FitnessForService.jl

API 579 Fitness For Service Methodologies

Installation

    ]
 add https://github.com/flare9x/FitnessForService.jl

Usage

API 579 Part 4 – Assessment of General Metal Loss - Level 1 & 2 Assessment

The assessment procedures in this Part are based on a thickness averaging approach. If local areas of metal loss are found in the component, the thickness averaging approach may produce conservative results. For these cases, the assessment procedures of Part 5 can be utilized to reduce the conservatism in the analysis. The exact distinction between uniform and local metal loss cannot be made without knowing the characteristics of the metal loss profile. For most evaluations, it is recommended to first perform an assessment using Part 4.

API 579 have specific conditions that must be met which determine the applicability of the level 1,2 or 3 assessment. Limitations of the assessments include:

The flaw type is metal loss
Assessment procedures may only be applied to components which are not operating in the creep range

Applicability of the level 1 and level 2 procedures

The original design criteria were in accordance with a recognized code or standard
The region of metal loss has relatively smooth contours without notches, i.e. negligible local stress concentrations.
The component is not in cyclic service
Level 1 Assessment – Type A Components Only
Level 2 Assessment – Type A and Type B class 1 components subject to internal pressure, external pressure, and supplemental loads
Level 2 Assessment - Type B class 2 components : pressure vessel nozzles, tank nozzles and piping branch connections , refinrocement zone of conical transitions and flanges subject to internal pressure, external pressure, and supplemental loads
Distance to structural discontinuity (Lmsd)

Applicability of the Level 3 Assessment Procedures

Level 3 Assessment – Performed when the Level 1 and Level 2 Assessment procedures do not apply

Two options for thickness readings are presented.

Option #1 = Point thickness readings used to characterize the metal loss - minimum of 15 readings and Coefficient Of Variation (COV) <= 10%.
Option #2 = Thickness readings on a prescribed grid used to characterize the metal loss - used when Coefficient Of Variation (COV) > 10% :: follow procedure 4.3.3.3 and figures 4.7,4.8,4.9

An example of performing a level 1/2 assessment using point thickness readings (PTR) to characterize the metal loss:

Step 1 - check applicability of the assessment procedures Step 2 - perform the assessment

# PART 4 – ASSESSMENT OF GENERAL LOCAL METAL LOSS

using Statistics

print("Begin -- Assessment Applicability and Component Type Checks\n")
creep_range = CreepRangeTemperature("Carbon Steel (UTS ≤ 414MPa (60 ksi))"; design_temperature=100.0, units="nmm-mm-mpa")
design = DesignCodeCriteria("ASME B31.3 Piping Code")
smoothness = Smoothness("Smooth Contour")
cyclic = CyclicService(100, "Meets Part 14")
x = Part4ComponentType("Straight Section of Piping, Elbow or Bend - No Structural Attachments", vessel_orientation="horizontal", material="Carbon and Low Alloy Steels", D=24.75,Lss=120.0,H=0.0, NPS=3.0, design_temperature=100.0, units="lbs-in-psi")
part4_applicability = Part4AsessmentApplicability(x,design,smoothness,cyclic,creep_range)


# single point reading data
x = [0.300, 0.300, 0.300, 0.3, 0.300, 0.275, 0.275, 0.275, 0.275, 0.275, 0.275, 0.240, 0.186, 0.250, 0.280, 0.290, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]

equipment_group = "piping" # "vessel", "tank"\n
annex2c_tmin_category = "Straight Pipes Subject To Internal Pressure" # ["Cylindrical Shell","Spherical Shell","Hemispherical Head","Elliptical Head","Torispherical Head","Conical Shell","Toriconical Head","Conical Transition","Nozzles Connections in Shells",
# "Junction Reinforcement Requirements at Conical Transitions","Tubesheets","Flat head to cylinder connections","Bolted Flanges","Straight Pipes Subject To Internal Pressure","Boiler Tubes","Pipe Bends Subject To Internal Pressure",
# "MAWP for External Pressure","Branch Connections","API 650 Storage Tanks"]\n
flaw_location = "external" # "External","Internal"\n
units = "lbs-in-psi" # "lbs-in-psi" or "nmm-mm-mpa"\n
tnom = .3 # nominal or furnished thickness of the component adjusted for mill undertolerance as applicable.\n
FCAml = 0.05 # Future Corrosion Allowance applied to the region of metal loss.\n
FCA = .0 # Future Corrosion Allowance applied to the region away from the metal loss (see Annex 2C, paragraph 2C.2.8).\n
LOSS = 0 #the amount of uniform metal loss away from the local metal loss location at the time of the assessment.\n
Do = 3.5 # Outside Diameter\n
D = Do - 2*(tnom)  # inside diameter of the shell corrected for FCAml , as applicable\n
P = 1480.0 # internal design pressure.\n
S = 20000.0 # allowable stress.\n
E = 1.0 # weld joint efficiency or quality factor from the original construction code, if unknown use 0.7.\n
MA = 0.0 # mechanical allowances (thread or groove depth); for threaded components, the nominal thread depth (dimension h of ASME B.1.20.1) shall apply.\n
Yb31 = 0.4 # coefficient from ASME B31 Piping codes used for determining the pipe wall thickness, the coefficient can be determined from the following table that is valid for tmin < Do / 6 Annex 2C .\n
t = tnom - LOSS - FCA  # thickness of the shell or pipe adjusted for mill tolerance, LOSS and FCA , or cylinder thickness at a conical transition for a junction reinforcement calculation adjusted for mill tolerance, LOSS and FCA , as applicable.\n
tsl = 0.0 # supplemental thickness for mechanical loads other than pressure that result in longitudinal stress; this thickness is usually obtained from the results of a weight case in a stress analysis of the piping system (see paragraph 2C.2.7).\n
RSFa = 0.9

