Background:
I work in a refinery where we have two cokers with 30 MOVs in each coker. We communicate to and from these MOVs using RS485 2 wire + shield. This design has failed and we believe it is due to the overall length of the cable (From I/O room to the MOVs) in addition to not having the third conductor for signal grounding. I am working on a project to redesign this system to something more reliable.
Current Design:
There are 7 segments in each coker with four to five daisy chained MOVs in each segment. The first MOV in the segment is wired directly to the I/O room into an 8-port MOXA then to Delta V serial cards.
New Design:
We are stripping the MOVs 2 wire cable and replacing it with a 3 wire + shield cable, keeping the daisy chain design. Instead of routing the cable to the I/O control room, we are taking each segment to MOXAs MGATEs MB3170I-T (Modbus-Ethernet). These MGATEs will then be wired to cisco switch IE2000 (Ethernet-Fiber) via a CAT 6 ethernet cable. This Cisco switch is then wired to a fiber patch panel which relays are the signals to the I/O control room via fiber. We are hoping this helps with the length concerns we have.
I am curious if anyone has ever come across similar issues or have any advice to our project team. We are a few months away from implementing this design.
I work in a refinery where we have two cokers with 30 MOVs in each coker. We communicate to and from these MOVs using RS485 2 wire + shield. This design has failed and we believe it is due to the overall length of the cable (From I/O room to the MOVs) in addition to not having the third conductor for signal grounding. I am working on a project to redesign this system to something more reliable.
Current Design:
There are 7 segments in each coker with four to five daisy chained MOVs in each segment. The first MOV in the segment is wired directly to the I/O room into an 8-port MOXA then to Delta V serial cards.
New Design:
We are stripping the MOVs 2 wire cable and replacing it with a 3 wire + shield cable, keeping the daisy chain design. Instead of routing the cable to the I/O control room, we are taking each segment to MOXAs MGATEs MB3170I-T (Modbus-Ethernet). These MGATEs will then be wired to cisco switch IE2000 (Ethernet-Fiber) via a CAT 6 ethernet cable. This Cisco switch is then wired to a fiber patch panel which relays are the signals to the I/O control room via fiber. We are hoping this helps with the length concerns we have.
I am curious if anyone has ever come across similar issues or have any advice to our project team. We are a few months away from implementing this design.