Api rp 584 Integrity Operating Windows Table of Contents




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Table of Contents

2. Introduction to Integrity Operating Windows 9

3. Terms, Definitions, Acronyms and Abbreviations 12

4. Parameters that May Require Different Types of IOW’s 15

5. IOW Work Process 18

5.1. In this section a general work process is outlined for identifying IOW’s and setting appropriate limits relative to a defined premise. Additional details on the type and levels of IOW’s are outlined in Section 4 and Section 6. For a specific example that closely follows the flow outlined in this section for one specific piece of equipment, see Appendix C. General guidance and considerations for identifying and setting appropriately conservative limits is outlined in Section 9. Note that this work process may be applied to a single equipment item, multiple equipment items in a group (corrosion circuit) or more generally to the overall process unit. A flow chart for the overall work process is shown below in Figure 5.1. 18

5.2. The first step in the process is to review the existing mechanical design conditions and prior operating conditions (normal, upset, start-up, shut-down, etc.). The identification of the likely or “active” damage mechanisms in Section 5.5 requires a fundamental understanding of the mechanical design,the process operating conditions (temperatures, pressures, service, inhibitors, etc.) and the materials of construction including the alloy and material grade, method of fabrication, prior thermal and mechanical treatments, etc. Consideration should be given to both the normal operation and any non-normal operation that could produce unanticipated damage mechanisms and/or accelerated damage rates. Other operating conditions such as startup, shutdown, catalyst regeneration, decoking, hydrogen stripping, etc. should also be considered. 20

5.3. The second step is to define any anticipated future unit/equipment operating conditions and establish a “premise” for establishing IOW limits. Any planned changes to the operation will need to be considered during the identification of the “potential” damage mechanisms that may be associated with those planned changes (i.e. higher sulfur in the feed stock to a refinery). 20

5.4. In the second part of this step, an operating premise needs to be developed that establishes the desired future run time for reliable operation and acceptable economic life of the asset. Generally the premise would be established on an acceptable damage rate or maximum amount of damage acceptable during the planned run time. In some cases, it may include setting limits on operating conditions that may introduce a new damage mechanism e.g. a limit may be placed on operating temperature in a Hydrotreater in order to avoid High Temperature Hydrogen Attack (HTHA). A key consideration for establishing a premise is the time frame for which it will apply. In some cases, the established time frame may be very short (for a specific operation to take advantage of an opportunity feed stock for example), but in general, the time frame for setting damage limits should be based on an acceptable life for the equipment and/or the time period until the next turnaround. A premise may be established on an individual equipment basis or on a unit specific basis. 20

5.5. The next step is to identify all of the active and potential types of degradation mechanisms that could occur in each piece of process equipment. A determine should be made of the historical damage rate for the equipment and predicted future rate considering any planned changes in operation. Section 7 and Appendix A contain examples of degradation mechanisms and potential operating variables within process units that may need IOW’s established. There are several other sources of industry data that specifically identify typical degradation mechanisms for various operating units. Specifically applicable to the refining and petrochemical industry is API RP 571 covering damage mechanisms and API RP 580 and RP 581 covering Risk Based Inspection. A list of common degradation mechanisms is also provided in API 579 / ASME FFS-1 Fitness-For-Service Annex G. Specific operating site programs that have been utilized to identify/establish equipment specific damage mechanisms and/or risk that should be considered during this process may include; 21

Risk Based Inspection Studies; 21

Corrosion Loop & Circuitization Programs or other Unit Corrosion Reviews; 21

Equipment Criticality Assessments; 21

PHA or HAZOP Studies. 21

5.6. After identifying all applicable degradation mechanisms, each process variable related to activation of, or progression of the equipment damage needs to be identified. In many cases, there will be multiple, sometimes co-dependant operating variables that are required to produce the damage e.g. temperature, reactive sulfur content and alloy are co-dependant variables that affect the high temperature sulfidation rate. There may also be multiple variables, product / reactants or other measurements that are indicators of the activity of a single specific damage mechanism e.g. desalter efficiency, pH, chloride content, iron content, conductivity, salt point, dew point and others are all indicators of corrosion potential in an crude unit atmospheric tower overhead system. The goal of the IOW program is not only to identify the key monitoring parameters but to also set limits around the most appropriate “controllable” parameters that can be adjusted by operations to achieve the desired level of equipment integrity and reliability. In general, the parameter that is most “controllable” and most effective at reducing the corrosion potential should be the primary variable for monitoring and applying limits. Other measurements or variables that are not primary indicators of damage may be considered as informational. 21

