Electro Hydraulic Valves When your hydraulic application requires a very accurate control of the flow, hydraulic valves may be equipped with advanced control electronics. This allows the use of inductive path measuring devices that monitor the position of the spool continuously to ensure optimum position of the spool.

Electro-pneumatic actionTheelectro-pneumatic actionis a control system forpipe organs, whereby airpressure, controlled by anelectric currentand operated by the keys of anorgan console, opens and closes valves within wind chests, allowing thepipesto speak.

This system also allows the console to be physically detached from the organ itself. The only connection was via an electrical cable from the console to the relay, with some early organ consoles utilizing a separate wind supply to operate combination pistons.

Hydraulic ValvesGet advice and suggestions from DTA in order to select the appropriate hydraulic valve, in terms of size and function, that suits your application and your budget. Contact DTA today!

A hydraulic valve properly directs the flow of a liquid medium, usually oil, through your hydraulic system. The direction of the oil flow is determined by the position of a spool. A hydraulic system can only function - as per requirements - by using valves. Thus, you should always look for the correct type of hydraulic valve to serve your intended purpose.

Hydraulic valves are available in a variety of sizes. The size required is determined by the maximum flow of the hydraulic system through the valve and the maximum pressure in the hydraulic system. Hydraulic valves are available with different mountings: e.G. Mounting in pipe lines, threaded connection as cartridges, subplate mounting, etc.

Different Types of Hydraulic ValvesHydraulic valves are sometimes referred to as hydraulic components. These are subdivided into three main categories: directional control valves, pressure control valves and flow control valves. We have added proportional and servo control hydraulic valves as a separate category below:

Directional control valvescheck valve;directional spool valvedirectional poppet valvePressure control valvescontrol task: variable throttle valveswitching task: fixed throttle valve

Flow control valvesthrottle valve: flow p dependentcontrol valve: flow p independent

Electro Hydraulic ValvesServo hydraulic valveProportional hydraulic valve

Different valves function in different ways. Check valves permit free flow in one direction and block flow in the opposite direction. The directional control valve is used to pass on the pressure medium (i.E. Flow) in an orderly fashion to a particular direction.Pressure control valves switch (or control) at a certain pressure; the switching pressure may be adjusted on the valve. Flow control valves regulate the flowthis is done by adjusting the size of the bores (orifices).

Electro Hydraulic ValvesWhen your hydraulic application requires a very accurate control of the flow, hydraulic valves may be equipped with advanced control electronics. This allows the use of inductive path measuring devices that monitor the position of the spool continuously to ensure optimum position of the spool.

Proportional hydraulic valves are able to control the opening to flow proportionally instead of gradually, as is the case for most standard hydraulic valves. The simplest type of proportional hydraulic valve is a variable throttle controlled by a manual lever, as illustrated below:

Proportional and servo hydraulic valves are usually classified as high-performance valves. This distinction gives an expected indication of performance, which tends to generalise the true differences between various types of servo and proportional hydraulic valves. Each type has its ownunique performance characteristics either in controlling pressure or controlling flow. Servo hydraulic valves use closed-loop control to monitor and feed back the main-stage spool position to a pilot stage (hydraulic/pneumatic) or driver (electronic). Proportional hydraulic valves, on the other hand, move the main-stage spool in direct proportion to an external piloted control signal and do not have any means of feedback within the valve.

Servo Hydraulic ValveThe main stage spool of a servo hydraulic valve is equipped with a path measuring system for accurate adjustment. This system measures the exact position of the main-stage spool and feeds its position directly to the electronic control unit. If sworn position is not consistent, the control signal corrects the position of the main-stage spool.Servo hydraulic valves are widely used in aerospace and industrial applications.

Proportional Hydraulic ValveThe most common proportional hydraulic valves are directional control valves, pressure relief valves, flow controllers and adjustable throttling. Proportional hydraulic valves convert an incoming mechanical or electrical signal directly proportional to a shear mode. The movement follows a continuously incoming signal. Different types of available proportional hydraulic valves are:

*Various directional control valves*Flow control valves*Pressure relief valves*Pressure reducing valves*Counter balance valves

MOTOR CONTROL VALVEMotor operated valve (MOV) is an important item of plant & piping system. These valves are generally of large size and are used for different applications such as pump discharge etc. Motor operated valves are often called as on-off valves as the motors serve the purpose of fully opening or fully closing valves in pipelines.For example, cooling water lines, process pipelines where controlling of fluid is not required, motor operated valves can be used to fully allow or fully stop the fluid flow. These valves are not used for throttling purposes as they serve mainly on-off service application.

