Principles, Standards and Implementation

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Prevention of Unexpected Power Up

Safety Isolation Systems

Safety isolation systems execute an orderly shutdown of a machine and also provide an easy method of locking off the power to a machine. This approach works well for larger machines and manufacturing systems, especially when multiple energy sources are located on a mezzanine level or at distant locations.

Figure 114 shows an overview of the system layout. Lockable stations are remotely located at convenient access points throughout the machine. When necessary, an operator uses the remote station to turn off the machine and lock the machine in the off state. The control box disconnects electrical and pneumatic power and provides a signal back to the operator that the energy has been disconnected.

Figure 114: Layout of Safety Isolation System

Figure 115 shows that the safety isolation system not only removes power from the machine but also grounds the load side. The operator gets a monitored, visible signal at the remote station that the machine is in a safe state, and the energy is dissipated.

Figure 115: Machine side is grounded with signal to operator.