flow control circuits
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Flow Control Circuits: Meter-In, Meter-Out, and Bleed-Off, Lecture notes of Hydraulics
The three types of flow control circuits - meter-in, meter-out, and bleed-off. It explains their applications, advantages, and differences using figures and examples. Meter-in circuits are used for controlled entry of fluid into the actuator, while meter-out circuits restrict fluid leaving the cylinder to retard its movement. Bleed-off circuits bypass fluid to the reservoir. Each type has its unique use cases in air and hydraulic systems.
Typology: Lecture notes
2019/2020
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flow control circuits
flow control circuits
- (^) There are three types of flow control circuits from which to choose. They are:
1. meter-in
2.meter-out
3.bleed-off (or bypass).
- (^) Figure 1-1 shows a meter-in flow- control circuit for a cylinder. Notice that a bypass check valve forces fluid through an adjustable orifice just before it enters the actuator. Figure 1-2 shows an extending hydraulic cylinder and indicates the pressures and flows in various parts of the circuit.
- Figure 1-
- Figure 1-
- (^) Meter-in control is used for opposing loads only. • It can’t prevent running away loads.
- (^) • This is because the head end port has free path towards reservoir.
- (^) • Running away load will pull the piston and piston can’t resist that.
- (^) • Meter-out control can be used for both opposing load as well as running away load.
- (^) • It can hold running away loads because there is FCV at outlet of cylinder, which maintains high-pressure fluid at cylinder outlet.
- (^) Meter-in speed control , Figure can be used where the cylinder is always under load on the controlled stroke. If the load is highly variable or has a tendency to run away, then meter- out speed control is generally preferred.
- (^) Meter-out controls restrict fluid leaving the cylinder to retard the cylinder’s movement. This type of flow-control circuit works for any type of load -- and works best with air-operated devices. Figure 10-27 shows a meter-out flow- control circuit in the at rest condition.
- (^) Pressure at the head end of the cylinder will be at system pressure or higher according to the rod size and force required to move the load. The action of meter-out flow controls is smooth and steady in hydraulic circuits
- (^) Meter-in systems are used primarily when the external load opposes the direction of motion of the hydraulic cylinder. An example of the opposite situation is the case of a weight pulling downward on the piston rod of a vertical cylinder. In this case Fluid Power Control Systems.
- (^) the weight would suddenly drop by pulling the piston rod down if a meter-in system is used even if the flow control valve is completely closed. Thus, the meter-out system is generally preferred over the meter-in type.