How can you implement a redundant PLC system?

At some point of time all electromechanical and electronic equipment are going to fail. It's virtually impossible to predict and prevent system downtimes, errors and resultant issues In automation & PLC systems the client invests to achieve higher efficiency and lower costs To achieve this and also to prevent losses and hazards in critical processes and environments it becomes necessary to have a fall back system which works on the same parameters and takes over in case of failure/s at single / multiple levels without allowing process alterations due to failure. Redundancy can be of multiple types for multiple sub systems and even at component levels for control systems Architectures must be carefully selected though for effectiveness

Orgs may have variations based on their needs. You have different kinds of redundancy like Cold, Warm, Hot Cold - Tier 3 apps, non critical, systems can be down for 24 hours Warm-Tier 2 apps, 2-20 hours of downtime is acceptable . Your primary and secondary may have human intervention to switch back, catchup may be required Hot-Tier 1 - critical apps, no data or msg loss, switch expected without human intervention

In addition to implementation of high level redundancies, alarming in case of failure of any single device/path for all redundancies is to be ensured in PLC system and Historian so as to correct the single device fault at the earliest. There should not be any compromise in getting this alarm signal for missing of proposed redundancy.

All systems based on their tiering need redundancy. Cloud providers have done good extent of automation & availability, orgs need to configure their own VPC's & AZ's. It is imp to be able to monitor & action alerts received during monitoring activity. There are 3 main types Cold, Warm, Hot Cold - Tier 3 apps, noncritical, systems can be down for 24 hrs Warm-Tier 2 apps, 2-20 hrs of downtime is acceptable . Primary & secondary may have human intervention to switch back, catchup may be required. Hot-Tier 1 - critical apps, no data/msg loss, switch expctd without human intervention. Ensure ur biz stakeholders understand tiering of the applications & what it means For preparedness, do DR's or Failure test simulations at regular frequency.