Proface LT3300 - 5.7 All-in-One HMI" - Manual (Page 3)

2
Essential Safety Precautions
All safety-related procedures stated in this document must be followed to operate the LT correctly and safely. Be sure to
read this and any related documents thoroughly to understand the correct operation and functions of the LT unit.
Safety Icons
Throughout this manual, these icons provide essential safety information for LT operation procedures requiring special
attention. These icons indicate the following levels of danger:
System Design
Indicates situations where severe bodily injury, death or major equipment damage
can occur.
Indicates situations where slight bodily injury or minor equipment damage can
occur.
Indicates actions or procedures that should NOT be performed.
Indicates actions or procedures that MUST be performed to ensure correct unit
operation.
Be sure to design your LT control system so that, in the event of a main power supply failure or a LT
accident, the user system’s overall safety integrity will be maintained. If this is not done, incorrect output
signals or a LT malfunction may cause an accident.
1) Interlock and other circuits designed to interrupt or oppose normal machine movement (such as
Emergency Stop, General Protection, and forward and reverse rotation), as well as those designed to
prevent machine damage (such as upper, lower, and traverse movement limit positioning) should all be
designed to be located outside of the LT.
2) When the LT generates a “Watchdog Timer Error,” during logic program operating, the logic program
operation will halt. Also, when Errors occur in Input/Output control areas that the LT cannot detect,
unexpected movement may occur in those areas. Therefore, and to prevent unsafe machine
movement, a “Failsafe Circuit” should be created which is completely external to the LT.
For a failsafe circuit, refer to “4.2.5 Installation Precautions” (page 4-13).
3) If a problem arises with an external unit’s relay or transistor, causing an output (coil) to remain either
ON or OFF, a major accident can occur. To prevent this, be sure to set up external watchdog circuits
that will monitor vital output signals.