Electrically Actuated Directional Control Valves PDF

ME ELECTIVE 1 (ELECTROPNEUMATIC) ENGR. PETER CLYDE B. LAMADRID MECHANICAL ENGINEERING DEPARTMENT 1ST SEM. A.Y. 2024 - 2025  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES SOLENOIDS An electrically actuated directional control valves fo...

ME ELECTIVE 1 (ELECTROPNEUMATIC) ENGR. PETER CLYDE B. LAMADRID MECHANICAL ENGINEERING DEPARTMENT 1ST SEM. A.Y. 2024 - 2025  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES SOLENOIDS An electrically actuated directional control valves form the interface between the two parts of an electro- pneumatic control. The most important tasks of electrically actuated Direct Control Valve (DCVs) include. ❑ Switching supply air on or off ❑ Extension and retraction of cylinder drives  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES SOLENOIDS Fig. 4.1 a) shows an electrically actuated valve that controls the motion of a single-acting cylinder. It has Actuation of a Single-acting Cylinder three ports and two switching positions: ❑ If no current is applied to the solenoid coil of the directional control valve, the cylinder chamber above the directional control valve is vented. The piston rod is retracted. ❑ If current is applied to the solenoid coil, the directional control valve switches and the chamber is pressurized. The piston rod extends. ❑ When the current is interrupted, the valve switches back. The cylinder chamber is vented and the piston rod retracts.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES The double-acting cylinder drive in Fig. 4.1b) is SOLENOIDS actuated by a directional control valve with five ports Actuation of a Double-acting Cylinder and two switching positions. ❑ If no current is applied to the solenoid coil, the left cylinder chamber is vented, the right chamber pressurized. The piston rod is retracted. ❑ If current is applied to the solenoid coil, the directional control valve switches. The left chamber is pressurized, the right chamber vented. The piston rod extends. ❑ When the current is interrupted, the valve switches back and the piston rod retracts.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES COMPARISON Actuation of a single-acting cylinder Actuation of a double-acting cylinder  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Initial position Solenoid In the initial position, all solenoids of an electrically actuated directional control valve are de-energized and the solenoids Electrically actuated DCVs are switched are inactive. A double solenoid valve has no clear initial with the aid of solenoids. They can be position, as it does not have a return spring. divided into two groups: i) Spring return valves only remain in the Port designation actuated position as long as current flows Directional control valves are also differentiated by the through the solenoid number of ports and the number of switching positions. The ii) Double solenoid valves retain the last valve designation results from the number of ports and switched position even when no current positions, for example: flows through the solenoid. ❑ Spring-return 3/2-way valve ❑ 5/2-way double solenoid valve  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid The following section explains the construction and mode of operation of the major types of valve. Directly controlled 3/2-way valve (Normally Closed)  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid The following section explains the construction and mode of operation of the major types of valve. Directly controlled 3/2-way valve (Normally Open)  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES COMPARISON Directly controlled 3/2-way valve (Normally Closed) Directly controlled 3/2-way valve (Normally Open)  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid Pilot Controlled Directional Control Valve In pilot controlled directional control valves, the valve piston is indirectly actuated. ❑ The armature of a solenoid opens or closes an air duct from port 1. ❑ If the armature is open, compressed air from port 1 actuates the valve piston.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid Pilot controlled 3/2-way solenoid valve (normally closed, with manual override)  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid Pilot controlled 5/2-way solenoid valve  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Construction and mode of operation of Solenoid  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES RELAYS Relays in Electro-Pneumatics are essential components that act as electrically operated switches to control pneumatic systems. They play a crucial role in enabling the interaction between the electrical and pneumatic components of a system. Here are some Functions of Relays in Electro-Pneumatics: ✓ Signal Switching - Relays allow low-power electrical control signals to actuate or switch higher-power pneumatic components like solenoid valves. ✓ Logic Implementation - Relays are used to create control logic for sequences, interlocks, or conditional operations in a pneumatic system. ✓ Isolation -They electrically isolate the control circuit from the power circuit, protecting sensitive components from voltage spikes or surges.