Are Mechanical Safety Edges Safe?

We are often asked if it’s ok to use mechanical safety edges rather than resistive ones. This normally happens when a member of Gate Safe is taking over an existing site where mechanical edges have previously been installed.

Mechanical edges work by having either an internal cable or lever running through the rubber profile which is attached to a switch at one end. When the edge is activated the cable or lever will pull the switch open. Resistive edges work by the controller looking for a resistor at the end of the edge. When the edge is activated the contact strip running through the edge changes the resistance seen by the controller.

The main concern with mechanical edges is that they cannot be monitored by the control circuit properly. The Standards do say that all electronic safety items should be a minimum of cat2. Unfortunately, this cannot be achieved with a mechanical edge, as the actual edge itself is not electronic. This means that there is potential for the edge to sustain damage and for the system to remain oblivious, consequentially leaving the gate operating in an unprotected and possibly dangerous mode.

While we are talking about self-testing, don’t forget that when possible use the test input on the logic board to monitor the photocells to verify that the relays aren’t stuck or welded together.

There is also the issue of coverage on mechanical edges. Often these have a large area at each end of the edge which is not active, sometimes up to 100mm, preventing coverage of the full height or length of a gate or barrier. This is likely to result in, leaving areas such as towards the hinges on swing gates unprotected - the very area on the gate with the most force!

If you do come across gates with mechanical safety edges fitted, please make sure you carry out a comprehensive risk assessment and test the edges thoroughly to make sure that they are in good condition and cover the areas of risk effectively. Inform the owner of the gates of the need to perform tests weekly to ensure that they are still working effectively and advise of the requirement to report any damage.

Whether you are dealing with mechanical or resistive edges it is important to remember that temperature, especially freezing conditions can have a massive impact on the sensitivity of the actuation with ice build-up possibly preventing the edge from switching at all. In these conditions, we would carry out more regular and stringent tests on the system to ensure the system is safe to be used.

If you have any doubts, we would thoroughly recommend replacing the edges with monitored resistive types.

To find out more about gate safety visit https://gate-safe.org/