Fixed Equipment and Pipe Templates

RBI + Required Fields reference Spreadsheet

RBI + for Fixed Equipment Guidance

RBI + for Tank Bottoms Guidance

API 5813rd for Fixed Equipment

Fluid Unit of Measures

Relief Device Templates

RBI+ for Relief Devices

Condition Based Model

You can download a RBI + Input definition workbook here. Within the Workbook it will describe:

• Field Names

• Defaults

• Required Fields

• Data Types

• Comments

• Sample formats of input values

Download the MS Excel workbook here.

1. Inventory 

For RBI purposes, inventory is the mass of fluid available to contribute to a risk event if there is a failure in the process boundary.  Inventory is difficult to calculate, so we have taken some steps to simplify the analysis of inventory.   Within a plant, inventory can be characterized by plant size - generally the larger the plant the more inventory as higher capacity plants generally have larger throughputs and larger equipment.  

Inventory sets an upper limit on release effect, but the release mass estimated in the NFPA calculator is more important than the total inventory.

The concept of "Isolated Inventory" is another simplification to better predict the inventory available for release by identifying equipment that are unlikely to deinventory multiple pieces of equipment in the event of a failure of the process boundary.

2. Detection and Isolation  

Detection and Isolation are a measure or predictor of the time required to first detect that a leak is occurring and secondly to isolate (stop) the leak.  These are separate, discrete events and can either be a fully manual process within the plant, or fully automated with appropriate instrumentation, or a combination of the two.  Rather than guessing how many minutes these events might take, the NFPA RBI allows the user to characterize the degree of automation and operator presence within the plant from which a factor is derived that is related to the effectiveness of the detection and isolation capability within the plant.

 3. Population Density 

This is a measure of the number of human beings per unit of area likely to be within the hazard zone in the event of a process safety event at a plant site.  There are two distinct categories of population - plant workers distinct from the general population, which can be affected if the risk event impacts people outside of the plant boundary.  There is a greater concern for off-site people (Non-employees) because typically there is greater liability for an off-site impact. Options are below:

• Remote from workers, public

• Remote from public, field personnel present 1 shift/day

• Remote from public, field personnel present 24 hrs

• Remote from public, located near occupied buildings

• Near public, remote from occupied buildings

• Near public, located near occupied buildings

Note that NFPA RBI does not use population density, but instead uses a qualitative description of the plant personnel and their proximity to a process safety event associated with a particular piece of equipment, as well as the potential for off-site people to be affected.  This description is converted to a factor that is calibrated to the likely Effect of the Release on these people.

 4. Thickness at coating/lining installation date

If a lining were installed in a vessel after it was placed in service, that would normally indicate the vessel would be experiencing higher than anticipated corrosion.  If the lining were installed some years after the vessel was placed in service, there could be considerable corrosion on the vessel wall by the time it was coated.  The owner/operator  should measure the wall loss in the vessel and make a decision whether to weld repair it before installing the lining.  Whether it is repaired or not, the minimum wall thickness (maximum wall loss due to the pre-lining corrosion) should be measured and recorded.  When the lining fails at a future date, the corrosion will start from the wall thickness measured at the coating installation date rather than from the original thickness.  If the vessel were repaired before installing the coating/lining or if the coating is installed before the vessel is put into service, the thickness at the coating/lining date would be the original thickness.  

 The field "Thickness at coating/lining installation date" should be an input field with a user-supplied number.  It will not be used in any further calculations, unless the lining installation date is also the last internal inspection date, in which case this thickness value should be entered Measured Wall Thickness - Last Inspection.

5. Allowable Stress, Yield, and Tensile Strength overrides

The model will perform a lookup to obtain the Allowable Stress, Yield Stress, and Tensile Strength. The lookup is based on Material Code Year, Material Code, Material Specification, Material Grade, and Design Temperature.

If the user cannot find these 5 variables, the override values are needed.

6. Isolated Inventory System (Yes or No)

The concept of "Isolated Inventory" is another simplification to better predict the inventory available for release by identifying equipment that are unlikely to deinventory multiple pieces of equipment in the event of a failure of the process boundary.

7. A, B, C, D, E Level Inspection Count

A ranking system defined in API 5813rd where A is the highest level of confidence you have inspected for the damage mechanism and E being the lowest.

A = 100% confident being the extreme

E = 0% confident being the extreme

You can review Part 2 Annex 2.c for a overview of the A-E categories, however the tables are provided as a matter of example only, and it is the responsibility of the owner-user to create, adopt, and document their own specific levels of inspection effectiveness tables.

This Inspection effectiveness categories (e.g. A,B,C,D, or E categories) are used to reduce uncertainty in the models for calculating the probability of failure.

8. External Corrosion Rate Override (optional)

For External, the model will calculate an External Corrosion rate based on bare steel, insulated, etc..However, the user can override the External rate if desired.

9. Max Inspection Interval

Per Damage Mechanism, the Max Inspection interval is asked by the user to determine if the acceptable thresholds can make it within this limit.

10. Corrosion Rate Determined (Thinning and External)

Documentation only. Used by Corrosion or Reliabilty engineer to document their assumptions. This allows the user to document was it based on Corrosion Allowance, Measured by UT, etc..

• Estimated

• Measured

• Calculated

11. Corrosion Rate Confidence (Thinning and External)

Level of confidence you have that the corrosion rates are accurate. Confidence the Expected Corrosion Rate provided as an input is High, Moderate, or Low. Based on this, the PrThin1, PrThin2, and PrThin3 Damage Factors are adjusted.

