Kuliah 12 - Material Selection and Design

8/3/2019 Kuliah 12 - Material Selection and Design

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Material Selection &Design for Corrosion

Control


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Design-Limiting Material Properties General:

Cost Density

Mechanical Elastic Moduli

Strength

Toughness Fracture Toughness Damping Capacity Fatigue Endurance Limit

Wear Archard Wear Constant

Thermal

Thermal Conductivity Thermal Diffusivity

Specific Heat

Melting Point Glass Temperature

Thermal ExpansionCoefficient

Thermal Shock Resistance

Creep Resistance Corrosion/Oxidation

Corrosion Rate

Pitting Resistant High Temperature

Oxidation


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Material Comparison TensileStrength


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Design for Corrosion

Common Corrosion Threats in Oil & Gas Industry


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Design forCorrosion:CorrosionPotential


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Avoid obvious design weakness as follows Use more reliable materials, if this entails

greater cost.

Introduce additional precautions (inhibitors,CP, coating)

Establish maintenance/repair teams havingdetailed procedures and including qualifiedsurveyors, inspectors and supervisors.

Ensure that standby products are available,fully labeled and properly stored (usingdessicants and noncorrosive packaging)


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Shape.Geometrical form is basic to design.The objectiveis to minimize or avoid situations that worsencorrosion. These situations can range from

stagnation (e.g., retained fluids and/or solids;contaminated water used for hydrotesting) tosustained fluid flow (e.g., erosion/cavitation incomponents moving in or contacted by fluids, aswell as splashing or droplet impingement).



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Storage containers or vesselsshould allow complete drainage;otherwise, corrosive species canconcentrate in vessel bottom, anddebris may accumulate if thevessel is opento the atmosphere.

Structural members should bedesigned to avoid retention ofliquids; L-shaped sectionsshould be used with open sidedown, and exposed seams

should be avoided



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Incorrect trimmingor poordesign of seals andgaskets can createcrevice sites

Drain valvesshould bedesigned withsloping bottomsto avoid pitting

of the base of thevalve

Non-horizontaltubing canleave pools ofliquid atshutdown.


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Examples of poor assembly that can lead to premature corrosion problems


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Movement.Fluid movement need not be excessive to damage amaterial. Much depends on the nature of the fluidand the hardness of the material. A geometricshape may create a sustained delivery of fluid ormay locally disturb a laminar stream and lead toturbulence. Replaceable baffle plates or deflectors

are beneficial where circumstance permit their use;they eliminate the problem of impingement damageto the structurally significant component



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Effect of design features on flow



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Compatibility.In plant environments, it is often necessary to usedifferent materials in close proximity. Sometimes,components that were designed in isolation can end up

in direct contact in the plant.In such instances, the ideals of a total design conceptbecome especially apparent, but usually in hindsight.Direct contact of dissimilar metals introduces the

possibility of galvanic corrosion, and small anodic(corroding) areas should be avoided wherever thiscontact is apparent.



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Design details that can affect galvanic corrosion



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InsulationInsulationrepresents another area for potential corrosionattack, although most problems arise because of poorinstallation. Insulation types and properties vary

considerably, and expert advice from suppliers isrecommended. The most common corrosion problemsinclude crevice corrosion (where insulation and/oradhesives are tightly held against ametal surface, for example when straps or ties are tootight) and pitting corrosion (where moisture condenses onthe metal, usually because the insulation barrier was toothin or was improperly installed). Moisture-absorbingtendencies vary from one insulation to another



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Corrosion problems associated with improper use of insulation and lagging



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Stress.From a general design philosophy,environments that promote metal dissolutioncan be considered more damaging if stresses

are also involved. In such circumstances,materials can fail catastrophically andunexpectedly. Safety and health may also besignificantly affected.



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Surfaces.Corrosion is a surface phenomenon, and

the effects of poorly prepared surfaces,rough textures, and complex shapes andprofiles can be expected to be deleterious



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Effects of design on effectiveness ofcleaning or painting.

