Hydraulic valves are components that control the direction, pressure, or flow of hydraulic fluid.

Common plate-type pressure control valves include remote control overflow valves, direct-acting overflow valves, pilot-operated overflow valves, low-noise overflow valves, high-pressure overflow valves, solenoid-controlled overflow valves (including low-noise types), H-type pressure valves (low-pressure overflow valves, sequence valves, or unloading valves), HC-type pressure control valves (balance valves or unidirectional sequence valves), seat valve type pressure control valves (unidirectional sequence valves or balance valves), pressure reducing valves, unidirectional pressure reducing valves, balance valves (pressure reducing overflow valves), brake valves, unloading overflow valves, pressure relays, etc.; common plate-type flow control valves include throttle valves, unidirectional throttle valves, speed control valves, unidirectional speed control valves, pilot-operated speed control valves, pilot-operated unidirectional speed control valves, speed reducers and unidirectional speed reducers (threaded and base-mounted), feed control valves, etc.; common plate-type directional control valves include solenoid directional control valves, (low-power type, with electronic switches, pressure-resistant and explosion-proof type) solenoid directional control valves, electro-hydraulic directional control valves, variable buffer type electro-hydraulic directional control valves, hydraulic directional control valves, manual directional control valves, rotary type directional control valves (threaded and base-mounted), cam-operated directional control valves, seat type solenoid directional control valves, seat type electro-hydraulic directional control valves, seat type two-way solenoid valves, seat type two-way solenoid directional control valves, right-angle check valves, hydraulic check valves, etc.

Hydraulic valves can be classified by function into: pressure control valves; flow control valves; directional control valves.

Hydraulic valves can be classified by connection method into: threaded connection control valves; plate connection control valves; flange connection control valves; plug valves; stacked connection control valves.

The design of the hydraulic system and the function of the hydraulic valve determine the valve type selection.

① Selection of pressure control valves The oil ports of hydraulic pressure control valves use the following codes:

A, B - working oil ports; L - drain port;

P - pressure oil port; X - control oil port.

T - return oil port;

The basic parameter names of pressure control valves are shown in Table 1-4.

 

② Selection of flow control valves The oil ports of hydraulic flow control valves use the following codes:

P1 - pressure oil inlet; L - drain port.

-- pressure oil outlet;

The basic parameter names of flow control valves are shown in Table 1-5.

 

③ Selection of directional control valves The oil ports of hydraulic directional control valves use the following codes:

A, B - working oil ports; L - drain port;

P - pressure oil port; X - control oil port.

T - return oil port;

The basic parameter names of directional control valves are shown in Table 1-6.

The oil port markings are not unified in various standards. Table 1-7 is excerpted from GB／T 17490-1998 "Identification of oil ports, base plates, control devices and solenoids of hydraulic control valves", Table 1, for reader reference.

Author's Note: 1. The basic parameters of solenoid directional control valves are limited to 6-way and 10-way hydraulic solenoid directional control valves.

2. Hydraulic check valves also have performance requirements such as minimum reverse opening pressure and maximum reverse closing pressure.

3. The load sensing performance requirements of multi-way directional control valves are also valuable for reference in the design of hydraulic systems using other valves.

Note: This table does not apply to GB8100, GB8098 and GB8101 standardized components.

In addition, GB／T 17490-1998 has regulations on solenoid identification: "The main or pilot stage solenoids should be identified consistently with the pressurized oil ports that are actuated by them."