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55-409: A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries ) by opening, closing, or partially obstructing various passageways. Valves are technically fittings , but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from

110-404: A ball check valve uses the ball to block reverse flow, but is not a rotor because operating the valve does not involve rotation of the ball. The "seat" is the interior surface of the body which contacts the disc to form a leak-tight seal. In discs that move linearly or swing on a hinge or trunnion, the disc comes into contact with the seat only when the valve is shut. In disks that rotate, the seat

165-477: A cover on the valve body. It is commonly semi-permanently screwed into the valve body or bolted onto it. During manufacture of the valve, the internal parts are put into the body and then the bonnet is attached to hold everything together inside. To access internal parts of a valve, a user would take off the bonnet, usually for maintenance. Many valves do not have bonnets; for example, plug valves usually do not have bonnets. Many ball valves do not have bonnets since

220-600: A handle attached to the stem. If the handle is turned ninety degrees between operating positions, the valve is called a quarter-turn valve. Butterfly, ball valves, and plug valves are often quarter-turn valves. If the handle is circular with the stem as the axis of rotation in the center of the circle, then the handle is called a handwheel. Valves can also be controlled by actuators attached to the stem. They can be electromechanical actuators such as an electric motor or solenoid , pneumatic actuators which are controlled by air pressure , or hydraulic actuators which are controlled by

275-451: A liner may be used which extends just above the shoe (bottom) of the previous casing interval and hung off downhole rather than at the surface. It may typically be 7", although many liners match the diameter of the production tubing . Few wells actually produce through casing, since producing fluids can corrode steel or form deposits such as asphaltenes or paraffin waxes and the larger diameter can make flow unstable. Production tubing

330-467: A long casing string, which typically will have the greatest axial tension and perhaps highest internal burst pressure differentials in the upper parts, and the greatest collapsing loads deeper in the well from external pressure vs lowered internal pressure. Casing strings are supported by casing hangers that are set in the wellhead , which later will be topped with the Christmas tree . The lower members of

385-444: A mechanism to indicate by how much the valve is open, but in many cases other indications of flow rate are used, such as separate flow meters . In plants with remote-controlled process operation, such as oil refineries and petrochemical plants, some 2-way valves can be designated as normally closed (NC) or normally open (NO) during regular operation. Examples of normally-closed valves are sampling valves , which are only opened while

440-461: A sample is taken. Other examples of normally-closed valves are emergency shutdown valves , which are kept open when the system is in operation and will automatically shut by taking away the power supply. This happens when there is a problem with a unit or a section of a fluid system such as a leak in order to isolate the problem from the rest of the system. Examples of normally-open valves are purge-gas supply valves or emergency-relief valves. When there

495-575: A solid when a sudden force is applied. Substances with a very high viscosity such as pitch appear to behave like a solid (see pitch drop experiment ) as well. In particle physics , the concept is extended to include fluidic matters other than liquids or gases. A fluid in medicine or biology refers to any liquid constituent of the body ( body fluid ), whereas "liquid" is not used in this sense. Sometimes liquids given for fluid replacement , either by drinking or by injection, are also called fluids (e.g. "drink plenty of fluids"). In hydraulics , fluid

550-477: A solid, shear stress is a function of strain , but in a fluid, shear stress is a function of strain rate . A consequence of this behavior is Pascal's law which describes the role of pressure in characterizing a fluid's state. The behavior of fluids can be described by the Navier–Stokes equations —a set of partial differential equations which are based on: The study of fluids is fluid mechanics , which

605-455: A spring to keep the valve shut, but allow excessive pressure to force the valve open against the spring-loading. Coil springs are normally used. Typical spring materials include zinc plated steel , stainless steel, and for high temperature applications Inconel X750. The internal elements of a valve are collectively referred to as a valve's trim . According to API Standards 600, "Steel Gate Valve-Flanged and Butt-welding Ends, Bolted Bonnets",

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660-467: A valve member, is a movable obstruction inside the stationary body that adjustably restricts flow through the valve. Although traditionally disc-shaped, discs come in various shapes. Depending on the type of valve, a disc can move linearly inside a valve, or rotate on the stem (as in a butterfly valve ), or rotate on a hinge or trunnion (as in a check valve). A ball is a round valve member with one or more paths between ports passing through it. By rotating

