Industry Knowledge | How to determine the installation distance of safety light curtains?
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- Issue Time
- May 30,2024
Summary
In order to stop the machine from working before the human body or object reaches the dangerous area or dangerous part, the minimum distance that the light curtain must be separated from the dangerous area or dangerous part is called the safety distance.
Safety light curtains are widely used, such as forging machines, punching and shearing machines, elevators, subway gates, textile machinery, paper cutting machinery, etc. In modern factories, people and machines work together, and some potentially dangerous mechanical equipment can easily cause personal injury to operators, so safety light curtains play an important role in safe production.
In order to stop the machine from working before the human body or object reaches the dangerous area or dangerous part, the minimum distance that the light curtain must be separated from the dangerous area or dangerous part is called the safety distance.
The safe distance when a person enters the light curtain detection area vertically (see the figure below) can be calculated by the following formula. When the person does not enter vertically, the calculation formula will be different, so please refer to the relevant standards of each country.
S=K*T+C
S: Safety distance (mm)
K: Movement speed of the body or body part entering the detection area (mm/s)
T: Total response time (seconds) (T=t1+t2)
t1: Maximum response time of the light curtain
t2: The longest stop time required for the machine to stop after receiving the signal from the protective device (seconds)
C: Additional distance calculated based on the diameter of the minimum detection object of the light curtain (mm)
The value that can be used as K is the speed of a certain hand movement. (Usually, the horizontal movement of the hand and arm when a person is sitting down). Although other values are used, 1.6m/s (63inch/s) is generally used. The hand speed constant does not include other body movements that affect the actual movement speed.
Therefore, it is necessary to consider the optimal value including the above value according to the actual application method of the safety device.
Ds=KxT+Dpf
Ds: Safety distance (inch) 1 inch = 25.4 mm.
K: Maximum speed of the body or part of the body approaching the dangerous area or source of danger
T: The total time required for the machine to stop its dangerous action or complete a dangerous cycle of the machine.
Dpf: Additional distance that varies with the minimum detection object of the light curtain. This value varies with the type of machine and the safety protection equipment used.
S=[Kx(Ts+Tc+Tr)]+Dpf
S: Safety distance (mm)
K: Movement speed of the body or part of the body entering the detection area (=63 inches/s)
Ts: The required stop time (seconds) when the final stop signal is sent to the machine
Tc: Maximum response time of the machine control system (seconds)
Tr: Maximum response time of the light curtain and its interface (seconds)
Dpf: Additional distance due to the proximity factor (mm)