Today, Wuxi Rihuan Sensing Technology Co., Ltd. will introduce to you the "non-passable principle" for the installation of safety gratings - having safety gratings installed does not mean safety is achieved.

After the safety gratings are installed and the indicator lights are on, and the equipment can operate normally - many users think this means "safety". But the reality is: having safety gratings installed does not mean safety is achieved. Only when the gratings are installed in the correct position can it be considered safe. If a person can bypass the gratings from the side, above, or below and come into contact with the dangerous moving parts, the gratings are useless.

Does a safety grating effectively prevent danger? In addition to depending on whether the grating itself and its control circuit meet the required safety performance level, it is also necessary to install the gratings correctly to effectively reduce risks. This leads to the core principle of safety grating installation - the "non-passable principle".

1. What is the "non-passable principle"?

Simply put, it is: the detection area of the grating must not have blind spots. After installing the grating, it is necessary to ensure that people cannot bypass the detection area from the top, bottom, or side and come into contact with the dangerous moving parts.

If there is a fixed protective device at the top or bottom of the grating, these protective devices must be able to effectively prevent people from bypassing the grating from the corresponding direction. If there is no fixed protective device at the top or bottom, there must be a sufficient safety distance between the grating and the dangerous point - this distance must be calculated according to the formulas and tables in the EN ISO 13855 standard.

2. Three most common "bypass" risks

1. Entering from the bottom

If the bottom beam of the grating is too high from the ground, a person can lie down or bend over and crawl into the dangerous area without being detected. This is the most easily overlooked blind spot in the field.

2. Crossing from the top

If the top beam of the grating is too low from the ground, a person can lift their leg and cross the grating to enter the dangerous area. Especially for low-height gratings, this risk is very prominent.

3. Bypassing from the side

If the installation width of the grating is less than the opening width of the dangerous area, or there are gaps on both sides of the grating, a person can directly bypass the detection area through the grating side and enter the dangerous area.

Any of these bypass methods being true means that the protection effect of the grating is completely ineffective.

3. How to meet the "non-passable" requirements?

Option 1: Install fixed protective devices

Add fixed mechanical protective devices (such as metal baffles, protective nets, etc.) at the top and bottom of the grating to physically block the bypass path. The size and strength of these protective devices must be sufficient to prevent people from passing through from the corresponding direction.

Option 2: Meet the standard installation height requirements

According to the EN ISO 13855 standard, when the grating is used as a safety detection device to prevent people's bodies from entering:

The bottom beam of the first detection beam from the detection plane (such as the ground) must be less than 300mm - to prevent people from crawling into from the bottom

The top beam of the first detection beam from the detection plane must be greater than 900mm - to prevent people from crossing from the top

The standard also gives recommended installation heights for multi-beam gratings: 4 beams are recommended at 300mm, 600mm, 900mm, 1200mm; 3 beams are recommended at 300mm, 700mm, 1100mm; 2 beams are recommended at 400mm, 900mm. The two red lines of bottom ≤ 300mm and top ≥ 900mm must be adhered to.

If the grating installation height cannot meet the above requirements, fixed protective devices must be added to make up for it.

Option 3: Calculate and meet the minimum safety distance

In addition to preventing bypassing, the grating must also be installed at a position far enough from the dangerous point to ensure that personnel will not touch the dangerous parts from detection to complete stop. The formula for calculating the safety distance is S = K × T + C (where K is the approach speed, T is the total stop time, and C is the added value). Specific values need to be calculated according to the EN ISO 13855 standard.

IV. Common Errors

Only installed photoelectric barriers without any anti-circumvention measures: The lowest beam is more than 300mm from the ground, or the highest beam is lower than 900mm, and no fixed protective device is installed - people can crawl in from the bottom or climb over from the top.

The width of the photoelectric barrier is less than the opening of the dangerous area: There are gaps on both sides, and people can bypass from the side.

Only calculating the safety distance without considering anti-circumvention: The safety distance ensures that "the device stops when it detects obstruction" within this period of time does not touch the dangerous point, but anti-circumvention ensures that "people cannot even enter at all". Both must be met simultaneously.

Believing that installing photoelectric barriers means no need for mechanical protection: The photoelectric barrier is an electro-sensitive protection device, and the fixed protective device is a physical barrier, they are complementary rather than substitutable.

Summary

Check items Requirements

Bottom anti-drilling Minimum distance from the bottom beam to the ground ≤ 300mm, or install a fixed protective device

Top anti-overturning Maximum distance from the top beam to the ground ≥ 900mm, or install a fixed protective device

Side anti-passing Gratings cover all openings in the dangerous area without any lateral gaps

Safety distance Calculated according to the EN ISO 13855 formula and met

The protective effect of the safety grating does not depend on how expensive the grating is, but on whether there is still a "way to bypass" after installation. If it is possible to drill through the bottom, cross over the top, or bypass the side - any of these situations exist, then this safety curtain is just a decoration.

The safety grating product line of Rihuan Sensor covers various protection heights and resolution specifications. We also provide professional installation guidance services to help users avoid blind areas and bypass risks during the design stage, ensuring that the grating installation complies with international standards such as EN ISO 13855. Welcome to follow Rihuan Sensor to obtain more complete and reliable safety protection solutions.