Engineering Applications of Pneumatics and Hydraulics

Ian C. Turner

• Publisher: Routledge
• Year: 2020
• ISBN:
  9781000077179
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

Requiring only a basic knowledge of the physics of fluids, Engineering Applications of Pneumatics and Hydraulics provides a sound understanding of fluid power systems and their uses within industry. It takes a strongly practical approach in describing pneumatics and hydraulics in modern industry and is filled with diagrams of components, equipment and plant.

The pneumatic and hydraulic graphical symbols used in everyday fluid power systems and circuits are particularly explained and well illustrated. In addition to descriptions of equipment and plant, maintenance and troubleshooting is also covered, with an emphasis on safety systems and safety regulations.

This second edition delves into the same fluid power technical areas as in the first edition, but with a complete update of current safety legislation and guidance on the latest regulations. Codes of practice, technical standards and standardisation organisations have also been updated to enable readers to search for the newest information and requirements regarding the use and application of pneumatics and hydraulics in industry whilst reflecting advances in technology.

The book is written for students from levels 3 to 5, and for a wide range of practising engineers, especially in the engineering disciplines of mechanical, plant, process and operations engineering, as well as measurement and control engineering within mechatronics.

Chapter 1

Applications of pneumatics and hydraulics in industry

Aims

At the end of this chapter you should be able to:

1. Appreciate a range of industrial applications for pneumatics and hydraulics.
2. Appreciate that pneumatics and hydraulics may be used in combination with other technologies in a given system.
3. Recognise that fluid power systems may be used for operating, controlling and/or taking measurements of equipment, machinery and plant.
4. Have an awareness that fluid power systems can be used in industrial processes requiring emergency and safety shut-down arrangements.

1.1 Industrial applications

Pneumatic and hydraulic systems have been used for many years within industrial processes and as such have acquired an established place in modern industry. Continuous development of fluid power technology over the years has significantly expanded and increased the applications to many areas hitherto not known for adopting pneumatic and hydraulic technology.

Some of the principal users of fluid power technology are:

• manufacturing industries, notably the automotive industry, machine tool manufacturers and domestic and commercial appliance manufacturers
• processing industries, such as chemical, petro-chemical, food processing, textiles, paper, etc.
• transportation systems, including marine and mobile construction plant
• utilities, particularly in the gas industry
• defence systems.

Over many years there has also been increased use of fluid power technology in the fields of offshore oil and gas development, space and aero-nautical systems and nuclear applications.

1.2 Combined technologies

Often, pneumatics and hydraulics are combined with other technologies such as mechanical, electrical and electronic systems to form an overall system. An example of this can be found in robotics.

In addition, safety conscious industries will sometimes adopt a number of technologies operating on different physical principles as a means of achieving diversity of operation, control and measurement on a given process. This is particularly significant as protection against common mode failure whereby if one system fails, the others remain active.

1.3 Uses of fluid power systems

Fluid power systems may be used for:

1. Carrying out work by operating plant and machinery using linear, swivel and rotary motion. Some general methods of material handling used in industry, for example, may be:
   • clamping
   • shifting
   • positioning
   • orientating.
   1. General applications may be:
      • packaging
      • feeding
      • door or chute control
      • material transfer
      • turning and inverting of parts
      • sorting
      • stacking
      • stamping and embossing.
   2. Some general machining and work operations may be:
      • drilling
      • turning
      • milling
      • sawing
      • finishing and buffing
      • forming.
2. Controlling processes and plant. Pneumatic and hydraulic systems may be used to sense the operational status of a process and feed this information back to a controller which will take a necessary control action, for example a limit switch may sense that an actuator needs to be operated.
3. Measurements of process and/or machine parameters. Pneumatics and hydraulics can be used to provide measurements of process or machine parameters, act on this information and subsequently display it to an operator.

The processes outlined in 1, 2 and 3 above may be used individually or in combination.

Figure  1.1  A combined wellhead control panel and hydraulic power unit for an offshore oil platform

1.4 Hydraulic and pneumatic safety systems

In addition to operating, controlling and measuring parameters of process plant and machinery, hydraulics and pneumatics may be used in high-integrity safety systems. This is expanded further in Chapter 14.

The high speed and reliability of operation embodied in a good, modern pneumatic and hydraulic system design coupled with inherent explosion-proof and overload-safe operation makes the choice of this technology ideal for applications in the marine, offshore and petro-chemical industries.

Figure 1.2 shows a practical hydraulic emergency shut-down system for three sub-sea oil wells on an offshore petro-chemical application. A further example of a safety system is that used in automatic reverse braking systems which can be fitted to any vehicle using air or air/hydraulic brakes. Such a system can bring a vehicle to a halt literally within centimetres once an obstruction is encountered. Figure 1.3 shows a typical arrangement of such a backstop system.

Figure  1.2  Practical hydraulic emergency shut-down system for three sub-sea oil wells

Figure  1.3  Typical backstop installation on a fully air braked rigid truck. 1 Gear change selector, 2 Reversing light switch, 3 Footbrake, 4 Brake actuating solenoid valve mounted adjacent to rear brake supply, 5 Rear spring brake actuators, 6 Backstop switching unit mounted close to rear of vehicle, 7 Backstop sensor mounted on rearmost part of vehicle, 8 Electrical junction box

Chapter 2

Basic principles of fluid power systems

Aims

At the end of this chapter you should be able to:

1. Appreciate the nature and physical properties of air.
2. Understand that a fluid power system is a compressed gas or incompressible liquid operating under enclosed conditions in order to produce work.
3. Recognise the SI system of units of measurement for use in pneumatics and hydraulics.
4. Be aware of the physical laws governing gases, namely Newton’s and Boyle’s laws.

2.1 Physical properties of air

The surface of the Earth is covered entirely by layers of air. It is an abundant gas mixture comprising:

• nitrogen (approximately 78% volume)
• oxygen (approximately 21% volume).

2.2 The principle of hydraulic systems

In hydraulic systems, the compressed air is replaced with a liquid-based solution, typically oil, which is used under pr...