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Compressed Air Applications, Study notes of Mechanical Engineering

Polytechnic University of the Philippines (PUP)Mechanical Engineering

Explains how machine applications of compressed air works, their use, advantages, etc.

Typology: Study notes

2021/2022

Uploaded on 07/10/2022

julianne-lavadia
julianne-lavadia 🇵🇭

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Air Cylinders
1. Air Cylinder
Gif: https://gfycat.com/discover/cylinder-gifs (after the image)
- A mechanical device that converts compressed air energy into a reciprocating
linear motion.
- A pneumatic cylinder works by forcing gas or air into a cylinder, which will move
a piston after a certain amount of pressure is reached. The piston is attached to
another mechanism that performs the desired function of the machine.
- Cylinders are typically controlled with a venting four-way valve. When the valve is
in one position, pressure is applied to one side of the piston and vented on the
opposite side.
- The force that can be utilized on air cylinder is described by the equation:
F = P x A
where,
pf3
pf4
pf5
pf8

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Air Cylinders

1. Air Cylinder Gif: https://gfycat.com/discover/cylinder-gifs (after the image)

  • A mechanical device that converts compressed air energy into a reciprocating linear motion.
  • A pneumatic cylinder works by forcing gas or air into a cylinder, which will move a piston after a certain amount of pressure is reached. The piston is attached to another mechanism that performs the desired function of the machine.
  • Cylinders are typically controlled with a venting four-way valve. When the valve is in one position, pressure is applied to one side of the piston and vented on the opposite side.
  • The force that can be utilized on air cylinder is described by the equation: F = P x A where,

𝐹 - force generated 𝑃 - air pressure 𝐴 - cross-sectional area of the cylinder

  • Air cylinders are the products used to provide linear or rotary motion and force to automated systems, machines and processes, for example in industrial applications.
  • Main components: piston, piston rod, and cylinder.
  • Advantages: o Simple to use o Cost-efficient o Safe o Flexible o Efficient and reliable Two types of Pneumatic (Air) Cylinder: a. Single-acting Cylinder - uses compressed air for one-way movement and a return spring for the other. b. Double-acting Cylinder - uses compressed air for one-way movement and a return spring for the other. 2. Diaphragm Air Cylinder

Gif: (File from Computer – send ko)

  • The principle of operation is based on the force applied to the area of the larger air cylinder being transferred to the smaller area of the hydraulic cylinder, creating a higher pressure. o The pressure is then a function of the differential piston areas described by the Pascal’s Law: P 1 = P 2

F 1 A 1 = F 2 A 2

F2 =

F 1 A 1 A 2 o Within this closed system (non-vacuum), the pressure increases as volume decreases described by Boyle’s Law: P 1 V 1 = P 2 V 2 P2 = P 1 V 1 V 2

  • Pressure-type air amplifiers are used in applications where a specific product or process must have a higher pressure than the compressor system can deliver. This includes applications such as: air clamps, presses, pressure testing, air brakes, and also blow molding. Air Motors
  • Air motors are almost always delivered in the form of a rotary vane device. The vane motor is a mechanical drive that converts the pressure of an inflowing gas or liquid into a rotary motion. Mechanism: o The motor consists of a cylinder with an internal rotor. The rotor is placed off-center so that its outside diameter is tangent to the cylinder’s inside diameter. The rotor carries four vanes that are placed into slots. The vanes are usually spring-loaded and slide within the slots so that they are always in contact with the inside diameter of the cylinder. o The compressed air feeds into the motor at one end and escapes through an opening in the cylinder. While the rotor is in rotation, the centrifugal force presses the vanes on the internal surface of the stator thereby splitting the space into several chambers of different volumes. o The volume of the compression chamber will increase and the air within will expand. The next compression chamber is in turn submitted to pressure and the same phenomenon occurs, allowing for the constant rotation of the rotor.
  • Air motor are compact, economical and with a simple design, they are perfectly adapted for use in numerous devices in various industry sectors such as the food, agricultural, petrochemical and even nuclear industries.
  • Sandblasting is the act of propelling very fine particles of an abrasive material at high velocity toward a surface in order to clean or grind it.
  • Main Components: o Abrasive o Air compressor o Blaster nozzle
  • In addition to sand, there are a variety of other blast media available including glass beads, walnut shells, steel shot, abrasives, and the like.
  • Sandblasting machines have a chamber on top in which the sand is poured. The sandblasting machine is then connected a conventional air compressor that, when activated, propels the sand out through a handheld nozzle.
  • Sandblasting is a method of surface treatment and is used to clean metal surfaces and to matt glass. The sandblasting of metals fulfills a double function, as the surfaces are both cleaned and roughened. Vacuum Generator
  • A vacuum pump is a device that is capable of evacuating (removing) air molecules from a closed volume allowing a less-than-atmospheric pressure condition to be attained. Compressed air-powered vacuum pumps are also called vacuum generators and can be simple single-stage pumps (venturi) or more complex high-flow, multi-stage ejector designs.
  • A single-stage vacuum generator consists of a jet nozzle or a Venturi nozzle through which the compressed air is passed. The narrowing of the jet nozzle causes the air to accelerate. As it passes through the narrow nozzle and starts to expand, a vacuum is created at the expanded side. The air is drawn through the inlet and the compressed air exits through the silencer. This mechanism operates based on the Venturi Effect. ➢ Venturi Effect: Increase in fluid speed results in decrease in internal pressure.

(Image for Venturi effect)

  • The accelerated compressed air produced generates a suction effect which is useful in wide range of applications, e.g. handling technology and process engineering
  • Though they are flexible due to their lightweight and compact design, vacuum generators are not energy-efficient. Video : https://www.youtube.com/watch?v=l- wZYJXpVFg&t=227s&ab_channel=Ms.Pneumatic (Timestamp: 2:53-3:39)