# For all assessments determine far enough from structural discontinuity
# Flaw-To-Major Structural Discontinuity Spacing
L1msd = [12.0] # distance to the nearest major structural discontinuity.
L2msd = [12.0] # distance to the nearest major structural discontinuity.
L3msd = [12.0] # distance to the nearest major structural discontinuity.
L4msd = [12.0] # distance to the nearest major structural discontinuity.
L5msd = [12.0] # distance to the nearest major structural discontinuity.
Lmsd = minimum([L1msd,L2msd,L3msd,L4msd,L5msd])
if (Lmsd[1] >= (1.8*(sqrt(D*(tnom - LOSS - FCA)))))
   print("Satisfied - Flaw is located far enough from structural discontinuity\n")
   lmsd_satisfied = 1
else
   print("Not satisfied - Flaw is too close to a structural discontinuity - Conduct a level 3 assessment\n")
   lmsd_satisfied = 0
end

# Perform level 1 assessment - Single Point Readings
if (part4_applicability[1] == 1 && lmsd_satisfied == 1) # begin level 1 assessment
part_4_l1_output = part4_PTR_Level_1_Assessment(x; annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group,flaw_location=flaw_location,units=units,tnom=tnom,
   FCAml=FCAml,Do=Do,D=D,P=P,S=S,E=E,MA=MA,Yb31=Yb31,tsl=tsl,t=t)
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 0)
   print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
elseif (part4_applicability[1] == 1 && lmsd_satisfied == 0)
   print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 1)
   print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
end

# Perform level 2 assessment  - Single Point Readings
if (part4_applicability[2] == 1 && lmsd_satisfied == 1) # begin level 2 assessment
   part_4_l2_output = part4_PTR_Level_2_Assessment(x; annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group,flaw_location=flaw_location,units=units,tnom=tnom,
       FCAml=FCAml,Do=Do,D=D,P=P,S=S,E=E,MA=MA,Yb31=Yb31,tsl=tsl,t=t,RSFa=RSFa)
   #end # let end
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 0)
   print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part4_applicability[1] == 1 && lmsd_satisfied == 0)
   print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 1)
   print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
end

Part 4 level 1 PTR readings output:

Begin -- Assessment Applicability and Component Type Checks
Design Temperature 100.0 C is below or equal to the creep temperature limit 343C for material Carbon Steel (UTS ≤ 414MPa (60 ksi)) - Criteria satisfied
Condition Satisfied - Code = ASME B31.3 Piping Code
Cyclic Service Condition Satisfied
Begin -- Component Type and Level 1,2,3 assessment applicability
Carbon and Low Alloy Steels
NPS Group = 0 to 4 inches
100.0F falls between the limit range of [-50.0, 400.0]F
Piping Component is a Type A component
The criteria for level 1 assessment application has been satisfied
The criteria for level 2 assessment application has been satisfied
The criteria for level 3 assessment application has been satisfied

Satisfied - Flaw is located far enough from structural discontinuity
Begin -- Part 4 LTA Level 1 Assessment (Point Thickness Readings) - API 579 June 2016 Edition
COV is <= 0.1 - Procced to Step 3 to complete the assessment using the average thickness tam :: COV = 0.1
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Average Measured Thickness from Point Thickness Readings (PTR) - (tam - FCAml) >= tcmin == True
Check the minimum measured thickness criterion.
Alternatively, determine MAWPcr using (tam - FCAml)
Reduced MAWPcr in circumferential or hoop direction = 2795.27psi
Reduced MAWPlr in longitudinal direction = 5921.588psi
MAWP from Point Thickness Readings (PTR) - (MAWPcr >= P) == True
Check the minimum measured thickness criterion.
Minimum Measured Thickness - (tmm - FCAml) >= maximum([0.5*tmin,tlim]) == True
Part 4 level 1 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 1 assessment (Averaged Measured Thickness)
Part 4 level 1 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 1 assessment (MAWP)

Part 4 level 2 PTR readings output:

Begin -- Part 4 LTA Level 2 Assessment (Point Thickness Readings) - API 579 June 2016 Edition
COV is <= 0.1 - Procced to Step 3 to complete the assessment using the average thickness tam :: COV = 0.1
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Average Measured Thickness from Point Thickness Readings (PTR) - (tam - FCAml) >= max([tcmin,tlin]) == True
Check the minimum measured thickness criterion.
Alternatively, determine MAWPcr using (tam - FCAml)
Reduced MAWPcr in circumferential or hoop direction = 2795.27psi
Reduced MAWPlr in longitudinal direction = 5921.588psi
MAWP from Point Thickness Readings (PTR) - ((min([MAWPcr,MAWPlr]) / RSFa) >= P) == True
Check the minimum measured thickness criterion.
Minimum Measured Thickness - (tmm - FCAml) >= maximum([0.5*tmin,tlim]) == True
Part 4 level 2 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 2 assessment (Averaged Measured Thickness)
Part 4 level 2 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 2 assessment (MAWP)

Using critical thickness profiles and defining inspecton data in a prescribed grid:

