Calculations

This topic provides a list of fields that are required in each family to calculate an RBI Criticality Analysis, RBI PRD Criticality Analysis, and an RBI Pipeline Analysis. Some fields are conditionally required, and these conditions are described in the Notes column in the following tables.

Fields Required to Calculate RBI Criticality Analyses

To calculate an RBI Criticality Analysis, values may be required in certain fields in the following families:

• Criticality Consequence Evaluation
• Criticality Env. Crack. Deg. Mech. Eval.
• Criticality Ext. Corr. Deg. Mech. Eval.
• Criticality Int. Corr. Deg. Mech. Eval.
• RBI Criticality Analysis

Criticality Consequence Evaluation family: The following table lists the fields in the Criticality Consequence Evaluation family that require values in order to calculate an RBI Analysis:

Criticality Env. Crack. Deg. Mech. Eval. family

The following table lists the fields in the Criticality Env. Crack. Deg. Mech. Eval. family that require values in order to calculate an RBI Analysis:

Criticality Ext. Corr. Deg. Mech. Eval. family

The following table lists the fields in the Criticality Ext. Corr. Deg. Mech. Eval. family that require values in order to calculate an RBI Analysis:

Criticality Int. Corr. Deg. Mech. Eval. family

The following table lists the fields in the Criticality Int. Corr. Deg. Mech. Eval. family that require values in order to calculate an RBI Analysis:

RBI Criticality Analysis family

The following table lists the fields in the RBI Criticality Analysis family that require values in order to calculate an RBI Analysis:

Fields Required to Calculate RBI PRD Criticality Analyses

Several fields in RBI families are required in order to calculate RBI PRD Criticality Analyses. If you try to calculate an RBI PRD Analysis and any required fields do not contain values, the analysis will not be calculated, and the Calculation Status dialog box will appear, displaying a list of the required fields that do not contain values. The required fields differ depending upon whether the RBI PRD Analysis contains a Leak Criticality Degradation Mech Evaluation record or an Over Pressure Criticality Degradation Mech Evaluation record.

Analyses Containing a Leak Record: The following lists describe the fields that are required in order to calculate RBI PRD Analyses that meet the following criteria:

• They contain an Over Pressure Criticality Degradation Mech Evaluation record (i.e., a record belonging to the Criticality Over Pressure Deg. Mech. Eval. family).

• They contain a Leak Criticality Degradation Mech Evaluation record (i.e., a record belonging to the Criticality Leak Deg. Mech. Eval. family).

The lists are categorized by the family to which the required fields belong.

PRD Consequence Evaluation:

• Cost of Fluid

• Environmental Cost

• Unit Production Margin

• Consequence for Protected Assets

  Note: The Consequence for Protected Assets field is required only when the pressure relief device protects equipment.

Criticality Leak Deg. Mech. Eval.:

• Date in Service

• Service Severity - Leak

RBI PRD Criticality Analysis:

• Criticality Item Type

• Operating Pressure

  Note: If the pressure relief device protects RBI Components, the Operating Pressure field is populated automatically from the Operating Pressure field in the driving RBI Component. If, however, the pressure relief device protects equipment, you must type a value in this field manually.

• Operating Temperature

• PRD Discharge Location

• Service Severity

• Driving Component

  Note: The Driving Component field must contain a value if the pressure relief device protects RBI Components.

• Damage Factor Class

  Note: The Damage Factor Class field must contain a value if the pressure relief device protects equipment.

• PRD Relief Area

  Note: The PRD Relief Area field is required and must contain a value greater than zero if the Multiple PRDs check box is selected.

• PRD Total Relief Area

  Note: The PRD Total Relief Area field is required and must contain a value greater than zero if the Multiple PRDs check box is selected.