715-473: A variety of requirements. Valves vary widely in form and application. Sizes typically range from 0.1 mm to 60 cm. Special valves can have a diameter exceeding 5 meters. Valve costs range from simple inexpensive disposable valves to specialized valves which cost thousands of dollars (US) per inch of the diameter of the valve. Disposable valves may be found in common household items including mini-pump dispensers and aerosol cans . A common use of

770-464: Is 13 + 3 ⁄ 8 inches (340 mm). Intermediate casing may be necessary on longer drilling intervals where necessary drilling mud weight to prevent blowouts may cause a hydrostatic pressure that can fracture shallower or deeper formations. Casing placement is selected so that the hydrostatic pressure of the drilling fluid remains at a pressure level that is between formation pore pressures and fracture pressures. In order to reduce cost,

825-450: Is a problem these valves open (by switching them 'off') causing the unit to be flushed and emptied. Although many 2-way valves are made in which the flow can go in either direction between the two ports, when a valve is placed into a certain application, flow is often expected to go from one certain port on the upstream side of the valve, to the other port on the downstream side. Pressure regulators are variations of valves in which flow

880-972: Is a term which refers to liquids with certain properties, and is broader than (hydraulic) oils. Fluids display properties such as: These properties are typically a function of their inability to support a shear stress in static equilibrium . By contrast, solids respond to shear either with a spring-like restoring force —meaning that deformations are reversible—or they require a certain initial stress before they deform (see plasticity ). Solids respond with restoring forces to both shear stresses and to normal stresses , both compressive and tensile . By contrast, ideal fluids only respond with restoring forces to normal stresses, called pressure : fluids can be subjected both to compressive stress—corresponding to positive pressure—and to tensile stress, corresponding to negative pressure . Solids and liquids both have tensile strengths, which when exceeded in solids creates irreversible deformation and fracture, and in liquids cause

935-435: Is also used for severe duty, high-pressure, high-tolerance applications. They are typically made of stainless steel, titanium , Stellite , Hastelloy, brass, or nickel . They can also be made of different types of plastic, such as ABS , PVC, PP or PVDF. Many valves have a spring for spring-loading, to normally shift the disc into some position by default but allow control to reposition the disc. Relief valves commonly use

990-537: Is always in contact with the disk, but the area of contact changes as the disc is turned. The seat always remains stationary relative to the body. Seats are classified by whether they are cut directly into the body, or if they are made of a different material: A closed soft seated valve is much less liable to leak when shut while hard seated valves are more durable. Gate, globe, and check valves are usually hard seated while butterfly, ball, plug, and diaphragm valves are usually soft seated. The stem transmits motion from

1045-851: Is bolted to the valve body. Valve bodies are usually metallic or plastic . Brass , bronze , gunmetal , cast iron , steel , alloy steels and stainless steels are very common. Seawater applications, like desalination plants, often use duplex valves, as well as super duplex valves, due to their corrosion resistant properties, particularly against warm seawater. Alloy 20 valves are typically used in sulphuric acid plants, whilst monel valves are used in hydrofluoric acid (HF Acid) plants. Hastelloy valves are often used in high temperature applications, such as nuclear plants, whilst inconel valves are often used in hydrogen applications. Plastic bodies are used for relatively low pressures and temperatures. PVC , PP , PVDF and glass-reinforced nylon are common plastics used for valve bodies. A bonnet acts as

1100-446: Is controlled to produce a certain downstream pressure, if possible. They are often used to control flow of gas from a gas cylinder . A back-pressure regulator is a variation of a valve in which flow is controlled to maintain a certain upstream pressure, if possible. Valves with three ports serve many different functions. A few of the possibilities are listed here. Three-way ball valves come with T- or L-shaped fluid passageways inside

1155-418: Is performed by circulating a cement slurry through the inside of the casing and out into the annulus through the casing shoe at the bottom of the casing string . In order to precisely place the cement slurry at a required interval on the outside of the casing, a plug is pumped with a displacement fluid behind the cement slurry column, which "bumps" in the casing shoe and prevents further flow of fluid through

