DA10 Hydraulic Pilot Unloading Valves

DA/DAW type 5X series Pilot Unloading Valve

Orifice (NG) 10-32 pressure to 21MPa flow to 450L/min
- For manifold block installation
- 4 control elements
      knob
      Adjusting screw with guard
      Locking knob with scale
      with scale knob
- 4 pressure ranges
- Solenoid Unloading Valve

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DA/DAW Pressure Control Valve is a pilot unloading valve.
They are used to charge accumulators, or to unload low pressure pumps in high/low pressure pump systems.

The composition of the unloading valve mainly includes a main valve (1) with a main valve core assembly (3) with a force adjustment 2) and a one-way valve (4). In size 10 valves, the Non-Return Valve (4.1) is in the main valve (1). In size 25 and 32 valves, the non-return valve (4.2) is in a separately mounted subplate below the main valve.

DA type unloading valve
The flow of the pump is switched from P to A to P to T.
The pump delivers oil to the hydraulic system (P-A) through the Check Valve (4). The pressure of oil port A enters the pilot control spool (6) through the control oil circuit (5). At the same time, the pressure of oil port P enters the loading side of the main spool (3) and the ball valve (9) in the pilot (2) through the orifice (7) and (8). The pressure of A reaches the pressure set by the Pilot Valve , the ball valve overcomes the elastic (10) and leaves its valve seat. The oil flows into the elastic chamber (11) through the orifice (7) and (8) at this time. The oil in the elastic chamber may be discharged through the control oil circuit (12) (in DA...5X/... valves), or externally to the mailbox via the control circuit (13) (in DA...5X/Y... valves). Due to the orifice (7) and (8), there is a drop in the upper and lower chambers of the main valve core (3), so that the main valve leaves its valve seat and opens the oil ports P to T. The check valve (4) closes the oil ports A to P at this time The ball valve (9) is now held open by the force passing through the pilot spool (6).

Pump flow switches from P to T to P to A.

The area of the pilot spool (6) is 10% (or optional 17%) larger than the effective area of the ball "9" on the seat. Therefore, the effective force acting on the pilot spool is 10% or 17% greater than the effective force acting on the ball valve.

The spring (10) pushes the ball valve (9) against the seat when the pressure drop of the actuator (system) is equal to the conversion ratio. At this time, the pressure acting on the spool (3) works together with (14) to close the main spool (3) and isolate P to T. The flow of the pump is again fed into the hydraulic system (P to A) via the check valve (4).

DAW type unloading valve
The function of this valve is basically the same as that of the DA type valve. Only the Solenoid Valve (15) is installed on the pilot valve, which can arbitrarily complete the conversion from P to A or P to T under the switching pressure set by the pilot valve.