120000
Figure 2.4 Pareto chart of total pump failures over the last 12 months for various processing units. The “cumulative percentage” line helps in determining how various groups add to the total failure population. For example, the Cat Cracker and Coker Unit failures represent about 35% of total plantwide pump failures.
Table 2.2 A forced ranking of pump failures in a hypothetical cat cracking unit.
| Pump | Failures in last 12 months | Total repair costs for the last 12 months |
| 31-P-09 A&B | 5 | $ 50,000 |
| 31-P-05 A&B | 4 | $ 40,000 |
| 31-P-04 A&B | 3 | $ 30,000 |
| 31-P-08 A&B | 3 | $ 30,000 |
| 31-P-17 A&B | 3 | $ 30,000 |
| 31-P-25 A&B | 3 | $ 30,000 |
| 31-P-02 A&B | 2 | $ 20,000 |
| 31-P-06 A&B | 2 | $ 20,000 |
| 31-P-10 A&B | 2 | $ 20,000 |
| 31-P-11 A&B | 2 | $ 20,000 |
| 31-P-12 A&B | 2 | $ 20,000 |
| 31-P-14 A&B | 2 | $ 20,000 |
| 31-P-16 A&B | 2 | $ 20,000 |
| 31-P-18 A&B | 2 | $ 20,000 |
| 31-P-19 A&B | 2 | $ 20,000 |
| 31-P-22 A&B | 2 | $ 20,000 |
| 31-P-23 A&B | 2 | $ 20,000 |
| 31-P-01 A&B | 1 | $ 10,000 |
| 31-P-03 A&B | 1 | $ 10,000 |
| 31-P-07 A&B | 1 | $ 10,000 |
| 31-P-13 A&B | 1 | $ 10,000 |
| 31-P-20 A&B | 1 | $ 10,000 |
| 31-P-21 A&B | 1 | $ 10,000 |
| 31-P-24 A&B | 1 | $ 10,000 |
| 31-P-15 A&B | 0 | $ - |
Now that we know most of the pump failures occurred in the Cat Cracking unit, we can narrow our focus to those pumps. Table 2.2 shows a forced ranking of the pumps with the most failures. In our hypothetical case, Pumps 31-P-09 A&B failed five times in the last 12 months. Assuming that each repair costs about $10,000, we now see that the worst actor cost us about $50,000 in the last 12 months.
You may choose to label the least reliable pumps at your site as “bad actors.” Bad actors typically make up 7% to 10% of the pumps at your site that cost the most to maintain and cause you the most headaches. It makes sense to aggressively address bad actors first.
Pareto Charts & 80-20 Rule
The Pareto Chart is a very powerful data analysis tool that can be used to show the relative importance of problem areas and their root causes. They are composed of both bars and lines, where individual values are represented in descending order by bars, and the cumulative total of the sample is represented by the curved line. The 80/20 rule (also known as the Pareto principle or the law of the vital few and trivial many) states that, for many events, roughly 80% of the effects come from 20% of the causes. Joseph Juran, a well-regarded Quality Management consultant, suggested the principle and named it after the Italian economist, Vilfredo Pareto, who noted the 80/20 connection in 1896. Pareto showed that approximately 80% of the land in Italy was owned by 20% of the population. Pareto also observed that 20%
