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© Matthews Engineering Training Ltd
API 570
PIPING INSPECTION
© Matthews Engineering Training Ltd
API 570 Piping Inspection Code
570
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API 570 COVERS IN-SERVICE INSPECTION OF PIPING
To fit in with the philosophy of ANSI B31.3‘DESIGN CODE FOR PROCESS PIPING’
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THE SCOPE OF API 570
Mandatory:Almost any metallic piping system:•Raw and finished oil products•Raw and finished chemical products•Hydrogen/fuel/flare gas systems•Sour/waste systems etc
Optional:•Water,steam and condensate•Piping related to mechanical equipment•(pumps/compressors etc)•Pressure vessels•Domestic sewers etc•Everything< ½ in dia•Non-metallic piping
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API 570 INSPECTION PRACTICES
Checks are needed for specific types of corrosion and cracking:
1. Injection points2. Dead legs3. CUI4. Soil /Air(S/A) interfaces5. Erosion and erosion/corrosion6. SCC7. Corrosion under linings8. Fatigue cracking9. Creep cracking10. Brittle fracture11. Freeze damage
We’ll look at some of these in more detail
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INJECTION POINTS
Why is particular inspection attention (and TMLs)needed at
injection points ?
….and what are TMLs anyway
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12in or 3D upstream
2nd change of flow
direction downstream
(or 7.6m after the first change)
INJECTION POINT INSPECTION AREAS
This area is known as:The
IPC(‘injection point circuit’)
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API 570 INSPECTION METHODS
Internal
visuals
TMLs(4 quadrants)
Externalvisual
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DEADLEGS
Deadleg
Corrosion rates are higher
around deadlegs
Redundant deadlegs should be removed
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CORROSION UNDER INSULATION (CUI)
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CORROSION UNDER INSULATION (CUI)
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CORROSION UNDER INSULATION (CUI)
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CORROSION UNDER INSULATION (CUI)
Almost total wastage of bolts
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CORROSION UNDER INSULATION (CUI)
API identifies the areas that are most susceptible to CUI
Mist from cooling towers
Near steam ventsand deluge systems
Acid vapours
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•All LCS pipework operating continually at –4<t<120 degC
•LCS pipework operating> 120 degC BUT INTERMITTENTLY
•Austenitic Stainless steel at 65-205 DegC (for SCC)
•Piping systems that vibrate a lot (insulation becomes damaged)
•Piping systems with damaged wrappings
CORROSION UNDER INSULATION (CUI)
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CORROSION UNDER FIXED LININGS
In general ,API does not require removal of
linings for inspections…AS LONG AS THE LINING IS IN GOOD CONDITION
BUT
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SOIL/AIR INTERFACES
All interfaces without cathodic protection
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The API 570 rule is that you should inspect areas for CUI where the
insulation is damaged
CORROSION UNDER INSULATION (CUI)
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RECOMMENDED EXTENT OF CUI EXAMINATION(BY CLASS)
Type of circuit
% NDT on areas with damaged insulation
% NDT on suspect areas
within CUI temperature
range
Class 1 75% 50%
Class 2 50% 33%
Class 3 25% 10%
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EROSION AND EROSION-CORROSION LOCATIONS
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•Control valves (especially when there is ‘flash-off’•Orifice plate•Pump discharges•Elbows•Pipe features that produce turbulence
TMLS FOR EROSION/CORROSIONDownstream of ………..
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An example
EROSION/CORROSION
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Erosion/Corrosion after flow-restriction
features
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STRESS CORROSION
CRACKING (SCC)
Rule:In most circumstances,SCC is
due to
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SCC ON A GAS PIPELINE COMPONENT
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SCC ON A GAS PIPELINE COMPONENT
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What is this?
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API 570 GUIDE ON REPAIR PATCHES
D
Max D/2
Repair patch
Not permitted
25mm min radii
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API 570 GUIDE ON REPAIR PATCHES
Requires a full repair sleeve
Min 2D
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API 570 INSPECTION INTERVALS
The maximum permitted interval depends on pipe ‘class’
Class 1:Highest risk/consequence
Class 2 : ‘Medium’ risk
Class 3: ‘Low’ risk
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MAXIMUM API INSPECTION INTERVALS (BY CLASS)
Type of circuit
Thickness measurements
External visual
Class 1 5 years 5 years
Class 2 10 years 5 years
Class 3 10 years 10 years
Injection points
3 years By class
S/A interfaces - By class
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API 570 PIPING CLASSES
Class 1Flammable services/flash-off leading to brittle fractureExplosive vapours after flash-offH2S gaseous
Hydroflouric acidPiping over public roads
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API 570 PIPING CLASSES
Class 2Most other process pipingOn-site hydrocarbonsH2, fuel gas and natural gas On-site acid and caustics
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API 570 PIPING CLASSES
Class 3Fluids that will not
flash off (even if they are flammable)
Distillate/product storage/loading lines
Off-site acids and caustics
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API 570 SUMMARY
•API 570 specifies the main points to look for
•Remember the pipe classes (and their inspection periods)
•Simple wall thickness determination
570
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