MCGG22D1CB0753C-2 ALSTOM Input and output module

MCGG22D1CB0753C-2 ALSTOM Input and output module

MCGG22D1CB0753C

The structure of the protection system should be designed to prevent random hardware failures. It should be demonstrated that the required reliability has reached a level commensurate with the required level of integrity. Defensive measures may include high reliability elements, automatic diagnostic features that indicate faults, and redundancy of elements (e.g., 2 out of 3 votes to provide fault tolerance for the sensor). The diversity of elements is not effective for preventing random hardware failures, but it is useful for protecting against common pattern failures in a system.

Sensors include their connection to the process, and both should be sufficiently reliable. In confirming the level of integrity of the protection system, a measure of its reliability is used. This measure should take into account the proportion of sensor failures and the risk of process connections.

Several measures can be taken, such as:

Use as direct a measurement method as possible (e.g. : pneumatic apparatus provides an inferred level measurement, but actually measures the back pressure to the head, is sensitive to density changes due to temperature changes in the process, and balances the gas flow on which they depend);

Control the isolation valve or bleed valve to prevent disconnection during the process between validation tests or monitoring, thereby causing its operation to cause failure;