Szacowany czas czytania: 5 minuty

1. The Structure of Hydraulic System

• The structure of hydraulic system is composed of two parts: signal control and hydraulic power. The signal control part is used to drive the control valves in the hydraulic power part.
• The hydraulic power part is expressed in the way of circuit diagram to show the interrelationship between different functional components. The hydraulic source contains hydraulic pumps, electric motors and hydraulic auxiliary components; the hydraulic control part contains various control valves for controlling the flow, pressure and direction of the working fluid; the execution part contains hydraulic cylinders or hydraulic motors, which can be selected according to the actual requirements.

• When analyzing and designing the actual task, a block diagram is generally used to show the actual operating conditions of the equipment. Hollow arrows indicate the signal flow, while solid arrows indicate the energy flow.
• Sequence of actions in the basic hydraulic circuit – reversal and spring return of the control element (two-position four-way reversing valve), extension and retraction of the actuating element (double-acting hydraulic cylinder) and opening and closing of the relief valve. For the actuators and control elements, the presentation is based on the corresponding circuit diagram symbols, which also prepares for the introduction of the circuit diagram symbols.
• Depending on the operating principle, you can number all circuits in turn. If the first actuator is numbered 0, the associated control element identifier is 1. If the element identifier corresponding to the actuator extension is an even number, the element identifier corresponding to the actuator retraction is an odd number. Not only should hydraulic circuits be numbered, but also the actual equipment should be numbered in order to detect system faults.
• The DIN ISO 1219-2 standard defines the number of components, which consists of the following four parts: equipment number, circuit number, component identifier and component number. If there is only one device in the whole system, the device number can be omitted.
• In practice, another way of numbering is to number all components in a hydraulic system consecutively, where the component number should be consistent with the number in the component list. This method is particularly suitable for complex hydraulic control systems, where each control circuit corresponds to its system number.

2. The Components of Hydraulic System

A complete hydraulic system consists of five parts, namely, power components, executive components, control components, auxiliary components and hydraulic oil.

Power Components

• The role of the power element is to convert the mechanical energy of the prime mover into liquid pressure energy, referring to the hydraulic system in the oil pump, which provides power to the entire hydraulic system. Hydraulic pump structure forms generally have gear pumps, vane pumps, piston pumps and screw pumps.

Executive Elements

• The role of the actuating element (such as hydraulic cylinders and hydraulic motors) is to convert the pressure energy of the liquid into mechanical energy, driving the load for linear reciprocating motion or rotary motion.

Control Elements

• Control elements (i.e., a variety of hydraulic valves) in the hydraulic system to control and regulate the pressure, flow and direction of the liquid. According to the different control functions, hydraulic valves can be divided into pressure control valves, flow control valves and directional control valves. Pressure control valves include relief valves (safety valves), pressure reducing valves, sequence valves, pressure relays, etc. Flow control valves include throttle valves, adjustment valves, shunt collector valves, etc. Directional control valves include check valves, hydraulic check valves, shuttle valves, reversing valves, etc. According to the different control methods, hydraulic valves can be divided into switching control valves, fixed value control valves and proportional control valves.

Auxiliary Components

• Auxiliary components include oil tanks, oil filters, coolers, heaters, accumulators, oil pipes and pipe joints, seals, quick-change couplings, high-pressure ball valves, hose assemblies, pressure measuring joints, pressure gauges, oil level gauges, oil thermometers, etc.

Hydraulic Oil

• Hydraulic oil is the working medium for transferring energy in the hydraulic system. There are various mineral oil, emulsion and synthetic hydraulic oil and other major categories.