Intro4u2u

Solenoid valves are devices that use a solenoid to control valve activation. Actuation methods include electric, electro-hydraulic, electro pneumatic, and pneumatic. Unpowered states include normally open and normally closed. In a tandem center solenoid valve, the pressure and tank ports are connected while the service ports are blanked. This allows system unloading while still providing isolation of the service lines. In a float center solenoid valve, the supply pressure port is closed. All others ports are interconnected. This allows the supply to be shut off while enabling the load to move or free wheel with flow available to other services.

Solenoid valves include ball and butterfly valves. Ball valves provide tight shut-off and characterizable control. They have high rangeability due to the design of the regulating element, without the complications of side loads typical of butterfly or globe valves. Butterfly valves control the flow of gas or liquid by means of a disk, which turns on a diametrical axis inside a pipe or by two semicircular plates hinged on a common spindle, which permits flow in only one direction. They are normally used as throttling valves to control flow. Butterfly valves are solenoid valves that offer a rotary stem movement of 90 degrees or less, in a compact design.  Unlike ball valves, butterfly valves do not have any pockets in which fluids may become trapped when the valve is closed.

Cartridge valves are solenoid valves that are inserted into manifolds to provide a cost effective compact system design. Pinch valves have a flexible elastomer body that can be pinched closed, cutting off flow, using a mechanism or fluid pressure. Diaphragm valves are similar to pinch valves, but use an elastomeric diaphragm, instead of an elastomeric liner in the valve body, to separate the flow stream from the closure element. Instead of pinching the liner closed to provide shut-off, the diaphragm is pushed into contact with the bottom of the valve body to provide shut-off.  Diaphragm valves are excellent for controlling the flow of fluids containing suspended solids and offer the flexibility of being installed in any position. These types of valves have found widespread use in the pharmaceutical, food processing, and water treatment industries.

Gate or knife valves are solenoid valves in which a flat closure element slides into the flow stream to provide shut-off. Gate valves are usually divided into two types: parallel and wedge-shaped. The parallel gate valve uses a flat disc gate between two parallel seats, upstream and downstream. Knife valves are of this type, but with a sharp edge on the bottom of the gate to shear entrained solids or separate slurries.

Globe valves are solenoid valves with rounded bodies. They are widely used in industry to regulate fluid flow in both on/off and throttling service. Needle valves have a slender, tapered point at the end of the valve stem that is lowered through the seat to restrict or block flow.  Fluid flowing through the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone shaped tip. These small valves are widely used to accurately regulate the flow of liquids and gases at low flow rates. The fine threading of the stem and the large seat area allow for precise resistance to flow.

Emergency shut-off valves (ESV) automatically close in the event of an emergency to prevent the loss of handled media. Emergency shut-off valves (ESV) are installed on fuel lines, steam and hot water pipes, vapor lines, and hoses carrying caustic or hazardous liquids and gases.

Emergency shut-off valves (ESV) are frequently installed on residential water and gas lines. A water shut off valve ensures that if there is a pipe leak or burst pipe somewhere in the house, the water supply to the pipe can be shut off at the source to minimize damage. Homes that are served by a well typically have an emergency shut-off valve outside to cut off the supply to the entire house. Homes heated with natural gas usually have a gas shut off valve located near the gas meter or gas service pipe coming into the house. Appliances such as a hot water heater or oven may also have a gas valve to shut off the supply.

Emergency shut-off valves(ESV) are vital safety components of any fuel-based system or manufacturing process that uses liquid or gas media in production. Emergency shut-off valves (ESV) are used in engines to cut off the supply of fuel and shut down the engine. Diesel engines may also use an air intake emergency shut off valve since a diesel engine can continue to run for a short period of time on hydrocarbon fumes even when the fuel supply is cut off. A fuel shut off valve is also commonly used in a gas pump to shut off the flow of gas when the car’s tank is full.

