Solenoid Valve Working Principle and Application Areas
Types of Solenoid Valves: Distributed direct-acting solenoid valves, pilot-operated solenoid valves, etc.
Distributed Direct-Acting Solenoid Valve
Principle: It combines direct-acting and pilot-operated principles. When there is no pressure difference between the inlet and outlet, upon energization, the electromagnetic force directly lifts the pilot valve and the main valve closing element sequentially upwards, opening the valve. When the inlet and outlet reach the starting pressure difference, upon energization, the electromagnetic force actuates the pilot valve, causing the pressure in the lower chamber of the main valve to rise and the pressure in the upper chamber to fall, thus using the pressure difference to push the main valve upwards. When de-energized, the pilot valve uses spring force or medium pressure to push the closing element downwards, closing the valve. Features: Reliable operation even at zero pressure difference or vacuum/high pressure, but requires higher power and must be installed horizontally.
Direct-acting solenoid valve
Principle: When energized, the solenoid coil generates electromagnetic force to lift the closing element from the valve seat, opening the valve; when de-energized, the electromagnetic force disappears, and the spring presses the closing element back onto the valve seat, closing the valve. Features: Can operate normally under vacuum or zero pressure, but the nominal diameter is generally no more than 25mm.
Pilot-operated solenoid valve
Principle: When energized, the electromagnetic force opens the pilot orifice, causing the pressure in the upper chamber to drop rapidly, creating a pressure differential around the closing element (higher at the bottom and lower at the top). The fluid pressure pushes the closing element upward, opening the valve; when de-energized, the spring force closes the pilot orifice, and the inlet pressure quickly passes through the bypass orifice, creating a pressure differential around the closing element (lower at the bottom and higher at the top). The fluid pressure pushes the closing element downward, closing the valve. Features: Higher upper limit of fluid pressure range; can be installed arbitrarily (customization required), but must meet fluid pressure differential conditions.
Solenoid valves are classified into three main categories based on their operating principle (i.e., direct-acting, step-by-step, and pilot-operated). Based on differences in valve disc structure and materials, as well as differences in operating principle, they are further divided into six subcategories, such as: direct-acting diaphragm structure, step-by-step diaphragm structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, and pilot piston structure.
