Flow controllers are also referred to as flow valves or flow control valves

These valves are used to control the flow rate of the medium used. This is usually a hydraulic fluid or compressed air. They are mainly used to control the speed of motors and, in particular, cylinders.

A basic distinction is made between throttle valves and flow control valves. These valves differ in that throttle check valves operate pressure-dependently, while flow control valves operate pressure-independently. In practice, there are various applications for flow controllers. Some of these are explained in more detail below.

Overview of various flow controllers

Measuring throttle: A measuring throttle is a conventional throttle valve with an adjustable throttle. By combining it with a control throttle, the flow remains constant regardless of changing load pressures. In this process, a variable cross-section is released by the control throttle. This cross-section is proportional to the load pressure. This means that the flow rate remains constant regardless of the pressure difference upstream and downstream of the valve.

2-way flow control valve: In a 2-way flow valve, a control throttle and a measuring throttle are connected in series. This means that this circuit has only one inlet and one outlet. Therefore, the volumetric flow that is not required must be removed from the circuit via the pressure relief valve of the hydraulic system. In some cases, this leads to very high losses.

3-way flow control valve: In this circuit, the control throttle and measuring throttle are connected in parallel, unlike the 2-way flow control valve. This creates a third port on the control throttle, which can be used to discharge the volumetric flow that is not required. This discharge process usually takes place at the respective prevailing load pressure plus approx. 5 bar. As a result, the circuit of a 3-way flow control valve has lower energy losses than the 2-way flow control valve.

Arrangement in the inlet, outlet and bypass

2-way flow control valve in the inlet: If the valve is located in the inlet of the system, the pump flow rate can be controlled very precisely. The pressure in the hydraulic cylinder corresponds to the operating pressure of the system. In contrast, the pressure at the pump corresponds to the rated pressure of the entire system. Therefore, when using a flow control valve in the inlet, a high power loss is to be expected.

2-way flow control valve in the outlet: This valve is installed in the outlet of the system in a circuit with an overrunning load. Both sides of the cylinder are under pressure because the outlet is throttled in the circuit. In this case, the smaller volume on the rod side is controlled. The system pump generally operates against the rated pressure of the system, so a significant power loss is to be expected.

2-way flow control valve in the bypass: If the valve is arranged in the bypass of the system, the controlled volumetric flow is routed to the tank and the remaining flow to the hydraulic cylinder. Fluctuations in the pump flow rate are transmitted directly to the cylinder. Therefore, a 2-way flow control valve is not suitable for accumulator operation. Since the system pump only works against the load pressure, a low power loss is to be expected in this system.

3-way flow control valve in the inlet: A 3-way flow control valve can only be arranged in the inlet. It operates, just like the 2-way flow control valve, only against the load pressure of the circuit. This means that the power loss is as low as possible in a system with a flow controller.