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I need some sources about valve (ball valve) design

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    I need some sources about valve (ball valve) design

    Assalam Alaikom
    Good moorning/after noon/ evening
    I am a mechanical engineering student and I was asked to do a project about valve (ball valve) design.
    I need some sources about this topic, so I will appreciate any help

    Thanks

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    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 be installed to operate rarely if ever e.g. safety valves. A valve can be an extremely simple, low cost 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 /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 open.

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

    Regulation of flow
    Many applications require the flow of the fluid be regulated (throttled) at some fixed or variable level between fully zero and maximum flow limits. This is achieved by introducing resistance to flow, 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 this duty is a non-return-valve (NRV) or check valve. The important criteria when selecting these valves are, tight shut off against reverse flow, low resistance to flow for forward flow, fast response. 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 valve is basically a globe valve biased open by an adjustable spring force 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

    The pressure regulator valve operates using the downstream fluid pressure as feedback. This is mostly 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 include internal 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 applications where excessive pressure in the system can cause damage or failure or can introduce a safety risk. Uncontrolled excessive pressures can result in disastrous accidents e.g. when potentially explosive 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 is simply a disc which ruptures when a set pressure is exceeded. The fluid then escapes through the ruptured disc. If the bursting disc operates the system has be be closed down and vented and the bursting disc is then replaced

    Relief valves when used for safety applications are engineered in line with safety regulations and require regular inspections to confirm the settings and the operation. An important part of the relief valve installation is the routing of the relieved fluid. This pipe route must be to a safe location 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 be controlled have a major impact on the design and materials of constuction 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 valve must be suitable to withstand resulting corrosion and erosion and if necessary the valve may have to be design for no internal hold up of fluids.

    Important considerations include for absolute internal and external leak tightness when handling toxic or explosive fluids. There regulations also include for the need for a firesafe valve to maintain 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 compression fittings
    Valve Containment
    An important requirement in valve design is to minimise the leakage of fluids into the surrounding environment. This is very important in the nuclear industry and when transferring toxic or flammable fluids. The possible leakage points on valves are listed below
    • The end connections with the piping.-
    • 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 eliminates the 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 can also be reduced by incorporating dual seals with a test point between. Pinch valves and diaphragm 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 flow characteristics for an on-off valve are fixed and can be evaluated directly using the relevant flow factor. 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 m3/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 ( Dp )in bar for a liquid with a specific gravity relative to water ( γw ).

    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 the critical Dp is at P1 /2 does not hold for all valves. For accurate flow calculations the valve manufacturers data sheets must be used


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


    T1 = Inlet gas temperature deg K = Deg C + 273
    γa =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..

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    Ball Valves
    The ball valve is basically a plug valve with a spherical plug and a round hole. Over recent years the materials of construction of the ball valve have been developed such that the ball valve is becoming the most popular valve for most process applications. There are two primary options 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 still with relatively low head loss compared to most other valve options e.g 25nb valve has a 20mm reduced bore,. The full bore option has a larger body but provides zero restriction to flow. The valve can be supplies as a multi-port design for flow diverting but only with the reduced bore option

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

    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 operations e.g rodding . Ball valves can also be used on branches to enable instruments to be fed into pipe systems during operating periods.

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


    Ball Valve - With Floating Ball

    Ball Valve Trunnion Mounted

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    Ball valves are flow valves that are quarter-turn and straight through apparatuses. These valves allow for shut-off and/or purposes of control. They have a round closure element that contains a matching pair of rounded seats. These seats allow necessary sealing to take place. The ball valve pressure rating and materials used determines what kind of seat is required. Not all valve seats are the same. Some are of the single molded variety while others have higher- pressure ratings, which often include a design known as a "trunnion." This design means that each ball valve face is sealed separately, not together.

    Ball valves have many good points and are often considered superior to many other kinds of valves. Ball valves are very easy to use and can both maintain and regulate three things-high pressure, high volume and high flow of temperature. Other advantages of ball valves are that they are sturdy devices that can be purchased for a low price and they have a long service life. An added plus is that the regulating element's design makes it easy for the ball valve to work without concern about side loads, which often plague globe or butterfly valves. The ball valve design allows for the easy ability to fix the seats if a problem arises and also seals without having to take away the body of the valves from the line.

    Ball valves can be found in a number of different styles. Some of these include one-piece, two-piece, three-piece and lastly, what is referred to as flanged body construction. Each form of ball valve has its own good and bad points, all dependent on what each application calls for. Ball valves are made using an assortment of materials, some of which include brass, bronze, cast iron, copper ductile iron, metal alloys, stainless and other steel types, and plastics (including CPVC and PVC). Ball valves are to be found being used in a number of different industries. Some of these include the chemical, oil, pharmaceutical, allied process and also services such as corrosive and cryogenic.

