Automation takes a bigger and bigger role in all industries. We exchange humans, for automated processes and actions. Safety in marine automation is very important. Proper design of automation systems can provide reliable effects. Processes will run smoothly. Maintenance will be realized on time. This brings us to questions: Is automation increasing safety? How we can define safe automation?

Direct & Indirect Safety

There are two major factors which You have to consider. The first is the fault of a single component. Brake of components can be costly, but in the same time they can create more complex problems in whole systems. This depends on whether the broken part can damage other components or not. Does the other components affect other systems? Fault tree can grow, and grow… In the same time, costs of failure of a single component can be thousands times higher than the cost of a failure part. How do You secure your system against that?

The second is how reliable is the design of the process. During the design of process or system, You have to consider an interactions between the systems. Function of components, priorities of operation, level of safety, have to be taken into account already at the design process. How to check the reliability? But firstly, let’s focus on the components.

Fault of component. Mechanical vs Electrical

The fault of components happens frequently. Everything has limits. Doesn’t matter if this is a solenoid valve, relay, contactor, or actuator. Every piece of equipment has a lifetime limit. This is why onboard are available service kits for certain equipment. For example, simple compressor. You have an available complete service kit, with all necessary spare parts to make proper maintenance. Mechanical parts, sealings, etc. No one is questioning that this is necessary, because parts get worn over time. If a part reaches its lifetime, it simply needs replacement. 10.000 running hours service kits, and all similar stuff is available for most of the equipment.

That way, mechanical equipment is maintain, quite well. However, the situation is a bit different with electrical and electronic equipment. Electrical and electronic equipment onboard is usually running until fault. For example, the crew has to control the vibration of electrical motors. Engineers are responsible to check the insulation of the equipment. Periodical tests of alarms take place from time to time. However, there are no service kits for electrical equipment. So You can (and You should) do the maintenance after discover of some issues. Ideally, before they become critical. But how to find that?

Safe Automation – Predictive maintenance

Predictive maintenance or condition monitoring, or name it is You want. Some of You could read something about this already. (Here is our article about big data in maritime industry) This kind of system is constantly monitoring the parameters of machinery. Systems can measure vibration, current, or temperature. A comparison of these parameters over time can predict where we are on the lifetime of the equipment. This is safe related functionality of predictive maintenance. General functionality is to reduce the cost of maintenance.

Maritime companies usually have 5 years intervals for the important systems. This interval can be reduced. For instance, if parameters of some equipment are showing that equipment is already at the end of its lifetime. Crew can also check some of the parameters. But having a constantly running system that collects this data, is definitely beneficial.

To summarize, if Your company like to reduce maintenance costs and increase reliability, a condition monitoring system is the way to go. More about condition monitoring systems itself, I will write in the next article.

Safe automation – Safety of a design

SIL – Safety Integrity Level is a standard described by IEC 61508. These are general safety rules which apply to the safety design systems. The design has to be in the sweet spot between 3 general areas. The design has to cover architectural constrains. In other words, design need to cover functionalities for the system. Therefore, If crane needs to lift 10 tons, You cannot say that the 8 ton crane is more safe. Second point is probability of failure. (If You are interested proffesionally in the subject, I refer to this article. Here I try to describe it simply). We have 3 different types of operation: Low demand operation, where frequency of demands is less than one per year. High demand operation, where frequency is higher then one per year. Third one is continues operation.

Third area is SIL Capability. Depends of the operation, failure probability have to be calculated in different way. The result You have to compare with the fault tolerance. Therefore, system can be secure from SIL level 1 to SIL level 4. Higher level of SIL, means more safe design is.

How to increase safety in automation?

The easiest way to reduce the risks / increase the safety is redundancy. However, redundancy usually increases the costs dramatically. Other good idea is use equipment which is certified at the higher level. So it means, that You can replace component from SIL 1 to SIL 2. At the graphic below I will try to explain how You can mix this two methods.

Very important in the safety systems is also communication. This means that not only components or the systems have to be certified, but also communication between them. Remember, the weakest point of the chain, determines safety level of a whole system. So if You use components of SIL level 3. But You don’t use certified communication between them, your effective SIL level is 0.

Safety depends of design and maintenance

Automation itself, does not increase the safety. Properly design systems, can be more safe, then systems without automation. But they need to cover several issues. On the other hand, proper maintenance of the systems also can increase reliability and safety. For every project, applied rules are different. But it’s good to keep in mind, that every challenge, can be approach differently.