.


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What kind of test ports are on the valve. You should have a port for temperature andanother for pressure.

Can you achieve a positive shut down for isolation purposes?

Gas Cock A gas cock is a valve that is used to regulate low pressure natural or LP gas.

The most common place to see this type of valvewould be on the incoming gas supply for a kitchen appliance.

The old school gas cock is a wedge type valve. Please see diagram below for a cross sectionalview. The wedge when closed blocks the flow of gas, when the wedge is turned to the open

position the wedge is hollow to allow the flow of gas. This is not a full port valve. New style gasvalves are ball valves with small gas valve type handle.

Flush Valve The diaphragm type flushometer was introduced by William Elvis Sloan

in 1906. The diaphragm flush valve remainslargely unchanged. The flush valve is comprised of two chambers, the upper and the lower.When the valve is not used both chambers are filled with water and equalized by the water supply pressure and it is kept equalized by the by-pass orifice. More about the by-pass orifice ina second. The handle is attached to a handle assembly, the flat end of the handle is butted upagainst the flat end of the operating stem. When the handle is depressed it pushes the operating
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stem which trips the stem of the diaphragm. This stem rocks the diaphragm out of the seatthereby releasing the water from the upper chamber. Because there is now less pressure in theupper chamber the diaphragm is pushed up from the water pressure in the lower chamber andflushing begins. The diaphragm slowly re-seats itself as water from the lower chamber entersthrough the by-pass orifice equalizing pressure between the two chambers.

Globe Valve A globe valve is aptly named for its rather spherical body. A globe valve

can be used to regulate flow in a plumbing line.Think of the valve body being bisected by baffles that are manufactured into the valve body andthose baffles come together in the middle of the valve and that opening is closed by seating adisc or plug.

The handle is attached to the stem which raises and lower the disc into place. Although this valveis affective as an isolation or regulating valve it does have its drawbacks. Because of the bafflesit does not allow for full flow, there are too many right angles. Since the flow is restricted thistype of valve may not meet engineering specifications where full flow is required.


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Double Detector Check Valve A double detector check assembly is one device that

houses two check valve assemblies in the line of flow. The check valves are spring actuated and are designed to open with 1 pound of pressure.

The double detector check assembly is installed with one (1) gate valve on the inlet of the valveand one (1) gate valve on the outlet side of the valve.These assemblies prevent back flow or back

pressure in nonhazardous situations and are most used to protect the potable water system of a building from the water in a fire prevention system.

A detector check is made with a by-pass assembly and meter to detect any unauthorized or illegaltaps, test cocks are also present so that required yearly testing can take place. Each check valvecan be isolated and tested independently to see if they are leaking and operating properly.

Reduce Pressure Zone Valve (RPZ) An RPZ is very similar to the double detector

check in that it houses two testable check valves.It has two gate valves one (1) on the inlet and one (1) on the outlet. Here is where things change,an RPZ is used in high hazard situations, where contamination of the water supply would pose asignificant health hazard.
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An RPZ is designed with two check valves like a Double Detector Check Valve and a relief

valve. The 1st check valve is calibrated to open at5lbs of pressure the 2nd check valve is calibrated to open with 1lb of pressure and the relief valve which is the last line of defense and it is set to open with 2lbs of pressure and discharge tothe atmosphere.

The relief valve is usually piped to a nearby floor drain so the room doesnt flood if a largedischarge occurs. This valve is built with redundancy in mind. If the pressure drops below 5lb of

pressure the check closes on the outlet side if the pressure drops below a 1lb of pressure thatcheck closes, if that check fails and the water by-passes the outlet check, it is released by therelief check.

Pressure Balance Valve Scald protection and thermal shock are two terms that are usedtogether and can overlap. Scalding can cause thermal shock which can then result in a fall or anynumber of injuries resulting from the shock of being scalded or blasted with ice cold water. Howmany of us have accidentally jumped in the shower just a few seconds before the hot water kicksin and nearly slipped and fallen?

A pressure balance valve is a valve that protects against these types of issues buy regulating theamount of pressure within the valve. Pressure balance valves come in two varieties.

The first is a diaphragm type , this valve has the hot coming from one side and the cold from theother, the balancing disk is in the middle. The disk slides back and forth on a piston. Changes in

pressure push against the disk and move the piston in the direction of the lower pressure and cutsoff flow from the high pressure side.

