A tank integrity assessment tells an owner whether a storage tank can stay in service and on what terms. TCR Engineering, TCR Advanced Engineering and TCR Arabia undertake it to API 653 in India and Saudi Arabia, with external partners and associate firms, combining visual inspection, ultrasonic thickness, settlement surveys, acoustic emission testing and robotic floor inspection.
- Standards: API 653, API 650, API RP 575 and API 579
- Fitness-for-service: API 579, by TCR Advanced Engineering on TCR Engineering's side and by TCR Arabia in Saudi Arabia
- Inspectors: NDT certification to SNT-TC-1A, with API 653 tank inspector training
- Output: condition findings, remaining life, repair recommendations and the next inspection interval
- Grain silos: condition assessment, with the evidence for the stability certificate that a chartered structural engineer signs
When industrial storage tanks show signs of deterioration or approach their scheduled inspection intervals, plant managers face a critical question: Is my tank still safe to operate? Across TCR Engineering, TCR Advanced and TCR Arabia, we answer this question with a standards-based condition assessment.
"Storage tank integrity is not just about compliance; it is about keeping the asset sound, the operation running and, most importantly, people safe," says Paresh Haribhakti, Managing Director of TCR Advanced. "Our approach combines rigorous technical standards with practical industry experience, so that each assessment stands on its evidence."
Understanding the Critical Need for Tank Condition Assessment
Storage tanks (whether containing water, chemicals, petroleum products, or wastewater) are subjected to continuous operational stresses. Corrosion, settlement, thermal cycling, and mechanical loading all take their toll over time. Without proper assessment and monitoring, seemingly minor defects can escalate into catastrophic failures.
The consequences of tank failure extend far beyond the immediate loss of contents. Production shutdowns, environmental contamination, regulatory penalties, and potential injuries create cascading impacts that can affect operations for months or even years.
TCR's Assessment Methodology
Tank condition assessment across the TCR group follows a systematic, standards-based approach, applied on projects in India and Saudi Arabia.
1. Visual Inspection and Documentation
Every assessment begins with a thorough visual inspection, conducted in accordance with API 653 (Tank Inspection, Repair, Alteration, and Reconstruction). Our certified inspectors examine:
- Tank shell condition: Looking for corrosion, pitting, deformation, or coating degradation
- Roof integrity: Checking for structural damage, leaks, or settlement
- Foundation and settlement: Identifying differential settlement or soil-related issues
- Appurtenances: Assessing nozzles, manholes, vents, and drainage systems
- Corrosion protection systems: Evaluating cathodic protection and coating condition
"The visual inspection is where experience truly matters," notes Haribhakti. "A trained eye can identify potential problem areas that might be missed by less experienced personnel. This guides where we focus our more detailed testing efforts."
2. Ultrasonic Thickness Testing (UTT)
Following API 653 requirements, we conduct systematic ultrasonic thickness measurements to assess remaining wall thickness throughout the tank structure. Our UTT programme includes:
- Shell course measurements: Multiple readings per course, with increased density in suspected corrosion areas
- Bottom plate scanning: Statistical sampling per API RP 575 recommendations, with coverage set by service and condition
- Critical zone focus: Concentrated measurements at known high-corrosion areas such as the critical zone of the bottom next to the shell
- Roof thickness evaluation: For fixed roof tanks, measurements of roof plates and structural members
All measurements are compared against the minimum thickness for continued service that API 653 sets.
3. Structural Stability Analysis
Tank settlement and out-of-roundness can indicate foundation problems or structural overstress. Our assessment includes:
- Settlement survey: Measurements of shell settlement around the tank circumference
- Out-of-roundness measurement: Determining if the tank shell has deformed beyond the acceptable limits of API 653
- Plumbness check: Vertical alignment measurements
- Structural calculations: When necessary, fitness-for-service evaluations per API 579 by TCR Advanced Engineering to determine if observed conditions are acceptable
4. Non-Destructive Testing (NDT) for Defect Characterisation
When visual inspection or thickness testing reveals potential defects, we deploy the NDT methods used in above ground storage tank inspection:
- Magnetic Particle Testing (MT): For detecting surface-breaking cracks in welds and shell plates
- Dye Penetrant Testing (PT): Alternative method for non-magnetic materials
- Radiographic Testing (RT): When internal weld quality must be verified
- Acoustic Emission Testing (AE): For detecting active crack growth during hydrostatic testing
5. Acoustic Emission Testing: TCR's Advanced Monitoring Capability
TCR Advanced carries out Acoustic Emission Testing (AET) of storage tanks, a technique that detects active defects in real-time during tank operation or hydrostatic testing.
