The 5 whys & 5 hows approach applied to industrial maintenance

Published 2023-11-21 by Diego Santos (a 2.4 minute read) | Back to the main page

In a nutshell

The "5 whys" and "5 hows" approach is a method of root cause analysis and problem solving that is widely used in industrial equipment maintenance.

Basic procedure

The basic idea is to ask "why" five times to identify the underlying cause of a failure, and then ask "how" five times to devise a corrective action plan - this requirement of asking five questions works surprisingly well as you will see. Here is an example of how this approach can be applied to a common equipment failure scenario:

Practical Example

Problem: A conveyor belt stopped working.

5 Whys

Q1. Why did the conveyor belt stop working?
Because the motor overheated.

Q2. Why did the motor overheat?
Because the lubricant level was low.

Q3. Why was the lubricant level low?
Because there was a leak in the lubricant system.

Q4. Why was there a leak in the lubricant system?
Because the seal was worn out.

Q5. Why was the seal worn out?
Because it was not replaced during the last preventive maintenance action.

Root cause: The seal was not replaced during the last preventive maintenance.

5 Hows

Q1. How can we fix the problem?
Replace the seal and refill the lubricant.

Q2. How can we prevent the problem from recurring?
Perform regular inspections of the lubricant system and check for leaks.

Q3. How can we improve the inspection process?
Use a checklist and record the results in a logbook.

Q4. How can we ensure that the checklist and logbook are followed?
Train the operators and technicians on how to use them and monitor their compliance.

Q5. How can we evaluate the effectiveness of the training and monitoring?
Conduct periodic audits and review the performance indicators.

Corrective action plan: Replace the seal and refill the lubricant, perform regular inspections of the lubricant system and check for leaks, use a checklist and record the results in the CMMS, train the operators and technicians on how to use them and monitor their compliance, conduct periodic audits and review the performance indicators.

Conclusion

The "5 whys" and "5 hows" approach is a simple and powerful tool but it can add quite a workload to the maintenance activity. The key may be to clearly identify the main (few) items that would benefit from this analysis (due to high impact to production efficiency, for example) and apply it only to those.