What is redundancy in control systems and why is it important?

Why is redundancy important for control systems? The primary goal of redundancy in a control system is to eliminate dependency on a single module while providing multiple options in the event of a failure. Redundancy in a control system decreases the consequences of a component failure. Makes resources available in the event of a problem. The importance of a redundant system is also increased in a variety of scenarios including: -Continuous processes -Irreversible processes -Long restart times  

• Continuous Processes

Some processes demand the availability of systems at the highest level at all costs. The interruption or loss of the system after the start of the processes will be very costly. The process is useless if it stops or fails in the middle of it. Furthermore, the process must be reversed to its initial stage to obtain the result. For example, in the pharmaceutical industry, there is a washing process before filling. If the washing machine is interrupted between wash cycles, the containers must be washed again.

• Irreversible processes

It is also important in the system where the processes are irreversible. That means that if the process starts, it cannot be reversed or stopped before completion. For example, in the case of the chemical or pharmaceutical industry, once the product has been manufactured, the containers in which it must go have to be filled quickly, otherwise its chemical properties will change and it will not do any good.

• Extended restart times

Some industries simply cannot afford to reboot because reboot timing is not an easy task. It takes a great deal of time to reboot some systems to make them fully functional, sometimes up to a month. An example of this long restart time can be seen in the steel industry where a furnace is used. The oven relies on a constant high temperature and it takes considerable time to reach that temperature. A system breakdown will drop the temperature and it will be days before work is restarted again.

Key Considerations for System Redundancies

While there are many benefits to redundant systems, there are a few considerations that need to be addressed and taken into account. Depending on the system, there may be many considerations to make, but some are, of course, basic.

• Additional equipment

Redundancy has to do with an extra piece of equipment similar to the original. When opting for redundancy, additional equipment is an important factor in the design. It is very important to decide at what level redundancy is required. If not designed properly, it will be a waste of resources and money, and the desired results will not be achieved.

• Cost consideration

Redundancy carries additional costs. The higher the level of redundancy, the higher the costs. To check whether the cost is worth it, the cost of redundancy is compared with the loss due to system failure. If the cost of a process failure is greater than the cost of redundancy, redundancy is profitable.

• Increased complexity

Although the redundant system is the duplication of the original system, this duplication often creates complexity. The complexity is due to additional programming algorithms or the transfer of control from the original components to the redundant ones. The interconnected cabling mechanism also increases the hardware complexity of the system.

• Training

The redundant system automatically takes over without human intervention, but the system requires humans for some processes, such as replacing faulty equipment and recovering lost hardware or software. This requires training on the associated hardware and software, recovery processes, and the actual cause of the failure to prevent it in the future.

What could happen without redundancy

The industrial world is moving towards smart practices and solutions, which help identify and eliminate the causes of problems and breakdowns before they occur. Different strategies are being implemented, redundancy being one of them. Some of the consequences of not using redundancy can be product loss, increased system failures, and increased operating costs.

• Loss of Complete Products or Processes

There are some industries, such as pharmaceuticals or water treatment, where once the process starts, it cannot be reversed. Unfortunately, any loss due to system failure may cause the product to be lost beyond use.

• Increase in breakdowns

Failures lead to non-use of resources. Obviously, the replacement of any component in case of failure takes time, which in turn causes the failure of the machine.

• Unavailability of spare parts

Parts availability can add an additional challenge, one that is time consuming and results in more machine downtime. For example, sometimes a part has been discontinued by the supplier or manufacturer or is not available in the local market.

• Increased operating costs

Even when a machine is in an unusable state due to a failure, the machine continues to consume electricity and other resources. This causes higher operating costs for a particular process or product, which directly affects production costs.]]>