The second in the spool type pressure balance valve, it has a spool inside the valve, the spoolslides towards the supply with the lower pressure. This cuts off the volume of water entering the

valve on the high pressure side and allows more water from the low pressure side. Output water temp cannot vary more than 3 degrees. ASSE Code 1016 defines scald protection valves. Bothvalves do not adjust for fluctuations in temperature.
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Thermostatic Mixing Valve This valve adjusts volume of water and protects the user

by sensing water temperature. The most commontype of thermostatic mixing valve has a paraffin wax element that expands and contracts basedupon the supply temperature. If the wax gets hot the spool slides over to pinch off the hot sideand vise versa. This type of valve is usually both temperature and pressure balanced.

There is another type of thermostatic mixing valve that uses a bi-metal strip. As the temperaturechanges so does the shape of the metal. As the metal changes shape it adjusts output temperature.As you can imagine a piece of metal that is constantly expanding and contracting can become

brittle and eventually break. Its one the reasons the wax element type valve has become thenorm.

We hope you enjoyed the article. As with all of our articles feel free to add a comment or pointout if you think something can be clarified.theplumbinginfo.com

A flow control valve regulates the flow or pressure of a fluid . Control valves normally respondto signals generated by independent devices such as flow meters or temperature gauges .

Control valves are normally fitted with actuators and positioners. Pneumatically -actuated globevalves and Diaphragm Valves are widely used for control purposes in many industries, althoughquarter-turn types such as (modified) ball , gate and butterfly valves are also used.

Control valves can also work with hydraulic actuators (also known as hydraulic pilots). Thesetypes of valves are also known as Automatic Control Valves. The hydraulic actuators willrespond to changes of pressure or flow and will open/close the valve. Automatic Control Valvesdo not require an external power source, meaning that the fluid pressure is enough to open andclose the valve. Automatic control valves include: pressure reducing valves, flow control valves,

back-pressure sustaining valves, altitude valves, and relief valves . An altitude valve controls thelevel of a tank. The altitude valve will remain open while the tank is not full and it will closewhen the tanks reaches its maximum level. The opening and closing of the valve requires no
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external power source (electric, pneumatic, or man power), it is done automatically, hence itsname.

Control valves are normally fitted with actuators and positioners. Pneumatically-actuated globevalves and Diaphragm Valves are widely used for control purposes in many industries, although

quarter-turn types such as (modified) ball, gate and butterfly valves are also used.

Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale. Each of these control loops is designed to keep someimportant process variable such as pressure, flow, level, temperature, etc. within a requiredoperating range to ensure the quality of the end product. Each of these loops receives andinternally creates disturbances that detrimentally affect the process variable, and interaction fromother loops in the network provides disturbances that influence the process variable. [1]

To reduce the effect of these load disturbances, sensors and transmitters collect informationabout the process variable and its relationship to some desired set point. A controller then

processes this information and decides what must be done to get the process variable back towhere it should be after a load disturbance occurs. When all the measuring, comparing, andcalculating are done, some type of final control element must implement the strategy selected bythe controller. The most common final control element in the process control industries is thecontrol valve. The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated processvariable as close as possible to the desired set point. [1]

Introduction

Valves are integral components in piping systems they are the primary method of controlling the

flow, pressure and direction of the fluid. Valves may be required to operate continuously e.g.control valves, or they may be operated intermittently e.g. isolation valves, or they may beinstalled to operate rarely if ever e.g. safety valves. A valve can be an extremely simple, lowcost item or it may be and extremely complicated, expensive item. In piping design the valves

probably require more engineering effort than any other piping component.

Valve Classifications

Isolation/Stop valve-

The isolation of the downstream system from the upstream system by use of and isolation /stopvalve is a critically important function..The prime requirements of this valve are tight shut off when closed and minimum restriction to flow when open.

Valves used for this function include gate valves, globe valves, ball valves, plug valves, butterflyvalves, diaphragm valves and pinch valves

Regulation of flow
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Many applications require the flow of the fluid be regulated (throttled) at some fixed or variablelevel between fully zero and maximum flow limits. This is achieved by introducing resistance toflow, or by bypassing flow or by changing the direction of the flow. An important feature for control valves is that the output variable (flow) is related to the input variable (valve position).An ideal operating characteristic of a hand operated flow control valve is that the flow is directly

proportional to the position of the handwheel

Valve types for this function include globe, needle, ball, butterfly. Globe and needle valves are best suited for this duty but ball valves are also easily adapted to give reliable flow control..