Motor operated valves can be of various types e.G. Gate/ ball/ butterfly etc. With actuator control. Design of motors and valves can be different. An electric motor is mounted on the valve and geared to the valve stem so that when the motor operates the valve will open or close.For this MOV, motor operated with actuator control from local panel or, from control room is required. There is arequirement of co-ordination among piping-electrical-instrumentation-process engineers and vendor for design and procurement of such motor operated valves.

Applications of motor operated valveswhenever frequent operation is required.Valves located in remote, inaccessible or hazardous places.Motorised control valve / motor operated valves are usually for full open and full close applications. However there are places where they are used for position control as well.

Types of motor operated valvesmotorised control valve can be classified into three types. However it must be noted that the main application of motorised valves are for flow control and flow isolation.Open/close valves - used to automate manual open close valves examples include, pump discharge / suction valves, boiler feed water isolation valves, drum vent valves, product line valves etc.Inching valves - used were some degree of control. Example a gradual opening and closing is required, applications include, reflux lines, boiler start up vent, boiler IBD valves, boiler main steam valves etc.Precision flow valves - this is a precision inching valve, in inching valve the motor operates in steps configured in the controller, e.G. 5%, 10% opening steps. In precision flow valves, a continuous control is enabled by the use of proper feedback from the field to the controller which is not usually found in other motor operated valves. An example is steam injection valve / water injection valves used in GT for nox control.Key differences betwen control valves and motor operated on/off valvesControl valves have a faster response as compared to the motorised valves.Control valves usually have an analog control element, while the motorised operated valves have a digital control element.

Control valves can be used for any type of control, pressure control, flow control, temperature control etc while motorised valves are usually (if not always) used for flow control.Control valve usually are used in closed loop control, while motorised valves are predominantly open loop (with the exception of precision flow control valves)Control valves are used for precision control. However motorised valves are not usually used for precision control.

Programmable logic controller

Aprogrammable logic controller,PLC, orprogrammable controlleris adigital computerused forautomationof typically industrialelectromechanicalprocesses, such as control of machinery on factoryassembly lines,amusement rides, orlight fixtures. Plcs are used in many machines, in many industries.

Plcs are designed for multiple arrangements of digital and analog inputs and outputs, extended temperature ranges, immunity toelectrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up ornon-volatile memory. A PLC is an example of a "hard"real-timesystem since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was mainly composed ofrelays,cam timers,drum sequencers, and dedicated closed-loop controllers. Since these could number in the hundreds or even thousands, the process for updating such facilities for the yearly modelchange-overwas very time consuming and expensive, aselectriciansneeded to individually rewire the relays to change their operational characteristics.

Digital computers, being general-purpose programmable devices, were soon applied to control of industrial processes. Early computers required specialist programmers, and stringent operating environmental control for temperature, cleanliness, and power quality. Using a general-purpose computer for process control required protecting the computer from the plant floor conditions. An industrial control computer would have several attributes: it would tolerate the shop-floor environment, it would support discrete (bit-form) input and output in an easily extensible manner, it would not require years of training to use, and it would permit its operation to be monitored. The response time of any computer system must be fast enough to be useful for control; The required speed varying according to the nature of the process.[1]since many industrial processes have timescales easily addressed by millisecond response times, modern (fast, small, reliable) electronics greatly facilitate building reliable controllers, especially because performance can be traded off for reliability.

Early plcs, up to the mid-1990s, were programmed using proprietary programming panels or special-purpose programmingterminals, which often had dedicated function keys representing the various logical elements of PLC programs.[2]Some proprietary programming terminals displayed the elements of PLC programs as graphic symbols, but plainasciicharacter representations of contacts, coils, and wires were common. Programs were stored oncassette tape cartridges. Facilities for printing and documentation were minimal due to lack of memory capacity. The very oldest plcs used non-volatilemagnetic core memory.

More recently, plcs are programmed using application software on personal computers, which now represent the logic in graphic form instead of character symbols. The computer is connected to the PLC throughethernet,RS-232,RS-485, orRS-422cabling. The programming software allows entry and editing of the ladder-style logic.Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC through aprogramming boardwhich writes the program into a removable chip such as anEPROM

Programmable logic relay (PLR)In more recent years, small products called plrs (programmable logic relays), and also by similar names, have become more common and accepted. These are much like plcs, and are used in light industry where only a few points ofI/O(i.E. A few signals coming in from the real world and a few going out) are needed, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger plcs to fill out their low end product range. Popular names include PICO controller, NANO PLC, and other names implying very small controllers. Most of these have 8 to 12 discrete inputs, 4 to 8 discrete outputs, and up to 2 analog inputs.Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage-stamp-sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular plcs that are usually modular and greatly expandable, the plrs are usually not modular or expandable, but their price can be twoorders of magnitudeless than a PLC, and they still offer robust design and deterministic execution of the logics

Programmable logic controller (PLC) also known as industrial computer is the major component in the industrial automation sector. Due to its robust construction, exceptional functional features likePID controllers, sequential control, timers and counters, ease of programming, reliable controlling capabilities and ease of hardware usageThis PLC is more than a special-purpose digital computer in industries as well as in other control-system areas. Different types of plcs from vast number of manufacturers are available in todays market. Therefore, in the subsequent paragraphs, let us study about plcs and their types.