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1210-544: Is subdivided into fluid dynamics and fluid statics depending on whether the fluid is in motion. Depending on the relationship between shear stress and the rate of strain and its derivatives , fluids can be characterized as one of the following: Newtonian fluids follow Newton's law of viscosity and may be called viscous fluids . Fluids may be classified by their compressibility: Newtonian and incompressible fluids do not actually exist, but are assumed to be for theoretical settlement. Virtual fluids that completely ignore

1265-405: Is therefore installed inside the last casing string and the tubing annulus is usually sealed at the bottom of the tubing by a packer . Tubing is easier to remove for maintenance, replacement, or for various types of workover operations. It is significantly lighter than casing and does not require a drilling rig to run in and out of hole; smaller "service rigs" are used for this purpose. Cementing

1320-420: Is typically held in place with cement . Deeper strings usually are not cemented all the way to the surface, so the weight of the pipe must be partially supported by a casing hanger in the wellhead . Casing that is cemented in place aids the drilling process in several ways: Optimum design of the casing program decreases the well construction costs, enhances the efficiency of operations and also diminishes

1375-547: Is used to manually control a valve from outside the valve body. Automatically controlled valves often do not have handles, but some may have a handle (or something similar) anyway to manually override automatic control, such as a stop-check valve . An actuator is a mechanism or device to automatically or remotely control a valve from outside the body. Some valves have neither handle nor actuator because they automatically control themselves from inside; for example, check valves and relief valves may have neither. A disc, also known as

1430-471: The Pressure Equipment Directive 97/23/EC (PED). Some fluid system designs, especially in chemical or power plants, are schematically represented in piping and instrumentation diagrams. In such diagrams, different types of valves are represented by certain symbols. Valves in good condition should be leak-free. However, valves may eventually wear out from use and develop a leak, either between

1485-400: The blood circulation , and heart valves controlling the flow of blood in the chambers of the heart and maintaining the correct pumping action. Valves may be operated manually, either by a handle or grip, lever , pedal or wheel. Valves may also be automatic, driven by changes in pressure, temperature , or flow. These changes may act upon a diaphragm or a piston which in turn activates

1540-525: The production tubing and associated hardware such as packers, gas lift mandrels and subsurface safety valves. Casing design for each size of designed pipes is done by calculating the worst conditions that may be faced during drilling and over the producing life of the well. Mechanical properties such as longitudinal tensile strength, and burst and collapse resistance (calculated considering biaxial effects of axial and hoop stresses), must be sufficient at various depths. Pipe of differing strengths often comprises

1595-778: The Latin valva , the moving part of a door, in turn from volvere , to turn, roll. The simplest, and very ancient, valve is simply a freely hinged flap which swings down to obstruct fluid (gas or liquid) flow in one direction, but is pushed up by the flow itself when the flow is moving in the opposite direction. This is called a check valve , as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems. Valves have many uses, including controlling water for irrigation , industrial uses for controlling processes, residential uses such as on/off and pressure control to dish and clothes washers and taps in

1650-478: The actuator lines control the supply of air or liquid going to the actuators. The fill valve in a toilet water tank is a liquid level-actuated valve. When a high water level is reached, a mechanism shuts the valve which fills the tank. In some valve designs, the pressure of the flow fluid itself or pressure difference of the flow fluid between the ports automatically controls flow through the valve. Valves are typically rated for maximum temperature and pressure by

1705-405: The ball, flow can be directed between different ports. Ball valves use spherical rotors with a cylindrical hole drilled as a fluid passage. Plug valves use cylindrical or conically tapered rotors called plugs. Other round shapes for rotors are possible as well in rotor valves, as long as the rotor can be turned inside the valve body. However, not all round or spherical discs are rotors; for example,

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1760-404: The casing to be placed inside it, allowing room for cement between the outside of that casing and the hole. Also, subsequent bits that will continue drilling obviously must pass through existing casing strings. Thus, each casing string will have a subsequently smaller diameter. The inside diameter of the final casing string (or penultimate one in some instances of a liner completion) must accommodate

