The Basics of Pneumatics: Understanding Compressed Air Systems

Pneumatics is a fascinating field of engineering that leverages compressed air to perform mechanical work. From industrial automation to everyday tools like air-powered drills, pneumatic systems are a cornerstone of modern technology. This article explores the basics of pneumatic systems, their components, and their applications.

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What Is a Pneumatic System?

A pneumatic system uses compressed air to generate mechanical motion. Unlike hydraulics, which rely on liquids, pneumatics employs air or other gases. These systems are popular because air is abundant, clean, and easy to compress.

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Key Components of Pneumatic Systems

1. Air Compressor
   The air compressor is the heart of a pneumatic system. It takes in atmospheric air, compresses it, and delivers it at high pressure for various uses. Compressors are available in types like reciprocating, rotary screw, and centrifugal models.

2. Air Storage Tank
   The compressed air is stored in an air receiver tank to stabilize pressure and ensure a steady supply. This component also helps reduce the workload on the compressor.

3. Valves
   Pneumatic valves control the flow, pressure, and direction of compressed air. Types include:

   • Directional control valves: Manage airflow direction.
   • Pressure relief valves: Protect the system from overpressure.
   • Flow control valves: Regulate airflow rate.

4. Actuators
   Pneumatic actuators convert compressed air into mechanical motion, such as linear or rotary motion. Examples include cylinders (linear actuators) and rotary actuators.

5. Air Treatment Units
   To ensure system longevity, air must be clean and dry. Filters, regulators, and lubricators (collectively called FRLs) prepare air for use.

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How Pneumatic Systems Work

1. Air Compression: The compressor compresses ambient air.
2. Storage: The air is stored in a tank at high pressure.
3. Control: Valves regulate the airflow to match system requirements.
4. Actuation: Actuators perform work, such as lifting, pushing, or rotating.
5. Exhaust: After use, the air is released into the atmosphere.

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Advantages of Pneumatic Systems

• Cost-Effective: Air is free, and components are relatively inexpensive.
• Safe: Pneumatic systems are less prone to catastrophic failure compared to hydraulic systems.
• Clean: Ideal for food and pharmaceutical industries where contamination is a concern.
• Energy-Efficient: Modern systems incorporate energy recovery mechanisms to enhance efficiency.

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Applications of Pneumatics

• Industrial Automation: Robots, conveyors, and assembly lines.
• Transportation: Air brakes in trucks and trains.
• Healthcare: Dental drills and ventilators.
• Construction: Pneumatic tools like nail guns and jackhammers.

Single tank level controlling with alarm controlling (S7-300 LAD).

This is PLC Program for single tank level controlling with alarm controlling.

 Problem Description:-

We need to control the level of water in the tank. Control the water level by simple PLC logic. Give the alarm for high level in the system and acknowledge button for the alarm reset .Write the ladder diagram logic for this application.

Problem Diagram

Problem Solution

To solve this this example we are using PLC programming. Here we have a tendency to use 2 sensors for level measurement, one is for prime level and second is for low level.

We use feeding valve for feeding Cycle for the tank and discharge valve for discharging cycle for the tank. Each valve are controlled by sensors. So once the water level goes below low level then feeding valve can activate mechanically and water level senses the high level then discharging method are activate mechanically.

Program

Here is PLC program for single tank level controlling with alarm controlling using PLC.

List of inputs/outputs

Digital inputs:-

Main switch:-I1.1

Start button:-I0.0

Stop button:-I0.1

High level:-I0.2

Low level:-I0.3

Feeding valve:-Q0.1

Discharge valve:-Q0.2

 

Digital outputs:-

Master coil:-Q0.0

Feeding valve:-Q0.1

Discharge valve:-Q0.2

Mixer motor:-Q0.3

 

Ladder diagram for single tank level controlling with alarm controlling using PLC.

Program Description

In network 1 we tend to used latching circuit for master coil ON (Q0.0) output.it will be started by pressing START Push button (I0.0) and stop by pressing STOP pushbutton (I0.1).

When cycle are going to be begin then system check level of the tank. If tank level is low then then feeding method can begin and tank level is high then Discharge cycle can begin.

Here we've taken NO contact for each sensors within the program for simplicity. It will be done by relay logic in field otherwise you will choose such variety of sensors.

In network 2,when tank can observe low level then low level sensor (I0.2) is going to be activated and feeding cycle are going to be ON. Here we've taken NC contact of high level sensor (I0.3) therefore once PLC can observe high level then it'll STOP feeding cycle.

In network 3,when tank can observe high level then high level sensor (I0.3)  is  to be activated and discharging cycle are going to be ON. Here we've taken NC contact of low level sensor (I0.2) therefore once PLC can observe low level then it'll STOP discharge cycle.

In network 4, mixer motor (Q0.3) will remain ON when discharge valve is ON.

In network 5 when high level (I0.3) is detected, alarm (Q0.4) will be activated.

In network 6 when acknowledge button is pressed, alarm will be reset.

 

Note:-Application is only for learning and educational purpose .Above application may be different from actual application. This application can be done in other PLC also. Users are responsible for correct operation of the PLC system and for any possible injuries and or material damages resulting from the use of this program. It is necessary to take care of safety during implementation, installation, maintenance and operation.

 

All parameters and graphical representations considered in this example are for explanation purpose only, parameters or representation may be different in actual applications. Also all interlocks are not considered in the application.

 

3 Phase motor control (Forward Reverse) using TIA portal (FBD language).

This is PLC Program for 3 Phase Motor control (Forward/Reverse).

 

Problem Description

Write the PLC program for 3 phase motor control (Forward Reverse) in TIA PORTAL using FBD language.

 

Problem Diagram

Problem Solution

In this case we'd like to control motor in each direction which will be attainable solely by forward/Reverse negative feedback circuit or Logic.

Here we tend to solve this downside by easy Forward/Reverse management Logic.

So here we are going to take into account one 3 phase motor for Forward and Reverse Operation.

And we can take 2 contactors or relays for control as a result of we'd like 2 totally different directions here.

Also we must always take into account 3 push buttons for forward, reverse and stop operate.

So here operator can use FWD PB for forward operation, REV PB for reverse operation and STOP PB for stop operate.

Program

Here is PLC program for 3 Phase Motor control (Forward/Reverse).

List of Inputs/Outputs

Inputs List:-

FWD PB-I0.0

REV-I0.1

STOP PB-I0.2

Motor Trip-I0.3

Outputs List:-

Forward motor contactor-Q0.0

Reverse motor contactor-Q0.1

 

FBD diagram for 3 Phase Motor control (Forward/Reverse).

Program Description

In this application we will use Siemens S7-300 PLC and TIA PORTAL Software for programming. We can also design this logic with relay circuit.

Network 1:-In this network forward motor contactor (Q0.0) can be start by pressing FBD PB (I0.0) and can be stopped by pressing STOP PB (I0.2).

Network 2:-In this network reverse motor contactor (Q0.1) can be started by pressing REV PB(I0.1) and can be stopped by pressing STOP PB (I0.2).

 

Note:-Application is only for learning purpose .Above application may be different from actual application. This application can be done in other PLC also. Users are responsible for correct operation of the PLC system and for any possible injuries and or material damages resulting from the use of this program. It is necessary to take care of safety during implementation, installation, maintenance and operation.

 

All parameters and graphical representations considered in this example are for explanation purpose only, parameters or representation may be different in actual applications. Also all interlocks are not considered in the application.