Entropy Part 1 – Fundamentals

Engineers are familiar with the concept of “entropy” and the laws of thermodynamics. The second law of thermodynamics states that the total entropy of an isolated system always increases over time. It can remain constant in ideal cases where the system is at a steady-state or undergoing a reversible process. So what does that mean for us in the world of asset management and maintenance?

Entropy (usually represented by the symbol “S”) is a measure of microscopic configuration making up a thermodynamic system – in simpler (practical) terms it provides a measure of randomness or chaos in a system.

The second law tells us that S (randomness or chaos) will increase unless we can keep our system in a steady-state or subject it to some form of a reversible process. Consider a factory, process plant, utility or fleet that we are maintaining. That factory… is our “system”. If we do nothing but use it (which is what the operations people will want to do), then entropy will increase. Chaos and randomness will increase. This presents itself to us as system deterioration – wear, random failures, fatigue, erosion, etc.

We can stop this process if our system can be kept in a steady-state, but that is more or less impossible given natural degradation processes that are inherent in virtually any system we devise. We can, however, apply a “reversible process” – maintenance. Maintenance is used to restore the system’s state to functional and then operational. We apply energy (maintenance) to reduce the system’s entropy (chaos).

Because maintenance has a cost and takes time, we want to apply as little of it as possible. If we do that we save money and have more time available for productive use of our system. So what activities will help us to achieve the low-cost application of this maintenance energy?

There are three main activities:

1. Design the system so it is inherently reliable (i.e. degradation is slow) and maintainable (i.e. quick to restore after it has degraded)
2. Maintain the system properly (i.e. addressing specific degradation processes and no others)
3. Operate the system as steadily as possible and within its capability, so it degrades at the slowest possible rate (i.e. don’t overload, shock or abuse the system)

From the thermodynamic perspective each of those is achieving a goal (respectively):

1. The steady-state system has a low level of entropy
2. We apply the right amount of energy to restore entropy increases back to original state quickly
3. We operate the system in as close to steady-state as we can to slow entropy growth

Financially the implications are:

1. We invest in an inherently reliable and maintainable design which often costs a bit more up-front
2. We spend money on the right kind of maintenance, focused on reliability, not on cost reduction leading ultimately to lower costs overall
3. We end up with a high level of predictable, steady output and low variability leading to stable revenue flows

Success with your system means high performance at low cost and low levels of risk to that performance.

There are three keys to success, much like 3 legs on a stool: inherent reliability and maintainability due to design, sustaining the performance through the right maintenance and avoiding accelerated degradation through the use of the correct operational practices. Just like any 3 legged stool, the system is stable so long as the three legs remain intact.

In part 2 I’ll explain the economics of this simple model.