Criticality PRD Component - Relief Valve:

• Inlet Size

• Set Pressure

• Rated Capacity

Analyses That Do not Contain a Leak Record: The following table lists the fields that are required in order to calculate RBI PRD Analyses that meet the following criteria:

• They contain an Over Pressure Criticality Degradation Mech Evaluation record (i.e., a record belonging to the Criticality Over Pressure Deg. Mech. Eval. family).

• They do not contain a Leak Criticality Degradation Mech Evaluation record (i.e., a record belonging to the Criticality Leak Deg. Mech. Eval. family).

The lists are categorized by the family to which the required fields belong.

PRD Consequence Evaluation:

• Cost of Fluid

• Environmental Cost

• Unit Production Margin

• Days to Repair

• Consequence for Protected Assets

  Note: The Consequence for Protected Assets field is required only when the pressure relief device protects equipment.

Criticality Over Pressure Deg. Mech. Eval.:

• Date in Service

RBI PRD Criticality Analysis:

• Criticality Item Type

• Operating Pressure

  Note: If the pressure relief device protects RBI Components, the Operating Pressure field is populated automatically from the Operating Pressure field in the driving RBI Component. If, however, the pressure relief device protects equipment, you must type a value in this field manually.

• Operating Temperature

• Protected Equipment Type

  Note: If the pressure relief device protects RBI Components, the Protected Equipment Type field is populated automatically based upon the value in the Criticality Item Type field in the driving RBI Component. If, however, the pressure relief device protects equipment, you must type a value in this field manually.

• PRD Discharge Location

• Service Severity

• Driving Component

  Note: The Driving Component field must contain a value if the pressure relief device protects RBI Components.

• Damage Factor Class

  Note: The Damage Factor Class field must contain a value if the pressure relief device protects equipment.

• PRD Relief Area

  Note: The PRD Relief Area field is required and must contain a value greater than zero if the Multiple PRDs check box is selected.

• PRD Total Relief Area

  Note: The PRD Total Relief Area field is required and must contain a value greater than zero if the Multiple PRDs check box is selected.

• MAWP (Maximum Allowable Working Pressure)

• Next Inspection Date

Fields Required to Calculate RBI Pipeline Analyses

In order to calculate an RBI Pipeline Analysis, you are required to enter values in fields in the following families:

• Criticality Consequence Evaluation
• RBI Pipeline Analysis
• Criticality Ext. Corr. Deg. Mech. Eval.
• Criticality Int. Corr. Deg. Mech. Eval.

Criticality Consequence Evaluation family

The following table lists the fields in the Criticality Consequence Evaluation family that require values in order to calculate an RBI Pipeline Analysis:

Criticality Ext. Corr. Deg. Mech. Eval.

The following table lists the fields in the Criticality Ext. Corr. Deg. Mech. Eval. family that require values in order to calculate an RBI Pipeline Analysis:

Criticality Int. Corr. Deg. Mech. Eval.

The following table lists the fields in the Criticality Int. Corr. Deg. Mech. Eval. family that require values in order to calculate an RBI Pipeline Analysis:

Criticality Third Party Deg. Mech. Eval.

The following table lists the fields in the Criticality Third Party Deg. Mech. Eval. family that require values in order to calculate an RBI Pipeline Analysis:

RBI Pipeline Analysis

The following table lists the fields in the RBI Pipeline Analysis family that require values in order to calculate an RBI Pipeline Analysis:

GE Digital APM automatically calculates the value in the Calculated Inventory field in the following RBI Component records:

• Criticality RBI Component - Cylindrical Shell
• Criticality RBI Component - Exchanger Header
• Criticality RBI Component - Exchanger Tube
• Criticality RBI Component - Tank Bottom
• Criticality RBI Component - Piping

The formula that is used to determine Calculated Inventory depends on the value in the Initial Fluid Phase field in the RBI Component record.

• If the value in the Initial Fluid Phase field is Gas, the Calculated Inventory for Gases formula is used.
• If the value in the Initial Fluid Phase field is Liquid, the Calculated Inventory for Liquids formula is used.