Emergency shut-off valves (ESV) used in industrial processing applications can be electromechanical or electropneumatic and can respond quickly to a variety of processing parameters such as flow rate, temperature, and pressure. Emergency shut off valves (ESV) are typically calibrated for a particular media, such as the type of gas or liquid being used

Control valves or proportional valves are power-operated devices used to modify fluid flow or pressure rate in a process system. These valves are used throughout industry in many applications.  Control valves types include globe, diaphragm, pinch, knife or gate, needle, butterfly, ball, and plug.  Globe valves are linear motion valves with rounded bodies, from which their name is derived.  They are widely used in industry to regulate fluid flow in both on/off and throttling service.  Diaphragm valves are related to pinch valves, but use an elastomeric diaphragm, instead of an elastomeric liner in the valve body, to separate the flow stream from the closure element. Instead of pinching the liner closed to provide shut-off, the diaphragm is pushed into contact with the bottom of the valve body to provide shut-off. Pinch valves includes any valve with a flexible elastomer body that can be pinched closed, cutting off flow, using a mechanism or fluid pressure. Pinch valves are full bore, linear action valves so they can be used in both an off/on manner or in a variable position or throttling service. Gate or knife valves are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off. Gate control valves are usually divided into two types: parallel and wedge-shaped. The parallel gate valve uses a flat disc gate between two parallel seats, upstream and downstream. Knife valves are of this type, but with a sharp edge on the bottom of the gate to shear entrained solids or separate slurries.  Needle control valves have a slender, tapered point at the end of the valve stem that is lowered through the seat to restrict or block flow.  Fluid flowing through the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone shaped tip.   Butterfly valves are quick opening valves that consist of a metal circular disc or vane with its pivot axes at right angles to the direction of flow in the pipe, which when rotated on a shaft, seals against seats in the valve body. They are normally used as throttling valves to control flow.  Ball valves provide tight shut-off and characterizable control. They have high rangeability due to the design of the regulating element, without the complications of side loads typical of butterfly or globe valves.  Plug control valves, also called cock or stop-cock valves, date back to ancient times, where they were developed for use in citywide Roman plumbing systems.  Today, they remain one of the most widely used valves for both on/off and throttling services.

Important specifications to consider when searching for power-operated control valves include diameter, working pressure, and operating temperature.  Media types include gases, liquids, and liquids with suspended solids.  The material temperature is also important to consider.  Metal material choices for valve body include brass, bronze, copper, cast iron, ductile iron, Monel, stainless steel and steel.  Plastic material choices include PVC and CPVC.  There are many choices for end configuration on control valves.  These include threaded, socket-weld or buttweld, push on, solder end, clamp, grooved end, flangeless wafer-style, lugged, mechanical joint, and flanged.  Valve actuation methods for control valves include electric, pneumatic, hydraulic, and manual.  Seat features include metal-to-metal, o-ring or soft seat, Class IV or V, and Class VI.  Control valves may configure to ANSI standards, API standards, MSS specifications, UL listings, ASME standards, and Federal specification WW-V-35C.  Check with manufacturer for exact listings.  Some control valves may come configured as a multi-piece design.  Common applications for control valves include general purpose, process control, oil or fuel, sanitary, wastewater, water, irrigation, gas or air, steam, fire service, cryogenic, refrigeration, chemicals, and laboratory or medical.

Manual valve actuators do not require an outside power source to move a valve to a desired position. Instead, they use a handwheel, chainwheel, lever, or declutchable mechanism to drive a series of gears whose ratio results in a higher output torque compared to the input (manual) torque. Most manual valve actuators use worm gears, mechanical devices that transmit motion between non-intersecting right-angle axes. Some manual valve actuators move rotary motion valves such as ball, butterfly, and multiturn valves a quarter-turn or more from open to close. Other manual valve actuators move linear motion valves such as gate, globe, diaphragm, pinch, and angle valves. Typically, these valves have a sliding stem that pushes the closure element open or closed. Depending on the valve’s design, the stem may rise during rotation or without rotation.  The clockwise rotation of a direct-acting actuator causes the valve to close in a clockwise direction. By contrast, the clockwise rotation of a reverse-acting actuator causes the valve to close in a counter-clockwise direction.

