Redundant PLC Systems in Forestry and Aggregate Industries

Redundancy is a crucial factor in any industry. It ensures that backup systems are available in the case of system or component failure. This entails maintaining duplicated or even triplicated components or systems, for prompt and efficient disaster management. This is why understanding redundant PLC systems is so important.

Understanding Redundancy Architectures: Hot Standby vs. Cold Standby

There are two possibilities within redundancy architecture — hot standby and cold standby. In hot standby, redundancy measures are always active and ready. In cold standby, they are inactive until needed.

Hot Standby

• The secondary system is continuously operational, and active at the same time as the primary system. There is continuous resource utilization with the hot standby strategy.
• It does not require activation when the primary system fails, but instantly takes over for seamless operational continuity. Activation time and recovery time are minimal.
• Synchronization is continuous and in real time.

Cold Standby

• The secondary (backup) system is powered down, and inactive until needed. Minimal resources are used in cold standby until the backup system is activated.
• It requires activation upon failure of the primary system. The activation time, and thus the recovery time, is longer than for hot standby systems.
• Synchronization is not continuous or in real-time. This strategy requires manual or periodic synchronization.

What the Differences Mean for Your Business

The US forest products industry accounts for about 4% of the manufacturing GDP. The aggregates industry mines and sells billions of tons of crushed stone, and is a significant contributor to the economy. These are some of our most important industries. They cannot afford the downtime after PLC failure.

So, how do cold and hot standby PLC redundancy strategies compare and what does it mean for business?

Cold standby PLC redundancy requires less maintenance and uses fewer resources. Initial costs will be lower, but it can have higher operational costs, with longer downtime. This could adversely impact your forestry or aggregate business.   

Hot standby PLC redundancy requires ongoing maintenance and uses more resources because it is always active and ready to take over. Initial costs are higher, but operational costs are typically lower, with only minimal downtime.

For PLC redundancy in these industries, backup should preferably take control automatically if the primary PLC fails, to ensure continuous operation with minimal downtime.

Which Should You Choose?

Cold standby redundancy strategies are easier to manage and more budget-friendly. If you have less staff or resources to commit to disaster management, this may be the right choice. But it should only ever be used for non-critical systems.

For critical system backup and uninterrupted operations, the hot standby strategy is best. It will require more resources. But if you cannot afford downtime, the real-time sync and instant backup this provides is the solution.

Failover Mechanisms and Communication Synchronization in PLC Redundancy

For aggregate businesses, a malfunction can bring rock crushing to a standstill. In forestry, a natural disaster can damage automated forestry equipment. Anything can happen in the future, resulting in costly downtime. But with a robust disaster recovery strategy, you’ll enjoy continued operations.

It’s all thanks to redundant PLC systems, failover mechanisms, and communication synchronization.

Failover mechanisms are essential in redundant PLC architecture. Failovers automatically switch to standby computer servers, systems, networks, or hardware components, when the primary ones fail.

They facilitate hot standby transition of system operations from a failed component to a standby component. When built into system design, they offer high availability automation with disaster recovery and redundancy and reduced downtime.

Communication synchronization is another must for continuous operations. In redundancy design, multiple communication channels address any systems communication failure.

In hot standby, both processors have ongoing access to the I/O over redundancy buses or networks. Data and information are exchanged and synced over a dedicated fiber optic link. If one fails, the other takes over in a seamless transfer.

Network Topologies for Redundant Control Systems

Network topology refers to how devices are connected. It is the physical arrangement in a network and the connections between them. There are different topologies, with mostly a linear or circular design.

With bus topology, every device is connected via a single cable. In ring topology, all nodes have equal access to the network. Star topology depends on a central hub. Tree topology offers enhanced scalability.

The best topology for PLC redundancy and recovery is a mesh topology. Each computer and network device is interconnected in a decentralized, web-like fashion, allowing continued transmission even if one fails.

Conclusion

Both the forestry and aggregate industries have time-sensitive processes. Downtime isn’t an option. Do you need custom-built automation and control panels and parts that support your redundant PLC systems strategy?

AEC is a licensed panel builder, specializing in custom industrial control panels and parts. We have helped many aggregate and forestry businesses with their automation and control needs. Contact us today and let us do the same for you.