What is Acoustic Emission Testing?
Acoustic Emission Testing monitors the ultrasonic stress waves released when materials undergo deformation or crack growth. Unlike other NDT methods that detect existing defects, AET identifies active damage as it occurs.
Key Advantages of AET for Storage Tanks:
- Real-time monitoring: Detects defects during operation or hydrostatic testing
- Global coverage: A few strategically placed sensors can monitor the entire tank structure
- No surface preparation: Can be performed on coated, insulated, or operational tanks
- Active defect detection: Identifies cracks that are actively growing, not just existing damage
- In-service capability: No need for tank shutdown in many cases
TCR's AET Capabilities:
- Tank floor examination to ISO 24489:2024, and tank shell monitoring during filling to ASTM E1930/E1930M-25
- Leak detection during tank filling operations
- Weld integrity assessment during proof testing
- Crack growth monitoring on tanks with known defects
- Fitness-for-service evaluation by TCR Advanced Engineering for tanks operating beyond design life
"Acoustic Emission Testing is particularly valuable for critical tanks that cannot easily be taken out of service," explains Haribhakti. "We can assess tank integrity while it remains in service, identifying areas of concern that warrant closer inspection during the next scheduled outage. That lets an owner plan the outage around what the tank actually needs."
TCR's acoustic emission technicians are certified Level II to SNT-TC-1A, and the system's signal processing separates relevant indications from environmental noise.
Real-World Application: Industrial Wastewater Treatment Facility Case Study
TCR Advanced's systematic approach was recently demonstrated in a comprehensive condition assessment of a wastewater treatment plant tank for a major industrial facility in India.
Project Scope:
- Industry: Environmental technology and wastewater treatment
- Facility: Large-scale wastewater treatment plant
- Assessment objective: Determine structural integrity and remaining service life
- Standards applied: API 653, API 650, API RP 575, ASME Section VIII
Assessment Activities:
Our team conducted a complete inspection programme including:
- External visual inspection of the entire tank structure
- Internal inspection of shell, bottom, and roof (following proper confined space protocols)
- Ultrasonic thickness measurements at strategic locations throughout the shell and bottom
- Settlement and out-of-roundness surveys
- Weld integrity assessment at critical connections
- Foundation condition evaluation
- Fitness-for-service calculations by TCR Advanced Engineering based on measured conditions
Key Findings:
The assessment revealed localised corrosion in the bottom plates near drainage points, minor settlement within acceptable limits per API 653, and shell thickness generally above minimum required values. Based on corrosion rate calculations, we provided recommendations for:
- Localised bottom plate repairs in affected areas
- Enhanced cathodic protection in identified zones
- Revised inspection interval based on observed corrosion rates
- Operational modifications to minimise corrosion acceleration
"This project exemplifies our approach," explains Haribhakti. "We don't just identify problems; we recommend practical repairs that extend asset life and keep the tank within its code."
Beyond Tanks: Grain Storage Silo Assessment
TCR Advanced's work extends beyond liquid storage tanks to grain storage silos, demonstrating our comprehensive capabilities in assessing diverse storage structures across multiple industries.
The Distinct Challenges of Grain Storage Silos
Grain storage silos present distinct assessment challenges compared to liquid storage tanks:
- Corrugated steel construction: Bolted corrugated plates require specialised inspection techniques
- Abrasive grain loading: Causes wear and thinning at specific stress points
- Moisture and condensation: Creates localised corrosion patterns
- Foundation settlement: More critical due to concentrated loading
- Structural stability: Requires analysis of columns, beams, roof systems, and foundations
TCR's Silo Assessment Methodology
Our grain silo assessment follows a comprehensive protocol developed through field experience:
1. On-Site Visual Inspection
- Exterior examination: Assessment of corrugated plates, bolted connections, coating condition, and structural supports
- Interior examination: Evaluation of internal surfaces, wear patterns, and structural members
- Foundation inspection: Checking anchor bolts, grout conditions, and settlement indicators
- Roof system evaluation: Assessing roof plates, support structures, and ventilation systems
- Conveyor and equipment assessment: Examining material handling systems and access platforms
2. Ultrasonic Thickness Measurements
We conduct systematic thickness measurements at multiple elevations throughout the silo structure:
- Shell plates: Measurements at each corrugation level from bottom to top
- Roof plates: Random sampling across the roof area
- Foundation plates: Assessment of base support structures
- Critical wear areas: Enhanced measurement density at high-stress locations
In a recent 10,000 MT capacity grain silo assessment, our team recorded shell plate thickness at every elevation from the bottom course to the top.
