Safety in fail-safe mode

The fail-safe circuit comes in three different versions, “Fail-Safe Standard“, “Fail-Safe Plus – Always Safe” and “Fail-Safe Plus – Manual Override” to suit different customer requirements. In all three fail-safe versions, the actuator assumes its predefined safety position if the compressed air and/or power supply fails. This is achieved by using compressed air from the reservoir to move the actuator.

This fail-safe circuit, configured by Festo in a ready-to-install control cabinet, is a low-cost and effective safety solution compared with a single-acting linear cylinder. The pre-assembled solutions simplify the engineering process. They are ideal for use in applications such as rainwater overflow tanks in water technology.

Fail-safe times three

If the power and/or compressed air fails, the actuator assumes its predefined safety position. This is the basic functionality provided by the “Fail-Safe Standard” version. With the “Fail-Safe Plus – Always Safe” version, the actuator moves into the predefined safety position unless the circuit is in manual operation. It is possible to switch between manual and automatic operation, but only when compressed air is available.

With the “Fail-Safe Plus – Manual Override” version, the “dominant” manual operation applies. If there is a compressed air and/or power failure, the actuator moves into the predefined safety position unless the circuit is in manual operation. It is possible to switch between manual and automatic operation. In manual operation, the actuator can be moved when there is no compressed air and power until the air reservoir is completely empty. The air reservoir must always be customised in accordance with the customer’s requirements.