You can specify that the Calculated Inventory value be used to populate the Inventory field in the associated Criticality Consequence Evaluation record by setting the Use Calculated Inventory field in the Criticality Consequence Evaluation to True.

Calculated Inventory for Gases

To determine the Calculated Inventory for gases, the following fields must be populated on the RBI Components record:

Calculated Inventory for gases is determined using the following formula:

Calculated Inventory for gases = (P x V) / (R / MolWt) x (T + 459.67)

...where:

• P is the value in the Operating Pressure field in the RBI Component record.
• V is the Volume that is calculated for the gas that is associated with the RBI Component.
• R is the value 1,545, a universal gas constant.
• MolWt is the MolWt defined by the RepresentativeFluids reference table for the fluid specified in the Process Fluid field in the RBI Component.
• T is the value in the Operating Temperature field in the RBI Component record.

• The value 459.67 is the temperature constant, 459.67

Example: Calculated Inventory for Gases

Suppose an RBI Component has the following values:

Based on these values, Calculated Inventory for gases would be determined as follows:

Calculated Inventory for gases = (P x V) / (R / MolWt) x (T + 459.67)

Calculated Inventory for gases = (500 x 40715.0408) / (1,545 / 28) x (100 + 459.67)

Calculated Inventory for gases = (500 x 40715.0408) / (55.1786 x 559.67)

Calculated Inventory for gases = (20357520.395) / (30,881.8071)

Calculated Inventory for gases = 659

Calculated Inventory for Liquids

To determine the Calculated Inventory for liquids, the following fields must be populated in the RBI Component:

Calculated Inventory for liquids is determined using the following formula:

Calculated Inventory for liquids = Density x Volume

...where:

• Density is determined for the Process Fluid in the RBI Component according to the RepresentativeFluids reference table.
• Volume is the value in the Volume field associated with the RBI Component record.

Inventory Calculations for Volume

Volume is calculated using values that are stored in the associated RBI Component. Volume is used an input to the calculations for Calculated Inventory for gases and liquids.

Volume is calculated using one of three calculations, depending on the value in the Component Type field in the associated RBI Component.

The following equations are used to calculate volume for the following RBI Components that contain a value other than Storage Tanks in the Component Type field:

Volume of Cylindrical Shell, Exchanger Head, and Exchanger Tube RBI Components = (22/7) x (D / 24) x (D / 24) x (L / 12)

...where:

• D = Inside Diameter

• L = Length

Volume of Tank Bottom RBI Components = (22/7) x (D / 24) x (D / 24) x (H / 12)

...where:

• D = Inside Diameter

• H = Fill Height

Volume of Piping RBI Components = (22/7) x (D / 24) x (D / 24) x PCL

...where:

• D = Inside Diameter
• PCL = Piping Circuit Length

The Equivalent Number of Inspections field is available on the baseline datasheets for the following Criticality Degradation Mech Evaluation families:

• Criticality Env. Crack. Deg. Mech. Eval.
• Criticality Ext. Corr. Deg. Mech. Eval.
• Criticality Int. Corr. Deg. Mech. Eval.

The value in this field is calculated automatically based on:

• The number of Inspections that you assigned to the associated degradation mechanism
• The values that exist in the Inspection Confidence fields in those Inspections
• The confidence equivalence factor (EF) that applies to those inspection confidence values

EF is determined as follows:

Equivalent Number of Inspections = (Very High EF x # Inspections with Very High Confidence) + (High EF x # Inspections with High Confidence) + (Medium EF x # Inspections with Medium Confidence) + (Low EF x # Inspections with Low Confidence)

The Allowable Stress field in an RBI Analysis datasheet is populated based on the component type.

For Pressure Vessels and Piping Components

Values in the following fields in an RBI Criticality Analysis datasheet are used to calculate the value in the Allowable Stress field:

• Stress Lookup Table
• Construction Code
• Code Year
• Material Spec
• Material Grade
• Design Temperature

If the value in the Design Temperature field matches a value in the Metal Temperature column in a Piping Stress or a PV Stress record, the corresponding Allowable Stress value is populated in the analysis.