Part 4 level 1/2 - CTP

# For all assessments - determine the inspection data grid
M1 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.3, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M2 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M3 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M4 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.100, 0.220, 0.280, 0.250, 0.240, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M5 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.215, 0.255, 0.215, 0.145, 0.275, 0.170, 0.240, 0.250, 0.250, 0.280, 0.290, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M6 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.170, 0.270, 0.190, 0.190, 0.285, 0.250, 0.225, 0.275, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M7 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M8 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.3, 0.300]
M9 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.3, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
CTPGrid = hcat(M9,M8,M7,M6,M5,M4,M3,M2,M1) # build in descending order
CTPGrid = rotl90(CTPGrid) # rotate to correct orientation

FCA_string = "external" # Application of FCA external / internal
equipment_group = "piping" # "vessel", "tank"\n
annex2c_tmin_category = "Straight Pipes Subject To Internal Pressure" # ["Cylindrical Shell","Spherical Shell","Hemispherical Head","Elliptical Head","Torispherical Head","Conical Shell","Toriconical Head","Conical Transition","Nozzles Connections in Shells",
# "Junction Reinforcement Requirements at Conical Transitions","Tubesheets","Flat head to cylinder connections","Bolted Flanges","Straight Pipes Subject To Internal Pressure","Boiler Tubes","Pipe Bends Subject To Internal Pressure",
# "MAWP for External Pressure","Branch Connections","API 650 Storage Tanks"]\n
flaw_location = "external" # "External","Internal"\n
units = "lbs-in-psi" # "lbs-in-psi" or "nmm-mm-mpa"\n
tnom = .3 # nominal or furnished thickness of the component adjusted for mill undertolerance as applicable.\n
FCAml = 0.05 # Future Corrosion Allowance applied to the region of metal loss.\n
FCA = .0 # Future Corrosion Allowance applied to the region away from the metal loss (see Annex 2C, paragraph 2C.2.8).\n
LOSS = 0 #the amount of uniform metal loss away from the local metal loss location at the time of the assessment.\n
Do = 3.5 # Outside Diameter\n
D = Do - 2*(tnom)  # inside diameter of the shell corrected for FCAml , as applicable\n
P = 1480.0 # internal design pressure.\n
S = 20000.0 # allowable stress.\n
E = 1.0 # weld joint efficiency or quality factor from the original construction code, if unknown use 0.7.\n
MA = 0.0 # mechanical allowances (thread or groove depth); for threaded components, the nominal thread depth (dimension h of ASME B.1.20.1) shall apply.\n
Yb31 = 0.4 # coefficient from ASME B31 Piping codes used for determining the pipe wall thickness, the coefficient can be determined from the following table that is valid for tmin < Do / 6 Annex 2C .\n
t = tnom - LOSS - FCA  # thickness of the shell or pipe adjusted for mill tolerance, LOSS and FCA , or cylinder thickness at a conical transition for a junction reinforcement calculation adjusted for mill tolerance, LOSS and FCA , as applicable.\n
tsl = 0.0 # supplemental thickness for mechanical loads other than pressure that result in longitudinal stress; this thickness is usually obtained from the results of a weight case in a stress analysis of the piping system (see paragraph 2C.2.7).\n
s_spacings=0.5 # grid spacing in longitudinal direction
c_spacings=0.5 # grid circumferential in longitudinal direction
RSFa = 0.9 # remaining strength factor - consult API 579 is go lower than 0.9

# For all assessments determine far enough from structural discontinuity
# Flaw-To-Major Structural Discontinuity Spacing
L1msd = [12.0] # distance to the nearest major structural discontinuity.
L2msd = [12.0] # distance to the nearest major structural discontinuity.
L3msd = [12.0] # distance to the nearest major structural discontinuity.
L4msd = [12.0] # distance to the nearest major structural discontinuity.
L5msd = [12.0] # distance to the nearest major structural discontinuity.
Lmsd = minimum([L1msd,L2msd,L3msd,L4msd,L5msd])
if (Lmsd[1] >= (1.8*(sqrt(D*(tnom - LOSS - FCA)))))
 print("Satisfied - Flaw is located far enough from structural discontinuity\n")
 lmsd_satisfied = 1
else
 print("Not satisfied - Flaw is too close to a structural discontinuity - Conduct a level 3 assessment\n")
 lmsd_satisfied = 0
end

# Perform level 1 assessment - Single Point Readings
if (part4_applicability[1] == 1 && lmsd_satisfied == 1) # begin level 1 assessment
part_4_l1_output = part4_CTP_Level_1_Assessment(CTPGrid; FCA_string=FCA_string,annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group,flaw_location=flaw_location,units=units,tnom=tnom,
 FCAml=FCAml,Do=Do,D=D,P=P,S=S,E=E,MA=MA,Yb31=Yb31,tsl=tsl,t=t)
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
elseif (part4_applicability[1] == 1 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 1)
 print("Level 1 Criteria Not Met - Perform Level 3 as applicable")
end

# Perform level 2 assessment
if (part4_applicability[2] == 1 && lmsd_satisfied == 1) # begin level 2 assessment
 part_4_l2_output = part4_CTP_Level_2_Assessment(CTPGrid; FCA_string=FCA_string,annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group,flaw_location=flaw_location,units=units,tnom=tnom,
     FCAml=FCAml,Do=Do,D=D,P=P,S=S,E=E,MA=MA,Yb31=Yb31,tsl=tsl,t=t,RSFa=RSFa)
 #end # let end
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 0)
 print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part4_applicability[1] == 1 && lmsd_satisfied == 0)
 print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part4_applicability[1] == 0 && lmsd_satisfied == 1)
 print("Level 2 Criteria Not Met - Perform Level 2 or 3 as applicable")
end

