IS & Ex

Preconfigured fail-safe circuit from Festo

November 2021 IS & Ex

The preconfigured Festo fail-safe circuit is ready to install in the control cabinet as a safe and low-cost alternative when it comes to fail-safe technology. It replaces a single-acting actuator and guarantees that the actuator assumes a predefined safety position in the event of pressure and/or power failure.

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. The actuator assumes its predefined safety position in all three fail-safe versions 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 and are ideal for use in applications such as rainwater overflow tanks in water technology.

Fail-safe times three

If the power 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 operates manually. 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 or power failure, the actuator moves into the predefined safety position unless the circuit is in manual operation. In manual operation, the actuator can be moved when there is no compressed air and power until the air reservoir is completely empty, which means the air reservoir must always be customised to meet customer requirements. It is also possible to switch between manual and automatic operation with this variant.

For more information contact Festo South Africa, 0860 033 786,,


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