Overview
There are two sets of models that calculate risk for air cooled exchangers (aka AC Exchangers); baseline and expanded. The following summarizes the capabilities of each set:
- Baseline models calculate risk for two risk components (Header, Tube) and then summarizes risk to recommend mitigation tasks.
- Expanded models calculate risk for multiple components as defined by the hierarchy and then summarizes risk to recommend mitigation tasks. The following components can be included in the hierarchy:
- up to 3 header sections (Header, Header 1, and Header 2)
- up to 3 tube sections (Tube, Tube 1, and Tube 2)
- up to 10 other components that can represent various things such as nozzles, jackets, etc.
Baseline Asset (RBI_AC_EXCHANGER)
Application
This parent asset model summarizes risk results from 2 components (Header, Tube) to recommend mitigation tasks.
Mitigation recommendations were developed based on API 510 “Pressure Vessel Inspection Code” and API 572 “Inspection Practices for Pressure Vessels”.
Model Boundaries
This parent model summarizes risk analysis results from child components so mitigation tasks can be recommended for the asset. The worst child component determines the overall risk of the asset.
Link Models
This parent model should be linked to a hierarchy item where Type is “Asset”. The child components must be linked to the following models:
- Header: RBI_CYLINDRICAL
- Tube: RBI_AC_TUBE
Hierarchy Templates
The following hierarchy templates should be selected for the parent asset: Air Cooled Exchanger – Metric (or SAE)
Dependencies
The child components must be children of the parent asset.
Expanded Asset (RBI_SP_AC_EXCHANGER)
Application
This parent asset model summarizes risk results from up to 6 components (e.g. 3 headers and 3 tubes) and up to 10 other components (e.g. jacket, nozzle) to recommend mitigation tasks.
Mitigation recommendations were developed based on API 510 “Pressure Vessel Inspection Code” and API 572 “Inspection Practices for Pressure Vessels”. Two sets of recommendations are provided that address the overall asset and “worst” other components by damage mechanism.
Model Boundaries
This parent model summarizes risk analysis results from child components and other components so that mitigation tasks can be recommended for both the asset and other components. The worst child component determines the overall risk of the asset.
Link Models
This parent model should be linked to a hierarchy item where Type is “Asset”. The child components and other components must be linked to the following models:
- Header: RBI_CYLINDRICAL
- Header 1 & 2: RBI_SP_CYLINDRICAL
- Tube: RBI_AC_TUBE
- Tube 1 & 2: RBI_SP_AC_TUBE
- Other components: RBI_SP_CYLINDRICAL
Hierarchy Templates
The following hierarchy templates should be selected for the parent asset: Air Cooled Exchanger – Metric (or SAE)
Dependencies
The child components or other components must be children of the parent asset.
Baseline Header (RBI_CYLINDRICAL)
Application
This child model applies to Air Cooled Exchanger Header that must be a child of the parent AC Exchanger asset which is linked to either RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER.
The model is designed for pressure equipment constructed of cylindrical sections but is adapted for Air Cooled Exchanger header boxes by calculating an equivalent diameter as follows:
``d=((2h+2w)/pi)``
Where:
d = diameter
h = height of header box
w = width of header box
Mitigation recommendations are provided by the parent model (RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER).
Model Boundaries
This child model applies to one risk component at a time.
The primary failure mode is loss of containment caused by one or many in-service damage mechanisms. Probability of failure categories are calculated for internal corrosion, external corrosion, corrosion under insulation and environmental cracking, but does not include the method for creep. Up to five additional damage mechanisms can be added manually as Other Damage Mechanisms.
A safety consequence of failure category is calculated based on one of four types of representative fluids: flammable, toxic, reactive (i.e. cause injury to skin upon contact such as acids, caustics and steam) or inert. An option allows a flammable fluid to also include a toxic mixture. If the representative fluid is inert and initial state is gas, then a burst consequence can be calculated. The user can also manually enter a production loss consequence to represent any type of financial loss. When both safety and financial consequence are included then the overall risk is based on the worst consequence.
Link Models
This child model should be linked to hierarchy items where Type is “Component” and parent is the AC Exchanger asset.
Hierarchy Templates
The following hierarchy templates should be selected for child components: Air Cooled Exchanger Header – Metric (or SAE)
Dependencies
This model provides risk analysis results that are summarized by the parent asset (RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER).
Baseline Tube (RBI_AC_TUBE)
Application
This child model applies to one representative Air-Cooled Exchanger Tube that must be a child of the parent asset linked to either RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER. Typically, the representative tube is the “worst” tube to result in conservative mitigation recommendations.
Mitigation recommendations are provided by the parent model (RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER).
Model Boundaries
The primary failure mode is loss of containment caused by one or many in-service damage mechanisms. Probability of failure categories are calculated for internal corrosion, external corrosion, and environmental cracking, but does not include the method for CUI or creep. Up to five additional damage mechanisms can be added manually as Other Damage Mechanisms.
A safety consequence of failure category is calculated based on one of four types of representative fluids: flammable, toxic, reactive (i.e. cause injury to skin upon contact such as acids, caustics and steam) or inert. An option allows a flammable fluid to also include a toxic mixture. If the representative fluid is inert and initial state is gas, then a burst consequence can be calculated. The user can also manually enter a production loss consequence to represent any type of financial loss. When both safety and financial consequence are included then the overall risk is based on the worst consequence.
