Glossary of Solenoid Valve Terminology

Apr 30th 2024

Glossary of Solenoid Valve Terminology

Solenoid valves are critical components in fluid control systems, widely used across various industries for their efficiency and reliability. This glossary aims to provide clear definitions of common solenoid valve terms to enhance understanding for professionals, students, and enthusiasts alike.

Let’s start with the obvious:

  • Solenoid Valves (SV): Electromechanically operated valves that control the flow of liquids or gasses by using a solenoid coil which is energized to open or close the valve.

Valve Structure & Components

3D CAD diagram of a 1/4'' 3-Way 110V AC Electric Solenoid Valve

  • Valve Body: The main housing or casing that contains the internal valve components.
  • Inlet Port: The opening where the fluid or gas enters the valve.
  • Outlet Port: The opening where the fluid or gas exits the valve after passing through the flow path.
  • Exhaust Port: Found only on 3-way solenoid valves; an additional port allows for the release of pressure or redirection of flow.
  • Plunger/Piston: The moving part within the valve that opens and closes the valve by lifting or lowering to and from the orifice, allowing or blocking the flow of media.
  • Orifice: The opening inside the valve that controls the flow rate and volume of media passing through the valve.
  • Seals: Internal components typically made of rubber or other flexible materials that prevent leakage around the plunger or between valve components.
  • Seat: The area within the valve body where the seal rests to create a tight closure.
  • Solenoid Coil: Coiled brass wire that generates a magnetic force when energized, moving the plunger to open or close the valve.
  • Internal Components: All parts within the valve body and any mechanisms involved in the actuation process.

Valve Types and Configurations

  • Direct Acting: A basic solenoid valve design where the solenoid coil directly moves the plunger or piston to open or close the valve without the need for fluid pressure.
  • Indirect Acting (Pilot-Operated): A valve design that utilizes fluid pressure (often from the same media) to assist in opening or closing the valve, with the solenoid coil acting as a pilot to control the fluid pressure.
  • 2-Way Solenoid Valve: The simplest SV configuration with two ports: an inlet and an outlet. This allows the media to flow through or be blocked completely.
  • 3-Way Solenoid Valve: A valve configuration with three ports - an inlet, outlet, and exhaust or diverting port. This allows the media to be directed to different paths for more complex flow control, such as diverting or mixing fluids.
  • 4-Way Solenoid Valve: A valve configuration with four ports - an inlet, outlet, exhaust, and a pressure port. This allows for more complex flow control, such as directing media to multiple paths or actuating other components.
  • Valve Position: The state of the valve, either open or closed, determined by the position of the plunger/piston relative to the orifice and seat
    • Normally Open (NO): A valve configuration where the valve remains open and allows flow when the solenoid coil is de-energized or not powered.
    • Normally Closed (NC): A valve configuration where the valve remains closed and blocks flow when the solenoid coil is de-energized or not powered.
  • Push-to-Connect Solenoid Valve: A valve with a type of quick-connect fitting used for attaching tubing or piping to the valve ports. Allows for easy installation and removal without the need for threaded connections or tools

Valve Materials and Compatibility

  • Valve Body Materials: Solenoid valve bodies can be constructed from various materials, each with different properties and suitability for specific applications.
  • Seal Materials: The seals or gaskets in the valve can be made from different elastomeric materials each with varying chemical compatibility and temperature resistance. Commonly used seal materials include:
    • NBR (Nitrile): A common choice with good general compatibility.
    • EPDM: Offers good compatibility in various applications
    • Viton (fluoroelastomer): Excellent chemical and temperature resistance
    • PTFE (Teflon): Superior chemical resistance and low friction.
  • Wetted Materials: All the valve components that come into direct contact with the media flowing through the valve, including the valve body, seals, plunger/piston, and other internal parts.
  • Material/Chemical Compatibility: The ability of a valve's wetted materials to withstand exposure to various media (liquids, gasses, chemicals) without degrading, corroding, or causing contamination.
  • NSF/ANSI 61: Valves or components with this certification meet strict safety standards that ensure the valve materials are safe for use with potable water (drinking water) and do not leach harmful contaminants above acceptable levels.

