Many listings and groupings of PoF exposures (threats) to pipeline systems are possible. Below is a fairly detailed example. It can be used to as a guide to setting up risk assessment algorithms or as a reference to ensure complete inclusion of possible failure mechanisms.

This list will generally also apply for downhole tubulars and other components of wells, including underground storage caverns, but additional threats would need to be added.

See also a discussion of Threat Interaction that challenges the notion that interactions are not already considered in a properly structured risk assessment.

Degradation Mechanisms (Time Dependent Failure Mechanisms)

Corrosion

External Corrosion

Internal Corrosion

• Internal Corrosion
• Chemical Corrosion
• Chloride (Pitting) Corrosion
• CO2 Corrosion
• Crevice/ Flange Face Corrosion
• Elemental Sulphur Corrosion
• Erosion and Erosion Corrosion & Cavitation
• Galvanic Corrosion
• H2S (Pitting) Corrosion
• High Temperature Oxidation
• Intergranular Corrosion
• Microbiologically Influenced Corrosion
• Oxygen Corrosion
• Preferential Weld Corrosion (PWC)
• Strong Acid (Well Workovers & Well Simulation) Corrosion
• Under Deposit Corrosion

Cracking

Fatigue

EAC–Environmentally Assisted Cracking

Non-Metallics

• Elastomer and Non-Metallics Degradation
• Elastomer Rapid Gas Decompression (RGD)
• Gasket
• Pump seal

Time Independent Failure Mechanisms (Random)

Elements of sabotage are listed here although the recommendation is to treat those types of mechanical damage separately from accidental in the risk assessment. The mitigation measures will be different for the two, warranting individual assessment.

Mechanical Damage

Damage 1st/2nd/3rd Party Impact (Onshore)

• Collapse and overstress at road/rail crossings
• Dropped objects on above ground facilities/pipe
• Excavator Impacts
• Failure of adjacent pipeline
• Farm equipment strikes e.g. ploughs or cultivators
• Previously Damaged Pipe
• Security Illegal Hot Taps
• Sabotage/Terrorism
• Transportation
• Unauthorized road crossings
• Vandalism
• Wildlife related damage

Damage Inflicted by 1st / 2nd / 3rd Party Impact (Offshore)

• Anchor Drag
• Anchor drag from abandoned vessel
• Dropped objects
• Shipwreck
• Incidental operations
• Marine wildlife related damage
• Pipeline/umbilical crossings
• Trawling
• Vessel impact

Geohazard/Weather-Related

• Freezing leading to overstress
• Snow/ice loads
• Coastal erosion
• Drilling mud mound formation
• Dune migration
• Frost Heave
• Ice sheet loading
• Karst
• Landslides
• Liquefaction
• Fault movement
• Loss of support
• Permafrost
• Pockmarks
• Pre-existing fault lines
• Seismic Activity
• Strudel scour
• Support/ foundation failure (including crossings and VSMs)
• Wildlife related soil movement

Water-Related, including Heavy Rains/Floods

Incorrect Operations (Human Error)

Flow Assurance

• Asphaltene Agglomeration
• Biological Fouling
• Emulsion Formation
• Foaming
• Gel Formation
• Hydrate Formation
• Hydrogen Sulphide
• Multiphase operations
• Naphthenate Formation
• Operating outside of flow assurance limits
• Scale Deposition
• Slugging
• Thermal Insulation Failure
• Wax Deposition

Operations

• Batching
• Closed flexible line vent
• Communications failure
• Opening pig trap under pressure
• Operation outside safe temperature pressure and flow operating limits
• Slackline
• Slug loading
• Stuck pig
• Surge
• Vacuum
• Water hammer

Threats That Aren’t Exposures

Recall that the term ‘threat’ is best interpreted as a failure mechanism or PoF exposure. While a weakness is technically a threat to a component’s integrity, using the term in such a broad fashion leads to confusion. Mixing weaknesses (resistance) with exposures leads to modeling complications in a risk assessment. So too does confusing more vulnerable locations or components with ‘threat’.

Resistance Elements (often misclassified as ‘threats’)

Manufacturing Related Defects

• Low toughness
• Defective Pipe
• Brittle fracture
• General pipe flaws
• Inclusions
• Laminations
• Less than minimum WT
• Poor weldability
• Rolled-in defects
• Understrength material
• Hard spots

Defective Pipe Seam

• ERW-hook, LOF, etc.
• Flaws at Ends of Pipe
• General SAW Weld Defects
• Brittle HAZ
• Low Frequency ERW issues

Location Elements (often misclassified as ‘threats’)

Similar to the misclassification of resistance elements, some ‘threat’ lists incorrectly include components or locations along a pipeline system as ‘threats’. Again, this leads to modeling confusion in a risk assessment. It is important to recognize that these items are NOT failure mechanisms but rather locations with increased susceptibility to certain failure mechanisms.

• Control / Pressure Relief Malfunction
• Bundle vent blockage
• Flexible pipeline vent blockage
• PSV Failure
• Flange/Connector Failure (Gasket O-Ring Failure)
• Corrosion of bolts
• External loads or vibration
• Improper installation
• Wrong material
• Miscellaneous Equipment Failure
• Bend stiffener
• Bundle/ PIP (Bulk head centralizer, vents, carrier pipe etc.).
• Casing Vents
• Failure at O-lets or other attachments
• Gauges
• Instrument tubing
• Leaking isolation joint
• Loss of support (anchor flange)
• Other
• Pig trap door failure
• Seals
• Spacers

Construction Elements (often misclassified as ‘threats’)

These are potential weaknesses introduced during installation or during repairs or maintenance. Some may be due to human error. Others were once standard practice but are now recognized as inappropriate practice. Some may be actionable while others are acceptable except under extreme conditions.

Where such weaknesses are known to exist, they can be unique dynamic segments being assessed. When their presence is only suspected, that too can be included with a probabilistic assignment in estimating effective wall thickness.

Damages

• Arc burns
• Buckle caused during installation
• Buckle Propagation
• Corrosion during pre-commisioning
• Damage to CRA e.g. seawater ingress
• Failure at wrinkle due to external loads
• Installation Damage including overstress while handling
• Defective Fabrication Weld
• Clad welding
• General – Potential for defect
• High/Low misalignment
• Lack of fusion
• Defective Pipe Girth Weld
• General girth weld defects
• High/Low misalignment
• Includes joining of non-metallic
• Lack of fusion
• Low toughness HAZ
• Stripped Thread/Broken Pipe/Coupling Failure
• Damaged thread

Past Practice

• Wrinkle bend
• acetylene weld
• mechanical coupling (Dresser, flange, screwed, etc)
• unreinforced branch
• stopple fitting
• clamps

Note that some of these appurtenances may still be acceptable practice. Some may enjoy long service lives if installed above grade but suffer short life spans when buried. They are listed here because many operating companies consider them to be more problematic (vulnerable, susceptible) than other components, at least under some circumstances. See full discussion under Resistance.