Part 4 level 1 CTP output:

Satisfied - Flaw is located far enough from structural discontinuity
Begin -- Part 4 LTA Level 1 Assessment (Critical Thickness Profile) - API 579 June 2016 Edition
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Average Measured Thickness from Longitudinal CTP (Circumferential Plane) - Level 1 assessment has not been satisfied :: (tsam - FCAml) >= tcmin == False
Average Measured Thickness from Circumferential CTP (Longitudinal Plane) :: (tcam - FCAml) >= tlmin == True
Check the minimum measured thickness criterion.
Alternatively, determine MAWPcr using (tsam - FCAml)
Reduced MAWPcr in circumferential or hoop direction = 715.311psi
Reduced MAWPlr in longitudinal direction = 1515.217psi
MAWP from CTP - Level 1 assessment has not been satisfied :: (MAWPcr >= P) == False
Part 4 level 1 - Does not satisfy June 2016 API 579-1/ASME FFS-1 Level 1 assessment (Averaged CTP (over L) Thickness)
Part 4 level 1 - Does not satisfy June 2016 API 579-1/ASME FFS-1 Level 1 assessment (Averaged CTP (over L) MAWP)

Part 4 level 2 CTP output:

Satisfied - Flaw is located far enough from structural discontinuity
Begin -- Part 4 LTA Level 2 Assessment (Critical Thickness Profile) - API 579 June 2016 Edition
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Average Measured Thickness from Longitudinal CTP (Circumferential Plane) - Level 2 assessment has not been satisfied :: (tsam - FCAml) >= tcmin == False
Average Measured Thickness from Circumferential CTP (Longitudinal Plane) :: (tcam - FCAml) >= tlmin == True
Check the minimum measured thickness criterion.
Alternatively, determine MAWPcr using (tsam - FCAml)
Reduced MAWPcr in circumferential or hoop direction = 715.311psi
Reduced MAWPlr in longitudinal direction = 1515.217psi
MAWP from CTP - Level 2 assessment has not been satisfied :: (MAWPcr >= P) == False
Part 4 level 2 - Does not satisfy June 2016 API 579-1/ASME FFS-1 Level 2 assessment (Averaged CTP (over L) Thickness)
Part 4 level 2 - Does not satisfy June 2016 API 579-1/ASME FFS-1 Level 2 assessment (Averaged CTP (over L) MAWP)

API 579 Part 5 – Assessment of Local Metal Loss - Level 1 & 2 Assessment

API 579 have specific conditions that must be met which determine the applicability of the level 1,2 or 3 assessment. Limitations of the assessments include:

The flaw is a LTA per API 579 or Groove-like-flaw
Assessment procedures may only be applied to components which are not operating in the creep range

Applicability of the level 1 and level 2 procedures

The original design criteria were in accordance with a recognized code or standard
The material is considered to have sufficient material toughness
The component is not in cyclic service
Level 1 Assessment – Type A Components Only
Level 2 Assessment – Type A and Type B, Class 1 components subject to internal pressure, external pressure, and supplemental loads
Distance to structural discontinuity (Lmsd)

Applicability of the Level 3 Assessment Procedures

Level 3 Assessment – Performed when the Level 1 and Level 2 Assessment procedures do not apply

The functions that check the applicability of the assessment procedure:

creep_range = CreepRangeTemperature("Carbon Steel (UTS ≤ 414MPa (60 ksi))"; design_temperature=100.0, units="lbs-in-psi")
design = DesignCodeCriteria("ASME B31.3 Piping Code")
toughness = MaterialToughness("Certain")
cyclic = CyclicService(100, "Meets Part 14")
x = Part5ComponentType("Straight Section of Piping, Elbow or Bend - No Structural Attachments", vessel_orientation="horizontal", material="Carbon and Low Alloy Steels", D=0.0,Lss=0.0,H=0.0, NPS=3.0, design_temperature=100.0, units="lbs-in-psi")
part5_applicability = Part5AsessmentApplicability(x,design,toughness,cyclic,creep_range)

Each component falls into a different Type and class category. Type A components have a design equation that specifically relates pressure (or liquid fill height for tanks) and supplemental loads, as applicable, to a required wall thickness, and the supplemental loads in combination with pressure do not govern the required wall thickness, i.e. the required thickness is based on pressure only.

Type A components are limited to Level 1, 2 and 3 assessments.

Type B, Class 1 components have the same geometry and loading conditions as described in Type A above but are not classified as Type A components because supplemental loads in combination with pressure may govern the required wall thickness.

Type B, Class 1 components are limited to Level 2 and 3 assessments.

Type B, Class 2 components do not have a design equation that specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness. These components have a code design procedure to determine an acceptable configuration. Type B, Class 2 components typically exist at a major structural discontinuity and involve the satisfaction of a local reinforcement requirement (e.g. nozzle reinforcement area), or necessitate the computation of a stress level based upon a given load condition, geometry, and thickness configuration (e.g. flange design). These rules typically result in one component with a thickness that is dependent upon that of another component. Design rules of this type have thickness interdependency, and the definition of a minimum thickness for a component is ambiguous.

