Category: Hydraulic Circuits

Double-Pump Hydraulic System

{0 Comments}

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 must extend rapidly over a great distance with low-pressure but high-flow requirements. This occurs under […]

Read More…

Regenerative Cylinder Circuit

{0 Comments}

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 valve is blockedby simply screwing a thread plug into the port opening. During retraction stroke, […]

Read More…

Pump-Unloading Circuit

{1 Comment}

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 in the pilot line of the unloading valve, it opens and unloads the pump pressure […]

Read More…

Control of a Double-Acting Hydraulic Cylinder

{0 Comments}

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 and the pump is unloaded back to the tank. 2. When the 4/3 valve is […]

Read More…

Fail-Safe Circuits

{0 Comments}

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 discuss two fail-safe circuits: One is protection from inadvertent cylinder extension and other is fail-safe […]

Read More…

Speed Control of a Hydraulic Motor

{0 Comments}

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 to the left envelope, the motor rotates in one direction. Its speed can be varied […]

Read More…

Speed Control of a Hydraulic Cylinder

{0 Comments}

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 the DCV is actuated, oil flows through the FCV to extend the cylinder. The extending […]

Read More…

Cylinders in Parallel

{0 Comments}

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, the cylinder with smaller load extends first. Thus, the two cylinders are not synchronized. Practically, […]

Read More…

Locked Cylinder Using Pilot Check Valves

{0 Comments}

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 of the valve. Pilot-operated check valves are used to lock the cylinder, so that its […]

Read More…