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES RELAYS Relays in Electro-Pneumatics are essential components that act as electrically operated switches to control pneumatic systems. They play a crucial role in enabling the interaction between the electrical and pneumatic components of a system. Here are some Functions of Relays in Electro-Pneumatics: ✓ Multiplexing - A single control input can trigger multiple output devices using relays. ✓ Safety Features - Relays can be configured to include safety features, such as emergency stops or overload protection.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES RELAYS Types of Relays in Electro-Pneumatics: Electromechanical Relays (EMRs): Time-Delay Relays: ❑ These use physical moving parts ❑ Provide delayed activation or (electromagnetic coils and contacts). deactivation of pneumatic ❑ Commonly used in traditional setups. components. ❑ Useful in timing sequences or Solid-State Relays (SSRs): staggered operations. ❑ No moving parts; use semiconductor switching. Reed Relays: ❑ Use magnetic fields to switch and are ❑ Faster, quieter, and more durable but more compact. expensive. ❑ Ideal for smaller pneumatic systems.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES TEMPERATURE SWITCH A temperature switch is a device used to monitor temperature and activate or deactivate an electrical circuit when a specific temperature threshold is reached. It is commonly used for temperature regulation, safety, and automation in various industrial and domestic applications. How Temperature Switches Work: ✓ Sensing Element - Contains a material (e.g., bimetallic strip, thermistor, or thermocouple) that reacts to changes in temperature. ✓ Set Point Adjustment - A user-defined temperature threshold determines when the switch will activate or deactivate. ✓ Switching Mechanism - When the sensing element detects the target temperature, it mechanically or electronically triggers a switch to open or close the electrical circuit.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES TEMPERATURE SWITCH Types of Temperature Switches: Electronic Temperature Switches: Bimetallic Temperature Switches: ❑ Use sensors like RTDs (Resistance ❑ Use two bonded metals with different Temperature Detectors) or thermocouples to expansion rates that bend with temperature measure temperature electronically and changes, activating the switch. trigger a relay or solid-state switch. ❑ Common in thermostats and heaters. ❑ Used in advanced industrial systems. Gas-Actuated or Liquid-Filled Switches: Thermistor-Based Switches: ❑ Use the expansion of gas or liquid in a sealed ❑ Use temperature-sensitive resistors bulb and capillary tube to actuate the switch. (thermistors) to detect changes in temperature. ❑ Suitable for high-temperature applications. Snap-Action Switches: ❑ Typically used in precision applications. ❑ Provide rapid on-off action and are ideal for applications requiring a quick response.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES TEMPERATURE SWITCH Applications of Temperature Switches: ✓ Industrial Automation: Controlling heating elements, fans, or cooling systems in manufacturing processes. ✓ HVAC Systems: Maintaining desired temperatures in heating, ventilation, and air conditioning systems. ✓ Safety Systems: Preventing overheating in motors, engines, or machinery by shutting them down or activating alarms. ✓ Household Appliances: Found in ovens, refrigerators, and water heaters to regulate and maintain temperatures. ✓ Pneumatics and Hydraulics: Monitoring fluid or air temperatures to prevent overheating or freezing.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Reed Proximity Switches Are electromagnetic switches that operate based on the proximity of a magnetic field. Reed switches are similar to relays, ✓Normally Open (NO) or Normally except a permanent magnet is used instead of a wire coil. They are Closed (NC): simple, reliable, and widely used in various applications for position The switch can be configured as: sensing, limit detection, and automation. o Normally Open (NO): The circuit Key Features of Reed Proximity Switches: closes when a magnet is nearby. o Normally Closed (NC): The ✓ Reed Element: Inside the switch are two thin, flexible metal circuit opens when a magnet is reeds (contacts) sealed in a glass tube filled with inert gas or nearby. vacuum to prevent corrosion. ✓Non-Contact Sensing: Unlike ✓ Magnetic Activation: When a magnet approaches the switch, mechanical switches, reed proximity the magnetic field pulls the reeds together (or apart, depending switches don’t require physical contact, on the design), closing or opening the circuit. making them less prone to wear and tear.  ELECTRICALLY ACTUATED DIRECTIONAL CONTROL VALVES Reed Proximity Switches Applications: ✓ Industrial Automation: Used for detecting the position of moving parts, like actuators or conveyor belts. ✓ Security Systems: Commonly used in doors and windows for burglar alarms. ✓ Pneumatics: Detect the position of cylinders in pneumatic systems. ✓ Consumer Electronics: Found in devices like laptops to detect when the lid is closed. ✓ Automotive: Used in gear position sensors, fluid level indicators, and seatbelt detection systems.