Muting (Bypassing)

Bypassing may be needed for different reasons. One of the most common reasons for bypassing is during in and out feeding of material on a conveyor, auto industrial trucks, etc. Another common application is bypassing while passing with a three-position device to the risk area.

Important aspects for bypassing are that it should be safe, not be activated by mistake and be difficult to defeat. In other words, it should give a reliable bypassing when a loading carrier comes but not allow a human to pass. To achieve the highest safety level a dual and supervised bypassing system is needed—usually with at least two independent signals. If this is done with sensors, it is recommended they be of different kinds, because the probability of them both malfunctioning for the same reason (e.g. common mode failure) is eliminated. An example of a solution is to use a mechanical limit switch and a photocell sensor.

To avoid deliberate defeating/manipulation of the bypassing sensors/signals a safety relay or a safety PLC is connected, thereby monitoring that both sensors are activated and deactivated in every bypassing cycle.

The amount of variants of bypassing systems are almost infinite, depending on the specific requirements of each plant/machine. For Focus there are a number of bypassing possibilities prepared.

Examples on how the Muting Sensors can be placed

A solution with two sensors(photocells shown)and ONE (or TWO) movement directions for material transport.

A solution with four sensors and ONE movement direction for material transport.

A solution with four sensors and TWO movement directions for material transport.