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API 570 practice questions

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Question 1Scope, Definitions, and Organization of API 570

Which of the following best describes the coverage of API 570?

  1. Design, fabrication, erection, and testing of new metallic piping systems
  2. Inspection, repair, alteration, and rerating of in-service piping Correct answer.
  3. Qualification of welding procedures and welders for new construction work
  4. Inspection, repair, and alteration of in-service pressure vessels and storage tanks

Explanation

API 570 is an in-service inspection code whose stated scope is the inspection, repair, alteration, and rerating of in-service metallic piping systems and pipelines. New construction and equipment such as vessels and tanks are covered by other codes.

Question 2Scope, Definitions, and Organization of API 570

API 570 is written primarily for application to piping systems in which setting?

  1. Power plants designed to ASME B31.1
  2. Petroleum refineries and chemical plants Correct answer.
  3. Nuclear power plants and their safety systems
  4. Commercial buildings and their HVAC systems

Explanation

API 570 applies to metallic piping systems and pipelines in refineries, chemical plants, and other process facilities. Nuclear, boiler external, and building-service piping are addressed by other codes and standards.

Question 3Scope, Definitions, and Organization of API 570

API 570 addresses a piping system at which stage of its life cycle?

  1. During shop fabrication and field erection only
  2. After the piping has been placed in service Correct answer.
  3. Only after the piping has been permanently retired
  4. During initial design and stress analysis

Explanation

API 570 is an in-service code: it begins to apply once the piping system has been placed in service and covers ongoing inspection, repair, alteration, and rerating. Design and construction are governed by the applicable construction code.

Question 4Scope, Definitions, and Organization of API 570

In API 570, the term 'owner/user' refers to:

  1. The manufacturer of the pipe and fittings
  2. The contractor that performs welding on the piping
  3. The organization that operates the piping system Correct answer.
  4. The agency that certifies the piping inspector

Explanation

The owner/user is the organization that owns or operates the piping system and is accountable under the code for its inspection and safe operation. Contractors, certifying bodies, and manufacturers are separate parties.

Question 5Scope, Definitions, and Organization of API 570

Under API 570, which party is responsible for ensuring that piping systems are inspected in accordance with the code?

  1. The owner/user Correct answer.
  2. The inspection contractor
  3. The piping designer
  4. The pipe fabricator

Explanation

API 570 places responsibility for inspection of the piping on the owner/user. Contractors and other personnel may perform inspection work, but accountability for the program remains with the owner/user.

Question 6Scope, Definitions, and Organization of API 570

Which statement defines 'repair' as used in API 570?

  1. Work needed to restore a system to safe operation at the design conditions Correct answer.
  2. The periodic examination of a system to determine its condition
  3. A change that increases pressure-containing capability beyond the original design
  4. A change in the design pressure or design temperature of the system

Explanation

Repair is the work necessary to restore a piping system to a condition suitable for safe operation at the design conditions. If the restorative work changes the design pressure or temperature, the rerating requirements must be met.

Question 7Scope, Definitions, and Organization of API 570

Which statement defines 'alteration' as used in API 570?

  1. Adding insulation or paint to a piping system
  2. Replacing a valve with one of the same rating
  3. Restoring a component to its original dimensions by welding
  4. A change with design implications affecting pressure containment Correct answer.

Explanation

An alteration is a physical change in a component that has design implications affecting the pressure-containing capability of the system beyond the scope of the original design. Cosmetic and like-for-like maintenance activities are not alterations.

Question 8Scope, Definitions, and Organization of API 570

In API 570, the 'remaining life' of a piping component is:

  1. The design life stated on the original drawings
  2. The time before the component reaches t-min Correct answer.
  3. The interval between the last two inspections
  4. The time the component has been in service since installation

Explanation

Remaining life is the time a component can continue to be used before its thickness reaches the minimum required thickness, calculated from the measured thickness and the corrosion rate.

Question 9Scope, Definitions, and Organization of API 570

A repair is completed and it results in a change to the design pressure of the piping system. What does API 570 require?

  1. The work shall be documented as a repair only
  2. The system shall be replaced within one year
  3. No further action, because the work is a repair
  4. The requirements for rerating shall be satisfied Correct answer.

Explanation

The definition of repair states that if the restorative work results in a change of design temperature or pressure, the requirements for rerating shall be satisfied. The rerating must also be documented accordingly.

Question 10Scope, Definitions, and Organization of API 570

Which of the following is an alteration rather than a repair?

