Ingénierie et gestion industrielles

Six sigma methodology leads to business excellence by improving process quality and reducing variations. It’s a
philosophy which enables processes to produce defect free products. A refrigerant manufacturing company was facing
increased operational cost, low quality, and increased lead time due to high defect rate in Metal Inert Gas (MIG) Welding.
This paper presents an empirical study about the implementation of six sigma Define, Measure, Analyze, Improve and
Control (DMAIC) methodology in MIG Welding facility of Heat Ventilation and Air Conditioning (HVAC) manufacturing
plant. Critical factors were identified and analyzed by using Ishikawa diagram and hypothesis testing. Fitted linear model
was used to identify optimal setting of process parameters. After-effects of project reduced the defect rate up to 25%
operations cost (US $ 0.8 Million), and customized the sigma level from 2 to 4 sigma.

This paper takes a deep look at the costs related to process safety. It is not confined to the costs of trips and alarms,
compliance with regulations and worker training, but also takes into consideration many aspects considered standard
process design practice. Factors that affect the cost due to the hazardous nature of operation have been listed. While
the exact cost would vary from one plant to another, this cost could, according to our thinking, amount up to one-third
to one-half, or even more, of the capital and operating costs of the new plant handling the hazardous operations. The
vision of the process industry globally is zero hazards and zero accidents. The costs of running the hazardous process
mentioned in this paper would hopefully drive the industry to consider inherently safer systems, green chemistry, process
intensification, and the like.