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    ball valve is a stop valve that is designed mostly for on/off service. It is essentially a plug valve with a round hole and a sphere-shaped plug. A ball valve contains a ball with a small hole in the middle that helps to control the flow of materials through the pipe. An actuator, which can be either electric or a manually operated handle, rotates the ball 90%. When the hole of the ball is facing away from the pipe opening, flow is restricted. When it is aligned with the opening, flow is restored. The position of the handle immediately indicates whether the valve is closed or open. Along with being easy to monitor, ball valves are also simple to clean and repair; as the ball rotates, the seat performs a self-wiping action that prevents any buildup.

    Two primary options exist for the design of ball valves. These are the floating ball design, a less costly option for lower duties, and a trunnion ball option, which is used for higher duties and, therefore, more costly. There are several body styles available, as well, including one-piece, two-piece, three-piece, even four- and five-piece and flanged body construction. The type of application determines which ball valve is the most appropriate. Sizes of ball valves range from very small up to 42 inches and in pressure ratings, up to 7,500 psi. Although they are manufactured from a wide variety of materials, some common materials of ball valves include stainless steel, plastic, bronze, copper, cast iron, ductile iron, metal alloys and brass. Metal valves are recommended for gases and high temperature fluids; use plastic valves for liquid applications only.

    Bore, or port, sizes differ as well. In a full bore valve, the diameter of the hole in the ball is the same size as the hole in the pipe. Looking down a piece of pipe, in other words, there would not appear to be any constriction at the location of the valve. If the diameter of the hole through the ball is less than that of the pipe, it is referred to as a reduced or standard bore/port. Some valves gradually narrow, while the reduction in others is basically a shoulder. Many times, the diameter tapers to the next standard size. There is very little pressure loss difference between the full bore and reduced bore valve.

    Advances in ball valve design and materials have significantly increased their popularity. Ball valves can be used for isolation of systems, regulation of some types of low flow (e.g. throttling the flow of air at differential pressures up to 1,000 psi) and backflow prevention, but only with a swing check component. They can handle high pressure and a large volume of fluids, gases and suspended solids (slurries). New valve designs have enabled ball valves to be used in high-vacuum situations. This possibility was not previously considered, due to the inherent tendencies of these valves to leak and trap gas. Aluminum construction of ball valves will be available in the near future.



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    Ball Valves Terms

    Actuator – Used to operate the ball valve. The actuator is often used to control the flow of materials.
    Ball – The closure portion of the valve that restricts or controls the fluid or gas flow.
    Butterfly Valve A valve that utilizes a circular disc or vane in order to control flow by turning the valve’s pivot axis at 90¼ angles to the pipe’s flow direction.
    Flange – A projecting rim or edge used to strengthen or attach one object to another.
    Full Bore Value – The diameter of ball inside the valve equals the diameter of the pipe. This is also called full port.

    Globe Valve – A globular shaped valve whose internal moving parts consist of the disk, the valve stem and the handwheel.

    Poppet Valve – A valve that moves up to or from its seat perpendicularly. This valve generally provides more flow than a ball valve.

    Port – Flow path.

    Pressure Control Valve – A valve that controls the amount of pressure. Typically the valve will shut when a pre-determined pressure is reached.

    Pressure Relief Valve – A valve that releases pressure if needed. This valve is self-operating.

    PSI (Pounds Per Square Inch) – A unit of pressure; equivalent to the metric unit of Kilonewtons per square centimeter.

    Reduced Bore Value – The ball inside the valve has a hole smaller than the opening in the pipe, allowing for better control. This is also called standard bore or port.

    Relief Valve – A valve that when open allows for the release of excess pressure or temperature.

    Slurry – A mixture of liquid, typically water, and solid materials to create a material similar in consistency to mud or plaster of Paris.

    Trunnion – Upper and lower supports used to keep the ball under pressure.

    Valve Seat – A stationary part of the valve which restricts fluid or gas flow when it comes in contact with the movable portion of the valve.

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    some notes guides you to select a ball valve
    material , this an example

    Design and Manufacture: API 6D, ASME B16.34, API 608, MSS SP-72, BS5351
    Face to Face Dimension: ASME B16.10, API 6D, BS EN558
    End Flange Dimension: ASME B16.5
    Welding Ends Dimension: ASME B16.25
    Pressure-Temperature Ratings:ASME B16.34
    Inspection and Test: API 598, API 6D, BS 6755
    Type of Operation: Manual, Gear, Electric, Pneumatic
    Size: NPS 1/2"-10"
    Pressure: Class150-600
    Anti-Static Design Fire Safe Design as per API607/6FA
    Materials: WCB, WCC, WC6, WC9, C5, C12, LCB, LCC, CF8, CF8M, CF3, CF3M, CF8C, CN7M, A105, LF2, F304, F304L, F316, F316L, F321, F51

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    Thumbs up

    Thank you so much Mr. Mohammed
    I appreciate your help.

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    اقتباس المشاركة الأصلية كتبت بواسطة 11011 مشاهدة المشاركة
    Thank you so much Mr. Mohammed


    I appreciate your help.
    Not at all

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    الأقصى فى خطر يا مسلمون

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    اللهم وفقنا لتحرير مسجدك الأقصى الأسير
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