Safe use of pneumatic systems

Machines with pneumatic actuators are used in many industrial areas. Even when used as intended, pneumatic systems can cause hazards. Protection against such hazards is required according to the Machinery Directive and related standards and safety regulations. For the practical use, the following examples of possible hazard and their causes are described and guidance for safe handling of pneumatic systems are given.

Hazardous machine movement
Dangerous machine movements, which can be caused by insufficient protective devices or inadequate control concepts. However, failure and return of power, component failure, pressure drop or residual energy contained in the system can also be the cause of dangerous machine movements.

Ejection of parts
Blowing away parts, the cause of which is improper assembly, unacceptable pressure increase (bursting of components) but also unacceptable pressure drop (e.g. on clamping devices).

Discharge of compressed air
Release of compressed air, especially if this occurs in conjunction with solid particles (contamination).

Ripping of hose assemblies
Reasons for whipping up hose assemblies can be the use of unsafe quick disconnect couplings, incorrect selection of hose assemblies, unfavorable hose clamps or external influences.

Protective measures

The hazards mentioned above can be avoided or reduced by design, control and equipment-related and organisational measures and by correct handling during use. It is very important that work on pneumatic systems may only be carried out by authorised personnel. The necessary personal protective equipment must be provided and used. In addition, the following instructions should be observed:

Selection and procurement

• The user must provide the machine manufacturer with all production-related data and the conditions at the installation site.
• Only machines that comply with the Machinery Directive may be procured (declaration of conformity in accordance with the Machinery Directive and possibly risk assessment).
• The pneumatic system should be designed according to EN ISO 4414.
• Accompanying documents (in particular operating instructions, circuit diagrams, parts lists, information on maintenance and repair, test certificates for pressure vessels) must be supplied.

Installation and commissioning

• Installation and commissioning may only be carried out in accordance with the information in the operating instructions.
• The conditions at the installation site must correspond to those for which the machine was designed.
• Protective measures to be taken by the operator must be carried out in advance, e.g. protection on pneumatic hose lines with large nominal diameters, use of quick disconnect safety couplings.
• All necessary user information must be affixed to or on the machine; in particular warnings against stored compressed air, e.g. on drives or pressure vessels.
• Safety devices, signalling and warning systems must be installed and function.
• The testing of pressure vessels at the place of installation according to the test group must be carried out before the machine has been put into operation.

Operation

• The machine must be operated in accordance with the operating instructions.
• Messages from the pneumatic system must be observed, e.g. pressure level, filter status.
• Attention must be paid to leaks.
• Immediate reaction must be made to malfunctions and/or changes in the normal operating sequence of the machine and the protective devices.
• All defects must be resolved immediately.

Servicing and inspection

• Regular checks and maintenance must be carried out and documented in accordance with the operating instructions.
• The function of the protective devices must be checked regularly.
• Hose lines, pressure vessels, pressure reducing valves, pressure switches and warning devices must also be checked regularly. The prescribed tests must be observed.
• Filter inserts must be checked regularly.

Repair and maintenance

• Repair work must be carried out professionally according to the operating instructions.
• The operating instructions should describe the procedure for troubleshooting.
• Only spare parts according to the spare parts list are to be used.
• After completion of the repair work, a function check must be carried out.

Rules of conduct

1. loads held up or machine parts on inclined planes must be lowered or supported
2. switch off the control unit.
3. disconnect all energy sources and secure them against re-connection.
4. All parts of the pneumatic system must be depressurized and checked. Attention must also be paid to stored energy.
5. If necessary, adjacent machines, e.g. in interlinked systems, must also be switched off or isolated.