FFS Analysis By 8 Step / Step 2 : Applicability and Limitations

Any fitness for service analysis is consists of eight stage which knowns as GADARRID process. GADARRID is the abbreviation of:

1.      General

2.      Applicability and Limitations of the Procedure

3.      Data Requirement

4.      Assessment Technique and acceptance criteria

5.      Remaining life assessment

6.      Remediation

7.      In service monitoring

8.      Documentation

Step 2- Applicability and Limitations of the Procedure

Determining the appropriate procedure for FFS based on the Damage Mechanisms. Table 2.1 of ASME FFS-1 is a useful guideline for applicability and limitation for selecting the appropriate procedure. For example, if local metal loss and pitting corrosion is present which procedure is used or is it possible to use the general metal loss procedure by critical thickness profile (CTP) for local metal loss?

Determining the construction codes for equipment with recognized standards and proper design allowable stresses for equipment with minimal documents.

 Some key points for assessing the damage mechanisms are as follows:

1- Assessment procedures for brittle fracture is the basic procedure before any procedure followed.

2- The assessment procedures for local metal loss (LML) can also be utilized to evaluate individual pits or blisters .

3. The assessment procedures for pitting analysis can also be utilized to evaluate a network of closely spaced blisters .

4- The fatigue assessment is used in conjunction with other procedure if the cyclic condition is govern. Cyclic condition is defined as if the component is subject to more than 150 cycles, i.e. pressure and/or temperature variations including operational changes and start-ups and shut-downs, throughout its previous operating history and future planned operation it needs to satisfy the requirements of fatigue analysis.

5- Recommendations for evaluating crack growth including environmental concerns are covered by crack like flaw analysis. Refer to API RP 571 for more than 17 EAC (environmental assisted cracking).

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