PLC is invented to replace traditional control panels whose operations depend on the electromagnetic logic relays that are based on timers inindustrial control systems.

Plcs are capable of monitoring the inputs continuously from sensors and producing the output decisions to operate the actuators based on the program. Every PLC system needs at least these three modules:

oCPU ModuleoPower Supply ModuleoOne or more I/O Module

Pneumatic actuatorApneumaticactuatorconverts energy (typically in the form ofcompressed air) into mechanical motion. The motion can be rotary or linear, depending on the type of actuator. Some types of pneumatic actuators include:

Tie rod cylindersrotary actuatorsgrippersrodless actuators with magnetic linkage or rotary cylindersrodless actuators with mechanical linkagepneumatic artificial musclesspeciality actuators that combine rotary and linear motionfrequently used for clamping operationsvacuum generatorsA pneumatic actuator mainly consists of a piston, a cylinder, and valves or ports. The piston is covered by adiaphragm, or seal, which keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm downward, moving the piston underneath, Which in turn moves thevalve stem, which is linked to the internal parts of theactuator. Pneumatic actuators may only have one spot for a signal input, top or bottom, depending on action required. Valves require little pressure to operate and usually double ortriplethe input force. The larger the size of the piston, the larger the output pressure can be. Having a larger piston can also be good if air supply is low, allowing the same forces with less input. These pressures are large enough to crush objects in the pipe. On 100 kpa input, you could lift a small car(Upwards of 1,000lbs) easily, and this is only a basic, small pneumatic valve. However, the resulting forces required of the stem would be too great and cause thevalve stemto fail.

This pressure is transferred to the valve stem, which is hooked up to either the valve plug (seeplug valve),butterfly valveetc. Larger forces are required in high pressure or high flow pipelines to allow the valve to overcome these forces, and allow it to move the valves moving parts to control the material flowing inside.

Valves input pressure is the "control signal." This can come from a variety of measuring devices, and each different pressure is a different set point for a valve. A typical standard signal is 20100 kpa. For example, a valve could be controlling the pressure in a vessel which has a constant out-flow, and a varied in-flow (varied by the actuator and valve). A pressure transmitter will monitor the pressure in the vessel and transmit a signal from 20100 kpa. 20 kpa means there is no pressure, 100 kpa means there is full range pressure (can be varied by the transmiters calibration points). As the pressure rises in the vessel, the output of the transmitter rises, this increase in pressure is sent to the valve, which causes the valve to stroke downward,And start closing the valve, decreasing flow into the vessel, reducing the pressure in the vessel as excess pressure is evacuated through the out flow. This is called a direct acting process.

Electro-hydraulic actuatorElectro-hydrostatic actuators(ehas), replacehydraulic systemswithself-contained actuators operated solely by electrical power. Ehas eliminate the need for separatehydraulic pumpsand tubing, simplifying system architectures and

Improving safety and reliability. This technology originally was developed for the aerospace industry but has since expanded into many other industries where hydraulic power is commonly used.Aircraft were originally controlled by small aerodynamic surfaces operated by cables, attached to levers that magnified the pilot'smechanical advantage. As aircraft grew in size and performance, the aerodynamic forces on these surfaces grew to the point where it was no longer possible for the pilot to manually control them across a wide range of speedsAircraft were originally controlled by small aerodynamic surfaces operated by cables, attached to levers that magnified the pilot'smechanical advantage. As aircraft grew in size and performance, the aerodynamic forces on these surfaces grew to the point where it was no longer possible for the pilot to manually control them across a wide range of speedsStarting in the 1940s, hydraulics were introduced to address these problems. In their early incarnations, hydraulic pumps attached to the engines would feed high-pressure oil through tubes to the various control surfaces. Here, small valves were attached to the original control cables, Controlling the flow of oil into an associated actuator connected to the control surface. One of the earliest fittings of a hydraulic boost system was toaileronson late-war models of the P-38L, removing the need for great human strength in order to achieve a higher rate of roll.[1]

Over time the systems evolved to replace the mechanical linkages to the valves with electrical controls, producing the "fly-by-wire" design,[2]and more recently, optical networking systems in what is known as "fly-by-light". All of these systems require three separate components, the hydraulic supply system,The valves and associated control network, and the actuators. Since any one of these systems could fail and render the aircraft inoperable, redundancies are needed that greatly increase the complexity of the system. Additionally, keeping the hydraulic oil pressurized is a constant power drain.