Type B, Class 2 components are limited to Level 3 assessments.

Type C Components – A component that does not have a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness. In addition, these components do not have a code design procedure to determine local stresses.

Type C components are limited to Level 3 assessments.

An example output of the Type and level 1,2,3 assessment applicability for carbon steel Straight Section of Piping, Elbow or Bend - No Structural Attachments, NPS 3 with design temperature 100F:

Design Temperature 100.0 F is below or equal to the creep temperature limit 650F for material Carbon Steel (UTS ≤ 414MPa (60 ksi)) - Criteria satisfied
Condition Satisfied - Code = ASME B31.3 Piping Code
Material Toughness Condition Satisfied
Cyclic Service Condition Satisfied
Begin -- Component Type and Level 1,2,3 assessment applicability
Carbon and Low Alloy Steels
NPS Group = 0 to 4 inches
100.0F falls between the limit range of [-50.0, 400.0]F
Piping Component is a Type A component
The criteria for level 1 assessment application has been satisfied
The criteria for level 2 assessment application has been satisfied
The criteria for level 3 assessment application has been satisfied

An example output of the Type and level 1,2,3 assessment applicability for component type: Flanges:

Design Temperature 100.0 F is below or equal to the creep temperature limit 650F for material Carbon Steel (UTS ≤ 414MPa (60 ksi)) - Criteria satisfied
Condition Satisfied - Code = ASME B&PV Code, Section VIII, Division 1
Material Toughness Condition Satisfied
Cyclic Service Condition Satisfied
Begin -- Component Type and Level 1,2,3 assessment applicability
Flanges qualifies as a Type B, Class 2 Component
(level 1) Component Type Not Satisfied
(level 2) Component Type Not Satisfied
The criteria for level 3 assessment application has been satisfied

Once the limitation and correct assessment applicability have been determined. Running the script part5_local_metal_loss_assessment.jl will apply the correct assessment to the applicable component type.

Each assessment is wrapped in a function. The Part 5 level 1 assessment function may be explored with @doc Part5LTALevel1. The function consists of the relevant input variables that are needed to perform the assessment:

Part5LTALevel1(annex2c_tmin_category::String; equipment_group::String="piping",flaw_location::String="external",metal_loss_categorization::String="LTA",units::String="lbs-in-psi",tnom::Float64=0.0,
trd::Float64=0.0,FCA::Float64=0.0,FCAml::Float64=0.0,LOSS::Float64=0.0,Do::Float64=0.0,D::Float64=0.0,P::Float64=0.0,S::Float64=0.0,E::Float64=0.0,MA::Float64=0.0,Yb31::Float64=0.0,
tsl::Float64=0.0,spacings::Float64=0.0,s::Float64=0.0,c::Float64=0.0,El::Float64=0.0,Ec::Float64=0.0, RSFa::Float64=0.9, gl::Float64=0.0, gw::Float64=0.0, gr::Float64=0.0, β::Float64=0.0)

Variables

CTPGrid = Inspection data grid as defined in Part4/5 API 579 2016

equipment_group = "piping" # "vessel", "tank"

annex2c_tmin_category = "Straight Pipes Subject To Internal Pressure" # ["Cylindrical Shell","Spherical Shell","Hemispherical Head","Elliptical Head","Torispherical Head","Conical Shell","Toriconical Head","Conical Transition","Nozzles Connections in Shells",
# "Junction Reinforcement Requirements at Conical Transitions","Tubesheets","Flat head to cylinder connections","Bolted Flanges","Straight Pipes Subject To Internal Pressure","Boiler Tubes","Pipe Bends Subject To Internal Pressure",
# "MAWP for External Pressure","Branch Connections","API 650 Storage Tanks"]

flaw_location = "external" # "External","Internal"

metal_loss_categorization = "Groove-Like Flaw" # "LTA" or "Groove-Like Flaw"

units = "lbs-in-psi" # "lbs-in-psi" or "nmm-mm-mpa"

Lmsd = Distance of defect to structural discontinuity

tnom = .3 # nominal or furnished thickness of the component adjusted for mill undertolerance as applicable.

trd = .3 # uniform thickness away from the local metal loss location established by thickness measurements at the time of the assessment.

FCAml = .00 # Future Corrosion Allowance applied to the region of metal loss.

FCA = .00 # Future Corrosion Allowance applied to the region away from the metal loss (see Annex 2C, paragraph 2C.2.8).

LOSS = 0.0 #the amount of uniform metal loss away from the local metal loss location at the time of the assessment.

Do = 3.5 # Outside Diameter

D = Do - 2*(tnom)  # inside diameter of the shell corrected for FCAml , as applicable

P = 1480 # internal design pressure.

S = 20000 # allowable stress.

E = 1.0 # weld joint efficiency or quality factor from the original construction code, if unknown use 0.7.

MA = 0.0 # mechanical allowances (thread or groove depth); for threaded components, the nominal thread depth (dimension h of ASME B.1.20.1) shall apply.

