PNEUMATICS

Pneumatics

introduction to pneumatics

     Pneumatics is the method of using compressed air as a power source in industrial environment. Most of the time compressed air used to do mechanical work that is to produce motion and to generate force. The energy stored in the compressed air, used for driving mechanical equipments.

Most commonly used cylinders for pneumatic drives. A large range of types, simple installation and favorable pice / performance characterizes them.

v  Opening and closing doors.

v  Handling of work pieces (clamping, positioning, separating, rotating, etc.)

v  Pick and place objects

v  To Control conveyer belts.

v  Lifting

Pneumatic systems start with compression of the air and distributions. The compressed air is stored in compressor. The compressed air is transferred using tubing to the working area. When pneumatic flow to the actuators it is important to check the quality of the air this is varies with the process or the operation. The service unit is used for this task.

The freely available air is included water in the form of natural air humidity, oil aerosols, solid particles in the form of dust (carbon black, corrosion particles) and salt particles (sea water droplets).    

The dust particles can classified as three types

v Course dust                               >10 micron

v Fine dust                                     1-10 micron

v Atomized dust                           < 1 micron

Contamination of these particles accelerates wear on sliding surfaces and seal elements. This can be affect the function and service life of pneumatic components. Therefore, compressed air should be as clean as possible for economic reasons. Filtration of 4-micron size, recommended for trouble free operation. The condensate that collects to the collector tank to avoid damp in the system and it is directly affects to the lifetime of the equipments.

ELECTRO pneumatics       

 In electro pneumatics it uses electrical current to get the signal and generate the force to closes or open the valves. Electric current flows through a coil and magnetic field generated. The strength of the magnetic field is dependent on.

v  Increasing the number of windings increases the field.
v  Increasing the strength of the current increases the field.

v  Lengthening the coil reduces the field.

A soft iron core (armature) is drawn into a coil through which a current is flowing.

electro pneumatics working theory

Conversion of Pneumatic signals into electrical signals 

electro pneumatics working theory

The PE converter actuated by compressed air. The pressure of a pneumatic signal works against an adjustable spring. If the pressure working against the diaphragm overcomes the spring force, a steam actuates an electrical switch contact. The electrical switching element may normally closed, normally open or changeover contact.

SOLENOIDS

A solenoid valve is an electro mechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid coil. Solenoid valves may have two or more ports. In the case of a two-port valve the flow is switched on or off. In the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold.

Solenoid valves are the most frequently used control elements in fluids. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.

Besides the plunger-type actuator which is used most frequently, pivoted-armature actuators and rocker actuators are also used.

TYPES OF ELECTRO PNEUMATIC VALVES

2/2 way solenoid valve without pilot control

 Normally closed position, spring return

When Solenoid coil de-energized

v  Port 1 is blocked.

v  Port 2 is blocked.

v  Exhausting is not possible.

When Solenoid coil energized

v  The armature raised.

v  Compressed air flows from port 1 to port 2.

2/2 Way Solenoid Valve without Pilot Control

Solenoid Valves with Pilot Control

Solenoid valves with pilot control consist of:-

v  An electro magnetically actuated pilot control valve.

v   Pneumatically actuated main valve.

In comparison with solenoid valves without a pilot control, solenoid valves with a pilot control are distinguished by:-

v  Lower force required to actuate the armature.

v  Smaller dimensions of the coil head.

v  Lower power consumption.

v  Less heat generated.

3/2-Way Single Solenoid Valve with Pilot Control

Normally closed position, spring return, manual override

 When Solenoid coil de-energized

v  Port 1 is blocked.

v  Port 2 vented to port 3.

v  The armature seal on the valve side block the pilot control channel.

v  The space above the valve piston is vented through the armature guide tube.When Solenoid coil energized

v  The armature is lifted and the armature seal on the coil side blocks the vent hole in the armature guide tube, while the armature seal on the valve side opens the pilot control channel.

v  Compressed air from port 1 flows through the pilot control channel and actuates the valve piston.

v  Port 3 is blocked.

v  Compressed air flows from port 1 to port 2.

3/2 Way Solenoid Valve with Pilot Control

 5/2-Way Single Solenoid Valve with Pilot Control

Spring returned, manual override

When Solenoid coil de-energized

v  Compressed air flows from port 1 to 2.

v  Port 4 is vented to 5.

v  Port 3 is blocked.

v  The pilot control channel is blocked.

v  The space above the valve piston is vented through the armature guide tube.

 When Solenoid coil energized

v  The armature is lifted and the armature seal on the coil side blocks the vent in the armature guide tube, while the armature seal on the valve side opens the pilot control channel.

v Compressed air from port 1 flows through the pilot control channel and actuates the valve piston.

• Port 5 is blocked.
• Compressed air flows from port 1 to port 4.
• Port 2 is vented to port 3.

5/2 Way single Solenoid Valve with Pilot Control and exhaust for pilot 

VALVE banks 

Valve banks are types of solenoid that attached together in a form of one solenoid. It is easy to handle when considering the handling of many solenoids and one valve bank. It can be easy to control by using PLC or any electronic circuit.  

Valve banks