  1. Increasing the diameter of a section of the line Correct answer.
  2. Replacing a corroded elbow with one of the same specification
  3. Renewing a gasket of the same type and material
  4. Removing and reinstalling a valve of the same rating

Explanation

Changing the size of a section of line is a physical change with design implications beyond the original design, so it must be handled as an alteration. Like-for-like renewal of components is repair or maintenance.

Question 11Scope, Definitions, and Organization of API 570

In API 570, 'rerating' means:

  1. Recalculating the corrosion rate after an inspection
  2. Replacing a component with one of a higher pressure class
  3. A change in the design pressure and/or design temperature Correct answer.
  4. Restoring the original design conditions after a repair

Explanation

Rerating is a change in the design pressure and/or design temperature of a piping system or component, and it may be either an increase or a decrease. It must be carried out in accordance with the applicable design code.

Question 12Scope, Definitions, and Organization of API 570

API 570 defines a 'repair organization' as an organization that:

  1. Provides third-party inspection of new construction
  2. Manufactures new piping components to an accepted specification
  3. Performs repairs and is responsible for the adequacy of the work Correct answer.
  4. Certifies piping inspectors on behalf of the owner/user

Explanation

A repair organization performs repairs, alterations, or rerating of piping systems and is responsible for the adequacy of the work it performs. The owner/user remains responsible for ensuring that only qualified organizations are used.

Question 13Scope, Definitions, and Organization of API 570

Welding procedures used for repairs and alterations under API 570 shall be qualified in accordance with:

  1. AWS D1.1
  2. ASME BPVC Section VIII Division 1
  3. API 1104
  4. ASME BPVC Section IX Correct answer.

Explanation

Welding procedure specifications, procedure qualification records, and welder performance qualification for repairs and alterations must satisfy ASME BPVC Section IX. The repair must also be designed and executed in accordance with the applicable construction code.

Question 14Scope, Definitions, and Organization of API 570

A piping system has an estimated remaining life of 12 years. Under the remaining-life rule of API 570, the inspection interval shall not exceed:

  1. 4 years
  2. 12 years
  3. 2 years
  4. 6 years Correct answer.

Explanation

The inspection interval may not exceed one-half of the estimated remaining life, subject also to the maximum intervals given in the code. One-half of 12 years is 6 years.

Question 15Scope, Definitions, and Organization of API 570

The measured thickness of a pipe is 0.500 in, the minimum required thickness is 0.350 in, and the corrosion rate is 0.010 in/yr. What is the remaining life?

  1. 15 years Correct answer.
  2. 35 years
  3. 10 years
  4. 20 years

Explanation

Remaining life equals the corrosion allowance divided by the corrosion rate: (0.500 minus 0.350) divided by 0.010 in/yr equals 15 years. The inspection interval would then be limited to half of that value.

Question 16Scope, Definitions, and Organization of API 570

In API 570, a 'piping system' is best described as:

  1. All the piping within a process unit boundary, whatever its service
  2. A single length of pipe between two flanges
  3. Interconnected piping subject to the same operating conditions Correct answer.
  4. The pipe and its structural supports

Explanation

A piping system is an assembly of interconnected piping components, such as pipe, fittings, flanges, gaskets, bolting, valves, and pressure-containing parts, that are subject to the same operating conditions and treated as a unit for inspection.

Question 17Scope, Definitions, and Organization of API 570

Non-destructive examination personnel performing inspections under API 570 shall be qualified in accordance with:

  1. AWS QC1 qualification
  2. API 570 certification of the individual
  3. ASME Section V and SNT-TC-1A Correct answer.
  4. API 510 certification of the inspector

Explanation

Examinations are performed in accordance with ASME BPVC Section V, and NDE personnel are qualified to a recognized standard such as ASNT SNT-TC-1A or an equivalent. Certification as a piping inspector alone does not qualify a person to perform NDE.

Question 18Scope, Definitions, and Organization of API 570

Which document does the owner/user prepare for a piping system, or group of similar systems, to define the inspection tasks, methods, and intervals?

  1. A weld procedure specification
  2. An inspection plan Correct answer.
  3. A rerating calculation
  4. A fitness-for-service report

Explanation

API 570 requires the owner/user to develop an inspection plan for each piping system or group of similar systems. The plan defines what will be inspected, how, and at what intervals.

Question 19Scope, Definitions, and Organization of API 570

Which of the following is a responsibility of the piping inspector under API 570?