1815-431: The disc has two passages to connect adjacent ports. It is operated with two positions. It can be used to isolate and to simultaneously bypass a sampling cylinder installed on a pressurized water line. It is useful to take a fluid sample without affecting the pressure of a hydraulic system and to avoid degassing (no leak, no gas loss or air entry, no external contamination).... Many valves are controlled manually with

1870-410: The effects of viscosity and compressibility are called perfect fluids . Casing (borehole) Casing is a large diameter pipe that is assembled and inserted into a recently drilled section of a borehole . Similar to the bones of a spine protecting the spinal cord, casing is set inside the drilled borehole to protect and support the wellstream. The lower portion (and sometimes the entirety)

1925-403: The environmental impacts. A slightly different metal string, called production tubing , is often used without cement inside the final casing string of a well to contain production fluids and convey them to the surface from an underground reservoir . In the planning stages of a well, a drilling engineer , usually with input from geologists and others, will pick strategic depths at which

1980-443: The handle or controlling device to the disc. The stem typically passes through the bonnet when present. In some cases, the stem and the disc can be combined in one piece, or the stem and the handle are combined in one piece. The motion transmitted by the stem may be a linear force , a rotational torque , or some combination of these (Angle valve using torque reactor pin and Hub Assembly). The valve and stem can be threaded such that

2035-434: The hole will need to be cased in order for drilling to reach the desired total depth. This decision is often based on subsurface data such as formation pressures and strengths, well integrity , and is balanced against the cost objectives and desired drilling strategy. With the casing set depths determined, hole sizes and casing sizes must follow. The hole drilled for each casing string must be large enough to accommodate

2090-880: The home. Valves are also used in the military and transport sectors. In HVAC ductwork and other near-atmospheric air flows, valves are instead called dampers . In compressed air systems, however, valves are used with the most common type being ball valves. Valves are found in virtually every industrial process, including water and sewage processing, mining, power generation, processing of oil, gas and petroleum, food manufacturing, chemical and plastic manufacturing and many other fields. People in developed nations use valves in their daily lives, including plumbing valves, such as taps for tap water , gas control valves on cookers, small valves fitted to washing machines and dishwashers , safety devices fitted to hot water systems , and poppet valves in car engines. In nature, there are valves, for example one-way valves in veins controlling

2145-519: The inside and outside of the valve or, when the valve is shut to stop flow, between the disc and the seat. A particle trapped between the seat and disc could also cause such leakage. Fluid Although the term fluid generally includes both the liquid and gas phases, its definition varies among branches of science . Definitions of solid vary as well, and depending on field, some substances can have both fluid and solid properties. Non-Newtonian fluids like Silly Putty appear to behave similar to

2200-476: The manufacturer. The wetted materials in a valve are usually identified also. Some valves rated at very high pressures are available. When a designer, engineer, or user decides to use a valve for an application, he/she should ensure the rated maximum temperature and pressure are never exceeded and that the wetted materials are compatible with the fluid the valve interior is exposed to. In Europe, valve design and pressure ratings are subject to statutory regulation under

2255-413: The most usual type of valve are the body and the bonnet. These two parts form the casing that holds the fluid going through the valve. The valve's body is the outer casing of most or all of the valve that contains the internal parts or trim . The bonnet is the part of the encasing through which the stem (see below) passes and that forms a guide and seal for the stem. The bonnet typically screws into or

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2310-627: The onset of cavitation . Both solids and liquids have free surfaces, which cost some amount of free energy to form. In the case of solids, the amount of free energy to form a given unit of surface area is called surface energy , whereas for liquids the same quantity is called surface tension . In response to surface tension, the ability of liquids to flow results in behaviour differing from that of solids, though at equilibrium both tend to minimise their surface energy : liquids tend to form rounded droplets , whereas pure solids tend to form crystals . Gases , lacking free surfaces, freely diffuse . In

2365-407: The other. Single handle mixer valves produce a variable mixture of hot and cold water at a variable flow rate under control of a single handle. Thermostatic mixing valves mix hot and cold water to produce a constant temperature in the presence of variable pressures and temperatures on the two input ports. A 4-port valve is a valve whose body has four ports equally spaced round the body and

