API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology
PART 1—INTRODUCTION TO RISK-BASED INSPECTION METHODOLOGY 1-25abis a variable provided for reference fluids for Level 1 COF analysisis a variable provided for reference fluids for Level 1 COF analysisC f is the COF, m 2 (ft 2 ) or $CA f is the consequence impact area, m 2 (ft 2 )finCA fis the financial consequence, $flamCA fis the flammable consequence impact area, m 2 (ft 2 )flamCAf ,n is the flammable consequence impact area for each hole, m 2 (ft 2 )D f (t)is the DF as a function of time, equal to D f-total evaluated at a specific timethinD f is the DF for thinningD f-totalF MSis total DF for POF calculationis the management systems factorFC is the financial consequence, $gffgff ngff totalkP f (t)P f (t,I E )P sRR(t)R(t,I E )t minXßηis the GFF, failures/yearis the GFF for each of the n release hole sizes selected for the type of equipment beingevaluated, failures/yearis the sum of the individual release hole size generic frequencies, failures/yearis the release fluid ideal gas specific heat capacity ratio, dimensionlessis the POF as a function of time, failures/yearis the POF as a function of time and inspection effectiveness, failures/yearis the storage or normal operating pressure, kPa (psi)is the universal gas constant = 8314 J/(kg-mol)K [1545 ft-lbf/lb-mol°R]is the risk as a function of time, m 2 /year (ft 2 /year) or $/yearis the risk as a function of time and inspection effectiveness, m 2 /year (ft 2 /year) or $/yearis the minimum required thickness, mm (in.)is the release rate or release mass for a Level 1 COF analysis, kg/s [lb/s] or kg [lb]is the Weibull shape parameteris the Weibull characteristic life parameter, years
1-26 API RECOMMENDED PRACTICE 5814.6 TablesTable 4.1—Numerical Values Associated with POF and Area-based COF CategoriesProbability Categorya, b, cConsequenceCategory dCategoryProbability Range DF Range Category Range (ft 2 )1 P f (t,I E ) ≤ 3.06E-05 D f-total ≤ 1 AflamCA ≤ 100fflam2 3.06E-05 < P f (t,I E ) ≤ 3.06E-04 1 < D f-total ≤ 10 B 100 < CA ≤ 1,000flam3 3.06E-04 < P f (t,I E ) ≤ 3.06E-03 10 < D f-total ≤ 100 C 1,000 < CA ≤ 10,000flam4 3.06E-03 < P f (t,I E ) ≤ 3.06E-02 100 < D f-total ≤ 1,000 D 10,000 < CA ≤ 100,000fff5 P f (t,I E ) > 3.06E-02 D f-total > 1,000 EflamCA > 100,000faPOF values are based on a gff of 3.06E-05 and an FMS of 1.0. If the suggested gff values in Part 2, Table 3.1 are used, theprobability range does not apply to AST shell course, AST bottoms, and centrifugal compressors.bIn terms of POF, see Part 1, Section 4.1.c In terms of the total DF, see Part 2, Section 3.4.2.dIn terms of consequence area, see Part 3, Section 4.11.4.Table 4.1M—Numerical Values Associated with POF and Area-based COF CategoriesProbability Categorya, b, cConsequenceCategory dCategoryProbability Range DF Range Category Range (m 2 )1 P f (t,I E ) ≤ 3.06E-05 D f-total ≤ 1 AflamCA ≤ 9.29fflam2 3.06E-05 < P f (t,I E ) ≤ 3.06E-04 1 < D f-total ≤ 10 B 9.29 < CA ≤ 92.9flam3 3.06E-04 < P f (t,I E ) ≤ 3.06E-03 10 < D f-total ≤ 100 C 92.9 < CA ≤ 929flam4 3.06E-03 < P f (t,I E ) ≤ 3.06E-02 100 < D f-total ≤ 1000 D 929 < CA ≤ 9290fff5 P f (t,I E ) > 3.06E-02 D f-total > 1000 EflamCA > 9290faPOF values are based on a gff of 3.06E-05 and an FMS of 1.0. If the suggested gff values of Part 2, Table 3.1 are used, theprobability range does not apply to AST shell course, AST bottoms, and centrifugal compressors.bIn terms of POF, see Part 1, Section 4.1.cIn terms of the total DF, see Part 2, Section 3.4.2.dIn terms of consequence area, see Part 3, Section 4.11.4.
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1-26 API RECOMMENDED PRACTICE 581
4.6 Tables
Table 4.1—Numerical Values Associated with POF and Area-based COF Categories
Probability Category
a, b, c
Consequence
Category d
Category
Probability Range DF Range Category Range (ft 2 )
1 P f (t,I E ) ≤ 3.06E-05 D f-total ≤ 1 A
flam
CA ≤ 100
f
flam
2 3.06E-05 < P f (t,I E ) ≤ 3.06E-04 1 < D f-total ≤ 10 B 100 < CA ≤ 1,000
flam
3 3.06E-04 < P f (t,I E ) ≤ 3.06E-03 10 < D f-total ≤ 100 C 1,000 < CA ≤ 10,000
flam
4 3.06E-03 < P f (t,I E ) ≤ 3.06E-02 100 < D f-total ≤ 1,000 D 10,000 < CA ≤ 100,000
f
f
f
5 P f (t,I E ) > 3.06E-02 D f-total > 1,000 E
flam
CA > 100,000
f
a
POF values are based on a gff of 3.06E-05 and an FMS of 1.0. If the suggested gff values in Part 2, Table 3.1 are used, the
probability range does not apply to AST shell course, AST bottoms, and centrifugal compressors.
b
In terms of POF, see Part 1, Section 4.1.
c In terms of the total DF, see Part 2, Section 3.4.2.
d
In terms of consequence area, see Part 3, Section 4.11.4.
Table 4.1M—Numerical Values Associated with POF and Area-based COF Categories
Probability Category
a, b, c
Consequence
Category d
Category
Probability Range DF Range Category Range (m 2 )
1 P f (t,I E ) ≤ 3.06E-05 D f-total ≤ 1 A
flam
CA ≤ 9.29
f
flam
2 3.06E-05 < P f (t,I E ) ≤ 3.06E-04 1 < D f-total ≤ 10 B 9.29 < CA ≤ 92.9
flam
3 3.06E-04 < P f (t,I E ) ≤ 3.06E-03 10 < D f-total ≤ 100 C 92.9 < CA ≤ 929
flam
4 3.06E-03 < P f (t,I E ) ≤ 3.06E-02 100 < D f-total ≤ 1000 D 929 < CA ≤ 9290
f
f
f
5 P f (t,I E ) > 3.06E-02 D f-total > 1000 E
flam
CA > 9290
f
a
POF values are based on a gff of 3.06E-05 and an FMS of 1.0. If the suggested gff values of Part 2, Table 3.1 are used, the
probability range does not apply to AST shell course, AST bottoms, and centrifugal compressors.
b
In terms of POF, see Part 1, Section 4.1.
c
In terms of the total DF, see Part 2, Section 3.4.2.
d
In terms of consequence area, see Part 3, Section 4.11.4.
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