Chapter 2 Fluid Power Systems

Chapter 2

Fluid Power Systems

The Basic System

1 Objectives

. Exppplain the functions of fluid power systems. . Identify the basic structure of fluid power systems. . List the basic component groups involved in the structure of fluid power systems.

Objectives

. Describe the function of the components involved in basic fluid power systems. . Describe the similarities and differences of hydraulic and pneumatic systems. . Explain the operation of basic hydraulic and pneumatic systems.

2 Functions of Fluid Power Systems

. Fluid power systems are made up of components designed to perform specific tasks . These components act together to perform desired work

Functions of Fluid Power Systems . Fluid power systems perform five functions diduring operati on: – Energy conversion – Fluid distribution – Fluid control – Work performance – Fluid maintenance

3 Functions of Fluid Power Systems

Structure of Fluid Power Systems

. Fluid power systems are structured using component groups that perform specific system functions: – Power unit group – Actuators group – Conductors group – Control valves group – Fluid maintenance group

4 Basic System Components

. Power unit group – Deals primarily with energy conversion – Consists of: • Prime mover • Pump or compressor • Reservoir or receiver

Basic System Components

. Actuators group – Performs the work of the system – Consists of both cylinders and motors

5 Basic System Components

. Conductors group – Conductors distribute fluid throughout the system – Consists of: • Pipes • Tubes • Hoses

Basic System Components

. Control valves group – Controls fluid pressure, flow direction, and flow rate – Three groups of valves: • Directional control valves • Pressure control valves • Flow control valves

6 Basic System Components

. Fluid maintenance group – Maintains system fluid by removing dirt, moisture, and excessive heat – Filters and other devices are used to perform these functions

Basic System Components

. Comparisons can be made between hydraulic and pneumatic systems . System terminology and designs may vary between hydraulic and pneumatic systems

7 Basic System Components

. Power unit – Electric motors and internal combustion engines are most often the prime movers – The pump or compressor produces the fluid flow – Fluid flow is created by internal pressure differences – Fluid flow transmits energy throughout the system

Basic System Components

. Power unit – System reservoir or receiver stores system fluid – Reservoir/receiver also contributes to system temperature control and fluid cleaning

8 Basic System Components

. Actuators – ClidCylinders are used di in both hydraulic and pneumatic systems – Cylinders produce linear motion

Basic System Components

. Actuators – MtMotors are use dibthd in both hydraulic and pneumatic systems – Motors produce rotary motion

9 Basic System Components

. Actuators – Motion is created when pressurized fluid moves an internal part of the actuators from a high pressure area toward a low pressure area

Basic System Components

. Actuators

(Used with permission of CNH America LLC)

10 Basic System Components

. Conductors – Pipes – Tubes –Hoses – Transmit system fluid to system components

Basic System Components

. Control valves – Directional control valves • Vary the direction of movement of cylinders and motors • Change fluid flow paths to and from the actuators

11 Basic System Components

. Control valves – Pressure control valves • Control pressure in a fluid power system • Restrict fluid flow into a part of the system • Allow fluid to return to a low pressure area after a desired pressure is reached

Basic System Components

. Control valves – Flow con trol val ves • Control fluid flow rate in a system • The size of an orifice is adjusted to change flow

12 Basic System Components

. Fluid maintenance devices – Filters – Separators – Lubricators – Used to remove contaminates and condition the fluid – Assure effective system performance and acceptable service life

Basic System Operation

. Hyyypdraulic system operation – Movement of oil originates at the pump – Low pressure at the pump inlet causes oil to pass through a filter as it flows from the reservoir into the pump – High pressure at the pump outlet forces oil to the directional control valve and on to the actuator – System work is performed by the actuator

13 Basic System Operation

. Hydraulic system operation – Pressure control valves limit pressure in the system – Flow control valves control the speed of actuator movement – Oil is returned to the reservoir to be recirculated througgyh the system

Basic System Operation

. Pneumatic system operation – Movement of air begins at the compressor – As air moves into the system from the atmosphere, it is: • Filtered • Compressed • Stored in the receiver under pressure – Pressurized air is distributed to system workstations

14 Basic System Operation

. Pneumatic system operation – At the workstation: •A pressure regulator sets working pressure • A filter and lubricator provide final conditioning – Air then moves through a directional control valve and on to an actuator – System work is performed by the actuator

