Pressure Vessel Failures: Common Causes and How to Prevent Them

Pressure vessels are critical components in industries such as oil and gas, chemical processing, power generation, pharmaceuticals, and food production. Despite their importance, pressure vessels can pose severe safety hazards if they fail. Catastrophic failures not only lead to production downtime but can also result in environmental disasters and loss of human life.

1. Common Causes of Pressure Vessel Failures
1.1 Corrosion and Erosion
Corrosion is the chemical or electrochemical deterioration of materials, often due to exposure to moisture, chemicals, or aggressive environments. Internal corrosion is common in vessels that handle corrosive fluids or gases, while external corrosion can occur when insulation traps moisture.

Erosion, on the other hand, results from high-velocity fluid or particulate matter physically wearing down the vessel walls, especially at bends, joints, and entry/exit points.

Notable risks:

Corrosion under insulation (CUI)

Galvanic corrosion due to dissimilar metals

Pitting and crevice corrosion in stagnant zones

Consequences:

Wall thinning

Leaks or rupture

Complete structural failure

1.2 Fatigue and Stress Cracking
Pressure vessels often operate under cyclic loading—regular pressurization and depressurization—which can lead to fatigue failure over time. Even small defects in materials or welds can grow into cracks under repeated stress.

Stress Corrosion Cracking (SCC) can occur when tensile stress and a corrosive environment combine. This type of cracking is often difficult to detect but can lead to sudden failures.

Risk factors:

Fluctuating pressure and temperature

Incompatible materials

Residual stresses from welding

Prevention requires:

Accurate fatigue analysis during design

Use of SCC-resistant alloys

Post-weld heat treatment (PWHT) to relieve stresses

1.3 Manufacturing Defects
Improper manufacturing processes can introduce flaws such as:

Incomplete weld penetration

Slag inclusions

Improper heat treatment

Dimensional deviations

These defects, if not detected during fabrication or commissioning, may propagate under pressure and stress during service.

Real-world examples:

Cracks originating from weld flaws

Delamination in composite vessels

Misalignment of flanges or nozzles

Quality assurance and non-destructive testing (NDT) during manufacturing are essential.

1.4 Design Flaws
Even when manufacturing is perfect, design errors can render a pressure vessel vulnerable. This includes:

Undersized wall thickness

Inadequate safety factors

Poor nozzle placement or support design

Ignoring dynamic loads or thermal expansion

Using outdated design codes or overlooking real operational conditions often leads to premature failures.

1.5 Overpressure Events
A common cause of vessel rupture is overpressurization, which can result from:

Blocked outlets

Failed control valves

Runaway chemical reactions

Operator error

If the pressure relief system fails or is improperly sized, the vessel may not withstand the excess pressure.

Consequences:

Explosions

Fire hazards

Flying shrapnel

Proper pressure relief devices and fail-safes are critical.

1.6 Poor Maintenance and Inspection
Over time, materials degrade and minor issues can escalate if left unchecked. Skipping routine inspections or lacking a preventive maintenance schedule is one of the most common causes of undetected vessel deterioration.

Warning signs often missed include:

Leaking flanges or valves

Unusual vibrations

Discoloration or rust streaks

Neglect can lead to:

Sudden leaks

Environmental contamination

Safety hazards to personnel

2. Prevention Strategies
2.1 Regular Inspection and Testing
Routine inspections help detect early-stage damage before it becomes critical. Techniques include:

Ultrasonic Testing (UT): Measures wall thickness and detects internal flaws

Radiographic Testing (RT): Identifies hidden cracks or inclusions

Magnetic Particle Inspection (MPI): Useful for surface cracks in ferromagnetic materials

Hydrostatic Testing: Pressurizes the vessel with water to check for leaks or weaknesses

Recommendation: Follow inspection intervals set by ASME, API 510, or local regulations.

2.2 Proper Material Selection
Material choice is vital. Different applications require different properties, such as:

Stainless steel: Excellent corrosion resistance, good for food/pharma

Carbon steel: Cost-effective but more prone to corrosion

Hastelloy, Inconel, or titanium: For highly corrosive or high-temperature environments

Failure to select compatible materials can lead to premature degradation.

2.3 Quality Manufacturing
Partner with manufacturers that comply with:

ASME Boiler & Pressure Vessel Code

ISO 9001 Quality Management Systems

Certified welders and procedures (WPS/PQR)

Tips:

Insist on third-party inspection

Review material test reports (MTRs) and fabrication drawings

2.4 Design According to Standards
Design should be based on comprehensive standards like:

ASME Section VIII (Div 1 & 2)

PED (Pressure Equipment Directive) for Europe

API 650/620 for specific storage applications

Design factors to include:

Safety margins

Fatigue analysis

Corrosion allowance

Seismic and wind loads if applicable

2.5 Install Safety Devices
Every pressure vessel should be protected with:

Pressure Relief Valves (PRVs): Automatically release excess pressure

Rupture Discs: Fail-safe device that breaks under critical pressure

Pressure and temperature sensors: Connected to alarm or shutdown systems

Periodic testing and recalibration of these safety devices are essential.

2.6 Training and Standard Operating Procedures (SOPs)
Operators are the first line of defense. Provide:

Ongoing technical training

Emergency response drills

Clear, accessible SOPs for normal and abnormal conditions

Human error is a major contributor to vessel failure—training minimizes this risk.

3. Case Studies of Pressure Vessel Failures
Case 1: BP Texas City Refinery Explosion (2005)
Cause: Overpressure in a tower due to faulty level indicators and alarms.

Consequence: 15 deaths, 180 injuries.

Lesson: Always verify instrumentation and install redundant safety systems.

Case 2: Grain Silo Explosion
Cause: Dust accumulation led to pressure spike and ignition.

Consequence: Total loss of facility.

Lesson: Ignoring small inspection issues can lead to massive losses.