3. Material Testing and Laboratory Analysis
Sample collection and laboratory testing provide critical information about material condition and remaining life:
- Chemical analysis: Verification of material grade compliance (typically EN 10346-2009 Grade S350GD for galvanised steel silos)
- Tensile testing: Confirming mechanical properties meet original specifications
- Coating thickness measurement: Assessing remaining galvanisation protection
- Microstructural examination: Evaluating material condition and detecting degradation
- Hardness testing: Verifying material strength properties
- Dye Penetrant Testing (DPT): Surface crack detection on shell plates and connections
- Wet Fluorescent Magnetic Particle Inspection (WFMPI): Assessing fasteners and structural bolts for cracks
- Visual weld examination: Evaluating bolted joint integrity
5. Structural Stability Assessment
A critical component of silo assessment is the structural stability analysis that supports the stability certificate:
- Load analysis: Verification of capacity for design grain loading
- Foundation adequacy: Assessment of bearing capacity and settlement
- Structural member stress analysis: Evaluation of columns, beams, and bracing
- Stability certificate: the evidence for the stability certificate required by regulatory authorities, signed by a chartered structural engineer
Recent Grain Silo Assessment Project
TCR Advanced recently completed a comprehensive condition assessment, with the evidence for its stability certificate, for a 10,000 MT capacity grain storage silo.
Project Highlights:
- Structure: cylindrical silo with a dome roof
- Construction: Corrugated galvanised steel plates with bolted connections
- Capacity: 10,000 MT of grain
- Scope: Complete condition assessment with the evidence for the stability certificate
Assessment Results:
- Shell plate thickness within acceptable limits at every elevation
- Roof plate thickness measured across the roof area
- Material testing confirmed compliance with EN 10346-2009 Grade S350GD
- Galvanised coating thickness adequate for continued protection
- Tensile properties above the minimum requirements of the grade
- No significant defects detected through DPT or WFMPI testing
- Foundation and structural members found stable
Conclusion: Structure deemed safe and stable for continued operation at design capacity, with recommendations for routine monitoring and minor maintenance items.
"Grain storage silos require a different assessment approach than liquid tanks, but the fundamental principles of thorough inspection and engineering analysis remain the same," notes Haribhakti. "Our experience across both tank and silo assessments allows us to provide comprehensive asset integrity services to the food processing, agriculture, and storage industries."
What Does a Tank Integrity Assessment Establish?
TCR plans each assessment from the tank's design records, operating history and earlier inspection reports, and uses API 580 (Risk-Based Inspection) principles where the owner ranks tanks by risk. The report a plant engineer receives states:
- the condition of the shell, bottom, roof, foundation and appurtenances, with photographic evidence
- thickness data compared with the acceptance criteria of the applicable code
- remaining life from the measured corrosion rates, with a fitness-for-service evaluation to API 579 by TCR Advanced Engineering where a defect is found
- repair recommendations in order of priority
- the next inspection interval to API 653
API Standards: The Foundation of Our Assessments
TCR's assessment methodologies are built on industry-recognised API (American Petroleum Institute) standards that represent global best practices:
API 653 - Tank Inspection, Repair, Alteration, and Reconstruction
This is our primary reference for inspection intervals, acceptance criteria, and repair standards. It provides specific requirements for minimum shell thickness, settlement limits, repair procedures, and fitness-for-service evaluations.
API 650 - Welded Tanks for Oil Storage
Used for design verification and minimum thickness calculations.
API RP 575 - Inspection Practices for Atmospheric and Low-Pressure Storage Tanks
Provides recommended practices for inspection planning, damage mechanisms, and inspection techniques. Particularly valuable for statistical sampling approaches for bottom plate inspection.