Yb31 = 0.4 # coefficient from ASME B31 Piping codes used for determining the pipe wall thickness, the coefficient can be determined from the following table that is valid for tmin < Do / 6 Annex 2C .

t = trd # thickness of the shell or pipe adjusted for mill tolerance, LOSS and FCA , or cylinder thickness at a conical transition for a junction reinforcement calculation adjusted for mill tolerance, LOSS and FCA , as applicable.

tsl = 0.0 # supplemental thickness for mechanical loads other than pressure that result in longitudinal stress; this thickness is usually obtained from the results of a weight case in a stress analysis of the piping system (see paragraph 2C.2.7).

spacings = 0.5 # spacings determine by visual inspection to adequately ccategorizse the corrosion

# Flaw dimensions

s = 5.5 # longitudinal extent or length of the region of local metal loss based on future corroded thickness,

c = 1.5 # circumferential extent or length of the region of local metal loss (see Figure 5.2 and Figure 5.10), based on future corroded thickness, tc .

Ec = 1.0 # circumferential weld joint efficiency. note if damage on weld see # 2C.2.5 Treatment of Weld and Riveted Joint Efficiency, and Ligament Efficiency

El = 1.0 # longitudinal weld joint efficiency. note if damage on weld see # 2C.2.5 Treatment of Weld and Riveted Joint Efficiency, and Ligament Efficiency

RSFa = 0.9 # remaining strength factor - consult API 579 is go lower than 0.9

# Groove Like Flaw dimensions

gl = .05 # length of the Groove-Like Flaw based on future corroded condition.

gw = .4 # width of the Groove-Like Flaw based on future corroded condition.

gr = 0.1 # radius at the base of a Groove-Like Flaw based on future corroded condition.

β = 40.0 # see (Figure 5.4) :: orientation of the groove-like flaw with respect to the longitudinal axis or a parameter to compute an effective fracture toughness for a groove being evaluated as a crack-like flaw, as applicable.

The Part 5 Level 1 assessment example:

# PART 5 – ASSESSMENT OF LOCAL METAL LOSS

# Determine Asessment Applicability
#Determine the assessment applicability
# @doc DesignCodeCriteria
# @doc MaterialToughness
# @doc CyclicService
# @doc Part5ComponentType
print("Begin -- Assessment Applicability and Component Type Checks\n")
creep_range = CreepRangeTemperature("Carbon Steel (UTS ≤ 414MPa (60 ksi))"; design_temperature=100.0, units="lbs-in-psi")
design = DesignCodeCriteria("ASME B31.3 Piping Code")
toughness = MaterialToughness("Certain")
cyclic = CyclicService(100, "Meets Part 14")
x = Part5ComponentType("Straight Section of Piping, Elbow or Bend - No Structural Attachments", vessel_orientation="horizontal", material="Carbon and Low Alloy Steels", D=24.75,Lss=120.0,H=0.0, NPS=10.0, design_temperature=100.0, units="lbs-in-psi")
part5_applicability = Part5AsessmentApplicability(x,design,toughness,cyclic,creep_range)

# For all assessments - determine the inspection data grid
M1 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M2 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.100, 0.220, 0.280, 0.250, 0.240, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M3 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.215, 0.255, 0.215, 0.145, 0.275, 0.170, 0.240, 0.250, 0.250, 0.280, 0.290, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M4 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.170, 0.270, 0.190, 0.190, 0.285, 0.250, 0.225, 0.275, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M5 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
M6 = [0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300, 0.300]
CTPGrid = hcat(M6,M5,M4,M3,M2,M1) # build in descending order
CTPGrid = rotl90(CTPGrid) # rotate to correct orientation


# Input variables
 annex2c_tmin_category = "Straight Pipes Subject To Internal Pressure" # ["Cylindrical Shell","Spherical Shell","Hemispherical Head","Elliptical Head","Torispherical Head","Conical Shell","Toriconical Head","Conical Transition","Nozzles Connections in Shells",
 # "Junction Reinforcement Requirements at Conical Transitions","Tubesheets","Flat head to cylinder connections","Bolted Flanges","Straight Pipes Subject To Internal Pressure","Boiler Tubes","Pipe Bends Subject To Internal Pressure",
 # "MAWP for External Pressure","Branch Connections","API 650 Storage Tanks"]
 equipment_group = "piping" # "vessel", "tank"
 flaw_location = "external" # "External","Internal"
 metal_loss_categorization = "LTA" # "LTA" or "Groove-Like Flaw"
 units = "lbs-in-psi" # "lbs-in-psi" or "nmm-mm-mpa"
 tmm_forcing = false
 tmm = 0.0
 tnom = .3 # nominal or furnished thickness of the component adjusted for mill undertolerance as applicable.
 trd = .3 # uniform thickness away from the local metal loss location established by thickness measurements at the time of the assessment.
 FCAml = 0.0 # Future Corrosion Allowance applied to the region of metal loss.
 FCA = 0.0 # Future Corrosion Allowance applied to the region away from the metal loss (see Annex 2C, paragraph 2C.2.8).
 LOSS = 0.0 #the amount of uniform metal loss away from the local metal loss location at the time of the assessment.
 Do = 3.5 # Outside Diameter
 D = Do - 2*(tnom) # Inside Dia.
 P = 1480.0 # internal design pressure.
 S = 20000.0 # allowable stress.
 E = 1.0 # weld joint efficiency or quality factor from the original construction code, if unknown use 0.7.
 MA = 0.0 # mechanical allowances (thread or groove depth); for threaded components, the nominal thread depth (dimension h of ASME B.1.20.1) shall apply.
 Yb31 = 0.4 # coefficient from ASME B31 Piping codes used for determining the pipe wall thickness, the coefficient can be determined from the following table that is valid for tmin < Do / 6 Annex 2C .
 t = trd - LOSS - FCA # thickness of the shell or pipe adjusted for mill tolerance, LOSS and FCA , or cylinder thickness at a conical transition for a junction reinforcement calculation adjusted for mill tolerance, LOSS and FCA , as applicable.
 tsl = 0.0 # supplemental thickness for mechanical loads other than pressure that result in longitudinal stress; this thickness is usually obtained from the results of a weight case in a stress analysis of the piping system (see paragraph 2C.2.7).
 spacings = 0.5 # spacings determine by visual inspection to adequately ccategorizse the corrosion -----------+ may add to CTP_Grid function for plotting purposes
 # Flaw dimensions
 s = 6.0 # longitudinal extent or length of the region of local metal loss based on future corroded thickness,
 c = 2.0  # circumferential extent or length of the region of local metal loss (see Figure 5.2 and Figure 5.10), based on future corroded thickness, tc .
 Ec = 1.0 # circumferential weld joint efficiency. note if damage on weld see # 2C.2.5 Treatment of Weld and Riveted Joint Efficiency, and Ligament Efficiency
 El = 1.0 # longitudinal weld joint efficiency. note if damage on weld see # 2C.2.5 Treatment of Weld and Riveted Joint Efficiency, and Ligament Efficiency
 RSFa = 0.9 # remaining strength factor - consult API 579 is go lower than 0.9