Back flow prevention

In some circumstances it is important to prevent reversed fluid flow. The type of valve for thisduty is a non-return-valve (NRV) or check valve. The important criteria when selecting thesevalves are, tight shut off against reverse flow, low resistance to flow for forward flow, fastresponse. The valve can be operated to close by gravity, fluid flow , or spring.

Two main valve types are available for this function lift check valves or swing check valves.

Pressure Regulation

In many applications, more generally associated with gases, there is a need to reduce the supply press to a set fixed value. It is also necessary to maintain this reduced pressure over a range of fluid flow conditions. The pressure regulator valve is engineered for this application. The valveis basically a globe valve biased open by an adjustable spring force with the feedback pressuretending to move the valve to a closed position such that at the set pressure the feedback pressureforce just exceeds the spring force

The pressure regulator valve operates using the downstream fluid pressure as feedback. This ismostly taken from within the valve (self acting). For more accurate control a 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 includeinternal or external relief valve functions to ensure no high pressures in the downstream system.

Pressure Relief Valves- Safety valves

A very important valve for safety is the pressure relief valve. This valve is used in applicationswhere excessive pressure in the system can cause damage or failure or can introduce a safetyrisk. Uncontrolled excessive pressures can result in disastrous accidents e.g. when potentiallyexplosive gases are being controlled. Relief valves are mainly spring loaded but they can also

be gravity operated and other more specialised designs are available.

The bursting /ruputure disc must be included under the general heading of safety valves. This issimply a disc which ruptures when a set pressure is exceeded. The fluid then escapes throughthe ruptured disc. If the bursting disc operates the system has be be closed down and vented andthe bursting disc is then replaced


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Relief valves when used for safety applications are engineered in line with safety regulations andrequire regular inspections to confirm the settings and the operation. An important part of therelief valve installation is the routing of the relieved fluid. This pipe route must be to a safelocation and must be engineered such that it is always fully open.

Special and miscellaneous valves

There are a wide variety of special valves developed for specific industries.

Fluid Properties and operating conditions

The properties of the fluid to be controlled have a major impact on the design and materials of construction of the valve. The piping industry, over the years, had developed a wide range of valve designs and material to handle virtually all of the fluids being handled. The selection of the valve should take into account fluid viscosity, temperature, density and flowrate. The valvemust be suitable to withstand resulting corrosion and erosion and if necessary the valve mayhave to be designed for no internal hold up of fluids.

Important considerations include for absolute internal and external leak tightness when handlingtoxic or explosive fluids. There regulations also include for the need for a firesafe valve tomaintain its internal and external integrity when the valve surrounded by flames from a fire..

Valve Connections

There are a number of methods of connecting valves into the piping systems- as follows

Flanges .. The valve is provided with suitable rated flanges. Wafer .. The valve is provided with suitable sealing faces and is

trapped between line flanges. Butt Welded ..The valve is provided with butt weld end and welded

into the piping system using high integrity joints. Socket Welded ..Socket welds allow and welded into the piping

system using fillet welds. Screwed Ends .. Ends can be provided with female or male screwed

ends . The threads can be taper or parallel

Compression Fittings .. Ends can be provided with compressionfittings

Valve Containment

An important requirement in valve design is to minimise the leakage of fluids into thesurrounding environment. This is very important in the nuclear industry and when transferringtoxic or flammable fluids. The possible leakage points on valves are listed below.

The end connections with the piping.-


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The spindle gland seals -allowing axial and rotary motion. For top entry valves the sealed top closure joint For three piece ball valves - the two split joints

Valve drain connections and vent connections

The best option for minimising risk of leakage from the pipe connections is to use butt welded joints which can be verified by non-destructive-testing(NDT). This option obviously eliminatesthe valve types which have to be removed for maintenance.

The options for eliminating risk of gland leakage is to use bellows sealed valves. The risk canalso be reduced by incorporating dual seals with a test point between. Pinch valves anddiaphragm valves do not include gland sealing and are therefore not at risk of gland leakage.

