Pneumatics Explained

PNEUMATICS

Pneumatic logic can be divided into three parts
1. Supply  Components - This is for the end user side application and for Logic sequence.
These components include - Compressors , Air filters , Water separators, Lubricaors and Air dryers

2. Logic components  : These form the intermediary conditional elements to achieve the required end action. These elements also encompass Feed back loop for proper process control.
Components include: Direction control valves with pneumatic/ electrical  actuation , Logic elements ,

3.End  Components : These are the user end side components incorporated in machinery to perform the necessary action in an automation system.
These include Rams , Motors. - Basically called as Actuators and Drives

Supply Components

Cleanliness is important in pneumatic system , as water vapour and dirt can clog the logical components , restrict their function and also corrode the casings of aluminium die cast components.Hence supply of de-humidified air is imporatnt with water removal by dryers/ dessicant systems , along with line water separators. Lubricators are provoded to ensure proper functioning of logical components.

                                      

Logic components

These can be divided into following :

1.Direction control valves : These valves change the direction of supply based on the actuation logic. These are designated as Number of ports/ Number of ways Valve (Ex: 5/2 valve - 5 ports / 2 way  valve). and the condition is designated as Normally open (NO) and Normally closed (NC) , based on the logic- control air passing through(NO) or control air not passing through(NC).

The ports are designated and standardized as described below.

2.Actuation methods

Direct actuation                   ·  Simplest possibility

·    Input element = Control element

Indirect actuation                 ·  Usual type of actuation

·    For cylinders with large diameters

·    In case of large distance between input element and working element

3.Non- return valves
4.Pressure control system includes  pressure regulating valves , pressure sequence valves.
Variable controls are indicated by slant lines on the valve notations.

End components

Representation of a Pneumatic logic with numbering

System number		1,2 etc
	·  Is used only if the entire switching circuit consists of more than one system
Circuit number	·	Components of energy supply, accessories		0
	·	Fluid circuits; Number assignment per cylinder		1, 2, ...
Component designation	by letter
	·	Working elements	A ( End components)
	·	Compressors	P
	·	Sensors	S ( Actuators or valves controlled by logic)
	·	Valves	V
	·	Other components	Z
Component number	·	Beginning with 1

·    Continuous numbering of the same types of component

Numbers assigned from left to right and from bottom to top

Direct actuation                   ·  Simplest possibility

·    Input element = Control element

Indirect actuation                 ·  Usual type of actuation

·    For cylinders with large diameters

·    In case of large distance between input element and working element 

A simple circuit is explained as under

A double-acting cylinder is used for the pressing  of components. By actuating a push button, the piston rod of the pressing cylinder slowly advances.When the pressing position is reached, the pressing force should be maintained for a time of approx. 10 seconds. After this time, the piston rod automatically retracts into its initial position. A re-start is possible only when the piston rod is located in its initial position.

 

 

 signal is present at both inputs of the dual pressure valve 1V1 by 1 S1 and 1 S2, the control element 1V3 switches and the piston rod of cylinder 1A moves forward till it reaches end point 1S3.

1S3 sends delay signal to port 12 of time delay valve 1V2 , which switches control  when time delay is elapsed , thus changing position on valve 1V3 - to return back to original position.

The possibilities are endless , as the logic remains the same so as the elements , but time delay sequences can also be enacted by electro- pneumatic valves (pneumatic valves activated by solenoids) .

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