INSTALLATION OF PNEUMATIC CIRCUITS


Presentation of the Module

"Assembly of pneumatic circuits" is a module of first
year of training that allows trainees of the specialty
"Electromechanics" to get acquainted with the basics of
pneumatic. The aim of the latter is to also treat
components, fittings and ducts of pneumatic circuits, the
symbolization and composition of schemes. Trainees acquire
from knowledge to the calculation of the various parameters and
realization of basic circuits. They are placed in a situation where they
can analyze the circuits, make necessary measurements and repair
failures using the appropriate tools.

STANDARD

1.1 Structure of an automated system

All automated systems generally have the same structure :
- an operational part
- one part command
- a desk (dialogue)
The operating part connects the actuators of electric, pneumatic or hydraulic type
to the various mechanical elements to perform actions following a logic
organized.
The control part controls the cycle. It provides signals from
electric or pneumatic control to the pre-actuators.
The console includes the buttons and LEDs that ensure the start-up, the stops
emergency and other system controls.

1.2 summary description of key elements

The actuators represent the visible organs of the mechanism. They perform the work
and must be adapted to the environment in which they work. Among the main
actuators used in automated systems include :
- Linear cylinders
- Rotary cylinders
- Rodless cylinders
- Pneumatic and hydraulic motors
- Electric motors
Pre-actuators (distributors): their role is to direct pressure to the actuator
and react to orders coming from the order part.
Detection (sensors): their roles are to control the execution of the work. They
issue an information to the order bet.
Pneumatic control involves the use of sequencer modules.
Electrical control involves the use of industrial programmable controllers
(API).

The management of machines and installations involves the establishment of a logical network
often very complex, switching States and conditions. This is the conjugated action
various sensors, processors, pre-actuators and actuators to ensure
the sequence of chains in pneumatic systems.

Structure of pneumatic systems
Signal tracking: from bottom to top
Control chain: C P A-principle: sensor, processor, actor
 E T s – principle: input, processing, output
Power supply: by pipe or pipe

1.4. structure of pneumatic systems


Structure of a pneumatic INSTALLATION

2.1 Description of a compressed air installation and distribution

Any pneumatic installation ensuring the production and distribution of compressed air
include :
- Compressor
- An air tank
- An air treatment system
- A safety and regulation device
- A set of distribution circuits generally made of steel tube or
copper.
In pneumatic systems, compressed air is used as a source of energy.
The compressed air used in pneumatic systems is at the start of the air at pressure
atmospheric pressure artificially brought to a high pressure called Working pressure.
The working pressure in pneumatic systems is between 3 and 10 bar.
Compressed air is provided by a compressor, driven by an electric motor. This
built-in compressor consists of a filter, air compression system, a
cooler-dryer and one last filter. The outlet pressure is of the order of 10 bar.
A tank allows to regulate the consumption.

2.2 network implementation

When the air consumption is significant the compressor, with its installations
annexes, will be quite consistent. Therefore, a room often soundproofed and clean, will be
reserved for this purpose. The compressed air produced must therefore be brought to the places of use.
For this, a pipeline network will go through the different workshops and sites of use.
Some rules to follow :
- Provision must be made for the main network to have a pipeline capable of providing
possible extensions. This pipeline must be properly sized.
- It is imperative to provide, on the pipes, a slight slope and place at
each bottom point a tank with purge in order to collect all the condensation
located in the pipes.
- The main pipe must be carried out in a closed loop and the various punctures,
smaller diameter, will start from it. The greatest care will have to be taken
to the different sealings in order to minimize leakage.
Compressed air must be stabilized. For this purpose, the compressor must have a tank
mounted downstream. This reservoir is used to compensate for pressure changes when the system
takes compressed air for its operation. As soon as the pressure in the tank
a certain value, the compressor turns on and fills the
tank until the upper pressure threshold is reached. This also allows the
compressor does not have to operate constantly.

2.3 air compressor

The compressor is the fluid generator (compressed air) that feeds the network
use. The pressure supplied must be as uniform as possible and the air of excellent
quality. The following conditions must be met.
- Clean air, filtered, free of impurities ;
- Minimum humidity, air should be as dry as possible ;
- Appropriate size of the compressor unit to avoid any irregularities in the
device level of use ;
- Purity of air in terms of its chemical composition.

