Error Categories

276 major human errors were estimated and hundreds of minor contributory causes. The values below indicate the number of times this specific type of major failure cause occurred. Note that there is almost always more than one contributory cause and a typical example of this is a calciner shell failure that was caused by pitting corrosion. The back resulted from the combined effects of a welding error during fabrication and an operating error. The total number in each category shows:

• 93 Maintenance errors
• 90 Design errors
• 34 Operational errors
• 28 Manufacturing errors
• 20 Original installation errors
• 11 Supervisory errors

From "Understanding Why It Failed" by Neville W. Sachs, P.E. Sachs, Salvaterra & Associates, Syracuse, NY pitting