169: Errors Not Detectable
Definition/Typical Issues
Were personnel unable to detect errors (by way of alarms or instrument readings) during or after the occurrence? Did a serious error go unnoticed because no means were provided to monitor system status?
Should multiple or redundant sources of critical information have been provided? Is there an inadequate update rate for sensed information (e.g., flow rates, tank levels)? Should methods or procedures have been provided to test and verify information? Should alternate means to acquire and verify information have been provided? Are components and devices needed to verify information not available in the area where the situation assessment is performed?
Note 1: Consider dual coding with the Workplace Layout Issue (#150) node.
Examples
Example 1
- An operator intending to stop flow to a tank accidentally closed the wrong valves. No level alarm was provided on the tank to indicate that overflow was imminent; therefore, the tank overflowed.
Example 2
- A warehouse stock person obtained the wrong bolts for a job. The bolts were in bins that were only labeled with the part numbers; no part descriptions were included. Small parts like these were not labeled with part numbers. As a result, the stock person could not verify that the materials in the bin were the ones that were supposed to be there.
Example 3
- An operator attempted to open a block valve underneath a relief valve. The gate separated from the stem, so even though the valve appeared open (based on stem position), the gate was still closed and obstructing the pressure relief valve inlet. No other means was available to determine the position of the valve.
Example 4
- A temperature indicator was indicating a low outlet temperature for a cooling system. However, the temperature indicator had failed low. There was no ready means for the operator to determine that the indication was wrong. As a result, the operator did not put the backup cooler into operation as required.
Typical Recommendations
- Ensure that important safety-related equipment is adequately equipped with error-detection systems.
- Ensure that systems important to reliability and quality are equipped with error-detection systems.
Cross-References
| Version 10 Element(s) | |
|---|---|
| Node ID | Node Name |
| 161 | Errors Not Detectable |
| Maritime Element(s) | |
|---|---|
| Node ID | Node Name |
| 176 | Errors Not Detectable |