Meter-out and Meter-in

Will present  meter out and meter in circuit

Meter out circuit

Meter out is a flow control method use with an application of 2 way flow control valves.

This type of control is apply to a hydraulic system with negative or pulling working loads. This system tend to cause the cylinder piston 2 to move more quickly than the speed which corresponds to the delivery flow of the pump 4. The flow control valve 1 is position between actuator and reservoir.

Therefore this control method is use to adjust the speed of the hydraulic cylinder piston rod when retract.

meter out control in meter in meter out circuit post
Fig. 1 Speed control using meter out control

A major disadvantage of this method is that pressure relief valve 3 needs to be set to the maximum actuator pressure. Apart from heat creation the rod side pressure can be very high particularly the case when cylinder has no load.

Meter in circuit

Meter in is a flow control method use with an application of 2 and also to a 3 -way flow control valves.

meter in control in meter in meter out circuit post
Fig. 2 Speed control using meter in control

This control method is use to adjust the speed of the hydraulic cylinder piston rod when extend.

The flow control valve is place in the pressure line between hydraulic pump and the actuator fig.2.

This method is used for hydraulic systems where the actuator acts against a positive resistance to the controlled flow. This could be load that is lifted or pushed. 

An advantage of this circuit is that the pressure between the flow control  valve 1 and cylinder 2 is present only when the cylinder is under load. The piston seal of the hydraulic cylinder wears out harder as there is less pressure, also lower friction from sealing ring in the cylinder.  

A disadvantage is position of the relief valve 3 is upstream of the flow control valve and it is regulate to the highest actuator pressure. Due to this the hydraulic pump 4 delivers the maximum set pressure even when the actuator only requires a low force.

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