Basic System Operation

. Pneumatic system operation – DiDuring syst em operati tiflon, flow cont tlrol val ves control the speed of actuator movement – Air is discharged back into the atmosphere after passing through the system

15 Review Question

Fluid power systems are made up of _____ contiitaining part s d esi gned dt to perf orm specifi c tasks.

component groups

Review Question

The fluid control function of a fluid power system cont rol s syst em pressure and dflidfl fluid flow _____ and _____.

rate; direction

16 Review Question

The number and appearance of components in a flu id power syst em i s i nfl uenced b y th e t ype of _____, application, and _____.

fluid; power output

Review Question

Fluids are distributed throughout a fluid power systbtem by component tfdts referred to as _____.

conductors

17 Review Question

Fluid power system filters may be located in one or more ofthf three t ypi cal ll locati ons. Li Litst these three locations.

Intake line; working lines; return lines.

Review Question

In the pneumatic fluid power system, after the pressurized syst em ai r h as compl ltditeted its work , it is exhausted to the _____.

atmosphere

18 Glossary

. Actuator – A component used to convert the energy in hydraulic fluid or compressed air into mechanical linear or rotary motion.

Glossary

. Component group – A group of commonly designed hydraulic or pneumatic components offered in a full range of sizes with appropriate accessories. . Compressor – The pneumatic system device that converts the energy input of the system prime mover into high-pressure compressed air.

19 Glossary

. Conductor – The element used in fluid power systems to allow the movement of hydraulic fluid or compressed air from component to component. Hose, pipe, and tubing are the most common fluid power conductors. . Control valve – Any valve designed to control fluid pressure , flow rate, or actuator direction in a fluid power system.

Glossary

. Cylinder – The common t erm f or li near act uat ors used t o generate movement and force in fluid power systems. . Directional control valve – Hydraulic and pneumatic control valves that direct fluid flow to start, control direction of movement , and stop system actuators.

20 Glossary

. Filter – A fluid power component that is used to remove solid contaminants from both air and liquid. The term is often used to designate the complete component including the filter element, case, and mounting hardware.

Glossary

. Flow control valve – AtdidtidtlfthtA component designed to provide control of the rate of flow of air or liquid in hydraulic and pneumatic systems.

21 Glossary

. Hose – A flexible conductor for carrying hydraulic fluid or compressed air to actuators. . Lubricator – A device designed to apply a lubricant to a bearing surface. In ppyneumatic systems, the lubricator is a component of the FRL unit located at the workstation.

Glossary

. Motor – AttthtiildAn actuator that primarily produces conti nuous, rotary motion. These components may be powered by electricity, hydraulics, or pneumatics. . Pipe – Rigid tube made from steel with adequate wall thickness to be threaded. Often used as a conductor in fluid power systems.

22 Glossary

. Power unit – The unit in a hydraulic system that provides energy for the system, moves fluid through the system, provides a safe maximum limit of system pressure, and maintains desired system temperature and fluid cleanliness.

Glossary

. Pressure control valves – Control valves in a fluid power circuit designed to protect the system from damage from excessive pressure, provide motion control, and protect operators from unexpected actuator movement.

23 Glossary

. Pressure regulator – A pneumatic system component used to control air pressure at the system workstations. The valve maintains a constant, reduced pressure for use by tools and equipment operated at the station.

Glossary

. Prime mover – The source of energy for any fluid power system. Commonly used prime movers are electric motors and internal combustion engines.

24 Glossary

. Pump – A hydraulic component turned by the prime mover that produces fluid flow, which transmits energy through the system. . Receiver – A tank in a pneumatic system, located close to the compressor, that stores and assists in conditioning compressed air.

Glossary

. Reservoir – A component in a hydraulic system that holds the system fluid not currently in use in the pump, control components, actuators, and lines.

25 Glossary

. Separator – A component, located in the compressor station area of a pneumatic system, that is designed to remove condensed water from the compressed air. The unit is often teamed with an aftercooler to optimize moisture removal.

Glossary

. System function – ThtThe task s compl ltdbeted by th e operati on of a fl fliduid power system. . Tube – Generally defined as a long, cylindrical body with an open center. Tubes are used extensively in the fluid power field as fluid conductors and as component parts, such as the barrel of cylinders.