API 580 - Risk-Based Inspection
Enables us to prioritise inspection activities based on consequence and probability of failure, optimising client resources while maintaining safety.
API 579 - Fitness-For-Service
Used when tanks have localised thin areas, dents, or other conditions that don't meet standard acceptance criteria. Provides engineering methodology to determine if the tank can safely continue operating despite these conditions.
"Adherence to these standards isn't optional; it is fundamental to providing defensible assessments," emphasises Haribhakti. "When we tell a client their tank is fit for service, that conclusion is backed by internationally recognised engineering standards."
The Future of Tank Inspection: TCR's Investment in Robotic Technology
While traditional inspection methods remain essential, TCR Advanced is investing in robotic inspection technology. The TCR Group has invested in a current-generation startup company developing robotic inspection systems specifically designed for storage tank applications.
In-Service Robotic Tank Bottom Inspection
The ITAS Rover, the startup's robotic rover system, can inspect tank bottoms while tanks remain in service, without a shutdown, cleaning or degassing. Key capabilities include:
Technical Specifications:
- Deployment through a standard roof manhole
- ATEX-certified and PESO-approved for explosive atmospheres
- Deployable on tanks up to 25 metres in height and 100 metres in diameter
- Ultrasonic thickness measurement with an 8-transducer array
- Navigation system that positions the rover on the tank floor
- Coverage: statistical sampling of the bottom area to API RP 575
- Extreme Value Analysis (EVA) software for remaining life predictions
Operational Advantages:
- No tank shutdown required, so production continues
- No cleaning or degassing
- No confined space entry, which removes that hazard
"The operational case is clear," notes Haribhakti. "For a floating roof tank, conventional inspection means a long period out of service plus cleaning and degassing. Robotic inspection completes the floor assessment with the tank in operation. For refineries and chemical plants, that means the tank keeps working through the inspection."
Robotic External Shell Inspection
The rover technology of that startup addresses another major challenge: external shell inspection on tall tanks where traditional methods require extensive scaffolding.
Rover Capabilities:
- Magnetic wheel drive for vertical and horizontal movement on tank shells
- Non-contact ultrasonic probes for continuous thickness scanning
- Eliminates need for scaffolding and work-at-height hazards
- PESO-approved for hazardous area operation
- Can also inspect pressure vessels, pipelines, and boiler tubes
Safety and Efficiency Benefits:
- Eliminates work-at-height risks
- No scaffolding required
- Comprehensive thickness mapping rather than spot measurements
- Can inspect tanks that are difficult to access with conventional methods
Data Analytics and Reporting
The robotic inspection systems integrate with advanced software platforms that provide:
- Real-time data visualisation during inspection
- Automated thickness mapping and heat map generation
- Extreme Value Analysis for statistical prediction of minimum remaining thickness
- Online reporting portals for interactive data review
- AI-powered defect detection and characterisation
- Historical data trending for corrosion rate analysis
"We are not replacing human judgement; we are supporting it with better data," explains Haribhakti. "The combination of our engineers' experience and this technology gives clients a fuller picture of their asset condition."
Why Choose TCR for Your Tank Assessment Needs
Certifications: Our inspection team holds NDT certifications to SNT-TC-1A and certifications from IOSH (Institution of Occupational Safety and Health), and has completed API 653 Tank Inspector training. We understand not just the testing methods, but the standards that govern acceptance criteria.
Comprehensive Service: From initial assessment through repair recommendations and re-inspection, TCR Engineering, TCR Advanced Engineering and TCR Arabia provide complete tank integrity management services, with external partners and associate firms. We can also coordinate repairs through our network of qualified contractors.
Technology: Our investment in robotic inspection technology and in techniques such as Acoustic Emission Testing serves our clients.
Industry Experience: With projects across refineries, chemical plants, tank terminals, grain storage facilities, and industrial facilities throughout India, we understand the unique challenges of different industries and operating environments.
Practical Recommendations: We provide actionable recommendations that balance safety, cost, and operational requirements. Our goal is to help you maximise asset life while maintaining safe, compliant operations.
Conclusion: Assess the Tank Before It Fails
Regular condition assessments give a tank owner the information to identify problems while they are still manageable and to plan maintenance around them.
"Don't wait for a leak or failure to find out your tank has problems," advises Haribhakti. "Proactive assessment, conducted by qualified professionals to recognised standards, finds problems while they can still be planned for, not handled as a crisis. More importantly, it is the responsible approach to the safety of your people, your assets and your operations."