This will be achieved :

- Either normal air, with an acceptable degree of humidity
- Is a charged air, the most common,
- Or fresh air, used for instrumentation.
Maintenance
Compressor → follow the manufacturer's instructions :
- Purge the tank
- Check the oil level regularly
- Check the correct operation of the safety valve
- Change filters
On the piping → purge the tanks placed in the different places, if they are not
equipped with automatic purges.

Air treatment

3.1 overview

For air treatment, the equipment used is a compressed air conditioning unit.
The air, at the compressor outlet, is conveyed by steel pipes on the site
use. The conditioning unit is intended to prepare the air for its
use, in systems, by clearing it of dust, water vapour and others
harmful particles that can cause failures in installations.
This modular assembly consists of two or three devices mounted in series in a
determined order.
Its composition is as follows :
- A filter that purifies the air and purges the water in it.
- A pressure regulator that keeps the air at a constant and adjustable pressure.
- A lubricator which has the role of incorporating an oil mist into the compressed air
to lubricate the moving parts of the components constituting the system
pneumatic.
Installation
On systems using compressed air as an energy source, air treatment
mounts to the entrance of the installation. It is also necessary to provide an isolation valve
for maintenance operations.
Symbolic representation :
Maintenance
On this type of component, maintenance is very limited, but should not in any case,
being neglected. It is limited :
- to change the filter when it is soiled,
- to the oil filling of the lubricator,
- to drain condensate, if it is not automatic on the filter.


A filter (F), a pressure regulator®, a lubricator (L). Other components that may
adapt on the processing unit :
Bypass blocks for dry air intake, mounting brackets, level metal tanks
adjustable, automatic filling system for lubricators.

3.2 the filter with water separator

The role of the filter is to remove dust and all kinds of unwanted impurities,
harmful to the proper functioning of the system.

Air from the compressor enters the filter and passes through the deflector
a swirling motion. Solid and liquid particles
are plated by centrifugation on the wall of the tank and fall into the bottom. A
separator ensures a quiet area. The air then passes through the filter element to y
complete its filtration. Impurities and water can be discharged manually or using
an automatic purge system.

3.3 pressure regulators

The role of this device is to maintain compressed air at a constant pressure which
whether the air fluctuations of the network. It must regulate the pressure according to the
network request.

3.3 pressure regulators

The role of this device is to maintain compressed air at a constant pressure which
whether the air fluctuations of the network. It must regulate the pressure according to the
network request.

3.4 the lubricator

The role of the lubricator is to inject into the air a quantity of the oil to allow the
lubrication of the moving parts of the components forming the systems
pneumatic.
Maintenance
Oil filling is done by unscrewing the filling cap (K). To adjust the
oil flow, just act on the screw (J). Cut off the air supply to isolate the system.

3.5 installation of filters in a compressed air network 

In the installation of a compressed air network it is necessary to provide for different types of filters.  

Most common cases of association
1. Inlet disconnector, filter, mano-regulator and lubricator. (most common case)

2. Filter, mano-regulator, lubricator, disconnector and progressive starter (Case of large installations with large actuators).

Filtered and relaxed air is required in the case of a pneumatic PC, Bellows and sprayers.

PNEUMATIC COMPONENTS

Distributors


ACTUATOR

The actuator, also known as the motor member, is used to transform pneumatic energy into
mechanical work. Processed in the control part, the output signal is then directed
to pre-actuators which, in turn, drive the actuators.
A pneumatic cylinder is subjected to compressed air pressures that allow to obtain
movements in one direction and then in the other.
 The movements obtained can be linear or rotary.

The cylinders consist of a cylinder, closed at both ends, inside which
slide a piston rod assembly.

 There are therefore two rooms:

  •  the rear chamber is the part of the cylinder that does not contain the cylinder rod.
  • the front chamber is the part of the cylinder containing the rod of the cylinder.
  • Single acting cylinders:
  • Double acting cylinders:

COCKPIT:

Pneumatic control :


When the configuration and complexity rate of the automated installation results in the
choice of an "all pneumatic" solution, the distributors are pneumatically controlled,
as their control is ensured by pressure signals emitted by the control part
pneumatic.

Electric control:

When the processing of information is carried out in an electrical or electronic version it is
necessary that the dispensers are equipped with one or two control solenoid valves
whose role is to transform the electrical signal from the PC into a signal
drive tyre of the distributor.


