Breakdowns in industrial manufacturing systems can have significant impact on the profitability of a business. Expensive production equipment is idled, labor is no longer optimized, and the ratio of fixed costs to product output is negatively affected. Rapid repair of down equipment is critical to business success; the process of addressing equipment breakdowns after occurrence is known as Corrective Maintenance and exists in some form in all manufacturing companies. However, when equipment breakdowns occur the cost can go well beyond the period of repair. Often process lines require significant run-time after startup to begin producing quality product, and the manufactured goods in process at breakdown as well as the goods manufactured for a period after breakdown may either be unusable or of less value. Because of the impact both during and beyond the immediate downtime, businesses have sought to prevent equipment breakdown by a process known as Preventative Maintenance. With preventative maintenance equipment is routinely inspected and serviced in an effort to prevent breakdowns from occurring. Such inspections are based on either calendar periods or equipment process time, and generally include recorded data that can be compared over time to determine if negative shifts indicate an imminent equipment problem.
The Corrective Maintenance and Preventative Maintenance approaches have been in use for decades, but each have some important drawbacks.
Corrective maintenance is probably the most commonly used approach, but it is easy to see its limitations. When equipment fails, it often leads to downtime in production. In most cases this is costly business. Also, if the equipment needs to be replaced, the cost of replacing it alone can be substantial. It is also important to consider health, safety and environment (SHE) issues related to malfunctioning equipment.
So to avoid the problems of correcting unfortunate situations that has already risen, many try to maintain equipment before it fails. By doing this, the goal is to avoid failure, unnecessary production loss and SHE violation. As you cannot possibly maintain your equipment at all times you need some way to decide when it is proper to perform to go out and perform maintenance. Normally this is done by deciding some inspection/maintenance interval, and sticking to this interval more or less affected by what you find during these activities. The result of this is that most of the maintenance performed is unnecessary; it even adds substantial wear to the equipment. Also, you have no guarantee that the equipment will continue to work even if you are maintaining it according to the maintenance plan.
Condition-based maintenance (CBM)
To try to maintain the correct equipment at the right time, condition-based maintenance
is introduced. CBM is based on using real-time data to prioritize and optimize maintenance resources. Observing the state of the system is known as condition monitoring
. Such a system will determine the equipment's health, and act only when maintenance is actually necessary. Development in recent years have allowed extensive instrumentation of equipment, and together with better tools for analyzing condition data, the maintenance personnel of today are more than ever able to decide what is the right time to perform maintenance on some piece of equipment.
Ideally condition-based maintenance will allow the maintenance personnel to do only the right things, minimizing spare parts cost, system downtime and time spent on maintenance.
However, there are some challenges.
Challenges of CBM
First and most important of all, starting to use CBM is costly. It will require improved instrumentation of your equipment. Often the cost of sufficient instrumentation can be quite large, especially on equipment that is already installed. It is therefore important to decide whether your equipment is sufficiently important to justify the investment. A result of this is that the first generation of CBM in the oil and gas industry has focused on vibration in heavy rotating equipment only.
Secondly introducing CBM will invoke a major change in how maintenance is performed, and potentially to the whole maintenance organization in a company. Organizational changes are in general difficult.
Also, the technical side of it is not always as simple as one would hope. Even if some types of equipment can easily be observed by measuring simple values as vibration (displacement or acceleration), temperature or pressure, it is not trivial to turn this measured data into actionable knowledge about health of the equipment.
Value potential of CBM
As systems get more costly, and instrumentation and information systems tend to become more cheap and reliable, CBM becomes an important tool for running a plant or factory in an optimal manner. More optimal operations will lead to lower production cost and lower use of resources. And lower use of resources may be one of the most important differentiators in a future where environmental issues become more important by the day.
A more down to earth scenario where value can be created is by monitoring the health of your car motor. Rather than changing parts at predefined intervals, the car itself can tell you when something needs to be changed based on cheap and simple instrumentation.
It is Department of Defense policy that condition-based maintenance (CBM) be ''"implemented to improve maintenance agility and responsiveness, increase operational availability, and reduce life cycle total ownership.
The Open Systems Architecture for Condition-Based Maintenance (OSA-CBM) specification is a standard architecture for moving information in a condition-based maintenance system. A more in depth look reveals a way to reduce costs, improve interoperability, increase competition, incorporate design changes, and further cooperation in the realm of condition-based maintenance. The OSA-CBM standard can be downloaded from the MIMOSA web site
Machinery Open Management Open Systems Alliance (MIMOSA)
- The largest PHM/CBM user community PHMinfo contains news feeds and forums for PHM/CBM related topics.