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A pinch valve is a full bore or fully ported type of control valve which uses a pinching effect to obstruct fluid flow.
| | This article may need to be rewritten to comply with Wikipedia's quality standards.(May 2009) |
A pinch valve is a full bore or fully ported type of control valve which uses a pinching effect to obstruct fluid flow.
Pinch valves employ an elastic tubing (sleeve/hose) and a device that directly contacts the tubing (body). Forcing the tubing together will create a seal that is equivalent to the tubing's permeability. [1]
Air-operated pinch valves consist of an elasticised reinforced rubber hose, a type of housing, and two socket end covers (or flanges). In air-operated pinch valves, the rubber hoses are usually press-fitted and centered into the housing ends by the socket covers. There is no additional actuator, the valve closes as soon as there is a pressurized air supply into the body. When the air supply becomes interrupted and the volume of air exhausts, the elastic rubber hose starts to open due to the force of the process flow.
Pinch valves are typically used in applications where the media needs to be completely isolated from any internal valve parts. The sleeve will contain the flow media and isolate it from the environment, hence reducing contamination. They are commonly applied to medical instruments, clinical or chemical analyzers, and a wide range of laboratory equipment. [2]
Pinch valves are also used for slurries or processes with entrained solids, because the flexible rubber sleeve closes droptight around solids. This avoids entrapment by the seat or in crevices, which would happen if using globe, diaphragm, butterfly, gate or ball valves.
Major industries that use pinch valves are:
On a smaller scale, pinch valves are used in some water pistols, notably the original Super Soaker 50. [3]
The most important benefits of using pinch valves are the full bore for the flow media, and 100% tight shut off – even on solids such as granules, powders, pellets, chippings, fibres, slivers, any kind of slurries and aggressive products.
Ball valves, piston valves or gate valves could fail when in contact with aggressive products, due to body seat or the gate/piston wearing out too quickly. Air-operated pinch valves work with less wear of the elastic rubber hose because the kinetic energy of the solids are absorbed through the high elasticity of the rubber that also helps to resist abrasion.
The sleeve material is selected among suitable synthetic polymer based upon the corrosiveness and abrasiveness of the flow media. A key selection criterion is the operation temperature, which needs to be within the limit of the polymer.
Several rubber qualities are available for pinch valves such as natural rubber, EPDM, nitrile, viton, neoprene and butyl. Different housings and end covers/flange materials such as aluminium, plastics and stainless steel are also available. [4]
A valve is a device or natural object that regulates, directs or controls the flow of a fluid 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 the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
A peristaltic pump, also commonly known as a roller pump, is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained in a flexible tube fitted inside a circular pump casing. Most peristaltic pumps work through rotary motion, though linear peristaltic pumps have also been made. The rotor has a number of "wipers" or "rollers" attached to its external circumference, which compress the flexible tube as they rotate by. The part of the tube under compression is closed, forcing the fluid to move through the tube. Additionally, as the tube opens to its natural state after the rollers pass, more fluid is drawn into the tube. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract. Typically, there will be two or more rollers compressing the tube, trapping a body of fluid between them. The body of fluid is transported through the tube, toward the pump outlet. Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid.
In the oil and gas industry, the term wireline usually refers to the use of multi-conductor, single conductor or slickline cable, or "wireline", as a conveyance for the acquisition of subsurface petrophysical and geophysical data and the delivery of well construction services such as pipe recovery, perforating, plug setting and well cleaning and fishing. The subsurface geophysical and petrophysical information results in the description and analysis of subsurface geology, reservoir properties and production characteristics.
A water gun is a type of toy gun designed to shoot jets of water. Similar to water balloons, the primary purpose of the toy is to soak another person in a recreational game such as water fight.
A diving regulator is a pressure regulator that controls the pressure of breathing gas for diving. The most commonly recognised application is to reduce pressurized breathing gas to ambient pressure and deliver it to the diver, but there are also other types of gas pressure regulator used for diving applications. The gas may be air or one of a variety of specially blended breathing gases. The gas may be supplied from a scuba cylinder carried by the diver, in which case it is called a scuba regulator, or via a hose from a compressor or high-pressure storage cylinders at the surface in surface-supplied diving. A gas pressure regulator has one or more valves in series which reduce pressure from the source, and use the downstream pressure as feedback to control the delivered pressure, or the upstream pressure as feedback to prevent excessive flow rates, lowering the pressure at each stage.
A gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. The gate faces can be parallel but are most commonly wedge-shaped.
A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates.
A hose is a flexible hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called pipes, or more generally tubing. The shape of a hose is usually cylindrical.
Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses, tubes, or pipes.
EPDM rubber is a type of synthetic rubber that is used in many applications. Dienes used in the manufacture of EPDM rubbers are ethylidene norbornene (ENB), dicyclopentadiene (DCPD), and vinyl norbornene (VNB). 4-8% of these monomers are typically used.
A stopcock is a form of valve used to control the flow of a liquid or gas. The term is not precise and is applied to many different types of valve. The only consistent attribute is that the valve is designed to completely stop the flow when closed fully.
Diaphragm valves consists of a valve body with two or more ports, a flexible diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve body may be constructed from plastic, metal, wood or other materials depending on the intended use.
A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.
A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, hydraulic pressure or electricity, allow a valve to be adjusted remotely, or allow rapid operation of large valves. Power-operated valve actuators may be the final elements of an automatic control loop which automatically regulates some flow, level or other process. Actuators may be only to open and close the valve, or may allow intermediate positioning; some valve actuators include switches or other ways to remotely indicate the position of the valve.
Well completion is the process of making a well ready for production after drilling operations. This principally involves preparing the bottom of the hole to the required specifications, running in the production tubing and its associated down hole tools as well as perforating and stimulating as required. Sometimes, the process of running in and cementing the casing is also included. After a well has been drilled, should the drilling fluids be removed, the well would eventually close in upon itself. Casing ensures that this will not happen while also protecting the wellstream from outside incumbents, like water or sand.
A slurry pump is a type of pump designed for pumping liquid containing solid particles. Slurry pumps changes in design and construction to adjust to multiple type of slurry which varies in concentration of solids, size of solid particles, shape of solid particles, and composition of solution. Slurry pump are more robust than liquid pumps; they have added sacrificial material and replaceable wear parts to withstand wear due to abrasion.
High-density solids pumps are hydrostatically operating machines which displace the medium being pumped and thus create a flow.
The mechanism of diving regulators is the arrangement of components and function of gas pressure regulators used in the systems which supply breathing gases for underwater diving. Both free-flow and demand regulators use mechanical feedback of the downstream pressure to control the opening of a valve which controls gas flow from the upstream, high-pressure side, to the downstream, low-pressure side of each stage. Flow capacity must be sufficient to allow the downstream pressure to be maintained at maximum demand, and sensitivity must be appropriate to deliver maximum required flow rate with a small variation in downstream pressure, and for a large variation in supply pressure, without instability of flow. Open circuit scuba regulators must also deliver against a variable ambient pressure. They must be robust and reliable, as they are life-support equipment which must function in the relatively hostile seawater environment, and the human interface must be comfortable over periods of several hours.