Selecting manual valve actuators requires an analysis of performance specifications. Manual actuators for rotary valves vary in terms of actuator torque and range of motion. Torque, the measure of force needed to produce rotary motion, is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied. Common ranges of motion include 90° (quarter-turn), 180°, 270°, and 360° (multi-turn). Manual valve actuators for linear valves differ in terms of valve stem stroke length, number of turns, and actuator force or seating thrust. Typically, stroke length is measured in inches (in) while actuator force is measuring in pounds (lbs). Other important specifications for manual valve actuators include stem diameter and, when applicable, handwheel diameter.

Manual valve actuators are often housed in enclosures that are rated by the National Electrical Manufacturers Association (NEMA), a trade organization which defines safety standards for electrical equipment. Type 4 NEMA enclosures are rated for indoor and outdoor use and provide protection from falling dirt, rain, sleet, snow, windblown dust, splashing water and hose-directed water. Type 4X NEMA enclosures provide protection against these same environmental variables and can also resist corrosion. Type 7 NEMA enclosures are constructed for indoor use in hazardous locations categorized as Class I; Division 1; Groups A, B, C, or D in NFPA70, a directive from the National Fire Protection Association (NFPA). Type 9 NEMA enclosures are constructed for indoor use in hazardous locations classified as Class II; Division 1; Groups E, F, or G in NFPA70.

Hydraulic linear actuators use a cylinder and hydraulic fluid for motive force. Like other hydraulic systems, the force applied at one point is transmitted to another point using an incompressible fluid. A hydraulic linear actuator requires relatively little maintenance and can operate for prolonged periods of time under adverse environmental conditions. Consequently, hydraulic linear actuators are often used in hydraulic table lifts and hydraulic cab lifts. A hydraulic table lift is designed to raise and position heavy workpieces for material handling and loading applications. A hydraulic cab lift is used in fire engines, tow trucks, and industrial equipment to raise or lower cabs or beds. Hydraulic linear actuators are an integral part of both hydraulic systems.

Hydraulic cab lifts and hydraulic table lifts consist of an electric hydraulic pump, dual lift cylinders, and a series of hoses and valves. Hydraulic cab lift cylinders are equipped with a velocity fuse that prevents the cab from accidentally descending when the control is moved to the tilt position. Hydraulic table lifts are fitted with similar safety mechanisms. Hydraulic linear actuators use motor control and hydraulic valves to provide variable acceleration and deceleration, as well as smooth load-raising and load-lowering characteristics. The force capability of some hydraulic linear actuators reaches 7,800 pounds of force. This amount exceeds the capabilities of similarly-sized screw actuators and electro-mechanical actuators.

Hydraulic linear actuators are used in applications and industries where high force-density, precision control, and long operating life are required. Some hydraulic linear actuators are used in steam turbines or process control valves. Others are used with dampers and motion control systems. Products with certifications and approvals are commonly available. The Hydraulic Institute (HI) is a non-profit industry association dedicated to excellence in the engineering, manufacture, and application of hydraulic equipment. HI uses methodology from the American National Standards Institute (ANSI) before issuing standards for hydraulic systems.

Valve actuators mount on valves and, in response to a signal, move a valve to a desired position using an outside power source. There are several basic types of valve actuators: manual, electric, pneumatic, and hydraulic. Manual valve actuators do not require an outside power source. They use a handwheel or lever to drive a series of gears whose ratio results in a higher output torque compared to the input (manual) torque. Electric valve actuators use a single-phase or three-phase alternating current (AC) or direct current (DC) motor to drive a combination of gears to generate the desired torque level. Pneumatic valve actuators adjust valve position by converting air pressure into linear or rotary motion. Similarly, electrohydraulic valve actuators and hydraulic valve actuators convert fluid pressure supply into linear or rotary motion.

