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27th International Conference of the TOC Practitioners Alliance ‐ TOCPA www.tocpractice.com
August 16‐18, 2016 Johannesburg, South Africa
Exploitation of the Critical Chain Thuso Machaba, Babock, South Africa 17th – 18th August, 2016
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THUSO Thuso Machaba was born on August 20, 1987 in Limpopo. He studied Metallurgy Engineering at University of Johannesburg. In 2011, he started working at Crown Cast foundry, where he was introduced to TOC. In the year 2013, he joined Rapid Allweiler pumps where he worked as a Metallurgist. In 2014, he Joined Babcock as a Bill of Material coordinator. He is currently involved with boiler shutdown projects, where he is using CCPM technology to run the sub-projects assigned to him.
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Cell: 071 362 2424 E-mail:
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INTRODUCTION Extended damage to boiler tubing was found during tube thickness inspections in the primary reheater, resulting in significant more work-scope than was predicted. It extended the outage duration by one month. The estimated cost ramification, due to the increase in time, for the client, is in the order of R 70 000 000 Project: Re-planned duration, catering for additional welding scope: 71 days It forced the Primary reheater path to become the critical chain of the project 27th International Conference of the TOC Practitioners Alliance ‐ TOCPA
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INTRODUCTION TOC five focusing steps: 1. Identify the constraint 2. Exploit the constraint 3. Subordinate to the constraint 4. Elevate 5. Repeat / go back to step 1
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Constraint 1
One of the main measures in boiler construction is “weld repair rate”. As a result, on a tube with multiple welds, the weld in the boiler is done first, it is then x-rayed and only the next day the second butt is welded. If both welds were done on the first day and the first butt fails, both have to be cut and will count as weld repairs. Because of the measure people will not risk it. It was then decided to run the risk, and the welding “policy” was waived. With the policy constraint lifted we could plan 32 butts per day, potentially pulling the due date back by 18 days. 27th International Conference of the TOC Practitioners Alliance ‐ TOCPA
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Constraint 2 Limited space to work in was identified as the second bottleneck, as we had to wait for butt welds to be x-rayed, before we could gain access to the next set of elements. Four work areas pulled open, between the elements, were considered optimal by the workforce, and they had done calculations to support the claim. Investigation revealed that more areas could be opened at times, and the work areas were later increased to 7. Average production per area was increased to: 49 (7 butts /welder X 7 areas)
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Results
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Butt Weld Graph
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Constraint 3
Bottleneck number 3, was identified as the construction method. By changing the methods we manage to eliminated having to weld 150 butts inside the boiler Weld number 2 (black) was done in parallel, a buffer time ahead, in the workshop, which effectively increased daily production achieved by 50%.
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Results By changing the construction methods we manage to pull back the path so that it was no longer the critical chain of the project. Project finished well before the project due date- more than a month earlier than planned. The client had no additional “replacement” cost, due to time overruns, and saved in maintenance costs as the path was completed early. All of which, can directly be contributed to the exploitation that was done, very good ideas generated by the team and the team work that was established in the area.
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I THANK YOU!!!!
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