About Associating Potential Degradation Mechanisms (PDMs)

Each RBI Corrosion Loop contains multiple RBI Components. Each of these components can fail in multiple ways. To indicate the ways in which components can fail, you can link Potential Degradation Mechanisms (PDMs) to the RBI Corrosion Loops.

Each PDM that is linked to the RBI Corrosion Loop represents a degradation mechanism (a way in which the components in that Corrosion Loop might fail). Once the RBI Corrosion Loop has been associated with a PDM, all components added to that RBI Corrosion Loop will inherit the PDM.

For each component, you can define the specific ways in which the RBI Component that it represents can fail.

Note: PDMs can be standardized and inherited from RBI Corrosion Loops. When a new RBI Component is generated from and linked to a specific RBI Corrosion Loop, the PDMs associated with that RBI Corrosion Loop will be inherited by the new RBI Component.

Example: Overhead (OVHD) System

Suppose you have created an RBI Corrosion Loop to represent an OVHD system. You may have determined that components in this corrosion loop can fail in the following ways:

Exchanger Failure: The tubes in the exchanger could foul and cause the exchanger to produce too much or too little cooling.
Column Failure: The column may be susceptible.

In this case, the RBI Corrosion Loop would be linked to two PDMs to represent each type of degradation mechanism in the preceding list. After the PDMs are linked to the RBI Corrosion Loop as a whole, and you have determined the components in the corrosion loop, you will need to validate the degradation mechanisms for each component.

Assuming that the OVHD system contains the Exchanger and the Column, the RBI Corrosion Loop representing the OVHD system would be linked to the following RBI Component records:

Column Top (belongs to the Column)
Outlet Nozzle (belongs to the Column)
Exchanger Shell (belongs to the Water Heater)

Each of these RBI Components would be linked automatically to all the PDMs that are linked to the Corrosion Loop. You would need to determine, however, which degradation mechanisms make sense for each component. To do so, you might decide that the RBI Component should be linked to the PDMs as described in the following table.

RBI Component	PDM
Column Top	Environmental Cracking
Outlet Nozzle	External Corrosion
Exchanger Shell	Environmental Cracking

So, while the RBI Corrosion Loop is linked to two PDMs, each RBI Component is linked to only one PDM in this case.