Flow Factors

It is clear that different sized valves have different flow rate capacities and it is very important to be able to assess the flow through a valve for a fluid at certain conditions. The flowcharacteristics for an on-off valve are fixed and can be evaluated directly using the relevant flowfactor. The flow through flow control valves, relief valves, pressure reducing valves and check valves depend on the operating condition for the valve and require a more detailed evaluation..

The most general method of identifying the flow capacity of a valve is the C v Factor..The C v factor based on american imperial units and is defined as follow

C v = The flow of water through a valve at 60 oF in US gallon/minute at a pressure drop of 1

lb/in2

The metric flow factor (K v) is used throughout outside of america and is defined as follows

K v = the flow of water through a valve at 20 oC in m 3/hr with a pressure drop of (1 bar)

The conversion between the two factors is K v = 0.865 C v

Also kv is defined as follows...

k v = the flow of water through a valve at 20 oC in litres/min with a pressure drop of (1 bar)

The conversion between k v and C v is ...k v = 14.42 C v

Liquid Flow

To establish the flow ( Q ) in litres /m at a differential pressure ( p )in bar for a liquid with aspecific gravity relative to water ( w ).


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Note: This relationship only applies for liquids similar to water at reasonable flows (sub-sonic).

Gas Flow

For gases and supersonic flows more complicated formulae are required....

The formulae below must be used only for rule of thumb estimates. The assumption that thecritical p is at P 1 /2 does not hold for all valves. For accurate flow calculations the valvemanufacturers data sheets must be used

For gases flowing at sub-sonic velocities the following relationship holds..

T1 = Inlet gas temperature deg K = Deg C + 273a =Gas specific gravity relative to air q n = gas flow at normal conditions ...P1 = Inlet Pressure (absolute)

For gases flowing at super-sonic velocities the following relationship holds..

Gas Reference conditions

Normal conditions: P=1013.25mb andT=273.15K Standard conditions: P=1013.25mb andT=288.75K.

VALVE DESCRIPTIONS

Gate Valves

Gate valves are generally used in the process industry for on-off service. The design is notsuitable 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 design


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give very poor flow control characteristics..

The gate valve can be manufactured in a wide range of sizes from 5mm to above 2000mm dia.The designs are proven and well tested. There is a tendency to move to butterfly 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, or a parallel faced based on two discs which slide between parallel sealing faces with a mechanismform forcing the discs out on the last part of the spindle travel. The valve can be based on asimple 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, penstock valves, sluice valves, and venturi valves.

Rising Spindle Gate Valve Fixed spindle Gate Valve

Globe Valves

The globe valve includes an orifice set into the body through which the fluid flows. A disclocated on the end of the spindle is engineered to move in and out along the axis of theorifice. When the disc is moved to sit in the orifice the flow path is shut-off. The flow path is

progressively increased as the disc is moved away from the orifice.

The surface of the orifice (seat) is generally engineering as a replaceable item made from erosionresistant material with a polished surface finish. The disc can be fitted with a soft seat if a tightshut-off is required. For flow control duties the disc is supplied with an engineered shape oftenwith a contoured skirt.

For manually operated valves the spindle screwed so that rotation of the handle moves the disc in


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and out. For actuated control valves the spindle is moved in and out using a linear actuator which can be pneumatic, hydraulic or electric..

The fluid flow path through globe valves is such that there is normally a high fluid head lossthrough the valve. The inline body design has the highest head loss, the angle pattern body

design has a lower head loss. There are certain designs of globe valves which have beenengineered to have low head loss characteristics. (Ref Dynamic Controls cartridge valves)..Globe valves are supplied in sizes from 3mm bore through 400mm and can be used, size limitingat pressures up to 450 barg. Depending on the sealing systems the valves can be used attemperatures up to 600 oC.

Small Size Screwed Globe Valve

Needle Valves

The needle valve is used specifically for accurately controlling the flow of fluids at lowflows. The valve is basically a globe valve without the disc. It is generally used provided insmall sizes of up to 20mm bore..


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Needle Valve

Plug Valves

The plug valve is the oldest of the valves. Plug valves have been in use for over 2000 years. Thisvalve has been in continuous development over recent years. The plug valve is basically and on-off valve based on a plug with a rectangular hole through which the fluid flows. The plug iseither tapered or cylinderical and is located in the valve body and can be rotated through aquarter 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 allow the valve to be used for diverting flow. Thevalve can be engineered with a lubricated plug which uses the lubricant to enable convenientoperation over a wide range of pressures. The lubrication film also provides a seal.