When Interpolation is Enabled

If RBI cannot find an exact match in the Piping Stress or PV Stress reference table, and the Application Settings specify that interpolation should be used, the interpolated Allowable Stress value is calculated using the temperature and stress values that make up a range that includes the Design Temperature.

The Design Temperature falls within the range established by the two Piping Stress records in the table. Assuming that stress varies linearly as a function of temperature within the defined range, the Allowable Stress value at 150 degrees Fahrenheit is calculated using the following formula:

Sx = S1 - (T1 - Tx) / (T1 - T2) * (S1 - S2)

Where:

• Sx is the calculated Allowable Stress value for the analysis
• S1 is the Allowable Stress value at lower boundary of the Metal Temperature
• S2 is the Allowable Stress value at upper boundary of the Metal Temperature
• T1 is the Metal Temperature value at lower boundary
• Tx is the defined Design Temperature value
• T2 is the Metal Temperature at upper boundary

Given the values from our example, Sx is calculated as follows:

Sx = 20000 - ((100 - 150) / (100 - 200) * (20000 - 18000))

So, Sx = 19000

This interpolated Allowable Stress value is used in the RBI Analysis.

When Interpolation is Disabled

If RBI cannot find an exact match in the Piping Stress or PV Stress reference table, and the Application Settings specify that interpolation should not be used, the Allowable Stress value that corresponds to the next highest temperature value in the temperature range is used.

In the same example, the Design Temperature is not an exact match to a Metal Temperature in the Piping Stress table. The Design Temperature, however, does fall within the temperature range established by the two Piping Stress records in the table. So, in this case, the Allowable Stress value that corresponds to the next highest Metal Temperature, that is 18,000 is used.

For Tanks

Values in the following fields in an RBI Criticality Analysis datasheet are used to calculate the value in the Allowable Stress field:

• Stress Lookup Table
• Construction Code
• Code Year
• Material Spec
• Material Grade
• Course Number
• Tensile Strength (from the Tank Stress record)
• Yield Strength (from the Tank Stress record)

Depending on the value in the Stress Lookup Table field, the values in the rest of the aforementioned fields are populated with the values in the corresponding fields in the PV Stress, Piping Stress, and Tank Stress Reference Tables. For example, if the value in the Stress Lookup Table field is Piping, then the value in the Code Year field is populated with the value in the Code Year field in the Piping Stress Reference Table.

If the value in the Course Number field is 1 or 2, then Allowable Stress is calculated as follows:

Allowable Stress = Minimum (0.80 x Yield Strength, 0.429 x Tensile Strength)

Otherwise, Allowable Stress is calculated as follows:

Allowable Stress = Minimum (0.88 x Yield Strength, 0.422 x Tensile Strength)

The Non-Intrusive Requirement Met field appears as a check box on the Criticality Int. Corr. Deg. Mech. Eval. datasheet. It indicates whether you can perform an intrusive or non-intrusive inspection on the component. The value in this field is used by the Appendix_B and Appendix_C policies to generate RBI Recommendations.

The following table provides a list of fields whose values are used to select or clear the check box.

The following table specifies the conditions based on which the Non-Intrusive Requirement Met check box is selected or cleared.

Policy Used to Select or Clear the Non-Intrusive Requirement Met Check Box

The RBI 580 Non-Intrusive Requirement (Appendix C) policy is used to select or clear the Non-Intrusive Requirement Met check box.

This policy uses the following inputs:

• The RBI Degradation Mechanism record that represents the Criticality Calculator Internal Corrosion DM.
• The Criticality Int. Corr. Deg. Mech. Eval. record.
• The entity key of the associated Asset.
• The RBI Criticality Analysis record.

This policy uses the following queries, which are located in the \\Public\Meridium\Modules\Risk Based Inspection\Queries folder.