 # For all assessments determine far enough from structural discontinuity
 # Flaw-To-Major Structural Discontinuity Spacing
 L1msd = [12.0] # distance to the nearest major structural discontinuity.
 L2msd = [12.0] # distance to the nearest major structural discontinuity.
 L3msd = [12.0] # distance to the nearest major structural discontinuity.
 L4msd = [12.0] # distance to the nearest major structural discontinuity.
 L5msd = [12.0] # distance to the nearest major structural discontinuity.
 Lmsd = minimum([L1msd,L2msd,L3msd,L4msd,L5msd])[1]
 if (Lmsd >= (1.8*(sqrt(D*(trd - LOSS - FCA)))))
     print("Satisfied - Flaw is located far enough from structural discontinuity\n")
     lmsd_satisfied = 1
 else
     print("Not satisfied - Flaw is too close to a structural discontinuity - Conduct a level 3 assessment\n")
     lmsd_satisfied = 0
 end

 # Groove Like Flaw dimensions
 gl = .05 # length of the Groove-Like Flaw based on future corroded condition.
 gw = .4 # width of the Groove-Like Flaw based on future corroded condition.
 gr = 0.1 # radius at the base of a Groove-Like Flaw based on future corroded condition.
 β = 40.0 # see (Figure 5.4) :: orientation of the groove-like flaw with respect to the longitudinal axis or a parameter to compute an effective fracture toughness for a groove being evaluated as a crack-like flaw, as applicable.

# Perform level 1 assessment
if (part5_applicability[1] == 1 && lmsd_satisfied == 1) # begin level 1 assessment
 #let part_5_lta_output = Array{Any,2},
 part_5_lta_output = Part5LTALevel1(CTPGrid; tmm_forcing=tmm_forcing, tmm=tmm, annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group, flaw_location=flaw_location, metal_loss_categorization=metal_loss_categorization, units=units, Lmsd=Lmsd,tnom=tnom,
     trd=trd, FCA=FCA, FCAml=FCAml, LOSS=LOSS, Do=Do, D=D, P=P, S=S, E=E, MA=MA, Yb31=Yb31, t=t,tsl=tsl, spacings=spacings, s=s, c=c, El=El, Ec=Ec, RSFa=RSFa, gl=gl, gw=gw, gr=gr,β=β)
 #end # let end
 part_5_lta_output

elseif (part5_applicability[1] == 0 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part5_applicability[1] == 1 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part5_applicability[1] == 0 && lmsd_satisfied == 1)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
end

Part 5 Level 1 assessment output:

Satisfied - Flaw is located far enough from structural discontinuity
Begin -- Part 5 LTA Level 1 Assessment - API 579 June 2016 Edition
eq 5.7 is Satisfied
eq 5.10 is Satisfied
eq 5.9 is Satisfied
The criteria for level 1 and 2 assessment has been satisfied - proceed to STEP 6
LTA - Proceed to STEP 7
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Region of metal loss is acceptable at MAWPr 1593.429 psi
MAWPr exceeds design pressure or equipment MAWP. Component is acceptable for continued operation
Part 5 level 1 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 1 assessment
The assessment is complete for all component types

The level 2 assessment is a more specific method of assessing and characterizing the corroded profile. As stated in API 579 paragraph 5.4.3.1:

"These procedures account for the local reinforcement effects of the varying wall thickness in the region of the local metal loss and ensure that the weakest ligament is identified and properly evaluated."

The API 579 methodology utilizes a numerical integration technique (Simpsons Rule or Trapezoidal Rule) to evalaute the the area of metal loss within the corroded profile. This julia code uses the Trapezoidal Rule being that the sub-intervals of the corroded profile are not in equal intervals (for simplicity vs simpsons rule).

