Temporary failure

There are obviously situations which demand considerable over-design of a cathodic protection system, in particular where regular and efficient maintenance of anodes is not practical, or where temporary failure of the system could cause costly damage to plant or product. Furthermore, contamination of potable waters by chromium-containing or lead-based alloy anodes must lead to the choice of the more expensive, but more inert, precious metal-coated anodes. The choice of material is then not unusual in being one of economics coupled with practicability. 

The laboratory should develop procedures for applying work arounds in case of temporary failure or inaccessibility of the system. 

The laboratory must establish and follow procedures for system backup and recovery. The laboratory should develop procedures for applying work arounds in case of temporary failure or inaccessibility of the system. All schedules, logs, and reports of system backups, system failures, and recoveries or restores must be retained by the laboratory. 

Although the stresses formed during cooling are temporary, failure can occur due to the high stress that occurs when the surface and bulk temperatures differ. The maximum possible stress will be generated if the surface is instantaneously cooled, while the bulk is still at the original temperature. Under these conditions, the stress is given by the simple expression ... 

DS operation seven permanent failures, fourteen temporary failures... 

Temporary failures, which disappear when the lEMI influence ends or when the system reboots, and... 

Table 1. Estimation of the probability of a temporary failure in a VIP convoy...

Effect Affected component Temporary failure Permanent failure ... 

Table 4 shows, as an example, the calculated risk priority numbers for the global effects of temporary failures caused by lEMI in the VIP convoy scenario. 

As can be seen in Table 5, the mean values for the three scenarios were in a relatively small range, with a minor advantage for the military convoy, which is due to the better hardening of military equipment and the positive image of the military in Austria. Generally, the higher vulnerability of components in respect to temporary failures is widely, if not fully, compensated by the more severe consequences of permanent failures. 

The field watchdog is an irreversible device for ensuring the maintenance of the system in a fallback position in case of a permanent failnre. These actions are to ensure that the system is not in a more permissive state than in the absence of failure. For this, the equipment power (all components) is cut off. This lack of power ensures the positioning of output in a restrictive state. This watchdog is periodically self-tested. This device detects, in the course of a program, a defect due to a temporary failure or random characteristic of the hardware or software equipment, and initiates the necessary actions. 

DS operation permanent failure 7, temporary failure 14 CB operation permanent failure 7, temporary failure 17... 

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