Guard presence sensing

Presence-Sensing Devices Presence sensing devices detect whether the operator s fingers or hands are or could be in the point-of-operation. If they are, the machine will not operate or will stop quickly enough to prevent injury. Presence-sensing devices are not a suitable alternative for some machines. Each type of device has particular limitations. Guards should protect all areas not protected by presence-sensing devices. 

Mechanical-power presses are required to have switches and brakes that are operator proof The size of some presses makes it imperative that they are switch-guarded as well as mechanically guarded. This section describes what actions must be taken to produce the most failsafe device possible. Minimum braking action and the proper brakes that must be installed on presses of differing specifications are outlined. Criteria for the use of presence-sensing devices and their proper utilization is described. 

In special circumstances, where plysical guarding is not firlfy possible, the application of quick-stop devices can be incorporated. In particular, rrse is made of photo-electric beams or other presence-sensing systems. As is the case with automatic guards, these types of devices present technical difficulties and reliability concerns if not properly installed and integrated into the operations of the machine. 

When will a presence-sensing guard stop a machine ... 

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