The Part 5 Level 2 assessment output example:

# Perform level 2 assessment
if (part5_applicability[2] == 1 && lmsd_satisfied == 1) # begin level 2 assessment
 #let part_5_lta_output = Array{Any,2},
 part_5_lta_output = Part5LTALevel2(CTPGrid; annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group, flaw_location=flaw_location, metal_loss_categorization=metal_loss_categorization, units=units, Lmsd=Lmsd, tnom=tnom,
     trd=trd, FCA=FCA, FCAml=FCAml, LOSS=LOSS, Do=Do, D=D, P=P, S=S, E=E, MA=MA, Yb31=Yb31, tsl=tsl, t=t,spacings=spacings, s=s, c=c, El=El, Ec=Ec, RSFa=RSFa, gl=gl, gw=gw, gr=gr,β=β)
 #end # let end
elseif (part5_applicability[1] == 0 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part5_applicability[1] == 1 && lmsd_satisfied == 0)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
elseif (part5_applicability[1] == 0 && lmsd_satisfied == 1)
 print("Level 1 Criteria Not Met - Perform Level 2 or 3 as applicable")
end

Begin -- Part 5 LTA Level 2 Assessment - API 579 June 2016 Edition
eq 5.7 is Satisfied
eq 5.10 is Satisfied
eq 5.9 is Satisfied
The criteria for level 1 and 2 assessment has been satisfied - proceed to STEP 6
LTA - Proceed to STEP 7
Piping MAWPc = 3680.982psi
Piping MAWPl = 7947.02psi
Final MAWP = 3680.982psi
Region of metal loss is acceptable at MAWPr 3008.189 psi
MAWPr exceeds design pressure or equipment MAWP. Component is acceptable for continued operation
Part 5 level 2 - Satisfies June 2016 API 579-1/ASME FFS-1 Level 2 assessment
The component is a cylindrical shell, conical shell, or elbow
Begin -- evaluate the circumferential extent
eq 5.13 satisfied - no further evaluation is required

Sensitivty Analysis

Understanding input varibles and their relative sensitivty on the assessment output.

Example of iterating through a range of FCAml values and observing the effect on the MAWPr output:

The plot shows permissible FCAml allowances up to stated design pressure.

Considering confidence levels in the ability of inspection / NDE to find the maximum loss in a region of metal loss. To account for variance in inspection / NDE in reporting the minimum thickness:

eg: If the NDE technique used has known error of up to 10%. One may observe the spectrum of error up to stated design pressure. If within expected reason further confidence can be obtained moving forward with the observed results.

API 579 - LTA Corroded Profile:

API 579 Remaining Life Iteration

Example of modelling time based corrosion and predicting the remaining life of the component using API 579 methodology. Use interchangeably with PART 4 and PART 5 procedures.

using Gadfly
using DataFrames
using Cairo

# STEP 1 – Determine the metal loss of the component, tloss
tloss = tnom - tmm

# STEP 2 – Determine the MAWPr for a series of increasing time increments using an effective corrosion
# allowance and the nominal thickness in the computation. The effective corrosion allowance is determined
# as follows:
time = collect(1.0:1.0:50.0) # years
crate = 0.005 # inches per year
Csrate = 0.005 # long growth
Ccrate = 0.005 # circ growth
CAe = tnom .- (crate .* time)

# STEP 3 – Using the results from STEP 2, determine the remaining life from a plot of the MAWP versus
# time. The time at which the MAWPr curve intersects the equipment design pressure or equipment
# MAWP is the remaining life of the component.
#crate = 0.01
MAWPr_out = zeros(size(time,1))
for i = 1:length(time)
     let c = c, s=s, crate=crate, tloss = tloss
 c = c + Ccrate * time[i]
 s = s + Csrate * time[i]
 tmm = CAe[i]
 out = Part5LTALevel1(CTPGrid; tmm_forcing=tmm_forcing, tmm=tmm, annex2c_tmin_category=annex2c_tmin_category, equipment_group=equipment_group, flaw_location=flaw_location, FCA_string=FCA_string, metal_loss_categorization=metal_loss_categorization, units=units, Lmsd=Lmsd,tnom=tnom,
     trd=trd, FCA=FCA, FCAml=FCAml, LOSS=LOSS, Do=Do, D=D, P=P, S=S, E=E, MA=MA, Yb31=Yb31, t=t,tsl=tsl, spacings=spacings, s=s, c=c, El=El, Ec=Ec, RSFa=RSFa, gl=gl, gw=gw, gr=gr,β=β)
MAWPr_out[i] = out[18,2]
end # let
end

# create dataframe for plotting
df = hcat(MAWPr_out,fill(crate,size(MAWPr_out,1)),time)
df = DataFrame(df)
names = ["MAWPr","Corrosion Rates (ipy)","Time"]
rename!(df, names)
# x axis label
x_label = join(["Time to Design P ",string(P)," psig - Years"],"")

# Plot data
p = plot(df, x=df.Time, y=df.MAWPr, color="Corrosion Rates (ipy)", Geom.line, Scale.y_continuous(format=:plain),
Guide.title("API 579 Remaining Life - tmm revised for specific corrosion rates - Years for MAWPr to reach equipment Design P at a specific corrosion rate (ipy)"), Guide.xlabel(x_label),Guide.ylabel("MAWPr"),
yintercept=[P],
Geom.hline(size=0.5mm, style=:solid, color="red"),
Guide.YTicks(ticks=collect(0:100:1500)),
Guide.XTicks(ticks=time))
draw(PNG("C:/Users/Andrew.Bannerman/OneDrive - Shell/Documents/remaining_life_static_cr_rate.png",12inch,9inch),p)

Unit Test Summary

Each fit for service assessment is tested to a correct known output and assessment functions are tested to established tables and plots in the API 579 June 2016 code:

Test Summary: | Pass Total
applicability.jl | 100 100
part5_LTA_functions.jl | 11 11

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