Operational Terms

  • Voltage: The type of electrical current the solenoid coil requires; alternating current (AC) or direct current (DC) voltage, with common voltages ranging from 12V DC to 24V DC or 120V AC.
  • Pressure Ratings: Critical specifications that indicate the maximum working pressure and pressure differential the valve can withstand during operation.
  • Flow Coefficient (Cv/Kv): measure of how much flow the valve allows at a given pressure drop – essential for sizing a valve correctly. Cv is measured in Imperial units (US Gallons per minute) whereas Kv is measured in metric units (cubic meters per hour).
  • Duty Cycle: The frequency that a given valve can be energized and de-energized, or opened and closed. A solenoid valve duty cycle is expressed as a percentage of the ON TIME (valve energized) to the total Cycle Time (ON TIME + OFF TIME).
  • Enclosure Rating (NEMA/IP): A standardized rating system that indicates the level of protection the valve’s internal components have against dust, water, and other environmental factors.
  • Response Time: The amount of time it takes for the valve to react and fully open or close after being energized or de-energized.
  • Water Hammer: A pressure surge or shock wave that can occur in piping systems when the flow of media is suddenly stopped or changed direction, potentially causing damage to the system and valves.
  • Actuating: The process of activating the valve, which in solenoid valves by energizing or de-energizing the solenoid coil, which moves the plunger/piston to control the flow path.
  • Flow Path: The route that the media takes through the valve body, passing through the inlet port, orifice, and out the outlet port when the valve is open.
  • Coil Resistance: The electrical resistance of the solenoid coil, which affects its power consumption, heat generation, and performance. Proper coil resistance is crucial for efficient operation. Usually measured in ohms.
  • IP65 Rated Solenoid Coil: An ingress protection (IP) rating that indicates the solenoid coil is dust-tight and protected against low-pressure water jets from any direction, making it suitable for outdoor or harsh environments.
  • Flow Rate: The volume of fluid or gas passing through the valve per unit of time, typically measured in gallons per minute (GPM) or liters per minute (LPM).
  • Hysteresis: A slight delay or lag in the valve's response time due to factors like friction, and magnetic forces.

Specialized Valve Types

  • Steam Solenoid Valve: A valve specifically engineered to handle the high temperatures and unique properties of steam, often constructed from heat-resistant materials like stainless steel.
  • Zero Differential Solenoid Valve: A type of solenoid valve capable of operating with minimal or zero pressure differential between the inlet and outlet ports.
  • Low-Pressure Gas Solenoid Valve: A valve designed to handle low-pressure gas applications, such as natural gas or propane systems, with appropriate materials and pressure ratings.
  • Check Valve: A valve that allows media to flow in only one direction, preventing backflow or reverse flow in piping systems. Often installed to protect solenoid valves from backflow.
    • Spring (Vertical) Check Valve: A type of check valve that uses a spring-loaded disc or piston to control flow direction, often oriented vertically to prevent backflow from gravity.
    • Swing Check Valve: A type of check valve that uses a hinged disc or plate to allow flow in one direction and prevent backflow in the opposite direction.
  • Y-Strainer: A filtering device installed in piping systems to remove debris, particulates, or contaminants from the flowing media, preventing clogging and protecting downstream components like valves from damage.

Solenoid Coil Parameters

  • Resistance (Ohms): Determines how much current the coil will draw at a given voltage and influences the heat generated during operation. The ratio of the applied DC voltage to the DC current at room temperature.
  • Impedance (Ohms): The total opposition to current flow in an AC circuit, combining resistance and reactance. The ratio of the applied AC voltage to the AC current for an AC coil.
  • Inductance (Henrys): The property of a coil that causes it to resist changes in electrical current. This characteristic affects the response time and operation of the valve.
  • Reactance (Ohms): The opposition to AC current caused by inductance, capacitance, frequency, and the magnetic properties of the solenoid valve actuator.
  • Turns Count: The number of times the wire is wrapped around the solenoid coil core. This affects the inductance, resistance, and magnetic field strength of the solenoid.

Additional Important Terms

  • Actuator: A broader term referring to the mechanism or component used to open and close a valve (in solenoid valves, the solenoid is the actuator).
  • Manifold: An assembly or mounting block designed that can house multiple valves in a compact and organized manner, simplifying complex fluid control systems.
  • Media: The substance or material, whether liquid or gaseous, that flows through the valve and piping system.
  • NPT Threading: An abbreviation for National Pipe Thread Taper; U.S. standard for tapered threads used to seal pipe fittings.
  • Burst Pressure/Proof Pressure: The maximum pressure limits the valve body or components can withstand before failure or permanent deformation, with burst pressure being the absolute maximum and proof pressure being the maximum recommended for safe operation.