Installation Precautions and Standards for Safety Light Curtains

Installation Precautions and Standards for Safety Light Curtains

A safety light curtain is an important “gatekeeper” in industrial automation for ensuring the safety of both personnel and equipment. It forms an “invisible protective line” by emitting infrared beams, and once a human body or foreign object enters the guarded area, the system can immediately send a signal to stop the machine’s operation, thereby preventing accidents. However, despite its compact and intelligent design, if not installed properly, even the best safety device may become “virtually useless.” Therefore, the scientific and proper installation of a safety light curtain is not only a technical task, but also a matter of responsibility.

First, from a scientific and standardized perspective, two things must be clarified before installation: who or what is being protected, and where the source of danger lies. Different types of equipment have different hazardous zones—for example, the upper and lower dies of a punch press, the rotation radius of a robotic arm, or the feed port of a packaging line. These areas pose a high risk of pinching or collision if personnel approach. Therefore, the installation position of the light curtain must ensure that there is enough response time to stop the equipment before dangerous motion occurs. Normally, the minimum safety distance between the light curtain and the danger point is calculated based on the operating speed and braking distance of the equipment. This is a hard requirement with established formulas and standards to follow (such as ISO 13855).

Second, the installation height must be appropriate. For hand protection, light beams are usually arranged at a height between 20 cm and 50 cm; for full-body protection (such as entering and exiting equipment zones), multiple beams or full-height coverage light curtains must be used. Do not “save effort” by installing only part of the system—that’s nearly the same as not installing it at all.

Third, the light curtain must be aligned—it cannot be tilted, nor have gaps. A safety light curtain operates based on precise alignment of multiple infrared beams between the emitter and receiver. If misalignment occurs due to tilted installation, frame vibration, or intermediate obstructions, blind spots or false alarms may result. Many companies find that everything runs normally right after installation, but after some time, equipment movement or a loose base causes the light curtain to deform. When an accident finally happens, they realize the “eyes have gone blind”—this is a typical consequence of neglecting stable installation and regular calibration.

Electrical connection and logical interlocking must also not be sloppy. Safety light curtains must be integrated into a safety control system that meets PL (Performance Level) or SIL (Safety Integrity Level) requirements, not casually connected to a regular relay. To achieve “machine stops when person enters,” it must be ensured that the signal can reliably interrupt the control circuit. This involves hardware such as safety relays and safety PLCs, and must comply with the equipment manufacturer’s instructions or relevant national standards (such as GB/T 19436.1).

To put it in more grounded terms: installing a safety light curtain isn’t just about whether the lights are “on”—it’s about whether it actually “does its job.” A qualified installation should be able to ensure that “the machine stops immediately when someone enters the danger zone,” not “the machine keeps running for three more seconds after someone enters.”

In addition, there are a few small details worth noting:

• Avoid strong light interference: Do not aim the light curtain toward windows or highly reflective backgrounds.
• Dust and oil protection: The curtain panel should be wiped regularly to prevent dirt and oil from affecting detection.
• Prevent bypassing: Evaluate whether someone could circumvent the curtain from below, above, or the sides, and use physical barriers accordingly.
• Post warning signs: Remind workers that “this is a safety protection area” to enhance onsite safety awareness.