Methodology Step 12

Step 12 Assign S-RBI Results to Inspection/Corrosion Schedules and/or update Monitoring Plan:

Below the Step 12 Methodology is described. See also Software Step 12.

The S-RBI results for Corrosion DM assessments should normally be included into the scope of:

• Inspection and Corrosion Schedules for Equipment (where internal inspection is possible)
• Corrosion Schedules for piping (and Equipment where internal inspection is not possible)

Assign S-RBI Results to an Inspection Schedule

Inspection Schedules are defined at Equipment level and should match the recommended strategy of S-RBI.

Inspection Schedule should contain:

• Scope: The scope should contain the Components that were assessed for the DM.
• Technique: An inspection technique matching the DM should be selected. The techniques should be able to detect the anticipated damage and, where applicable, quantify that in terms of RL. Where applicable, refer to the DM’s Required Inspection Effectiveness determined in Step 11.
• Coverage: The inspection coverage describes the (amount of) susceptible areas to be inspected to confidently monitor the condition of an item and, where possible, predict its RL. Where applicable, refer to the DM’s Required Inspection Effectiveness, determined in Step 11.
• Location: Representative locations (susceptible areas) should be related to the Components that are in Scope for the Inspection Schedule.
• Interval: At maximum this should be the maximum inspection interval from the S-RBI assessment at Component level.
• Requirement: This describes whether the inspection is intrusive or non-intrusive and on-stream or off-stream – need for the Unit or Equipment to be taken offline (out of service). This enables the identification of TA scope from IMS (S-RBI).

Next Inspection Date

If the Component/DM RBI assessment, which is assigned to an Inspection Schedule, resulted in an RBI NID or MII, this date will take part in the Inspection Schedule’s horserace. IMS will look at all the dates in the race: e.g., User Date, Event (TA) date, and RBI NID. For a Recurring Schedule, the Time interval information also becomes applicable. The earliest date will be selected as the NID for the Inspection Schedule.

The Inspection Schedule NID is a horserace. If the assigned Component/DM RBI assessment resulted in an RBI NID/MII, this date also takes part in the race.

Inspection Strategy, required Inspection Effectiveness – Plan Codes

The specific Component/DM’s S-RBI results (Inspection Strategy, required Inspection Effectiveness), which you reviewed in Step 11, should determine the inspection’s Plan Codes. These are selected in the Scope and plan codes section of the Schedule. This section covers Scope, Technique, Coverage, and Location.

For Corrosion DMs: Assign S-RBI Results to a Corrosion Schedule

A Corrosion Schedule should contain similar information as an Inspection Schedule (see above). However, in this case most of this information (Scope, Technique, Coverage, Location, Interval) are defined on the Circuit and CMLs. The Corrosion Schedule is created automatically for a Circuit. The Interval and Requirement information can be edited in the Corrosion Schedule.

Linking the S-RBI results to the Circuit

• For Corrosion DMs, the S-RBI IF can be linked to a Corrosion Schedule, by linking the Component to the Circuit and setting the Circuit IF Strategy to “SRBI”. This is done by setting the inheritance on either the Component or Circuit details page - see Step 1 and Relationship between CLs, Components and Circuits . This way the S-RBI NID will take part in the Corrosion Schedule’s NID horserace.
• In addition, the linked Circuit’s CMLs must be defined as such that the Inspection technique (= Required Inspection Method) and coverage (= number and location of CMLs) is adhered to. This comes from the Required Inspection Effectiveness which was determined in Step 11.

Next Inspection Date

The Circuit calculates the NID from the CR and the Circuit IF. If the IF Strategy is set to “SRBI”, the Circuit IF will be the S-RBI IF of the linked Component. Furthermore, IMS adjusts this Circuit IF when data quality is poor (DSCF), or when the number of measured locations is inadequate (PERF). So, if the quality of data is poor (DSCF IF <1), or not enough (PERF IF <1), then the total IF (TIF) will be lower than the S-RBI IF.

The NID for the Circuit is calculated as follows:

IMS Calculated NID = LID + MII

Where:

MII = TIF x RL

RL =RCA/CR

If Calc Method 1 is used: TIF = DSCF IF * Circuit IF * PERF IF

If Calc Method 2 is used: TIF = Circuit IF * PERF IF

When IF Strategy is set the “SRBI”, the S-RBI IF is used to calculate the IMS Calculated NID.

The above IMS Calculated NID will take part in the Corrosion Schedule’s NID horserace. IMS will look at all dates in the race, including the Time-Based NID, and the TA date, if applicable. The earliest date will be selected as the NID for the Corrosion Schedule.

The Corrosion Schedule NID is a horserace. If IF Strategy is set the “SRBI”, the Calculated Date is calculated from the S-RBI IF.

Required Inspection Effectiveness (Technique and Coverage) – CMLs 

The S-RBI assessment should provide guidance on what part of the Equipment to inspect, i.e., what areas are more susceptible to the DM. The DM and number of CMLs are also closely related.

