Honeywell ControlEdge 900 platform Hardware Planning And Installation Manual page 162

162
but if operating circumstances permit, disconnecting power from
the rack is the preferred option. Plan and develop an action
sequence before beginning the replacement procedure. Primary
considerations include:
When replacing I/O module, the voltages to the modules must be
disconnected at the field device before removing the terminal
block from the module.
Loss of control/monitoring in a running process - Each signal at
each of the terminals for an I/O module has a specific function.
Any or all of the signals may be vital for safely controlling a
process. Determine the functions of all signals to the modules
and know the potential consequences of losing each. If possible,
transfer control to alternate mechanisms; otherwise, bring the
process to a safe and controlled shutdown.
You will need a #2 Philips screwdriver.
To replace an I/O module:
CAUTION: Explosion hazard. Removal and Insertion Under Power
is not supported in Division 2/ Zone 2.
1. Disconnect all signals from power sources. Use a meter to ensure
that all voltages are disconnected.
2. If a power-down replacement procedure is opted, also disconnect
power from the rack, using the (user-supplied) switch in the
source main power.
3. Loosen the captive screws at top and bottom of the module;
loosening the screws will cause the terminal block to be partly
extracted from the module connector. Remove the terminal block
from the module.
CAUTION: The UIO module will continue to drive the
configured failsafe output if the UIO module is removed
along with the terminal block with the field power not de-
energized. So it is recommended to de-energize field power
before UIO module removal.
4. Using the extractor loop on the cover of the module, pull the
module from the slot with a long flat-tip screwdriver an extraction
lever. as shown in the following illustration.