The unlubricated design includes seals in the plug and requires plastic bearing systems. Thevalve can include a cage between the plug and the body which includes the bearing a sealingsystems and allow convenient maintenance. These valves have be specially developed for use inindustries requiring high performance operation under arduous conditions and allowing remotemaintenance e.g. the nuclear industry.

The valve is a full bore and has virtually no internal cavities..


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Lubricated Plug Valve

Ball Valves

The ball valve is basically a plug valve with a spherical plug and a round hole. Over recentyears the materials of construction of the ball valve have been developed such that the ball valveis becoming the most popular valve for most process applications. There are two primaryoptions for the ball valve design

Floating Ball Design- This is low cost option for the lower duties

Trunnion 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 stillwith relatively low head loss compared to most other valve options e.g 25nb valve has a 20mmreduced bore,. The full bore option has a larger body but provides zero restriction to flow. Thevalve can be supplied as a multi-port design for flow diverting but only with the reduced boreoption

The engineering of the ball valve has to include for fitting and removing the ball and seatsystem. Ideally this has to be engineered to enable the valve to be maintained inline.. Onemethod of achieving this is to use the top-entry version - all of the internals are accessible byremoving the top flange. Another method is to use a three piece body based on a central piecesandwiched between two pieces connecting the valve to the pipework. The central piece can bereleased and pivotted away from the two outer pieces allowing access to all of the valvecomponents.

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 cleaningoperations e.g rodding . Ball valves can also be used on branches to enable instruments to be fed


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into pipe systems during operating periods.

Ball valves are available in all materials in sizes from 5mm to over 600mm. The valves can beused at pressures up to 700 bar. The main components limiting the performance of ball valvesare the ball seals and valves are available with metallic seals.

Ball Valve - With Floating BallBall Valve Trunnion Mounted

Butterfly Valves

The butterfly valve has head loss characteristics of a full bore valve. The design is based on useof an engineered disc of the same dia as the bore of the pipe arranged to pivot such that when itis across the bore is closes off the flow path. When turned through 90 o the disc providesminimum resistance to the flow. The valve is a quarter turn valve.

The main variations for this valve are the methods of sealing the perimeter of the disc in itsclosed position. The simplest variation is to use an elastomer lined bore which is an interferencefit on the disc. The other variations are based on offsetting the disc plane from the axis of

rotation allow the disc to close against a circular face seal such that the fluid pressure increasesthe seal effect. Metallic seals are available allowing the valve to be used for a wide range of fluids at high temperatures

The butterfly valve has been developing such that for many duties it now provides optimumsolution for a leak tight on-off valve supplanting the gate valve. The butterfly valve can beengineered as a small valve of 25mm bore and can be made for extremely large sizes above5000mm bore. Depending on the valve size working pressures up to 100 bar can be handled


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Butterfly Valve - Lined

Diaphragm Valves

The diaphragm valve has a significant advantage over most of the other available designs, apartfrom the pinch valve, in that there is no gland seal requirement. The fluid flows straight throughthe valve via a chamber over which is an elastomer diaphragm. This diaphragm is normallyarranged to provide no resistance to the flow. The perimeter of the diaphragm is simply clampedto a seal face of the valve body as a static seal.

To close off the valve the diaphragm is simply forced down into the chamber to block off theflow. The chamber can include a weir across the flowpath against which the diaphragm can be

pressed to affect a more efficient seal with reduced diaphragm distortion.

The straight through variation is effectively a full bore valve design with all the associated benefits. However this option results in a much more arduous duty on the diaphragm which hasto be a softer material

This type of valve is manufactured in sizes from 6mm to 400mm and is generally limited torelatively low fluid pressures (less than 7 barg). However in the smaller sizes (up to 50mm)valves can be specially engineered for use at pressures up to 30barg. The diaphragm must bechosen to be compatible with the fluid. Whatever the fluid the diaphragms must be replaced atregular intervals and it is advisable to operate the valves frequently.

These valves are often used for duties which require a high degree of cleanliness as they can besupplied lined, and polished and can be very conveniently cleaned.