(a) Poor access in some structures makessurface preparation and paintingdifficult; access to the types of areas

shown should be maintained at aminimum of 45 mm (1 in.), or one-thirdof the height of the structure.

(b) (b) Sharp corners and profiles shouldbe avoided if the structure is to bepainted or coated.



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Material Selection GuidanceNACE SP0106 - Control of InternalCorrosion in Steel Pipelines and PipingSystems

NACE MR-0175/ISO 15156

Metals forSulfide Stress Cracking and StressCorrosion Cracking Resistance in SourOilfield Environment

NORSOK M-001

Design PrincipleMaterial Selection


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Material Selection Guidance If liquid water is not present in a steel

pipeline, corrosion does not occur. The presence of oxygen, CO2 or H2S in a

steel in the absence of liquid water does notcause corrosion at temperature below 200deg C (390 deg F).


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NACE SP0106 - Control of Internal Corrosionin Steel Pipelines and Piping Systems

If no liquid water is present, carbon dioxide (CO2)tend to be non-corrosive. In the presence of liquid

water, the partial pressure of CO2 (mole percent ofCO2 system pressure in kPa [psi]) is used as aguideline to determine the corrosiveness of CO2.

A partial pressure of CO2 above 207 kPa (30 psi) isusually corrosive in the presence of water.

A partial pressure of CO2 between 21 kPa (3 psi) and207 kPa (30 psi) may be corrosive in the presence ofwater.

A partial pressure of CO2 below 21 kPa (3 psi) is

generally considered non-corrosive.

Material Selection Guidance


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NACE SP0106 - Control of Internal Corrosionin Steel Pipelines and Piping Systems


Sulfide stress cracking occurs in high

strength steels, exposed to moist H2Sconditions. Four conditions required for SSCto occur Presence of H2S Presence of water High strength materials Under tensile or loading stress (residual or applied)


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NACE MR-0175/ISO 15156

Metals for Sulfide Stress Cracking andStress Corrosion Cracking Resistance in Sour Oilfield Environment



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Conditions for SSC

- Minimum H2S Partial Pressure 0.05 psia

- Minimum Total Pressure 65 psia

- Free Water Exist

- Additional condition : Cl- content - accelerator

Material Selection GuidanceNACE MR-0175/ISO 15156

Metals for Sulfide Stress Cracking andStress Corrosion Cracking Resistance in Sour Oilfield Environment


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The Basics of Sulfide Stress Cracking



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CRA Evaluation for SSC based on NACE MR-0175/ISO15156


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Komposisi dan Nama Pasar 304/304L

316/316L


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Material Selection GuidanceCRA Evaluation for SSC based on NACE MR-0175/ISO

15156


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15156


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15156


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15156


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Komposisi Paduan

Nama Pasar


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(a) Duplex 22Cr (b) 28Cr


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15156


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15156


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15156


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15156


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15156


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15156


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15156


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15156


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15156


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15156


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15156


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Material Selection GuidanceCarbon Steel Evaluation for SSC based on NACE MR-

0175/ISO 15156


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Material Selection GuidanceCarbon Steel Evaluation for SSC based on NACE MR-

0175/ISO 15156


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Material Selection GuidanceCRA Evaluation for SSC based on NORSOK M-001


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Material Selection GuidanceCRA Evaluation for SSC based on NORSOK M-001


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Komparasi Cost Index Unsur Paduan


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Plain End ProductsNo Jenis Bahan Rentang Perbandingan

Harga1 Baja Karbon L80 1 (Basis Perbandingan)2

Baja Tahan Karat Martensitik Varian 13Cr

3 - 5

3 Baja Tahan Karat Duplex 22Cr 7,5 - 94 Baja Tahan Karat Superduplex 25Cr 9 - 125 Paduan Nikel 28Cr 13 - 146 Paduan Nikel 825 17 - 18


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Kuliah 12 - Material Selection and Design

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