  1. Authorizing changes to process operating conditions
  2. Setting the operating budget for the unit
  3. Evaluating inspection results and recommending action Correct answer.
  4. Performing all repairs personally

Explanation

The inspector plans and performs inspection work, evaluates the results, and makes recommendations to the owner/user. Operating decisions, budgets, and the actual repair work are outside the inspector's role.

Question 20Scope, Definitions, and Organization of API 570

In API 570, 't-min' refers to:

  1. The minimum required thickness Correct answer.
  2. The nominal wall thickness ordered for the pipe
  3. The thickness measured at the most recent inspection
  4. The corrosion allowance plus the measured thickness

Explanation

t-min is the minimum required thickness determined from the applicable design code. Measured thickness readings are compared with t-min to determine corrosion rate and remaining life.

Question 21Scope, Definitions, and Organization of API 570

Which statement correctly describes how API 570 relates to ASME B31.3?

  1. API 570 replaces B31.3 once the piping is placed in service
  2. B31.3 covers design; API 570 covers in-service inspection Correct answer.
  3. B31.3 governs in-service inspection while API 570 governs design
  4. The two codes cover different industries and are never used together

Explanation

B31.3 provides the design and construction rules for process piping, while API 570 provides the in-service inspection, repair, alteration, and rerating rules. Alterations and rerating performed under API 570 must still satisfy the applicable design code.

Question 22Scope, Definitions, and Organization of API 570

A 20-ft section of carbon steel line is replaced with stainless steel pipe of the same size and schedule to resist a new corrosive stream. Under API 570 this work is:

  1. An alteration, because the material change affects the design Correct answer.
  2. A repair, because the pipe was replaced and the size did not change
  3. Routine maintenance, which needs no inspection involvement
  4. Neither a repair nor an alteration, because the size did not change

Explanation

A change of material alters the design basis, including allowable stress and corrosion assumptions, so it is a physical change with design implications beyond the original design and is an alteration. A replacement using pipe of the original specification would have been a repair.

Question 23Scope, Definitions, and Organization of API 570

An inspection shows that the minimum measured thickness of a line is below t-min. What does API 570 require?

  1. Immediate scrapping of the entire piping system
  2. Repair, replace, rerate, or show fitness for service Correct answer.
  3. An increase in inspection frequency only
  4. Continued operation until the next scheduled inspection

Explanation

Piping below the minimum required thickness is not suitable for the current design conditions. It must be repaired, replaced, or rerated to lower conditions, or it must be shown to be fit for continued service by a fitness-for-service assessment.

Question 24Scope, Definitions, and Organization of API 570

A piping system shows a long-term corrosion rate of 0.004 in/yr and a short-term corrosion rate of 0.012 in/yr. Which rate governs the remaining life?

  1. The short-term rate, because the greater rate governs Correct answer.
  2. The average of the two rates
  3. The long-term rate, because it uses more data
  4. Neither; remaining life depends only on t-min

Explanation

Remaining life is based on the greater of the short-term and long-term corrosion rates so the estimate is conservative. Here the short-term rate of 0.012 in/yr governs, producing a shorter remaining life.

Question 25Scope, Definitions, and Organization of API 570

A piping system must be operated at a lower design pressure because of wall loss. Under API 570, which of the following is required?

  1. Rerating in accordance with the applicable design code Correct answer.
  2. No action at all, because a lower rating is inherently safe
  3. Replacement of every component with thicker-walled pipe
  4. An entry in the operating log recording the new pressure

Explanation

Operating at a pressure lower than the original design is a rerating, and rerating must be performed in accordance with the applicable design code with the change properly documented. Relief protection and records must be consistent with the new rating.

Question 26Scope, Definitions, and Organization of API 570

API 570 covers the inspection, repair, alteration, and rerating of which of the following?

  1. Aboveground storage tank shells and bottoms
  2. Pressure relief valves installed in process service
  3. Fired heater tubes in the radiant and convection sections
  4. In-service process piping in a petroleum refinery Correct answer.

Explanation

API 570 applies to in-service metallic and reinforced thermosetting resin (FRP) piping systems, typically process piping in refineries and chemical plants. Tanks, relief valves, and heater tubes are addressed by other documents because they are not piping systems.

Question 27Scope, Definitions, and Organization of API 570

Under API 570, which party has overall responsibility for establishing and maintaining the piping inspection program?

  1. The jurisdictional authority that regulates the facility
  2. The authorized inspection agency, whenever one is engaged
  3. The owner/user of the facility Correct answer.
  4. The repair organization that performs repairs on the piping

Explanation

API 570 places the responsibility for the inspection program, including inspection plans, intervals, and recordkeeping, on the owner/user. Some activities may be delegated to inspectors or inspection agencies, but the responsibility itself is not transferred.