Whether you operate a single tank or many across several facilities, the TCR group assesses each one to the same API standards.
About Paresh Haribhakti
Paresh Haribhakti is the Managing Director of TCR Advanced, an engineering testing and inspection services company based in India. With experience in asset integrity management and non-destructive testing, Paresh has led TCR Advanced's expansion into current-generation inspection technologies while maintaining the company's commitment to rigorous technical standards. Under his leadership, TCR Advanced combines traditional engineering with innovative solutions for clients across the petroleum, chemical, food processing, and industrial sectors.
Contact TCR Advanced
For more information about storage tank condition assessment services or to schedule an inspection, contact TCR Advanced.
Frequently Asked Questions About Storage Tank Condition Assessment
How often should storage tanks be inspected?
Inspection frequency depends on tank service, age, corrosion rate and regulatory requirements. API 653 sets the maximum intervals for external and internal inspections from the measured corrosion rate and remaining thickness, and a risk-based inspection assessment can set the internal interval instead. TCR sets the schedule for each tank from its own condition and history.
Can tanks be inspected while in service?
Yes, many inspection activities can be performed on in-service tanks. External visual inspection, thickness testing, settlement surveys, and Acoustic Emission Testing can all be done while tanks operate. TCR's robotic inspection technology enables bottom plate assessment of in-service tanks without shutdown. However, internal inspections still require the tank to be emptied, cleaned, and gas-freed per API 653 requirements.
What is Acoustic Emission Testing and when should it be used?
Acoustic Emission Testing (AET) monitors ultrasonic stress waves released when materials deform or crack. It is particularly valuable for detecting active defects during hydrostatic testing or monitoring tanks with known defects during operation. TCR Advanced recommends AET for critical tanks where shutdown costs are high, tanks with suspected cracking, or as part of fitness-for-service evaluation for aged tanks. AET can be performed while tanks remain in service, providing real-time integrity assessment.
What happens if my tank doesn't meet API 653 requirements?
If a tank doesn't meet standard acceptance criteria, it doesn't automatically mean the tank must be taken out of service. TCR Advanced can perform a fitness-for-service evaluation per API 579 to determine if the tank can safely continue operating at reduced capacity or with operational modifications. We provide detailed recommendations including repair options, operational restrictions, and revised inspection intervals. Our goal is to help you make informed decisions that balance safety and economics.
What does robotic tank inspection avoid compared with traditional methods?
Robotic inspection measures the tank floor with the tank in service, so it avoids the shutdown, cleaning, degassing and confined space entry that a traditional internal inspection needs. Whether a robotic inspection suits a given tank depends on its product, roof type and access, which TCR checks before the job is planned.
What are the most common causes of tank failure?
The most common causes we encounter are: bottom plate corrosion (especially in the annular ring and areas near drains), foundation settlement causing shell distortion and leaks, corrosion of the bottom shell course, weld cracking due to thermal cycling or settlement, and roof collapse due to vacuum conditions or snow loading. Regular assessment helps identify these conditions before they become critical.
Can TCR Advanced help with tank repairs, or just inspections?
While TCR Advanced specialises in assessment and inspection services, we work closely with qualified repair contractors and can help coordinate repairs based on our findings. We can provide detailed repair specifications, review repair procedures for code compliance, and perform post-repair inspection to verify work quality. This gives continuity from assessment through repair completion.
How does grain silo assessment differ from liquid tank assessment?
Grain silos require different assessment approaches due to their bolted corrugated construction, different loading patterns (dry bulk vs. liquid), and unique corrosion/wear patterns. Silo assessment focuses more on bolted connections, wear at discharge points, foundation loading, and structural stability of the support system. TCR Advanced applies appropriate standards (EN, ASTM) for silos while following similar systematic assessment principles. We also provide the evidence for the stability certificate required for grain storage facilities in India, signed by a chartered structural engineer.
What documentation will I receive after the assessment?
TCR provides a comprehensive report including: executive summary with condition rating, detailed findings with photographs, thickness measurement data with statistical analysis, comparison to code requirements, specific repair recommendations with priority levels, and the next inspection interval recommendation. For grain silos, we also provide the evidence for the stability certificate required by regulatory authorities, signed by a chartered structural engineer.