The different types of drivers :

Depreciation

When a piston moves, it undergoes two pressures that generate two opposing forces. A
the other that is due to the pressure exerted by the other piston side. This pressure will depend on the rate of air discharge to
exhaust. Then we talk about back pressure.
This back pressure can be either to control the speed of movement of the cylinder, or
to control the position of a cylinder using a sensor.
The masses moved by double-acting pneumatic cylinders and the importance of
achieved speeds generate high inertia forces. It is necessary to reduce these
efforts at the end of the stroke to avoid impact of pistons on the bodies of the cylinders.
 Two types of shock absorber can be incorporated directly into the cylinder, one elastic
and other pneumatic:

A. adjustable pneumatic shock absorber:

When moving the rod, air can pass through either orifice No. 1 or orifice No. 2.
On the other hand, when the rod obstructs passage No. 2, the air must necessarily pass through
orifice # 1. In this orifice is placed a screw that will allow to adjust the flow and so
check the damping of the cylinder.

B. elastic shock absorber :

In this case, it is a "trilobed" seal that will take shocks to the bottoms of cylinders,
thus allowing shock absorption.
The blockers are 2/2 dispensers that are used, in general to block a cylinder
in an intermediate position. In this case we will use two blockers to block the
Jack in position.

Maintenance of a pneumatic system

Lubricator maintenance

A few years ago, we were still convinced that the oil removed from the
compressor could be used pour grease drive members. In the meantime,
it was realized that the heat released by the compressor causes a
calamination and evaporation of oil. This is therefore quite inappropriate as
and would even tend to behave like an abrasive on cylinders and cylinders.
distributors and seriously compromised their rendering.
Another problem that arises when maintaining networks running with
the lubricated compressed air is the oil deposit on the inland parks of the pipelines. This
deposition can be absorbed uncontrollably into the air flow and cause elevation
sensitive adjustment of compressed air pipelines. Maintenance of
installations with this type of problem est extremely difficult Un cars pipe
clogged by an oil deposit can only be cleaned if it is dismantled.
Oil deposits can also lead to scrubbing of certain components, in
particular after a prolonged stop. After a work stoppage of a few days, it happens that
lubricated components no longer work properly. D in general, on
will therefore always give preference to compressed air conditioning without lubrication.
In conclusion, the following points should be respected:
  •  Do not allow compressor oil into the compressed air network
(UN mount on oil separator).
  • Only fit self-accommodating components of non-compressed air
lubricate.
  • A system that has operated once with lubrication must be of this type
because the original lubrication device could in the long run
be rinsed.

Filter maintenance

The maintenance time for filter replacement depends on the air condition
compressed, the consumption of the connected pneumatic components and the size of the
filter. Maintenance of the filter includes the following points:
  •  replacing or cleaning the filter cartridge ;
  •  purging of condensate water.
When cleaning, the manufacturer's instructions should be followed carefully.
what concerns cleaning products. A cleaning with warm soapy water followed
from one blow to compressed air is usually enough.

Reliability of distributors

Mounting of roller dispensers: the reliability of an automation depends first and foremost
place of care taken for the installation of limit switches. These must be designed so
to make adjustments and adaptations as easy as possible at any time. This is important if
the aim is to ensure precise coordination of cylinder movements within a
automatism.
Installation of distributors: besides the importance of the scrupulous choice of
distributors, it is also a major requirement that should not be overlooked, namely the
Correct Assembly of these distributors to guarantee the maximum fidelity of the
features, trouble-free operation and easy access in case of repair
or maintenance. This applies equally well to distributors of the power part
only for the sensors of the control part.
To facilitate maintenance and repairs, it is necessary:
  •  number components ;
  •  Mount optical indicators ;
  •  complete documentation.
The muscle-controlled sensors for the input of the signals are in
general mounted on a control panel or console. It is therefore convenient
selecting sensors and control elements that can be connected
directly on the base element. There is a whole choice of control modes for
ensure the different and many input functions.
Sensors and pre-actuators control the operation of the actuators. They
should be designed to trigger as rapid a reaction as possible to the
actuator level. The sensors must therefore be installed as close as possible
of the engine components so as to minimize the
and response times, the ideal is to connect the sensor directly to the
the motor organ. In addition, this makes it possible to use fewer materials and reduce the
assembly time.