Valve motion and operation style are important specifications to consider when selecting valve actuators. Rotary motion valves (rotary valves) such as ball, plug, and butterfly valves rotate a quarter-turn or more from open to close. Linear motion valves (linear valves) such as gate, globe, diaphragm, pinch and angle-style valves have a sliding stem design that pushes the closure element open or closed. The valve stem may rise during rotation, or may rise without rotation. There are two basic operating styles for valve actuators. On/off or isolating devices limit actuator motion to preset or open and closed positions. Modulating devices provide controllable motion so that valves can be throttled as necessary. Performance specifications for rotary actuators include actuator torque and range of motion. Rotary devices move a quarter-turn (90°), through multiple turns (360°), or a nominal 180° or 270°. Performance specifications for linear actuators include valve stem stroke length, actuation time, number of turns, and actuator force or seating thrust.

General specifications for all types of valve actuators include control signal input type, voltage, supply pressure, valve stem diameter, actuation time, fail-safe method, location type, and operating temperature. There are three basic types of control signal inputs: milliampere, voltage, and pressure. Devices that use AC voltage or DC voltage are commonly available. Supply pressure is the input pressure needed to achieve a desired torque or thrust output. Companies specify air supply pressure for pneumatic actuators and fluid supply pressure for hydraulic actuators. There are several fail-safe methods for valve actuators. Devices can open or close valves in case of power failure, or in case of loss of control signal. Valve actuators for hazardous locations are designed for environments with atmospheres that contain combustible or potentially explosive mixtures. Devices for non-hazardous locations are designed for environments without the risk of combustion or explosion.

Electrohydraulic valve actuators and hydraulic valve actuators convert fluid pressure into motion in response to a signal. They use an outside power source and receive signals that are measured in amperes, volts, or pressure. Some electrohydraulic valve actuators and hydraulic valve actuators move rotary motion valves such as ball, plug, and butterfly valves through a quarter-turn or more from open to close. Other valve actuators move linear valves such as gate, globe, diaphragm, and pinch valves by sliding a stem that controls the closure element. Throttling valves can be moved to any position, including fully open or fully closed, within the stroke of the valve. Typically, valve actuators are added to throttling valves as part of a control loop that includes a sensing device and circuitry.

Electrohydraulic valve actuators and hydraulic valve actuators use several different types of actuators. Diaphragm actuators are used mainly with linear motion valves, but are suitable for rotary motion valves with a linear-to-rotary motion linkage. Rack-and-pinion actuators transfer the linear motion of a piston cylinder actuator to rotary motion. They are ideal for automating manually-operated valves. Scotch yoke actuators also transfer linear motion to rotary motion. With lever and link actuators, a splined or slotted lever attaches to the valve shaft in order to transfer the linear motion of a diaphragm or piston cylinder to rotary motion. Vane actuators are used only with rotary motion valves.

Important specifications for electrohydraulic valve actuators and hydraulic valve actuators include actuation time and hydraulic fluid supply pressure range. Devices that move rotary motion valves vary in terms of actuator torque and range of rotary motion. Devices that move linear motion valves vary in terms of valve stem stroke length and actuator force or sealing thrust. For both types of electrohydraulic valve actuators and hydraulic valve actuators, acting type is an additional specification. With single-acting devices, fluid pressure actuates the valve in one direction while a compressed spring actuates the valve in the other. With double-acting devices, fluid pressure actuates the valve in both directions. Since electrohydraulic valve actuators and hydraulic valve actuators work with multi-turn valves, the number of turns is another important specification.

Features for electrohydraulic valve actuators and hydraulic valve actuators include NEMA enclosures and actuator action. The National Electrical Manufacturers Association (NEMA), a non-profit trade organization, rates enclosures for electrical equipment. Devices with NEMA 4 and 4X ratings are suitable for indoor or outdoor use and provide protection against dirt, rain, sleet, and snow. For manual valve actuators, the actuator action can be direct (clockwise) or reverse (counterclockwise). Other features for electrohydraulic valve actuators and hydraulic valve actuators include overtorque protection, local position indication, and integral pushbuttons and controls. Travel stops or limit stops restrict linear or rotary motion. Manual overrides use handwheels, levers, or hydraulic hand pumps for emergency operation.