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Diaphragm Valve - With weir Diaphragm Valve - straight

Pinch Valves

The pinch valve is a theoretically ideal solution for fluid on-off duties. The valve is simple alength of pipe made from an elastomeric material with a mechanical system for squeezing thetube closed when a shut off is required. The valve is a true full bore valve - there are nomechanical parts in contact with the fluid- The operation of the valve is ideally simple- Thevalve 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 endflanges. This option provides a method of monitoring for tube leaks and provides a degree of secondary containment

The valve has similar limitations to the diaphragm valve. The diaphragm valve is really avariation on the pinch valve principles.. Pinch valves are supplied is for diameters 25 mm - 1000mm, temperatures -50 C - +160 C, and pressures 0 - 100 bar.

Pinch Valve

Check Valves


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Check valves are automatic in operation and designed to prevent reversal of flow in fluid pipingsystems. The valves are maintained open by the flow of fluid in the forward direction and areclosed by back pressure of the fluid or by the weight of the closing mechanism or by a springforce. Various designs are available as listed below..

Swing check Tilting disc Ball lift type Disc lift type Piston check

Stop check

The range of check valve sizes range from 6mm to massive units of 3000mm dia and more.

The swing check variation is a low pressure drop unit based on a hinged disc. This type of valve

is suitable for low velocity applications with infrequent velocity reversals. The valve can befitted with external weights to allow faster closure to reduce water hammer or shock pressure onflow reversal. External systems can also be included to force the valve closed in the event of alocal fire...

The lift check valve and piston check variation are used for higher duty applications. The valveis forced open by the fluid flowing up through the valve and is closed on fluid reversal bygravity, back pressure or by spring force.

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 process

industry..

Lift Check ValveSwing Check Valve

Control Valves Do What They Are Told!Being the Final Control Element in a system is not an easy job. To start with, you are blamed for any

and all problems that crop up in the process. You are subjected to corrosion, high velocity, cavitation,flashing liquids, cryogenic temperatures, high temperatures, abrasion, and thermal shock. You areexpected not only to throttle along through all this, but most likely, you are also being asked to act as ablock valve and shut off tight. As you work with control valves always keep in mind that a control valve only does what it is told to do . A Control Valve is a power-operated device used to modify thefluid flow rate in a process system. Well, what happens if the power is cut off? When a Control Valve is


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sized or selected to do a particular job, one of the first questions you should consider is how that valve willrespond in the event of a loss of signal or power. This is called its "fail-safe mode" and knowing the fail-safe mode is the key to troubleshooting it . In most applications (about 80%), it is desirable for valves to fail closed . In other applications, you might want a valve to fail open or fail in place . Safetyconcerns and process requirements will mandate the fall mode of the valve. When a valve is not sittingin its fail position, is is being told how and when to move by some external signal. By thecomments one hears, you would be led to believe that control valves sit around and think up things to doon their own. Perhaps this will some day be true when all control valves are "smart." If a Control Valveis observed in an unstable condition or appears to not be responding correctly to an input signal,remember that something is telling the valve to behave that way . A control valve is only as strongas its weakest link. When the 1965 Ford Mustang first appeared, it was powered by a 6-cylinder engine with a 3-speed transmission - but it had a 140 m.p.h.(225 k.p.h.) speedometer. The fact that it hada 140 m.p.h.(225 k.p.h.) speedometer did not mean it could actually travel that fast. In the same way, acontrol valve with a 600# rated valve body cannot throttle and shut off against 1440 pounds of pressure.

There are two basic types of control valves: rotary and linear . Linear-motion control valves commonlyhave globe , gate, diaphragm , or pinch - type closures. Rotary-motion valves have ball , butterfly , or plug closures. Each type of valve has its special generic features, which may, in a given application, beeither an advantage or a disadvantage.

Linear Valve Features

TORTUOUS FLOW PATH LOW RECOVERY CAN THROTTLE SMALL FLOW RATES OFFERS VARIETY OF SPECIAL TRIM DESIGNS SUITED TO HIGH-PRESSURE APPLICATIONS USUALLY FLANGED OR THREADED

SEPARABLE BONNET

Rotary Valve Features

STREAMLINED FLOW PATH HIGH RECOVERY MORE CAPACITY LESS PACKING WEAR CAN HANDLE SLURRY AND ABRASIVES FLANGELESS INTEGRAL BONNET

HIGH RANGEABILITY

In addition to linear and rotary, control valves are also classified according to their guiding

systems and the types of services they are used in.Control Valve Classification
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plumbing valve and their applications

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