In order to do a complete, thorough risk estimation, fluid power devices must be considered. Fluid power devices are the final control elements in most systems and must be taken into account because they have the potential to create hazards when a fault occurs.

If there are pinch points, shearing points, and puncture points that are caused by fluid power devices, these hazards must be addressed. Take time to understand the potential failure modes of the valves used in the system; and the severity associated with the particular hazards based on the pressures and forces being used in the pneumatic or hydraulic system.

Each fluid power actuator (cylinder or otherwise) in the machine's system must be evaluated as to how it is controlled and what pressures are applied in order to determine the forces that may be generated. The control scheme of the valves in the system must also be examined in order to determine both normal and faulted conditions of the fluid power circuit. It is also important to consider what happens when a safety event occurs. Therefore, it is crucial to determine what the actuators will do when the valves are deenergized or if a fault occurs at that time.

Even though most pneumatic systems operate in the 80 to 100 psi (5.5 to 6.8 bar) range, there are many variations to this, both higher and lower. It is important to consider the actual system pressure when doing a risk assessment on your own equipment. Although it may be obvious to most, it is important to note that the pressures and forces associated with hydraulics are typically much greater than those associated with pneumatics. Therefore, this evaluation is equally, if not more, important with regard to hydraulic systems.