Question 28Scope, Definitions, and Organization of API 570

In API 570, the abbreviation CML stands for:

  1. Certified Maintenance Level
  2. Corrosion Monitoring Line
  3. Condition Monitoring Location Correct answer.
  4. Critical Measurement Limit

Explanation

A CML is a designated location on a piping circuit where examinations and thickness measurements are made to monitor the condition of the system. CMLs are selected by the inspector and identified on inspection drawings or records.

Question 29Scope, Definitions, and Organization of API 570

In API 570 terminology, which statement best distinguishes 'examination' from 'inspection'?

  1. Examination is the performance of visual, dimensional, or nondestructive checks; inspection is the broader assessment and evaluation of condition by the inspector. Correct answer.
  2. Examination may be performed by any plant personnel; inspection is restricted to the repair organization.
  3. Examination is the overall fitness-for-service judgment; inspection is the physical measurement of wall thickness.
  4. Examination applies only to welds; inspection applies to all other parts of the piping system.

Explanation

Examination refers to the physical activities such as visual checks, dimensional checks, and nondestructive testing. Inspection is the wider function that includes those examinations plus the evaluation and judgment made by the inspector.

Question 30Scope, Definitions, and Organization of API 570

In API 570, a 'piping circuit' is best described as:

  1. The piping that is drained and ventilated to permit entry during a turnaround
  2. A single spool of pipe between two flanges
  3. All piping within one process unit, from battery limits to battery limits
  4. A section of piping with similar design and service conditions that is treated as a unit for inspection Correct answer.

Explanation

API 570 groups piping into circuits so that inspections, corrosion rates, and remaining life can be managed for a representative section rather than for every individual component. A circuit shares similar materials, service, and operating conditions.

Question 31Scope, Definitions, and Organization of API 570

Which API document is referenced by API 570 for detailed piping inspection practices and techniques?

  1. API 577
  2. API 580
  3. API 574 Correct answer.
  4. API 571

Explanation

API 574 is the companion document that describes inspection practices and techniques for piping system components. API 570 states the requirements, while API 574 supplies the supporting how-to guidance.

Question 32Scope, Definitions, and Organization of API 570

Under API 570, a person acting as an inspector on in-service piping may be employed by:

  1. Only the jurisdictional authority that regulates the plant
  2. The owner/user or an authorized inspection agency Correct answer.
  3. The repair organization that carries out the repairs
  4. Only a third-party inspection company that is independent of the plant

Explanation

Inspectors may be employees of the owner/user or of an authorized inspection agency acceptable to the owner/user, such as an insurance inspection organization. Independence from the organization performing the repair work is the key point.

Question 33Scope, Definitions, and Organization of API 570

In API 570, an 'injection point' is a location where:

  1. Two piping systems of different materials are joined by a flanged connection
  2. A fluid such as a chemical or wash water is injected into the process stream Correct answer.
  3. A piping circuit crosses the battery limits of a process unit
  4. A branch connection is provided for a pressure instrument

Explanation

Injection points are singled out because the injected stream can mix with the process fluid and cause locally accelerated corrosion, erosion, or cracking. API 570 requires that these locations be specifically identified and included in the inspection plan.

Question 34Scope, Definitions, and Organization of API 570

In API 570, the maximum allowable working pressure (MAWP) of a piping system is:

  1. The pressure that was used for the original hydrostatic test of the system
  2. The highest pressure the system has actually experienced during operation
  3. The maximum internal pressure permitted at the design temperature, accounting for the current condition of the system Correct answer.
  4. The pressure at which the relief valve on the system is set to open

Explanation

MAWP is a design and condition-based limit, determined at the design temperature and adjusted for any wall loss or deterioration found in service. It is not an operating history value or a test pressure.

Question 35Scope, Definitions, and Organization of API 570

Which of the following is an example of a deadleg in a piping system?

  1. A standby pump suction line that is isolated by a closed valve and has no normal flow Correct answer.
  2. A header that continuously carries process fluid to several users
  3. The section of line immediately downstream of a control valve in continuous service
  4. A line that is being steam flushed during a unit start-up

Explanation

A deadleg is a portion of piping that does not have a continuous flow, such as a standby branch, bypass, or vent that is normally closed. These stagnant sections can accumulate corrosive fluids and are therefore given attention in the inspection plan.