Piezoelectric ceramics produce an electrical charge when a load is applied and deformation occurs. Piezoelectric ceramics can also produce force or deformation when an electrical charge is applied. The production of an electrical charge is useful in pressure or load sensing applications. The production of force or deformation is useful in microactuators, nanoactuators or piezoelectric motors.

Piezoelectric ceramics consist of ferroelectric materials and quartz. Ferroelectric materials include barium titanate, bismuth titanate, lead magnesium niobate, lead metaniobate, lead nickel niobate, lead zinc titanates (PZT), lead-lanthanum zirconate titanate (PLZT) and niobium-lead zirconate titanate (PNZT). Important parameters for piezoelectric ceramics include electromechanical coupling constant, distortion or charge constant, mechanical dielectric constant (relative permittivity), loss tangent, electrical resistivity, and Curie temperature.

Barium titanates and bismuth titanates are common types of piezoelectric ceramics Modified barium-titanate compositions combine high-voltage sensitivity with temperatures in the range of -10° C to 60° C. Barium titanate piezoelectric ceramics are useful for hydrophones and other receiving devices. These piezoelectric ceramics are also used in low-power projectors. Bismuth titanates are used in high temperature applications, such as pressure sensors and accelerometers.  Bismuth titanate belongs to the group of sillenite structure-based ceramics (Bi12MO20 where M=Si, Ge, Ti).

Lead magnesium niobates, lead metaniobate, and lead nickel niobate materials are used in some piezoelectric ceramics. Lead magnesium niobate exhibits an electrostrictive or relaxor behavior where strain varies non-linearly. These piezoelectric ceramics are used in hydrophones, actuators, receivers, projectors, sonar transducers, and in micro-positioning devices because they exhibit properties not usually present in other types of piezoelectric ceramics. Lead magnesium niobate also has negligible aging, a wide range of operating temperatures and a low dielectric constant. Like lead magnesium niobate, lead nickel niobate may exhibit electrostrictive or relaxor behaviors where strain varies non-linearly.

Piezoelectric ceramics include PZN, PLZT, and PNZT. PZN ceramic materials are zinc-modified, lead niobate compositions that exhibit electrostrictive or relaxor behavior when non-linear strain occurs. The relaxor piezoelectric ceramic materials exhibit a high-dielectric constant over a range of temperatures during the transition from the ferroelectric phase to the paraelectric phase. PLZT piezoelectric ceramics were developed for moderate power applications, but can also be used in ultrasonic applications. PLZT materials are formed by adding lanthanum ions to a PZT composition. PNZT ceramic materials are formed by adding niobium ions to a PZT composition. PNZT ceramic materials are applied in high-sensitivity applications such as hydrophones, sounders and loudspeakers.

Piezoelectric ceramics include quartz, which is available in mined-mineral form and man-made fused quartz forms. Fused quartz is a high-purity, crystalline form of silica used in specialized applications such as semiconductor wafer boats, furnace tubes, bell jars or quartzware, silicon melt crucibles, high-performance materials, and high-temperature products. Piezoelectric ceramics such as single-crystal quartz are also available.

Piezoelectric drivers and piezoelectric amplifiers are power sources that provide the high voltage levels needed to drive other piezoelectric devices such as actuators, motors, transducers, and sensors. They are also used for the open-loop and closed-loop control of complete piezoelectric systems. Most piezoelectric drivers and piezoelectric amplifiers are sold as single-channel benchtop instruments; however, multi-channel devices and original equipment manufacturer (OEM) designs are also available. Many devices exhibit bi-directional power flow capabilities in order to provide efficient operation with minimum power loss. Battery-powered and line-powered models are commonly available.

Selecting piezoelectric devices requires an analysis of inputs, outputs, mounting styles, and approvals. Input voltage is the voltage needed to drive or operate the device. Input impedance is the equivalent impedance at the device’s input terminals. Outputs include voltage range, root mean square (RMS) current, frequency range, capacitive load, and number of channels. Frequency range is the range of input voltage frequencies that piezoelectric drivers and piezoelectric amplifiers are designed to operate. Capacitive load is the maximum amount that devices can drive. Rack-mounted piezoelectric drivers and piezoelectric amplifiers may include rail guides, flanges, or tabs. Wall-mounted units often include screws, bolts, and rails. Desktop devices are also available. In terms of approvals, some devices meet requirements from the Federal Communications Commission (FCC), Underwriters Laboratories (UL), or the Canadian Standards Association (CSA). Others have the CE mark or approvals from TÜV Rheinland/Berlin-Brandenburg.

