Japanese production system - equipment maintenance criticality plan.
The Japanese Path to Maintenance Excellence
By Mike Sondalini
"A component of the Japanese production system is the equipment maintenance and how equipment criticality is determined."
In August 2002 I spent a week in Japan at the chemical plant of an internationally renowned chemical manufacturer. While there I asked them about how they do their maintenance. They told me about their maintenance philosophy. And I want to pass on to you what I learnt about the Japanese way of doing maintenance on that trip.
You will read a number of topics in the next two months. You will read about how this Japanese company determines its equipment and component criticality. You will learn about a new, truly effective way, of making next year’s maintenance plan. We will cover condition monitoring the Japanese way. The Japanese are great maintenance investigators and you will be impressed when you learn how they do their failure analyses. We will also cover their psychology of maintenance – the way they think about maintenance and how they look at it. You will be astounded at their mind-set.
A Japanese way to decide equipment criticality.
How do you decide what level and type of maintenance to use on an individual item of plant and its sub-assemblies? Not all equipment is equally important to your business. Some are critical to production and without them the process stops. Others are important and will eventually affect production if they cannot be returned to service in time. While other items of plant are not important at all and can fail and not affect production for a very long time.
As a maintainer you want to know which equipment in your plant falls into each of those categories so you can determine your response. Furthermore you want to know which sub-assemblies in each item of equipment are critical to the operation of the machine.
From this information you can decide which spares to hold on-site and which to leave as outside purchases. The equipment criticality also determines what level of preventative maintenance to use, what type and amount of condition monitoring to use and what type and amount of observation is required from the operators. You can also use it to justify on-line monitoring systems to protect against catastrophic failure.
The western approach to determine criticality is often to use either Reliability Centered Maintenance or Risk Based Maintenance to determine consequences of failure and then address the appropriate response to prevent the failure. The Japanese chemical manufacturing company I visited had a novel way of determining their equipment criticality. They based the equipment and component criticality on the knock-on effect of a failure and the severity of the consequences. It is the same intention as the previously mentioned methods but they arrive at the rating and the response to it in a unique, quick four-step process.
They used a simple flow chart that production and maintenance worked through together, equipment by equipment. Those failures that caused safety and environmental risks were not allowed to happen and either the parts were carried as spares and changed out before failure or the plant item was put on a condition monitoring program. Those failures that caused production loss or affected quality also were either not allowed to happen or put into a condition-monitoring program. And those failures that didn’t matter were treated as a breakdown.
The flowchart let one arrive at a rating and a corrective action for each piece of equipment and component fast. No need to spend hours and days looking at failure modes and deciding what to do about them. If an equipment or component loss produced dangerous situations, or if the failure stopped production or affected quality, it was either changed out before the end of its working life or it was put on a monitoring program.
The maintenance philosophy for every bit of plant could be arrived at in a four-step decision process. It was very easy to use and to decide what action to take.
If you want a copy of the flow chart email me and I’ll send it to you. (This is a good way to find out how many people read this far into the article.)
How to turn a maintenance plan into a strategy.
The maintenance plan my Japanese hosts showed me in August 2002 was on a big spreadsheet. It listed all the equipment in a plant by tag number covering the period 1994 through to 2003. The maintenance histories of problems on a piece of equipment for the past eight years were listed. A short note detailing the month of occurrence and the failure was made in the column of the year it happened. For this year, 2002, and the next, 2003, the spreadsheet listed what maintenance and modifications were going to be done on the equipment.
It was a ten-year plan the like that I had never seen before!
The ten and five-year plans I had seen were always ten and five years into the future and never covered the past. So why did they do it that way – 1994 to 2003? They never told me their reasons. But now, as I write, it has become clear why it’s worthwhile doing it like that. What I saw was not a plan! What I saw was a strategy! It was a strategy to reduce the known production stoppages and to focus the maintenance effort.
Can you see how something like that would work? You know what has gone wrong with the equipment over the last eight years, it’s listed right there in front of you. You can see how effective the past practices, methods and solutions have been. From that you can wisely decide what to do over the next two years to prevent the reoccurring problems. Instead of writing the usual ‘blue sky’ 5 or 10 year maintenance plan that no one believes anyway, you only plan for the believable two years ahead. You write down exactly what can really be done in the foreseeable future to reduce or prevent the real problems.
The plan for the next two years would include proposed modifications, equipment replacements, new condition monitoring plans, etc.
Now that is a great way to make next year’s maintenance plan! It would be one that is totally defendable and fully justifiable to upper management because it is well thought out, rooted in getting the best return for your money and based on the important business requirements to continue in operation.
My suggestion to cover the period beyond the next two or three years (and only if it is necessary in your company), is to use the spreadsheet to make forecasts. Project ahead based on what you plan to do in the coming two to three years to fix the current problems. If you aren’t going to fix the problems then don’t assume less maintenance in the future. Remember that a forecast is not a plan! A forecast is a best-guess suggestion, often known as ‘blue sky dreaming’. A plan is a set of action steps that over time will produce a desired result. They are totally different to each other.
To get your own copy of the spreadsheet that was passed to me (It’s now fully translated into English) please email me at email@example.com or click "The Japanese Path to Maintenance Excellence" to download the book.
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