Question 36Scope, Definitions, and Organization of API 570

Inspection of which of the following is governed by a separate API standard rather than by API 570?

  1. Block valves in process service
  2. Flanges and their bolting
  3. Pressure relief valves Correct answer.
  4. Pipe fittings such as elbows, tees, and reducers

Explanation

Relief valves are covered by API 576, while API 570 covers the piping system itself, which includes pipe, fittings, flanges, bolting, gaskets, and valves. The inspection of a relief valve is therefore handled under a different standard.

Question 37Scope, Definitions, and Organization of API 570

In API 570, the corrosion rate of a piping circuit is:

  1. The difference between the nominal thickness and the lowest measured thickness
  2. The total metal loss measured since the piping was placed in service
  3. The rate of metal loss with time, calculated from thickness measurements taken over an interval Correct answer.
  4. The thickness below which the component must be removed from service

Explanation

Corrosion rate is expressed as metal loss per unit time and is computed from thickness data gathered at condition monitoring locations. API 570 uses both long-term and short-term rates, and the higher of the applicable rates governs the remaining-life calculation.

Question 38Scope, Definitions, and Organization of API 570

An owner/user wants to use risk-based inspection to establish inspection intervals for piping under API 570. Which documents provide the RBI methodology referenced by API 570?

  1. API 510 and API 653
  2. API 570 and API 574
  3. API 579-1/ASME FFS-1
  4. API 580 and API 581 Correct answer.

Explanation

API 570 permits inspection intervals to be set using risk-based inspection in accordance with API 580 and API 581. Those documents supply the risk assessment methodology that the piping code relies on.

Question 39Scope, Definitions, and Organization of API 570

A flaw is found in a piping system, and the remaining strength cannot be evaluated using the rules of API 570. Which document does API 570 point to for a fitness-for-service assessment?

  1. ASME B31.3
  2. API 574
  3. API 577
  4. API 579-1/ASME FFS-1 Correct answer.

Explanation

API 570 allows a fitness-for-service assessment in accordance with API 579-1/ASME FFS-1 when the condition falls outside the evaluation rules of the piping code. The assessment determines whether the component can continue to be operated safely.

Question 40Scope, Definitions, and Organization of API 570

Under API 570, inspection and repair records for a piping system are to be retained:

  1. Only until the process unit is sold or ownership changes
  2. For the life of the piping system Correct answer.
  3. Until the next scheduled inspection has been completed
  4. For a minimum of five years after the record is created

Explanation

API 570 requires the owner/user to keep inspection, repair, and alteration records for the life of the piping system. These records support corrosion-rate determination, remaining-life calculation, and later rerating or fitness-for-service evaluations.

Question 41Causes of Deterioration and Failure in Piping Systems

Uniform general corrosion of carbon steel piping is characterized by which of the following?

  1. Thinning at a fairly even rate over the wetted surface Correct answer.
  2. Deep isolated pits that penetrate rapidly through the wall
  3. Cracks that follow grain boundaries in the heat-affected zone
  4. Metal loss confined to a narrow band at the weld toe

Explanation

General corrosion attacks the surface broadly and produces relatively uniform wall loss, so it is evaluated by averaging thickness readings over an area and computing a corrosion rate. The other patterns are localized forms that require different inspection strategies.

Question 42Causes of Deterioration and Failure in Piping Systems

What is the essential condition for external corrosion under insulation (CUI) to occur on carbon steel?

  1. Trapped moisture at the steel surface Correct answer.
  2. Sustained metal temperatures above 500 °F (260 °C)
  3. Frequent cyclic operation of the piping system
  4. Insulation that contains chlorides only

Explanation

CUI is an aqueous corrosion process, so water must be present at the steel surface; insulation, jacketing damage, and the temperature range influence whether that water persists but do not replace it. Carbon steel CUI is most aggressive in the roughly 10 °F to 350 °F metal temperature band where wetting and evaporation cycles occur.

Question 43Causes of Deterioration and Failure in Piping Systems

In a galvanic couple between carbon steel and a copper alloy in an electrolyte, which metal corrodes?

  1. The carbon steel, because it is anodic Correct answer.
  2. The copper alloy, because it is the cathode
  3. Both metals at rates that are always equal
  4. Neither metal, because the couple stops all corrosion

Explanation

In a galvanic couple the more active metal, which is anodic in the galvanic series, corrodes while the more noble metal becomes the cathode and is protected. Carbon steel is anodic to copper alloys in most aqueous environments, so the steel suffers accelerated attack, with severity strongly influenced by the cathode-to-anode area ratio.

