P. 3 ~ Continued - Gas plant improves C3 recovery with Lean Six Sigma approach

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Each element in this FMEA analysis was rated according to FMEA rating guidelines, and the analysis was carried out in a brainstorming session. Detailed deliberation of the FMEA analysis led to the conclusion that poor chilling performance had been the root cause of the problem.

In the measure phase, all data were collected to verify the findings from the FMEA. Appropriate statistical tools, such as mean, variance, average, and standard deviation, were employed to analyze the data. In addition, a "five-why" analysis and hypothesis testing was used to verify the root cause. The accompanying box (p. 102) shows an example of a "five-why" analysis to illustrate the cause of lower C₃ composition from a poor chilling performance, which is due to accumulation of solid particles in the chiller tube.

The team analysis, then, found that the causes of the lower C₃ products in NGL were:

• Accumulation of solid particles that result in a significant pressure drop in the chiller tubes.

• Poor performance of propane refrigeration.

The focus then is on eliminating these causes through implementing the solution strategy.

Lean Six Sigma—a definition

"Lean" manufacturing refers to a production process that expedites throughput of goods. The concepts started in the automotive industry, and the focus began and remains one of speed, gained by elimination of waste.

"Six Sigma" has its roots in the semiconductor industry (Motorola) and focuses on quality, maintaining consistent quality by controlling deviations.

Lean manufacturing

Anything that adds no value to a product in the course of its manufacture is waste. The measure in Lean is the value-added component: Will the buyer pay for the function? Defining what the buyer actually pays for is key to identifying waste.

Another area of waste elimination in Lean is reducing time spent in queue. How much time does a product "wait" along the production line for value to be added to it? Actually tightening a bolt adds value; a pile of bolts waiting to be tightened is waste.

The Lean process identifies six types of waste:

1. Transportation: movement of goods that has no value. Moving goods from one step in the process to the next is necessary; moving them into a holding area to wait is wasteful.

2. Inventory: components that are merely waiting for value to be added.

3. Motion: unnecessary movement of either people or equipment. Taking 10 steps to accomplish what five will do.

4. Over production: producing more than is needed, either in parts or products.

5. Over processing: more work done to add value than results warrant.

6. Defects: time wasted in inspecting for and correcting them.