Switching Module Replacement Procedure; Iop B Should Be Secondary; Battery Backup Exhaustion; Introduction - Honeywell HPM Service

4 Fault Isolation

4.7 Battery Backup Exhaustion

Switching module replacement procedure

The procedure in the following table is required when any of the outputs are in the "on" state and the
switching module is defective.
Step
1
Verify that a current Checkpoint for the problem IOP is available, and if not, save a
Checkpoint before proceeding.
2
Connect an Analog Output Standby Manual device to the FTA and balance the outputs.
3
On the Analog Output Standby Manual device, switch control of the FTA output field
terminals from the IOP to the Analog Standby Manual device.
4
Remove the switching module on the FTA and then disrupt power at IOP A.
5
IOP A should now be in the idle state and the primary IOP. Restore the Checkpoint to
the IOP and start the IOP. IOP B should be in Soft failure with a MISSING FTA status
and should synchronize with IOP A.
6
Replace the switching module on the FTA and verify that IOP B clears its Soft failure
and synchronizes with IOP A. The HPM Status display should now indicate OK/BKP.
7
Align the outputs with those on the Analog Output Standby Manual device and switch
control of the field terminals from the Analog Standby Manual device back to the IOP.

IOP B should be secondary

Always remember that IOP B should be the secondary during normal operation to provide the best
subsystem availability. IOP B's functions should be periodically tested using the procedure found
subsection "Redundant 8-Channel Analog Output IOPs" ("Periodic Redundancy Tests" section).
4.7 Battery Backup Exhaustion

Introduction

When the 48 Vdc backup batteries become exhausted after approximately 20 minutes of operation
because of Power Supply Module failure or loss of ac power, the 24 Vdc output from the Power System
collapses abruptly to zero. Until that time, the 24 Vdc output from the Power System remains within
specification. There is no gradual decay of the 24 Vdc output.

Loss of 24 Vdc

If the 24 Vdc output is lost, the control signals from the Analog Output and Digital Output FTAs in the
cabinet or cabinet complex that are powered by the particular Power System will become inactive, with
the AO FTA outputs dropping to a nonpowered condition and the DO FTAs output relays assuming their
deenergized state.

Multiple battery backup

Be aware that other Power Systems (additional cabinets) with battery backup that may be in the High-
Performance Process Manager subsystem may not exhaust their battery capacity at the same time. The
effect of the situation on the overall control and safety of the process being controlled should be
considered.

US response to 48 Vdc battery failure

As a result of the loss of 24 Vdc power, the HPM cabinet becomes nonpowered. The HPM status
displays at the Universal Station (US) will show the status of the HPMMs to be OFFNET or
UNKNOWN. Without access to the HPMMs, the IOP displays are not available.
354 HPM High-Performance Process Manager Service
Honeywell
Action
R688
December 2020