Directly Operated Proportional Pressure Relief Valve
The proportional pressure relief valve is designed as a poppet valve It basically consists of the housing (1), proportional solenoid (2) with inductive positional transducer (3), valve seat (4), valve poppet (5) as well as compression spring (6)
The proportional solenoid is a position controlled solenoid. In this case, it replaces to a certain extent the manual setting by means of the adjusting spindle.
A signal provided via the amplifier results in a stroke at the solenoid proportional to the signal. This preloads the compression spring (6) via the spring plate (7) and presses the poppet against the seat. The position of the thrust pad (i.e. solenoid armature) and therefore indirectly the pressure setting is recorded by the inductive positional transducer and monitored by the electronic control system in a closed loop position control Any control deviations from the signal are corrected by the closed loop control system. Solenoid friction is thus compensated resulting in a high precision, repeatable pretensioning force of the spring: hysteresis 1 % referred to max. setting pressure, repetition accuracy 0.5 % referred to max setting pressure.
The max setting pressure depends on the pressure rating (25 bar, 1S0 bar, 315 bar). The various pressure ratings are achieved by different valve seats, i.e. with different seat diameters Since the solenoid force remains constant, the highest pressure rating has the smallest diameter.
By way of example for the pressure rating 25 bar (Dtag 12), it can be seen from the characteristic curves that the maximum setting pressure also depends on flow.
At command signal 0 – power failure to the proportional solenoid or cable breakage at positional transducer – the lowest setting pressure is assumed. (Dependent on the pressure rating and flow).
The spring (8) must also be mentioned in this connection It ensures, at signal 0. that the moving parts, such as armature, are shifted back in order to always achieve the minimum value p^. It also serves the purpose of compensating the weight of the armature when the valve is installed vertically
Categories: Hydraulic Servo | Tags: Pressure Relief Valve, Proportional Pressure | Leave a comment