• Low

• Moderate

• High

12. Inspection Effectiveness (Thinning and External)

Is the effectiveness the Inspections performed thus far, if any, has detected the associated failure mechanism.

13. Equipment Design allows Water to Pool?

Used for Corrosion Under Insulation and External Corrosion Rate calculations. The response influences the External Damage Factor calculation.

14. Does Component enter soil or water?

Influences the Interface Corrosion factor for External Corrosion.

15. Basis for Thickness

Documentation only. Used by Corrosion or Reliabilty engineer to document their assumptions. This allows the user to document was it based on Nominal, etc..

• Estimated

• Measured

• Calculated

16. Tmin override

The model will determine a Thickness Minimum to be used in Flow Stress calculations. However, if the user will like to drive a lower or higher Tmin you can override it with this value.

The calculations performed by this or any calculator are linear and absolute. What AsInt means by this is that while there are “Safety Factors” built into the design codes i.e. ASME Sect VIII is 3.5. So it is this safety factor that allows end users to dictate or direct what they use for T-Min. Or, consider API which mandates that we inspect ½ the remaining life but stops short of stating how t-min is defined, rather it refers you back to the design code for this.

Therefore some users opt to use Nominal Thickness minus Corrosion Allowance as t-min, because it gives the flexibility in their inspection planning. This is not handled in the remaining life calculations as a variable but rather in the procedures and best practices of each facility/owner operator.

The direction chosen in the defined best practices will in turn drive things like intervals if time-based. Time-Based intervals used when a customer has decided to use a calculated t-min will be shorter and/or less flexible since in theory these assets would be at or very near end of life when reached. Just as an example.

These are great questions, and our assumption is they are handled via policy and procedure not via an algorithm. There are no “additional” conservative values built into the calculations, this is left to the practitioner.

17. Representative Fluids and Initial Phase for Tank Roofs

Though the tank roof may be condensate, or something other than the product stores, we want to calculate the Consequence based on the product stored. With this in mind, choose the product stored. For the Initial Phase for roofs, also choose the phase (Gas or Liquid) of the product stored.

You can download a RBI + Input definition workbook here. Within the Workbook it will describe:

• Field Names

• Defaults

• Required Fields

• Data Types

• Comments

• Sample formats of input values

Download the MS Excel workbook here.

1. Hight of Tank

The Height of the tank (Ft or M) will be the maximum fill height of the tank. Is used to calculate static pressure (Height x Density of Fluid/144)

2. Initial Floor Thickness

Initial Floor Thickness will have an impact on the leak rate to water.

3. Foundation Type

Based on the foundation type, a leak rate factor is determined. This has a further impact in the daily adjusted leak rate.

4. Release Prevention Barrier

If the tank has a release prevention barrier installed.

5. Environmental Sensitivity

The Environmental Sensitivity is a descriptor selected from a picklist and the choices are Low, Medium, or High. Based on this factor, it is used to determine Remediation Cost Per Barrel.

6. Joint Efficiency

For tank bottoms, general guideline is to use .70.

7. Tmin override

The model will determine a Thickness Minimum to be used in Flow Stress calculations. However, if the user will like to drive a lower or higher Tmin you can override it with this value.

The calculations performed by this or any calculator are linear and absolute. What AsInt means by this is that while there are “Safety Factors” built into the design codes i.e. ASME Sect VIII is 3.5. So it is this safety factor that allows end users to dictate or direct what they use for T-Min. Or, consider API which mandates that we inspect ½ the remaining life but stops short of stating how t-min is defined, rather it refers you back to the design code for this.

Therefore some users opt to use Nominal Thickness minus Corrosion Allowance as t-min, because it gives the flexibility in their inspection planning. This is not handled in the remaining life calculations as a variable but rather in the procedures and best practices of each facility/owner operator.

The direction chosen in the defined best practices will in turn drive things like intervals if time-based. Time-Based intervals used when a customer has decided to use a calculated t-min will be shorter and/or less flexible since in theory these assets would be at or very near end of life when reached. Just as an example.

These are great questions, and our assumption is they are handled via policy and procedure not via an algorithm. There are no “additional” conservative values built into the calculations, this is left to the practitioner.

Information not published. Please send request to info@asint.net requesting the data.

The following are fluid properties and associated unit of measure. Fluids are used for the RBI+ Fixed Equipment and Tank model to determine Loss of Containment.

• Chemical

• Common Names

• NFPA Flamability

• NFPA Health

• NFNT

• Boiling Temerature (F)

• Flash Temperature (F)

• AIT (F)

• Pigf

• HofC KJ/KG

• EPA End Point (mg/Liter)

• OSHA 8 hour TWA PEL Limit (mg/M3)

• PPM STEL

• Molecular Weight (g/mol)

• Liquid Density (Lb/Ft3)

• Ratio of Specific Heats K

• Fluid Viscosity Factor

• Viscosity (Cp (Relative Viscosity to liquid water (dimensionless)))

• K = (CP/CV)

This section is used to define the data needed for the RBI+ Relief Device model.

Within the Workbook it will describe:

• Field Names

• Defaults

• Required Fields

• Data Types

• Comments

• Sample formats of input values

To download the MS Excel workbook, tap here.

This section is used to define the data needed for the PRD Condition Based model.

Within the Workbook it will describe:

• Field Names

• Defaults

• Required Fields

• Data Types

• Comments

• Sample formats of input values

To download the MS Excel workbook, tap here.

This section is used to define the data needed for the bundles model.

Within the Workbook it will describe:

• Field Names

• Defaults

• Required Fields

• Data Types

• Comments

• Sample formats of input values

To download the MS Excel workbook, tap here.