Lean Maintenance II
by Christer Idhammar
To continue where we ended part I of this series of articles about lean maintenance, I like to give an example on the impact of reliability in a situation where you can not sell everything you manufacture as a result of increased reliability. The example also shows the importance of including the quality component of the reliability formula.
In a pharmaceutical industry there was a lot of over capacity and it was thought that manufacturing reliability wasn’t that important, after all they could catch up losses with the extra capacity they had and they could use overtime to compensate for any production losses. Management viewed that it was much was more important to have lower maintenance costs. When manufacturing efficiency was measured the only thing considered was availability. One day a tumbler broke in the end stage of the manufacturing of tablets. In the tumbler the tablets were covered with a coating before packaging and delivery. The break down was caused by a burnt and worn out v-belt. The shut down, which only lasted for 45 minutes, resulted in that lots of expensive medicine had to be scrapped at the cost of £49 000. Since that had happened one time before, two years prior, quality began to be included in how you measured manufacturing reliability.
Instead of talking in terms of availability this plant now include quality performance when they identify losses and measure manufacturing reliability.
Increased manufacturing reliability will increase product throughput and reduce the time between incoming raw materials to the finished product. Better reliability is the foundation to a faster and safer manufacturing flow. This will result in lowered losses in delayed deliveries, over production, work in progress and energy expenditure. Here lie the biggest gains if you can’t sell everything you produce. This cannot materialize if you don’t have equipment with very high reliability. If you do have it then you can, with prosperity, apply the “Dell model” or “Just- In- Time” manufacturing principles very successfully.
In addition work related injuries and energy costs are always positively affected by high reliability.
I often get the question, ”What is good manufacturing reliability?” It obviously has to do with your process and equipment quality. Also pay attention that we aren’t only talking about equipment efficiency. It is common to use the concept OEE – Overall Equipment Efficiency when measuring manufacturing reliability, but that is only a part of the reliability concept, the other part is Overall Process Efficiency which is the manufacturing process, or the chemistry of making your product such as raw materials, pressures, temperatures, chemical mixtures, packaging material, operating practices etc.
In this concept we are discussing OMR - Overall Manufacturing Reliability.
From the maintenance point of view there are three elements that we have seen that affect how good OMR can be.
- Equipment quality.
- The number of components that can cause a problem.
- The maintenance organization’s efficiency.
Equipment quality including maintainability and reliability design I have covered in the previous articles.
The number of components that can cause a problem.
I often use paper machines as a guideline when I judge possible reliability in different processes that I don’t have data on. The most reliable paper machines are machines that produce, for example, towel and tissue paper. Such machines often have one or two driers, so called yankee cylinders or driers, each with one drive unit. A paper machine with several layersand surface coatings has many more components that can cause problems. Such a machine can have over 100 drier cylinders. Thus OMR differs between 96 % for a tissue/towel machine and 82 % for the more complicated machine. A package line with good OME can reach 85 - 90 %. All of these calculations are based on 8760 hours per year (in 2008 we have 8784 hours per year).
The maintenance organization’s efficiency.
One of the best indicators of effective maintenance is still the degree of planned and scheduled maintenance. This is because it affects both manufacturing reliability and maintenance efficiency to a very high degree. Furthermore, a high level of planning and scheduling cannot be reached without the support of all of the other elements of good maintenance including maintenance prevention, preventive maintenance, store room support, root cause problem elimination etc.
In studies that we have performed we have established a strong correlation between high manufacturing reliability and a high degree of planning and scheduling of all maintenance and operations work.
In this study we evaluated the Manufacturing Reliability of 38 very similar process lines. The blue line shows the lowest to the highest manufacturing reliability. The only thing we could correlate to higher manufacturing reliability was the level of professional planning and scheduling. Depending on what different plants included in their maintenance costs, this cost was lower the higher the level of manufacturing reliability and level of planning and scheduling was.
Over manufacturing and over maintenance
Over manufacturing is to make more than what has been sold and before it needs to be delivered. This is one of the biggest sins in lean manufacturing. The same view should be taken when it comes to maintenance. To perform more maintenance than is needed or to perform maintenance before it is needed should be considered a waste or an opportunity to improve.
The biggest improvement the opportunities lie in:
- Optimizing old preventive maintenance systems.
- Decide if work that is performed during scheduled downtime actually needs to be done.
- Prioritize, plan and schedule work in a disciplined way.
Optimize Preventive Maintenance (PM)
Please see earlier articles where I have described optimization of preventive maintenance more in detail. Here I like to add more information as it relates to lean maintenance.
To optimize your PM is one of the efforts that can give the fastest return on investment. If you have a PM system that has all PM activities documented under each equipment identification number, optimization can be done relatively quickly. If you have a system where all PM inspections and other PM activities are documented in a work order, then the work becomes much more extensive, if not impossible. If you want to optimize your PM then you must have a system that can collect all PM efforts in a lucid way under respective identities on the maintenance object. This is important because more than 95% of all PM activities are performed as route based activities while the manufacturing process is operating. Through more and more integration between what lubricators, mechanics, electricians and operators do, the system must always change and it has to be able to change in a very simple way. It can be easier to start from the beginning with a route based system if your existing system is based on work orders. A route based system can be set up at a very low cost.
During the 1970’s I myself led the implementation of many PM systems in industry. Thirty years later I have visited many of those plants and I am surprised to see that many of these systems still looked like they did thirty years ago. The distribution between what is done by different work groups is still the same as back then. In many of these companies the operators are now involved in the preventive maintenance but their efforts are added to all the other PM measures. Here lies a big opportunity to optimize PM inspections, lubrication, etc.
As an example. In a chemical plant most pump units had the following PM measures done on most of their pumps.
- Lubricators lubricate everything, except for electric motors.
- Electric motors are lubricated by electricians. (Believe me, even if it is old-school and a waste of the electricians skills, it still happens today when you come across old work systems that should have been changed forty years ago)
- A mechanical PM inspector performs mechanical inspections.
- Gear couplings are overhauled during a scheduled shut down each year. (This can easily be moved to inspections while equipment is running and repair are done when needed)
- Electricians and instrument technicians inspect electrical components and sensors.
- Vibration analysis is done by a technician.
- Operators do general inspections of unit.
In this case PM activities were reduced by 50% and the new PM activities were better than before.
It can be a good idea to take photos of several pieces of the equipment and then show which PM is performed and by whom. Then show how you can integrate and optimize all PM. After that you can determine costs and savings.
To be continued.