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Working principle and troubleshooting of excavator solenoid valve

2022-05-27

Solenoid valve classification

Looking back at the development history of solenoid valves, so far, solenoid valves at home and abroad are divided into three categories in principle (ie: direct-acting type, step-by-step pilot type), and the difference in valve structure and material is related to the difference in valve structure and material. The difference in principle is divided into six sub-categories (direct-acting diaphragm structure, step-by-step heavy-plate structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure).

Direct acting solenoid valve:

Principle: When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, the spring presses the closing member on the valve seat, and the valve closes.

Features: It can work normally in vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.

Distributed direct acting solenoid valve:

Principle: It is a combination of direct-acting and pilot-type. When there is no pressure difference between the inlet and the outlet, after the power is turned on, the electromagnetic force directly lifts the pilot valve and the main valve closing piece upward in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, the electromagnetic force pilots the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, so that the main valve is pushed up by the pressure difference; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing member, moving downward, causing the valve to close.

Features: It can also act safely under zero pressure difference or vacuum and high pressure, but the power is large and it must be installed horizontally.

Pilot operated solenoid valve:

Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between the upper and lower sides is formed around the closing member, and the fluid pressure pushes the closing member to move upward, and the valve opens; When the hole is closed, the inlet pressure passes through the bypass hole to quickly form a pressure difference between the lower and upper parts around the valve closing member, and the fluid pressure pushes the closing member to move down to close the valve.