Piezoelectric drivers and piezoelectric amplifiers use several types of electrical connectors. Bayonet Neil-Concelman (BNC) connectors were designed for military applications, but are used widely in video and RF applications to 2 GHz. They have a slotted outer conductor and a plastic dielectric that causes increasing losses at higher frequencies. Both 50   and 75  BNC connectors are commonly available. American wire gauge (AWG) connectors include connection points that accept two wires. A U.S. standard for non-ferrous wire conductor sizes, AWG uses the term “gauge” to refer to a wire’s diameter. The higher the gauge number, the smaller the diameter and the thinner the wire. For example, AWG 26 connectors accommodate wires that are 15.9 mils in diameter while AWG 30 connectors accept wires that are 10.0 mils in diameter. Some piezoelectric drivers and piezoelectric amplifiers use LEMOÒ connectors, push-pull devices that lock in place for demanding applications. LEMO is a trademark of LEMO S.A. Typically, LEMO connectors are marked with the LEMO name and the first five characters of the part number, which represent the model, size, and series.

ELECTROMAGNETIC ENGINEERING. Expert has 20 years of experience in electromagnetic engineering and has acquired 10 patents in this area. He has designed or supervised the design of linear and rotary actuators, brushless DC motors, solenoid-related devices, VALVE ACTUATORs, sensors, and magnetic instruments using electromagnetic principles.

BRUSHLESS DC MOTOR DESIGN. As a former Chief Scientist of a major producer of brushless DC motors, Expert has expertise in these motors for disk drive, pump, medical, vehicle, and robotic applications.

COMPUTATIONAL ELECTROMAGNETICS; MAGNETICS. Expert has used finite element and finite difference analyses and other computational methods to solve for magnetic forces, fields, eddy currents, and more. He has also conducted seminars and taught college classes in these areas. He has written special programs for pulse effects versus time motion due to magnetic effects.

MAGNETIC DESIGN. Expert is familiar with permanent magnets, magnetizing methods, and magnetic equipment. He has designed magnetic devices and analyzed permanent magnetic fields. He has worked with magnetic lenses and focusing, magnetic clutches and brakes, magnetic clamps, separators, and instruments. He has studied permanent magnets for power generation, materials separation, position and velocity sensors, and direction detectors.

ACTUATOR DESIGN. Expert has 20 years of experience in the design of rotary and linear actuators. He has designed linear actuators for the Cray 1 supercomputer and a host of other actuators from very small (1/4-inch wide) to very large (6 ft. long stator, thousands of pounds of force).

VALVE ACTUATOR. Expert has worked on many designs of VALVE ACTUATORs for servo-valves, flow control, ultra-fast response, and minimum-energy activation.

AUTOMATIC CONTROL. He is experienced with control of machine tools, valves, disk drive head assemblies, motors, and actuators. He has studied stability, minimum access time, position, and acceleration as it relates to automatic control. He has industrial experience with control theory and active damping of vibration.

FATIGUE ANALYSIS. He is experienced with the failure of materials due to accumulated damage from stress and strain in shapes, structure, surfaces, plates and the effects of surface roughness, stress concentration, and stress history versus time as it is applied to machinery. He has taught this subject as a college professor.

PNEUMATIC CONVEYOR DESIGN. Expert has designed conveyors which move bulk materials through tubes by entrained air flow both vertically, horizontally, or in combination.

THERMAL ANALYSIS. With many years of experience in this area, Expert has studied heat flow and distribution in machines, structures, motors, and electronic devices. He understands thermally-induced stress and deformation, forced and natural convection, conduction, and radiation.

FLUID DYNAMICS. Expert is familiar with the flow of gasses and liquids and the associated drag and pressure changes due to flow.