Pneumatic system of machines – Machinery Directive (2006/42/WE)

BLOG

We want to familiarize you with the principles of machine building to expand your knowledge of the field in which we specialize. Our goal is to explain complex principles in the field of industrial mechanical engineering and automation.

Today, we take the pneumatic system and start from the basics, which are our everyday life so that the machines we build are safe for your employees.

Pneumatic systems play a key role in the automation of industrial processes, providing precise and efficient control of various machine components. Understanding the basics of their design and operating principles is essential to ensure the safe and reliable operation of the entire system. In this article, we will introduce you to the most important components of pneumatic systems, their functions and applications, as well as discuss which safety measures must be implemented to meet the requirements of the Machinery Directive.

What is the Machinery Directive?

The Machinery Directive (2006/42/WE) is a European regulation to ensure that machinery placed on the EU market is safe for users and the environment. It covers a wide range of requirements for the design, manufacture, and conformity assessment of machinery.

Key safety requirements

The Directive requires that machinery be designed and constructed in such a way that:

Minimize usage risks.
Protect operators from injury.
Meet specific standards for noise, vibration, and emissions.

Therefore, the compressor room where the compressor is located must be equipped with additional elements to prepare the air for forwarding. These include dryers that remove excess moisture, filters that eliminate solid and oil contaminants, and condensate separators that separate and drain condensed water. Thanks to the use of these devices, the compressed air generated is properly cleaned and dried, which ensures its high quality and reliability in further production processes.

Design principles for safe pneumatic systems

The design of safe pneumatic systems in accordance with the Machinery Directive includes:

Risk analysis: Identification and assessment of potential hazards.
Risk reduction: Implement technical and organizational measures to minimize risks.
Documentation: Maintaining detailed design documentation and conformity assessment.

What is included in the pneumatic system.

Air service station – the most important part of the system

The air preparation station is a key component of the pneumatic system. It consists in the basic and minimal version of the main manual valve, air filters, electric main valve (in the case of automatic machines), which together ensure that the air used in the system is clean, dry and at the right pressure. It can be equipped with:

Manual master valve: responds to the conscious and manual application of pressure to the machine. The valves are equipped with the possibility of securing using the LOTO system. LOTO system – it is a health and safety protection in the event of work carried out on the mass. By closing the valve and securing it with the LOTO system, the mechanics servicing the machine can be sure that no one will accidentally start the machines or lines during the work they are carrying out.

Air filters: Remove pollutants from the air of a certain size.
Dehumidifiers: Remove residual water directly in front of the machine, preventing corrosion and damage to pneumatic components. In the dryer, you can see whether the air prepared in the compressor is properly prepared and dehumidified.

Pressure regulators: Maintain a stable air pressure set and recommended for a given line machine by the manufacturer.
Electric Main Valve: Responsible for releasing pressure from the machine when the safety system is activated.

Controls

Valves:

Pneumatic valves on industrial lines can be found in the form of:

Single valves: serving one valve with individual pneumatic connection and control.
Valve terminals: a set of valves with one electrical and pneumatic connection to support a module or the entire machine.

The valves are controlled in a way that

electric – found in automatic machines. Most often controlled by a PLC.
manual – used in simple assembly stations, operated by the operator. A good example is the operator‘s control of individual elements of the excavator arm (admittedly the hydraulic system)

pneumatically – these are valves used for indirect control, e.g. a small electrically operated valve is used to start the flow in a valve with a high flow (it plays the role of a pilot initiating the flow).

Valves have their own functions and types

Valve types: normally open, closed, vented, aerated
Functional: 3/2, 5/3, 5/2, 2/2, 2×3/2 ect.

Control valves:

Throttling–feedback: with manual flow rate setting
Controlled: Prevents the actuator from moving in the event of a broken hose or a leak in the system.

Proportional valves: allow precise control of airflow. With the ability to regulate the flow continuously and in proportion to the control signal, these valves are used in a variety of industrial applications requiring high precision and dynamic control.

Elementy wykonawcze

Actuators (pneumatic cylinders) – are executive elements of the pneumatic system. There are several types of actuators:

Basic: Rectilinear piston movements.
Rodless: Movement without direct piston.
Rotary: Rotary motion instead of linear.

Actuators come in different varieties. Basic, every manufacturer has the same due to the ISO standard. When it comes to special non–standard cylinders, i.e. cylinders with various types of guides, rodless or rotary cylinders, each manufacturer has freedom in the case of the selected size of the housing, fasteners and it is not always possible to use them interchangeably.

Other less common and specialized elements, such as:

pneumatic motors,
Screwdrivers,
Grinders,
paint guns,
adhesive systems.

Pneumatic hoses

In industry, the most commonly used cables are:

Polyurethane (PU): Highly flexible, abrasion resistant, ideal for applications in dynamic systems where high flexibility is required. Polyurethane hoses are most often used when welding or welding elements are close to assembly. In places where resistance to falling welding sparks is necessary.

Polyamide (PA): They have high mechanical and thermal strength, resistant to oils and chemicals, used in high–pressure applications.

Summary:

The pneumatic system, although it may seem like the simplest system in a machine, requires careful design and selection of appropriate components to meet the requirements of the Machinery Directive. It is crucial to properly size the actuators, the intermediate valves responsible for the operation of the actuator and the type of control to ensure the safe and efficient operation of the entire system.

Safety aspects such as protection against sudden pressure loss or overnight shutdown must also be kept in mind to avoid the cylinders dropping down and causing collisions when restarted. With the right design of the pneumatic system, not only compliance with standards can be ensured, but also the safe and trouble–free operation of the machine, which is crucial for the protection of employees and the optimization of production processes.