What is criticality and why is it important for your machines? Machine criticality makes it possible to define the prioritization of maintenance actions, in order to ensure that the production system works as close to its nominal capacity as possible. Each of the analyzed machines must be classified accordingly by three levels of impact (ABC Method):
A= High Impact; Highly Critical Equipment
B= Medium Impact; Moderately Critical Equipment
C= No Impact; Low Criticality Equipment
(A) High Impact and Critical Machines: When analyzing your machines and assigning a critical level think of how your productivity will be impacted if your machine breaks down and the process stops for an entire shift, or more than 8 hours. How expensive would it be to repair that machine? Will it be difficult to get replacement parts quickly?
An example in the food processing industry, the processing line may be set-up to process 1000 turkeys per hour. The turkey plucking machine is the bottleneck operation; an unscheduled stoppage of 8 hours is a production loss of 8000 turkeys.
(B) Medium Impact & Moderately Critical Machines: Think of machines that might only be down for less than 4 hours. The repair cost is about average for expenses. They are usually pretty simple machines.
An example is a heat exchange operation such as cooling towers and associated circulation pumps. In many industries the addition and removal of heat is critical to maintaining output.
(C) No Impact & Low Criticality Machines: If the machine breaks down it results in a short stop in production or doesn’t impact production at all. Repairs are minimal costs or it’s often more cost efficient to replace the machine.
An example: In many operations such as metal manufacturing (Engine Plants) compressed air is required for the process to operate. In addition, the loss of one compressor in a situation where you have three available and only need two to operate.
Six criteria are taken into account:
- Safety: Dangerous machines, such as presses and guillotines, can cause serious damage to the health of the operator
- Product Quality: Some machines carry out high precision processes and, in this way, the lowest level of misalignment can result in loss of quality of the manufactured product.
- Impact on Production: Failures in production process bottleneck machines can have a strong impact on productivity to the plant. In some cases, they can even lead to total production stops. Therefore, this is an extremely important criterion in criticality analysis.
- Mean Time Between Failures (MTBF): This criterion deals with the time elapsed between failures in a machine
- Mean Time To Repair (MTTR): This criterion represents the average time required to replace or repair a faulty component, or even to restart the machine.
- Maintenance Costs: Money to be spent on repairing a specific machine that may fail. This expense varies according to the failure, but in general, it’s possible to infer if the asset requires high expenses with spare parts and so on. For example, if the asset is sourced overseas, the cost of replacing defective parts may be higher.
Analyzing the criticality of each piece of machinery is an essential step to take when developing routes and implementing a PdM program.
This downloadable guide on Criticality Analysis will help guide you identify A, B, and C machinery and guide you in the right direction to determine which machines are the most critical to operations.
