User manual

Chapter 5: Installation and Wiring
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Hardware User Manual, 4th Edition, Rev. B
Three Levels of Protection
WARNING: The control program must not be the only form of
protection for any problems that may result in a risk of personal
injury or equipment damage.
The publications mentioned provide many ideas and
requirements for system safety. At a minimum, you should
follow these regulations. Also, you should use the following
techniques, which provide three levels of system control.
1. Orderly system shutdown sequence in the PAC
control program.
2. Mechanical disconnect for output module power.
3. Emergency stop switch for disconnecting system power.
Orderly System Shutdown
The first level of fault detection is ideally the PAC control program, which can identify machine
problems. Certain shutdown sequences should be performed. These types of problems are
usually things such as jammed parts, etc. that do not pose a risk of personal injury or equipment
damage.
System Power Disconnect
You should also use electromechanical devices, such as master control relays and/or limit
switches, to prevent accidental equipment startup at an unexpected time. These devices should
be installed in a manner that will prevent any machine operations from occurring.
For example, if the machine in the illustration has a jammed part, the PAC control program can
turn off the saw blade and retract the arbor. If the operator must open the guard to remove the
part, you should also include a bypass switch that disconnects all system power any time the
guard is opened.
Jam
Detect
RST
Retract
Arm
Turn off
Saw
RST