of 5
7/27/2019 BSR CI Case Study_Coupling Diode - OK
1/5
C&I CASE STUDYCoupling Diode for Redundant DC Power system
28/7/2014
BSR C&I Team
Install coupling Diode For Redundant Power system
General information
In general, the Longer the power sup-plies warranty, the Longer the power
supply and the end-product will operate without a failure. Power supplies
contain Large electrolytic capacitors, which over time will dry out and
eventually fail. High quality industrial grade power supplies use higher grade
and more expensive electrolytic capacitors that resist drying out and therefore
ensure the longest power supply Life possible.
In addition, most medium to high power supplies use fans to keep them at the
correct operating temperature. Since fans are electro-mechanical devices theyhave the shortest lifespan of any compo-nent in a power supply or system and
will overtime, fail.
Install coupling Diode For Redundant Power system
General information
In Refinery, where a system cannot tolerate any downtime, a redundant power
supply or system configuration should be considered.
Typical configuration of redundant Power supply as figure 1
Install coupling Diode For Redundant Power system
General information
Figure 1 is a schematic of a redundant power system. Note that there are three
power supplies connected in parallel by means of internal Isolation (O Ring)
Diodes connected in series to the system Load. The isolation diodes' function is
to become back-biased (as an open-switch) in the event one of the powersupplies fails. In this situation, the failed supply is automatically disconnected
from the system load, its fault indicator turns from green to red, and the System
Load continues to receive full power from the remaining two redundant power
supplies.
7/27/2019 BSR CI Case Study_Coupling Diode - OK
2/5
Install coupling Diode For Redundant Power system
General information
The failed supply is designed to be replaced while the system input and output
power remains ON (hot-swapped); therefore it can replaced at the user's
convenience without impeding the operation of the system.
One of the main reasons for using 'Redundant Power Supplies' is to construct a
'fault-tolerant' power system. This means that even if one of the paralleled
supplies should fail the system will continue to provide full power to its
power bus. This is sometimes referred to as 100% power availability. In
redundant power systems, each supply must include a circuit that automatically
disconnects its output from the others, should it malfunction.
Install coupling Diode For Redundant Power system
From commissioning, we got 2 troubles related to this issues
ETP package (Unit 058) was suddenly stopped on 11-April-2011All process parameters of air dryer A-3502B were BAD value on DCS display
on 8-Jan-2012.
History of issue
MCBs tripped
PS shorted
Install coupling Diode For Redundant Power system
7/27/2019 BSR CI Case Study_Coupling Diode - OK
3/5
Install coupling Diode For Redundant Power system
Install coupling Diode For Redundant Power system
The redundant 24VDC Power supply system (for Air Dryer A3502A/B, and
ETP _ Unit 058) does not have the coupling diode to prevent short circuit in
case 1 power unit fail and become short circuit at Output Similar configuration applied for power supply of control system for
compressor C-1201A/B, C-1202A/B/C
One Power supply unit fails, it leads to short circuit of whole power supply
system.
Finding:
Install coupling Diode For Redundant Power system
To avoid the downtime of equipment, MOC-12-12-063; MOC-035-12-048;
MOC-058-12-058 have been issued to re-design the redundant power system with
coupling diode in 2nd
Turn Around;
Solution
7/27/2019 BSR CI Case Study_Coupling Diode - OK
4/5
MOC for Installation coupling Diode For U12MOC for Installation coupling Diode For U58
MOC for installation coupling Diode U35Procedure for Installation coupling Diode
7/27/2019 BSR CI Case Study_Coupling Diode - OK
5/5
Install coupling Diode For Redundant Power system
No coupling diode
installed for
redundant Power
supply
Install coupling Diode For Redundant Power system
The modification was carried out as below configuration:
Coupling diode
installed for
redundant Power
supply
Install coupling Diode For Redundant Power system
Benefits:
In case of one Power supply unit fails, the system load still in receive
power from redundant Power supply unit. The process will not be upset;
THANK YOU FOR YOUR ATTENTION
E.O.D
