A pump in a factory kept failing. The maintenance team replaced it four times in two years, each replacement costing a week of production. Every report recorded the same cause: bearing failure. Every report was correct and none of them helped.
An engineer new to the site asked a different question. Not what failed, but why that thing failed, and then why that happened, and so on down the chain. The bearings failed because they were running dry. They were running dry because the lubrication line was blocked. The line was blocked because metal filings were in the oil. The filings were there because a worn seal upstream was shedding material. The seal was worn because it had been replaced with a cheaper part that was not rated for the temperature.
Five questions reached a part worth eleven dollars. Replacing it correctly ended a problem that had cost four pumps and four weeks.
The method has a name in manufacturing and the number five is arbitrary; sometimes the chain is three links and sometimes eight. What matters is the discipline of not stopping at the first answer that is technically true. 'Bearing failure' is true, and it is the description of a symptom wearing the clothes of a cause.
The same trap appears far outside factories. A student is told they failed because they did not revise. True, and useless, unless somebody asks why the revision did not happen, and then why that was, until the chain reaches something that can actually be changed.
Vocabulary in this text
- maintenance /ˈmeɪntənəns/ — the work of keeping something in good condition
- replace /ɹˌiˈpleɪs/ — to put something new in place of something old
- bearing /ˈbɛɹɪŋ/ — relevance to something, or direction
- rate /ɹˈeɪt/ — a measurement of speed or frequency
- temperature /ˈtɛmpɹətʃɚ/ — how hot or cold something is
- worth /ˈwɝθ/ — having a particular value or use
- arbitrary /ˈɑɹbətɹˌɛɹi/ — decided by chance or personal choice rather than by reason
- symptom /ˈsɪmptəm/ — a sign that you have an illness
- appear /əˈpɪɹ/ — to become possible to see, or to seem
- revise /ɹɪˈvaɪz/ — to change a text to improve it, or to study again