Used in heat exchangers, HEXTUBEs are used to carry gas and/or liquids from one side of the heat exchanger to the other. They only require that you define the general properties and then review the calculated results.
The General Properties tab contains information about the HEXTUBE and is divided into two nodes: General and Financial.
IMPORTANT: For fields that you set the measurement unit for, if you change the unit, you must also manually change the specified value as the RBI software will not change the values.
The properties in this node determine the basic properties of the HEXTUBE. Note the following:
The Initial HexTube Model is optional and allows you to assign a model, which may represent a fixed time or a distribution, to describe the damage properties of the HEXTUBE. You can choose an existing model or create a new one. If no model is assigned, it is assumed that the HEXTUBE cannot fail.
The model can be generated from previous inspection data of HEXTUBEs in identical or similar process environments. If no previous data is available, you can create a model from whatever information is available, such as estimated corrosion rates and corrosion allowance information.
Use the Date of Component Installation to specify when the HEXTUBE was installed in the system. It must be before the current date.
Use the Plan Date to specify the date when the HEXTUBE is scheduled to be maintained. It must be later than the current date.
Use the Planned Shutdown Date After Current Plan Date to specify the date of inspection (shutdown) following the plan date.
The Financial properties are used to determine the monetary cost of the HEXTUBE failing. These calculations take into consideration or calculate the hole costs, material costs, plant downtime, cost of the equipment, the cost on the surrounding area and the personal injury costs. Note the following:
Use the Date of Last Inspection to indicate the last date that the component was inspected. If there was no inspection, use date the component was installed.
If desired, you can use the Notes
column, 
, to record any notes about the information
supplied. These notes only appear in the RBI Properties tab and do not
display in any reports. Double-click inside the cell to open the Notes
window. An icon in the cell indicates that notes have been saved for that
field.
The results are displayed in the following nodes:
The Financial Consequence Results node displays the total cost of the HEXTUBE if it breaks (i.e., the repair, clean-up, replacement and other costs).
The RBI Date Results node displays the results as of the date the results were calculated:
The Probability Category displays the probability of the component failing (as based on the Risk Category values for the project) at the given date.
The Consequence Category displays similar information for the financial consequences of failure.
The Risk Priority displays the calculated value based on the scoring matrix (i.e., Low, Medium, Medium High or High).
Plan Date Results: This node displays the same type of results as the RBI Date Results node, but shows the risk values on the plan date (i.e., the date of the planned maintenance) assuming you do nothing until then.
If the analysis indicates that an inspection is required before the plan date, the Target Date Results node specifies the target date and provides information about when you should inspect the HEXTUBE and the anticipated state of the HEXTUBE on that date.
If the risk on the plan date is less than the maximum acceptable risk, then no target date is given as no inspections are needed until the plan date.
Plan Date with Inspection Results: This node displays the same type of results as the RBI Date Results node, but shows the risk values on the plan date assuming that the recommended inspections on the target date are carried out. If no inspections are needed, the node states that.
Inspection Planning without Repair: This node displays the recommended actions if you do not repair the HEXTUBE, but only inspect and replace it.
Perform Inspection displays Yes if you should inspect the HEXTUBE at the next plan date, or No if you should wait until following plan date to inspect the HEXTUBE.
Perform Replacement displays Yes if you should replace the HEXTUBE at the next plan date, or No if you should wait until following plan date to replace the HEXTUBE.
Optimal Replacement Frequency is the optimal time between replacements assuming no repairs are done.
The RBI Plot tab shows the risks associated with the HEXTUBE versus the various critical dates during the analysis in a financial risk plot. (Note that the Area Risk plot does not show any data as HEXTUBES are not concerned with the risk to the surrounding area.)
The risk values that always appear for a component are those associated with the RBI date and the Plan Date without any recommended inspections. If calculated results indicate that the component require inspections prior to the Plan Date, then the risks at the Target date (for inspections) and the Plan Date (with Inspections performed) are also shown. In addition, if by estimation the component reaches minimum wall thickness, a red line will be shown to signify the date associated with reaching minimum wall thickness.
When working with the RBI Plot tab, you have the same capabilities that you have when working with plots in an FMEA or functional failure analysis. For more information, refer to Basic Plot Features.
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