By Peter PhillipsMachinery and Equipment Maintenance Operations
ow we are going to learn how to find the root cause of equipment failures. So far in Maintenance 101, we’ve covered: Stage 1 – Preparing for Professional Maintenance (Nov. 2011 issue, page 28), and Stage 2 – Equipment...
ow we are going to learn how to find the root cause of equipment failures. So far in Maintenance 101, we’ve covered: Stage 1 – Preparing for Professional Maintenance (Nov. 2011 issue, page 28), and Stage 2 – Equipment Evaluation and Deterioration (Dec. 2011 issue, page 20). [Editor’s note: Digital editions of previous issues are available online at www.mromagazine.com.]
Now we are going to explore Stage 3 – Breakdown Analysis. The purpose of doing breakdown analysis is to:
• Control reoccurring serious failures and to prevent similar problems and unscheduled repairs.
• Improve production yield that has been reduced by failures.
• Improve the problem-solving and breakdown analysis techniques of the maintenance staff.
There are two main types of breakdowns: Sporadic Failures, which are problems that have easy-to-identify root causes and easy-to-implement countermeasures; and Chronic Losses, which involve problems that need deep failure analysis, have difficult-to-find root causes and require innovative countermeasures.
To conquer breakdowns, maintenance departments need a complete, detailed analysis of the equipment and process failures.
We know that maintenance departments are measured on their ability to respond and to repair production and facility equipment. However, to be effective, we need to do more than just reactive maintenance. The majority of maintenance departments – large to small – focus on reactive maintenance. Very little time is spent finding the root cause of the problem and even less time on is spent on corrective measurements.
This is why we need to spend maintenance time on Root Cause Analysis.
To do this, we need to start by recording breakdown details. This is where a computerized maintenance management system (CMMS) can be used to gather and record breakdown history. This would include information on all breakdowns that cause losses, the time to do the repair, and the recording of the parts used.
These breakdown details allow the maintenance department to focus on and react to reliability problems.
In order to support the breakdown analysis process, there needs to be a process put in place that will be followed by maintenance personnel when breakdowns occur.
Executing a breakdown analysis is a systematic process. To start with, there are several areas from which to gather information:
Collect and tag physical evidence. Damaged and failed components need to be gathered in order for craftspeople to examine them for clues about the cause of the breakdown.
Examine CMMS records to review previous breakdown and repairs on the failed equipment and on other similar equipment.
Examine the CMMS preventive maintenance (PM) report results for reoccurring problems during regular preventive maintenance routines.
Find out if other divisions or operations within your company use the same equipment. Have they had the same breakdowns?
Review lubrication records.
Take note of what the equipment was doing prior to the breakdown. Had it been running, or was it just started up? What other processes were happening at the time?
We also need to arm our maintenance team with the tools it needs to find the root cause of the failure and the solutions for it. There are several problem-solving techniques that can be used. A common one is the 5Ws and 1H technique (asking what, when, where, who, which and how):
What: What thing or product did you see the problem on?
When: When did the problem occur?
Where: Where did you see the problem?
Who: Who is the problem related to? A team or a single person, or their skill or knowledge?
Which: Which trend (pattern) did you see with the problem?
How has the state of the equipment changed?
Let’s look at each point in more detail.
What product was the machine on? What material was used? What size is the problem?
When did the problem occur? Was it continuous, intermittent or an immediate failure? Was it on start-up? Was it before or after a change-over? What time or period did it take place?
Where did you see the problem? Line/Machine/Location? Which particular part did you see the problem on? Where on the material did you see the problem?
Is the problem skill- or knowledge-related? Did a particular operator have the problem? Did a particular shift have the problem? Did the maintenance person have the problem?
Which trend or pattern does the problem display? Does the problem happen randomly or in a set pattern? Is the problem going in a particular direction, i.e. getting worse or better?
How has the state of the equipment changed from its normal running condition? How many times does the problem occur (daily, weekly or hourly)?
From the 5Ws and 1H information, sporadic failures should be able to be solved. Deeper problems will need further analysis with other problem-solving techniques, such as the 5 Why Technique.
The 5 Why Technique is one of the most popular and successful problem-solving techniques in the world. Basically, it involves asking ‘why’ five times. By the time the fifth ‘why’ is asked, the real cause or causes of the problem are revealed.
Lets look at two examples of the
5 Why Technique.
As a very simple example of the 5 Why process, there are two injection moulders that stop intermittently. The moulding machines are connected to the same compressed air distribution network, each with its own pressure switch. The chain of events takes the form shown in Figure 1, where a drop in pressure caused both presses to stop.
In this example, the question ‘Why’ is asked at each possible cause.
Moulder machine stops.
Why did the moulder stop? Answer: Because the motor stopped.
Why did the motor stop? Answer: There was no current/electricity.
Why was there no current? Answer: The pressure switch was open.
Why did the pressure switch open? Answer: Pressure was low in the Air Mains.
So low pressure caused the moulders to stop. Additional ‘Why’ questions need to be asked to determine why the air mains pressure dropped to find the root cause(s).
This Japanese transplant automobile manufacturer uses a hybrid form of the technique that includes a trend chart and Pareto chart to guide the 5-Why thinking of its problem-solving teams. On one piece of paper, the form captures historical data, problem priorities, root cause analysis, corrective action and verification.
Once the root cause has been found, the corrective actions can be developed and tested.
The ultimate goal of Stage 3 of world-class maintenance is to resolve production-robbing failures, with the goal of reducing reactive maintenance so that more important maintenance activities can be worked on, such as lubrication charts, updating equipment PM instructions, and so on.
Get out of the reactive maintenance mode and take the time to do breakdown analysis. That way, you can show your production department that you are much more than a repair shop.
Peter Phillips of Trailwalk Holdings, a Canadian CMMS consulting and training company, can be reached at 902-798-3601 or by e-mail at firstname.lastname@example.org.