Question 44Causes of Deterioration and Failure in Piping Systems

Severe erosion-corrosion in carbon steel piping is most likely at which location?

  1. On the outside radius of an elbow in wet steam Correct answer.
  2. On the upstream face of a fully open gate valve
  3. Along a long straight run of pipe with steady laminar flow
  4. In a dead leg where there is essentially no flow

Explanation

Erosion-corrosion is driven by high local velocity and turbulence, which strip the protective oxide film and expose bare metal to fresh corrodent. The outside radius of an elbow carrying wet steam combines high velocity, changing direction, and two-phase flow, making it a classic location for rapid metal loss.

Question 45Causes of Deterioration and Failure in Piping Systems

Stress corrosion cracking requires the simultaneous presence of which three conditions?

  1. Susceptible alloy, corrosive environment, tensile stress Correct answer.
  2. High hardness, low temperature, and cyclic loading
  3. Hydrogen, a weld defect, and low hardness
  4. A susceptible alloy, oxygen, and a compressive residual stress

Explanation

SCC occurs only when a susceptible alloy is exposed to a specific cracking environment while under sustained tensile stress, whether applied or residual. Removing any one of the three legs prevents cracking, which is the basis for mitigation by stress relief, environment control, or material upgrade.

Question 46Causes of Deterioration and Failure in Piping Systems

Hydrogen blistering of carbon steel in wet sour service occurs by which sequence?

  1. Hydrogen ions react with carbides to form methane at grain boundaries
  2. Sulfide scales lift the surface layer away from the base metal
  3. Atomic hydrogen diffuses in and recombines at inclusions Correct answer.
  4. Dissolved carbon dioxide expands inside laminations on pressure release

Explanation

Corrosion in wet sour service generates atomic hydrogen that enters the steel and recombines to molecular hydrogen at inclusions, laminations, and other planar discontinuities. The trapped gas cannot diffuse out, so pressure builds and deforms the steel into blisters, often accompanied by stepwise internal cracking.

Question 47Causes of Deterioration and Failure in Piping Systems

Which atmospheric condition most accelerates external corrosion of uncoated carbon steel piping?

  1. Dry desert air with very low relative humidity
  2. Repeated wetting with chloride-laden moisture Correct answer.
  3. Continuous sub-zero temperatures
  4. Clean air that carries no contaminants

Explanation

Atmospheric corrosion needs a thin electrolyte film, so alternating wet and dry cycles with chloride contamination are far more aggressive than steady exposure. Chlorides raise conductivity and break down protective films, and the drying cycle concentrates them at the surface.

Question 48Causes of Deterioration and Failure in Piping Systems

Creep damage in carbon steel piping becomes a concern under which condition?

  1. Short-term loading at ambient temperature
  2. Hydrogen charging during a shutdown
  3. Sustained stress at metal temperatures above about 800 °F Correct answer.
  4. Cyclic stress applied at high frequency at room temperature

Explanation

Creep is time-dependent deformation that becomes significant when carbon steel operates above roughly 800 °F (425 °C) under sustained stress. It shows up as diametral growth, sagging, and eventually intergranular creep cracking, so hot lines are monitored by periodic dimensional checks.

Question 49Causes of Deterioration and Failure in Piping Systems

Which set of conditions most favors chloride stress corrosion cracking of 300-series stainless steel?

  1. Dry chloride salt with no moisture present
  2. Anhydrous ammonia under high flow
  3. Warm chloride solution, tensile stress, and dissolved oxygen Correct answer.
  4. Cold concentrated chloride solution under compressive stress

Explanation

Austenitic stainless steels crack in chloride environments when tensile stress is present and the metal is warm enough, generally above about 140 °F (60 °C), with oxygen supporting the crack chemistry. Residual weld stress often supplies the stress even when no external load exists.

Question 50Causes of Deterioration and Failure in Piping Systems

A carbon steel line carrying hydrogen at elevated temperature shows internal fissures and decarburization along grain boundaries. Which damage mechanism is indicated?

  1. High-temperature hydrogen attack Correct answer.
  2. Sulfide stress cracking of hard weld zones
  3. Caustic stress corrosion cracking
  4. Chloride stress corrosion cracking

Explanation

Above roughly 400 °F, hydrogen reacts with carbides in steel to form methane that cannot diffuse out, so pressure builds at grain boundaries and produces fissuring together with decarburization. The Nelson curves give the temperature and hydrogen partial pressure limits for each steel grade.