Compared with common power operated doors, radiation shielding doors possesses two additional safety-relevant features. On one hand, door leafs can have a depth of more than 300 mm, up to 2000 mm and on the other hand, door leafs weight more than 10 kN, up to 1300 kN.
These enormous depth of the leaf grant space for a person to stand in between the inner and outer end of the sliding door leaf, without being recognized by a non-contact safety presence sensor. Non-contact safety presence sensors are installed at the front side, and, or at the back side of the door. The intermediate space is not monitored. Without a working clamp force limitation, a person could be crushed between the closing edge and the wall.
Also narrower door leafs are not safe with a solely non-contact safety presence sensor. Given the case that a person grabs into the area of the doors front edge near to the shearing edge, while the door is closing, and triggers the non-contact safety device, because of the significant mass the stopping distance could be too long to prevent a crushing or shearing of limbs.
Complementary be mentioned, that someone grabbing into the danger closing edge isn’t unusually. Maybe you’ve already seen someone grabbing into closing elevator doors, trying to trigger the light curtain and reopening the door for another person standing outside. With light elevator doors that may only lead to a mild clamping, but in case of heavy shielding doors this may result in serious injuries.
A relief for both cases is a limitation of the clamp forces, in compliance with EN 12453.
An expert opinion available to us, which has examined the described issue, comes to the following conclusion. “The operational safety can’t be solely implemented by non-contact safety features. An effective safety feature is the limitation of the clamp forces. The resultant clamp forces have to meet the restrictions of EN 12453.”