Improving safety is our number one priority. One of the principles of lean thinking is respect for the individual. This can be demonstrated in several ways, as shown in Figure 1, in the lean thinking house of quality that we adapted for maintenance, repair and overhaul.
Figure 1: Lean thinking house of quality adapted for MRO
At Luminant, safety for the individual is one of our key approaches to the principle of respect for people. An example is a recent switchyard upgrade and overhaul. At one of our power plants, we were building a new plant next to the existing plant while conducting a major retrofit of the existing plant. Additionally, another power plant company was tearing down three old units adjacent to our unit, along with maintaining smelter operations.
This required a redesign and upgrade of the electrical switchyard. Given the danger of the high voltages present, our overall objective for the job was safety. Secondly, we could not interrupt the smelter operations for very long without risking irreparable damage to the pot lines.
The lean thinking approach we use is a combination of 5S2, process mapping, eliminating the seven wastes3 and best practices wrapped in the Single Minute Exchange of Die (SMED)4 method.
SMED started as a technique to reduce die changeover time to less than 10 minutes on machines that processed a variety of parts.
For example, it typically would take eight to 16 hours for a changeover from left-handed to right-handed door panels. The long changeover time drove the economic need to produce enough units to amortize the downtime cost across the parts produced. Large batch sizes dramatically increased lead time and inventory costs.
Dr. Shigeo Shingo, an industrial engineer, originated and perfected the SMED technique over time by applying it very successfully in the Toyota Production System (TPS). Applied systematically, it lowered the cost of vehicles and created shorter lead times to deliver cars, giving Toyota a market advantage.
We took the SMED approach and adapted it for MRO jobs with a variation on the goal. Our objective was to ensure safety and a 12-hour max changeover. There wasn’t a large economic payoff for reducing the downtime.
If an accident occurred handling the high voltage, it could be fatal or cause serious injury. Not being able to repower the pot lines would render them useless, while requiring extensive equipment replacement and lost production.
The total duration for most MRO jobs can be divided into the following task categories:
Gather necessary parts, tools, instructions and equipment.
Shutdown/start-up, remove/replace covers, guards, or get access.
Adjust, test and align parts, material, or equipment to be production ready.
In many cases, the majority of the time is spent on items 1, 2 and 4. SMED divides all tasks into two categories:
Tasks that can be done while the equipment is running are considered external.
Tasks that only can be done when the equipment is down are considered internal.
The process we adapted from SMED for MRO is these six steps:
Measure total time to complete the job.
Separate internal and external tasks.
Convert internal tasks to external tasks.
Streamline internal and external tasks.
Assess risks and identify countermeasures.
Document and maintain new procedure.
The lean thinking approach can be used successfully on any type of MRO or construction job. The jobs can be one time, highly repetitive, or infrequent. In any case, the benefits are improving overall availability, safety and cost.
The SMED method is a proven approach to applying lean thinking for improving MRO or construction jobs. The key advantage is the use of the collective knowledge of the individuals who do the work to create an improved process.
1. Womack, James P. and Jones, Daniel, T. Lean Thinking: Banish Waste and Create Wealth in Your Corporation. New York: Simon and Schuster, 1996, rev. 2003. 2. Womack, James P. and Jones, Daniel, T and Roos, Daniel. The Machine That Changed The World. New York: Productivity Press, 1991. 3. The seven wastes were enumerated in 1940s by the Toyota Corporation's Taiichi Ohno. www.businessdictionary. com/definition/seven-wastes.html 4. Shingo, Shigeo and Dillon, Andrew P. A Revolution in Manufacturing: The SMED System. New York: Productivity Press, 1985. 5. Ishikawa diagrams (cause and effect) are causal diagrams created by Kaoru Ishikawa (1968). http:// en.wikipedia.org/wiki/Ishikawa_diagram
Robert Crotty is a Director for the Luminant Generating Company’s Nuclear Supply Chain. He has been practicing lean thinking for over 30 years.