2420-876: The position of the disc or rotor in the valve. Some valves are made to be operated in a gradual change between two or more positions. Return valves and non-return valves allow fluid to move in 2 or 1 directions respectively. Operating positions for 2-port valves can be either shut (closed) so that no flow at all goes through, fully open for maximum flow, or sometimes partially open to any degree in between. Many valves are not designed to precisely control intermediate degree of flow; such valves are considered to be either open or shut. Some valves are specially designed to regulate varying amounts of flow. Such valves have been called by various names such as regulating , throttling , metering , or needle valves . For example, needle valves have elongated conically tapered discs and matching seats for fine flow control. For some valves, there may be

2475-507: The pressure of a liquid such as oil or water. Actuators can be used for the purposes of automatic control such as in washing machine cycles, remote control such as the use of a centralised control room , or because manual control is too difficult such as when the valve is very large. Pneumatic actuators and hydraulic actuators need pressurised air or liquid lines to supply the actuator: an inlet line and an outlet line. Pilot valves are valves which are used to control other valves. Pilot valves in

2530-402: The rotor. The T valve might be used to permit connection of one inlet to either or both outlets or connection of the two outlets. The L valve could be used to permit disconnection of both or connection of either but not both of two inlets to one outlet. Shuttle valves automatically connect the higher pressure inlet to the outlet while (in some configurations) preventing flow from one inlet to

2585-399: The shoe. This bump can be seen at surface as a pressure spike at the cement pump. To prevent the cement from flowing back into the inside of the casing, a float collar above the casing shoe acts as a check valve and prevents fluid from flowing up through the shoe from the annulus. A prolonged, recurrent axial and rotational movement within casing would cause wear to the casing interior, with

2640-404: The stem can be screwed into or out of the valve by turning it in one direction or the other, thus moving the disc back or forth inside the body. Packing is often used between the stem and the bonnet to maintain a seal. Some valves have no external control and do not need a stem as in most check valves. Valves whose disc is between the seat and the stem and where the stem moves in a direction into

2695-471: The surface casing, and to prevent collapse of the loose soil near the surface. It can normally vary from sizes such as 18 to 30 in (460 to 760 mm). The purpose of surface casing is to isolate freshwater zones so that they are not contaminated during drilling and completion. Surface casing is the most strictly regulated due to these environmental concerns, which can include regulation of casing depth and cement quality. A typical size of surface casing

2750-407: The term valve refers to the poppet valves found in the vast majority of modern internal combustion engines such as those in most fossil fuel powered vehicles which are used to control the intake of the fuel-air mixture and allow exhaust gas venting. Valves are quite diverse and may be classified into a number of basic types. Valves may also be classified by how they are actuated: The main parts of

2805-401: The trim consists of stem, seating surface in the body, gate seating surface, bushing or a deposited weld for the backseat and stem hole guide, and small internal parts that normally contact the service fluid, excluding the pin that is used to make a stem-to-gate connection (this pin shall be made of an austenitic stainless steel material). Valve positions are operating conditions determined by

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2860-515: The valve body is put together in a different style, such as being screwed together at the middle of the valve body. Ports are passages that allow fluid to pass through the valve. Ports are obstructed by the valve member or disc to control flow. Valves most commonly have 2 ports, but may have as many as 20. The valve is almost always connected at its ports to pipes or other components. Connection methods include threadings , compression fittings , glue , cement , flanges , or welding . A handle

2915-416: The valve to shut it are normally-seated or front seated . Valves whose seat is between the disc and the stem and where the stem moves in a direction out of the valve to shut it are reverse-seated or back seated . These terms don't apply to valves with no stem or valves using rotors. Gaskets are the mechanical seals, or packings, used to prevent the leakage of a gas or fluids from valves. A valve ball

2970-446: The valve, examples of this type of valve found commonly are safety valves fitted to hot water systems or boilers . More complex control systems using valves requiring automatic control based on an external input (i.e., regulating flow through a pipe to a changing set point) require an actuator . An actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned accurately, and allowing control over

3025-415: The wellhead usually are installed on top of the first casing string after it has been cemented in place. Typically, a well contains multiple intervals of casing successively placed within the previous casing run. The following casing intervals are typically used in an oil or gas well: The conductor casing serves as a support during drilling operations, to flowback returns during drilling and cementing of

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