This section provides overview, applications, and principles of safety curtains. Also, please take a look at the list of 10 safety curtain manufacturers and their company rankings.
Table of Contents
Safety curtains are used in automated production facilities as sensors to monitor worker entry under certain conditions into hazardous areas and entrances where partitions and doors surrounding production facilities are unavoidable due to the production process, mainly for the purpose of providing safety measures for workers. Safety curtains are used as sensors to monitor worker entry under certain conditions.
Due to their safety-critical nature, safety curtain is designed and evaluated in accordance with the international standard IEC61496-1/2, General Safety Standard for Sensors, and are certified as safety equipment by a third-party certification body.
Safety curtains are mainly used to detect worker intrusion into hazardous areas around machinery, such as production facilities.
Partitions and doors surrounding production equipment for the purpose of safety measures for workers are sometimes unavoidable in the production process, especially in automated production equipment. Safety curtains are used as sensors for safety measures to monitor workers entering the operating range of equipment during the operation of automated facilities.
Safety curtains are designed and evaluated in accordance with the international standard IEC61496-1/2, the general safety standard for sensors, to ensure safety even in the event of a sensor malfunction, by detecting a circuit failure within the response time and immediately turning off the signal if an error is detected. If an abnormality is detected, the signal is immediately turned off to ensure safety.
ISO 13855 also specifies a minimum distance before a human body, such as a worker, reaches the detection area of the safety curtains and the production equipment to which the safety curtains are connected stops.
The light source that determines the sensing performance of the safety curtains used for this detection is defined as having a wavelength in the range of 400 nm to 1500 nm, so LEDs with a wavelength of 900 nm are mainly used.
Safety curtains with high safety performance generally require a pair of light emitting and light receiving units, and must be installed in such a way that multiple parallel beams of light emitted from the light emitting side are received by the light receiving side.
Safety curtains are considered being in a safe state when all the light from the projection side reaches the receiver side and the output from the receiver side is turned ON. If the light is blocked by a part of the worker's limbs, the output from the receiver side is considered being in a dangerous state and the output from the receiver side is turned OFF.
Like safety curtains, area sensors are used to detect people and objects in factories. The mechanism by which area sensors detect people and objects is similar to that of safety curtains. However, the control after detection is different. While safety curtains maintain their detection status and continue output, area sensors do not maintain their detection status.
This can lead to a serious accident if the operator misses that he or she has entered a hazardous area. Therefore, area sensors are not certified to international standards and cannot be used in safety applications. Careful attention should be paid to the selection of devices when building safety systems.
The minimum distance that must be observed when installing safety curtains is called the safety distance. This section describes the installation of safety curtains and the safety distance.
The safety distance can be determined from the walking speed of a human body, the penetration speed of a finger, the response time of the system, and the size value of the smallest detectable object that can completely block one beam in the detection area of the light curtain. The method of calculating the safety distance varies depending on the standards of each country and the individual standards of the machine. When designing a system, be sure to check the details in the standards document.
Safety curtains ensure safety, but if all inspection areas are enabled, productivity will decrease. Therefore, the safety curtains are equipped with a function to disable some of the safety functions.
This function keeps outputting a non-detection status even if the safety curtains detect it. The muting function is applied to a part of the detection area. For example, if a product or part is being manufactured and passes through the safety curtains, only the part that passes through the safety curtains will be left in a non-detected state.
This function disables a portion of the safety curtains at any time. It is used in equipment where the optical axis is constantly blocked by a fixed object such as a workbench.
*Including some distributors, etc.
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