Category Archives for Hydraulic Circuits
Double-Pump Hydraulic System
Figure 1.5 shows an application for an unloading valve. It is a circuit that uses a high-pressure, low-flow pump in conjunction with a low-pressure, high-flow pump. A typical application is a sheet metal punch press in which the hydraulic cylinder … Continue reading
Regenerative Cylinder Circuit
Figure 1.3 shows a regenerative circuit that is used to speed up the extending speed of a double-acting cylinder. The pipelines to both ends of the hydraulic cylinder are connected in parallel and one of the ports of the 4/3 … Continue reading
Pump-Unloading Circuit
Figure 1.4 shows a hydraulic circuit to unload a pump using an unloading valve.When the cylinder reaches the end of its extension stroke, the pressure of oil rises because the check valve keeps the high-pressure oil. Due to high-pressure oil … Continue reading
Control of a Double-Acting Hydraulic Cylinder
The circuit diagram to control double-acting cylinder is shown in Fig. 1.2. The control of a double-acting hydraulic cylinder is described as follows: 1. When the 4/3 valve is in its neutral position (tandem design), the cylinder is hydraulically locked … Continue reading
Fail-Safe Circuits
Fail-safe circuits are those designed to prevent injury to the operator or damage to the equipment. In general, they prevent the system from accidentally falling on an operator and also prevent overloading of the system. In following sections we shall … Continue reading
Speed Control of a Hydraulic Motor
Figure 1.12 shows the speed control circuit of a hydraulic motor using a pressure-compensated FCV.The operation is as follows: – In a spring-centered position of the tandem four-way valve, the motor is hydraulically blocked. – When the valve is actuated … Continue reading
Meter-In Versus Meter-Out Flow-Control Valve Systems
A meter-out flow control system is one in which the FCV is placed in the outlet line of the hydraulic cylinder. Thus, a meter-out flow control system controls the oil flow rate out of the cylinder. Meter-in systems are used … Continue reading
Speed Control of a Hydraulic Cylinder
The speed control of a hydraulic cylinder circuit can be done during the extension stroke using a flow-control valve (FCV). This is done on a meter-in circuit and meter-out circuit as shown in Fig. 1.11. Refer to Fig. 1.11(a). When … Continue reading
Cylinders in Parallel
Figure 1.10 shows a hydraulic circuit in which two cylinders are arranged in parallel. When the two cylinders are identical, the loads on the cylinders are identical, and then extension and retraction are synchronized. If the loads are not identical, … Continue reading
Locked Cylinder Using Pilot Check Valves
A check valve (Fig. 1.9) blocks flow in one direction but allows free flow in the opposite direction. A pilot-operated check valve permits flow in the normally blocked opposite direction when pilot pressure is applied at the pilot pressure port … Continue reading