5.7. Once the primary controllable operating variables/parameters have been identified, the next step in the process is to establish upper and lower limits to avoid unacceptable damage mechanisms/rates. There are multiple aspects to consider when establishing each of the operating limits as follows; 21

5.11. The last box in the flow chart in figure 5.1 is to determine the appropriate actions that need to be taken and response timing for each IOW exceedance. As has been previously mentioned, Critical IOW exceedances will normally require a somewhat urgent specific response by the operator to avoid more rapid equipment degradation problems. That response should be spelled out and agreed to by the IOW team. Standard IOW exceedances will vary in their response actions and timing and will be less urgent than those associated with Critical IOW exceedances, but should also be spelled out and agreed to by the IOW team. Some of those actions will likely be for operators, but other response actions may be for designated SME’s. Response actions and timing for IIL’s will generally be mostly related to which SME should be notified in order to determine what response action is needed, if any, over the longer term. 23

6. IOW Risk Ranking 23

6.4. For a simple example of the use of this risk assessment approach, time is used in place of a probability of failure, where a probability of “5” = highly likely to fail within hours to days. For consequence of failure we will use a combination of safety and business interruption where the consequence of “D” = Significant exposure risk to personnel and potential loss of profit. This result would yield a “5D” category on the matrix in Table 1 with a corresponding “high” risk. Using Table 2, we determine that Critical Limits are required to be established with appropriate alarms where operators are required to take fairly urgent predetermined actions to return the process to normal operation. In addition, the appropriate SME’s are notified for this parameter exceedance along with operations supervision. 26

6.5. A second example of the use of this risk assessment approach involves an unexpected process change that results in a likely to fail corrosion situation within a few months, if something is not corrected. So it’s not immediately urgent, but clearly needs attention relatively soon. A probability of 4 is assigned. The consequence involves a big leak which would involve a possible environmental citation and business interruption, as well as undesirable media attention. A consequence of C is assigned, resulting in a 4C medium high risk on the matrix in table 1. Using table 2, Critical or Standard IOW’s would be established and operators would have predetermined actions associated with the exceecance which would need to be implemented within the predetermined time and likely also a notification to corrosion specialist would be implemented to assess the situation and recommend further actions, if necessary. 26

7. Examples of IOW’s 26

8. IOW Development 31

9. General Considerations for Establishing IOW’s and Their Limits 34

10. Documenting, Implementing and Training on Established IOW’s 37

11. Monitoring and Measuring IOW Parameters 40

12. Updating IOW’s 41

13. Roles, Responsibilities and Accountabilities for IOW’s 41

14. Integrating IOW’s with Other Related Work Processes 43

Appendix A: Examples of Potential Process Parameter’s for IOW’s for Generic Process Units 45

Appendix B: Sample Format for Recording IOWs 49

Appendix C: Example of an IOW Development for a Heat Exchanger 50



Purpose and Scope

    1. The purpose of this RP is to explain the importance of IOW’s for process safety management and to guide users in how to establish and implement an IOW program for refining and petrochemical process facilities for the express purpose of avoiding unexpected equipment degradation that could lead to loss of containment. It is not the intent of this document to provide a complete list of specific IOW’s or operating variables that might need IOW’s for the numerous types of hydrocarbon process units in the industry (though some generic examples are provided in the text and in Appendix A); but rather to provide the user with information and guidance on the work process for development and implementation of IOW’s for each process unit.

    2. The scope of this standard includes:

      • Definitions of IOW’s and related terminology,

      • Creating and establishing IOW’s,

      • Data and information typically needed to establish IOW’s,

      • Descriptions of the various types of IOW’s needed for process units,

      • Risk ranking IOW’s,

      • Documenting and implementing IOW’s,

      • Monitoring and measuring process variables within established IOW’s,

      • Communication of IOW exceedances,

      • Reviewing, changing and updating IOW’s,

      • Integrating IOW’s with other risk management practices,

      • Roles and responsibilities in the IOW work process, and

      • Knowledge transfer to affected personnel.

1.3 This recommended practice outlines the essential elements in defining, monitoring and maintaining Integrity Operating Windows (IOW’s) as a vital component of corrosion management (materials degradation control) and inspection planning, including RBI. Other PSM systems may be affected by or involved with the IOW program, including Management of Change (MOC), Process Safety Information (PSI) and Training. For purposes of this RP, these systems are only addressed to the extent of mentioning the integration aspects that are needed with the IOW program.

1.4 This RP does not cover operating windows established for normal process control for the purposes of maintaining product quality and other operating factors that do not relate to control for the purpose of maintaining equipment integrity and reliability.


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