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Se ti interessa guardare il nostro video in lingua italiana clicca questo link: • Find out more about our project: • Here are some products installed by our technicians: JAES is a company specialized in the maintenance of industrial plants with a customer support at 360 degrees, from the technical advice to maintenance, until final delivery of the industrial spare parts. Linkedin: Facebook: In this video we will explain the operation of the most famous types of Actuators for Hydraulic Valves and in the videos of this playlist you will see in detail each of their variants. The most common actuators are: the Manual, Electric, Pneumatic and Hydraulic ones. Let's see them in detail. Manual actuators use human energy as a source of energy, as they are controlled by an operator, who manually intervenes on the shutter through a lever or handwheel actuator. The Lever actuator is the simplest model; connected directly to the stem, it is usually used for fast-Rotary motion valves, where with a quarter-turn (90 °) it opens or closes the disc; it is therefore mainly used in ball, plug, and butterfly valves. The Handwheel actuator, on the other hand, can be connected to a threaded stem, or to a Gear train, these allow several turns of the handwheel to open and close the disc; for this reason it is usually used for linear motion valves, in situations where the flow rate must be adjusted, and where more clamping force is required; it is therefore mainly used in globe and gate valves. Moving on to Electric actuators, we enter that category which uses electricity as an energy source. The Electric actuator usually uses a reversible Electric motor, so that, by reversing the power supply, it can reverse its rotation and thus determine the direction of rotation of the shutter. It is almost always connected to a speed reducer which increases the torque. Limit switches are arranged to automatically stop the motor when the valve is fully open or closed. The control signal is always of the electrical type but with low energy. It is usually given by a PLC, which receives status signals from the actuator. Modern actuators can also include integrated PLCs. Sometimes a second handwheel type actuator is added to this system, so that the valve can be operated even in the event of a power failure. Among the actuators that use electricity as a source of energy, we also have the electromechanical solenoid actuator. The solenoid valve has a coil which, if energised by electric current, forms an electromagnetic field that attracts a plunger to itself, and consequently the disc connected to it. It exists the single solenoid valve, that is, with a solenoid and a spring, which can be: - normally open if it is opened by the pressure of the spring and closed by energizing the solenoid; - or normally closed if it is closed by the pressure of the spring and opened by energizing the solenoid. - Otherwise it exists in the double solenoid version, that is, equipped with two solenoids, each with its own power supply, in which the piston moves from one energized solenoid to the other. The next step is the pneumatic actuators, which are usually controlled by solenoid actuators. Pneumatic actuators as a source of energy use compressed air. In fact, through the air pressure, an actuator such as a piston or a diaphragm acts on the disc. - in the single-acting version there is direct action, that is when the air pressure closes the valve and the spring opens it; - and reverse action, when the air pressure opens the valve and the spring closes it. - Or there is the double-acting version in which there are two air inlets to open or close the valve. The pneumatic actuators allow, (by increasing the size of the piston or diaphragm) to increase the air inlet force; and are generally cheaper than other types of actuators even if they require a compressed air system. Similar to pneumatic actuators are the hydraulic actuators. They work on the same principle, but use a pressurized hydraulic fluid, usually oil, as an energy source. The hydraulic actuator usually uses a hydraulic cylinder which can be single acting (with a return spring) but also double acting, (with two fluid inlets on the sides of the cylinder) where a piston moves according to any difference in force between the two sides. Solenoid actuators are usually used for fluid control. Since liquids are nearly impossible to compress, a hydraulic actuator can perform great force.
