Q: What can you tell me about condition-based maintenance? Is it more economical than preventative maintenance?
A: Condition-based maintenance, or CBM as it is referred to, is a subset of preventative maintenance. The difference between them is the tools they utilize. Preventative maintenance systems use checklists and OEM recommendations to develop PM routines. The tools that condition-based maintenance use are different.
The common tools used in CBM are oil analysis, heat monitoring, vibration analysis, ultrasonic testing and electric load monitoring. Oil analysis is used to detect foreign materials, excessive heat buildup in the machine and the presence of metals, which indicates machine internal wear.
Thermography is used to sense heat buildup within a machine, a concentration of heat within electrical components, or even abnormalities in roofing systems. Vibration analysis is used to determine the impending failure of bearings or to sense an eccentric load putting stress on equipment. Ultrasonic testing senses sound changes to indicate changes in the operation of a machine. Strip ammeters are used to determine whether more power is being used to operate a piece of equipment than normal. As you can see, there is some possible overlap between some of these tools.
The upfront cost of utilizing condition-based maintenance tools is higher than that of a preventative maintenance system. This is why assets with high values and those with high costs associated with their downtime are targeted initially for condition-based maintenance. It doesn't make sense to put complicated monitoring equipment on a machine that, if it fails, would result in little cost and downtime. This is why a risk and criticality assessment should be done on equipment before you make the CBM investment.
The effectiveness of CBM is not immediate. Once monitoring equipment is installed you will need to establish norms for each machine. In most case, it is the deviation from the norm that acts as the telltale sign of equipment failure.
The total cost associated with any system is based upon effectiveness and the dollars it requires to operate. In the short term, for non-critical pieces of equipment, preventative maintenance is less costly than CBM, but is also less effective. The offset is that its ineffectiveness is shrouded because the overall cost of failure is less. On high-risk, highly critical pieces of equipment, CBM is much more effective and in the long term more economical.
This article originally appeared in the September 2013 issue of Food Processing Magazine.