Link Models
This child model should be linked to hierarchy items where Type is “Component” and parent is the AC Exchanger asset.
Hierarchy Templates
The following hierarchy templates should be selected for child components: Air Cooled Exchanger Header – Metric (or SAE)
Dependencies
This model provides risk analysis results that are summarized by the parent asset (RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER).
Expanded Header (RBI_SP_CYLINDRICAL)
Application
This child model applies to Air Cooled Exchanger Header components where the parent AC Exchanger asset is linked to RBI_SP_AC_EXCHANGER.
The model is designed for pressure equipment constructed of cylindrical sections but is adapted for Air Cooled Exchanger header boxes by calculating an equivalent diameter as follows:
Where:
d = diameter
h = height of header box
w = width of header box
Mitigation recommendations are provided by the parent model (RBI_AC_EXCHANGER or RBI_SP_AC_EXCHANGER).
Model Boundaries
This child model applies to one risk component at a time.
The primary failure mode is loss of containment caused by one or many in-service damage mechanisms. Probability of failure categories are calculated for internal corrosion, external corrosion, corrosion under insulation and environmental cracking, but does not include the method for creep. Up to five additional damage mechanisms can be added manually as Other Damage Mechanisms.
A safety consequence of failure category is calculated based on one of four types of representative fluids: flammable, toxic, reactive (i.e. cause injury to skin upon contact such as acids, caustics and steam) or inert. An option allows a flammable fluid to also include a toxic mixture. If the representative fluid is inert and initial state is gas, then a burst consequence can be calculated. The user can also manually enter a production loss consequence to represent any type of financial loss. When both safety and financial consequence are included then the overall risk is based on the worst consequence.
Link Models
This child model should be linked to hierarchy items where Type is “Component” and parent is the AC Exchanger asset. This model provides the following expanded number of child components:
- Header 1 & 2 (these are distinct from the baseline child component "Header")
Hierarchy Templates
The following hierarchy templates should be selected for child column components: Air Cooled Exchanger Header – Metric (or SAE)
Dependencies
This model provides risk analysis results that are summarized by the parent asset (RBI_SP_AC_EXCHANGER).
Expanded Tube (RBI_SP_AC_TUBE)
Application
This child model applies to two representative Air-Cooled Exchanger Tubes that must be a child of the parent asset linked to RBI_SP_AC_EXCHANGER. Typically, each representative tube is the “worst” tube to result in conservative mitigation recommendations.
Mitigation recommendations are provided by the parent model (RBI_SP_AC_EXCHANGER).
Model Boundaries
This child model applies to one risk component at a time.
The primary failure mode is loss of containment caused by one or many in-service damage mechanisms. Probability of failure categories are calculated for internal corrosion, external corrosion, and environmental cracking, but does not include the method for CUI or creep. Up to five additional damage mechanisms can be added manually as Other Damage Mechanisms.
A safety consequence of failure category is calculated based on one of four types of representative fluids: flammable, toxic, reactive (i.e. cause injury to skin upon contact such as acids, caustics and steam) or inert. An option allows a flammable fluid to also include a toxic mixture. If the representative fluid is inert and initial state is gas, then a burst consequence can be calculated. The user can also manually enter a production loss consequence to represent any type of financial loss. When both safety and financial consequence are included then the overall risk is based on the worst consequence.
Link Models
This child model should be linked to hierarchy items where Type is “Component” and parent is the AC Exchanger asset. This model provides the following expanded number of child components:
- Tube 1 & 2 (these are distinct from the baseline child component Tube)
Hierarchy Templates
The following hierarchy templates should be selected for child components: Air Cooled Exchanger Tube – Metric (or SAE)
Dependencies
This model provides risk analysis results that are summarized by the parent asset (RBI_SP_AC_EXCHANGER).
Other Components (RBI_SP_CYLINDRICAL)
Application
This child model applies to Other components of the parent AC Exchanger asset such as nozzles which must be children of the AC Exchanger asset.
Mitigation recommendations are provided by the parent model (RBI_SP_AC_EXCHANGER).
Model Boundaries
This child model applies to one risk component at a time.
The primary failure mode is loss of containment caused by one or many in-service damage mechanisms. Probability of failure categories are calculated for internal corrosion, external corrosion, corrosion under insulation and environmental cracking, but does not include the method for creep. Up to five additional damage mechanisms can be added manually as Other Damage Mechanisms.
A safety consequence of failure category is calculated based on one of four types of representative fluids: flammable, toxic, reactive (i.e. cause injury to skin upon contact such as acids, caustics and steam) or inert. An option allows a flammable fluid to also include a toxic mixture. If the representative fluid is inert and initial state is gas, then a burst consequence can be calculated. The user can also manually enter a production loss consequence to represent any type of financial loss. When both safety and financial consequence are included then the overall risk is based on the worst consequence.
Link Models
This child model should be linked to hierarchy items where Type is “Component” and parent is the AC Exchanger asset. This model provides up to 10 Other components (e.g. nozzles).
Hierarchy Templates
The following hierarchy templates should be selected for other components: Jacket without Creep – Metric (or SAE)
NOTE: The term “jacket” has been generalized to include any type of component including heating/cooling “jacket”, nozzles, water boot, etc.
Dependencies
This model provides risk analysis results that are summarized by the parent asset (RBI_SP_AC_EXCHANGER).