It is recommended to define the number of CMLs in IMS in such a way that PERF will never reduce the effective interval factor (get >25% of CMLs at each inspection). It is also recommended to define a corrosion Circuits in such a way that data spread among CMLs in the Circuit is low enough, to prevent the DSCF from reducing the IF. Both these factors are not part of the S-RBI methodology but will reduce the inspection intervals.

Piping Corrosion Inspection:

• For piping inspections, Condition Monitoring Locations (CMLs) should be specified as part of a Circuit that requires inspections measurement.
• A Piping System should contain at least one Circuit. The Circuit should contain all CMLs for which a similar CR is expected. If different CRs in a Piping System are expected (e.g., for Deadlegs), the system should contain more Circuits. Note: More than one Circuit can be linked to a single (S-RBI) Component and inherit its IF.
• The General Thinning table in Methodology Step 11 can be used to determine the inspection technique and coverage. Use IMS to document the basis for an increased or reduced number of CMLs.
• Each piping Circuit with a S-RBI Consequence Class of E, H, M or L should be monitored, by taking thickness measurements at designated CMLs.
• The number and location of CMLsshould be established with the assistance of a Materials and Corrosion Engineer: The following is advised:
  • S-RBI Consequence classes E, H, and M - off plot (i.e., tank farm and pipe rack) piping with anticipated uniform internal corrosion: CMLs established approximately every 150m.
  • S-RBI Consequence classes M and L: CMLs established approximately every 300m.
  • Consequence class N: does not require CMLs.
  • Tank farm piping can be treated as part of the tank inspection scope. After a review of the history of the unit-piping portion of a Piping System, the inspector may elect to use unit piping CML inspection as representative of the internal CR for the entire Piping System.

For more detail on Corrosion Schedules, CMLs and CR calculations, refer to PEI Circuits and PEI Corrosion Calculations and Calc Summary.

Update Proactive Monitoring Plans

The emphasis for NAR DMs should be on Control and proactive monitoring of the IOWs. NAR DMs are more dependent on process conditions and generally associated with excursions outside IOWs. Monitoring and control of the relevant process parameters is therefore required to ensure that these types of degradation are controlled properly. This is done with a proactive monitoring plan. Refer to Operational Control Barriers in Barrier Types and Definition for more information.

Sustained operation outside the IOW increases the Susceptibility to Failure (StF) in S-RBI. Therefore, in Step 10, when the Confidence is Assessed, one of the Key Questions is to determine if relevant process parameters are reliably monitored, i.e., determine if they are in a proactive monitoring plan. For Medium to high Confidence, it must be assured that the existing proactive monitoring plan is followed. But for lower Confidences and low Criticalities, improvement of the proactive monitoring plan should be considered. For low Confidence, the IOW should be (re)defined and monitored to increase Confidence.

Proactive Monitoring Plan Requirements

For each variable, it is advised to have the following information as a minimum in a proactive monitoring plan:

• Corrosion Loop that the variable applies to (not necessarily where it is measured).
• Name of the parameter (description; e.g., overhead vessel boot water level).
• PI field instrument or LIMS tag name (e.g., 010LIA211.PV). Note: LIMS is a Lab information management system; generally LIMS has an interface to PI, where sample data can be visualized in PI.
• Reason for monitoring and reference to associated CL in IMS and source of limit (e.g., sour water corrosion due to water slip to downstream piping).
• DM that is influenced / controlled by the IOW limit (e.g., sour water corrosion).
• Unit of measure (UoM) in SI or US Customary Engineering Units (e.g., wt.%).
• Low Limit: The value for the limit below which Operations needs to act to bring operation within the window again and, if applicable, to notify Operations Support staff.
• High Limit: The value for the limit above which Operations needs to act to bring operation within window again and, if applicable, to notify Operations Support staff. Note: At least a high OR a low limit, needs to be specified.
• Limit Classification: Critical (C), Standard (S) or Monitoring (M). Refer to Integrity Operating Windows (IOWs) - Theory.
• Measurement Frequency at which the parameter is measured, which can range from every 2 seconds (e.g., a temperature measurement) to annually (e.g., furnace tube skin temperature infrared survey).
• Maximum Time in Exceedance:
  • Maximum single time in exceedance; allowed between the onset of an exceedance and moment operation has returned to within IOW (either automatically or by Operator intervention).
  • Maximum total time in exceedance.
  • Maximum number of single time exceedances per …
• Mitigating Action(s) required to be taken by Operations (and others) to bring operation back inside the window and/or specify which Operations Support staff need to be proactively notified of the IOW excursion (for exceedance of Standard and Critical limits).

Note: The proactive monitoring plan is outside of IMS. The MCE is typically responsible for such a plan and it should be part of the ESP work process.

Specific Guidance Summary

Guidance per Special Emphasis (see the table below) gives additional information with regards to Special Emphasis Components. Also seethe table in Methodology Step 11 for additional guidance on interpreting the results (NID, MII, IS, Inspection Effectiveness) per Special Emphasis Component and DM.

Specific guidance summary - Assigning RBI results to the Inspection / Corrosion Schedules: