Recommendations for Maintenance and Operation of Petroleum Storage Tanks, Part 2: Inspection

IS 9964 Part 2 (1981) - Scope Summary with Key Tables & Forms

The scope covers inspection and maintenance planning for atmospheric storage tanks, focusing on:

Key Components:

• Internal & External Inspections (Appendix A, B, C)
• Inspection Reporting (Appendix D, F)
• Testing Methods (Pneumatic test - Appendix E)
• Roof Structure Measurements (Appendix G)

Important Tables & Forms:

Typical Inspection Checklist (Appendix D):

• Roof (Fixed/Floating, Pontoon)
• Ladders, Hinges, Nozzles
• Vents, Breather valves, Splash plates
• Spray risers, Foam connections
• Manholes, Level indicators, Handrails
• Insulation and painting condition

Ultrasonic Thickness (Appendix F) Sample:

Pneumatic Test Setup (Appendix E):

• Use U-tube pressure indicator
• Apply air pressure between bottom and base
• Observe for leaks or deformation

This scope ensures systematic inspection, maintenance, and documentation for tank safety and longevity.

Statutory Requirements per IS 9964 Part 2 (1981)

• Compliance: Mandatory adherence to Factory Act 1948, Petroleum Act, and related rules for inspection, maintenance, and operation of atmospheric storage tanks (Clause 2.1).
• Inspection Planning: Use long-term and yearly planning sheets for scheduling internal tank inspections (Appendix B & C, Clause 6.1).
• Inspection Reporting: Detailed inspection reports covering roof, shell, nozzles, vents, valves, and other accessories with observations and repairs (Appendices A, B, D).
• Typical Inspection Report Items:
  • Roof structure (fixed/floating)
  • Suction/inlet devices
  • Vents, valves, and manholes
  • Level indicators, ladders, handrails
  • Coils, nozzles, insulation, and painting

Key Tables (Examples)

Recommended Inspection Cycle (Typical)

Summary Diagram: Inspection & Compliance Workflow

flowchart TD
    A[Statutory Acts Compliance] --> B[Inspection Planning]
    B --> C[Internal Inspection]
    B --> D[External Inspection]
    C --> E[Inspection Report]
    D --> E
    E --> F[Repairs & Maintenance]
    F --> G[Next Inspection Scheduling]

Note: For detailed inspection checklists and planning sheets, refer to Appendices A-D of IS 9964 Part 2.

Purpose of Inspection (IS 9964 Part 2 - 1981)

Inspection aims:

• Assess tank condition (internal/external)
• Identify corrosion, leaks, structural damage
• Plan maintenance and repairs
• Ensure safety and serviceability

Key Documents for Inspection Planning (Clause 6.1):

Typical Inspection Report Elements (Appendix D):

Inspection Planning Sheet (Appendix B Example):

Summary

• Use planning sheets for systematic inspections.
• Maintain detailed inspection reports for tracking.
• Schedule inspections based on tank type, age, and condition.
• Focus on critical components: roof, shell, nozzles, and safety devices.

flowchart TD
    A[Inspection Purpose] --> B[Planning Sheets]
    B --> C[Long-term (Appendix B)]
    B --> D[Yearly (Appendix C)]
    A --> E[Inspection Report (Appendix D)]
    E --> F[Observations]
    E --> G[Repairs]

This structured approach ensures effective monitoring and maintenance of atmospheric tanks per IS 9964 Part 2.

IS 9964 Part 2 - Frequency of Inspection for Storage Tanks

Key Points from Clause 4.3 (Table 4):

Clause 4.1 - Factors Determining Inspection Frequency:

• Nature of stored material
• Visual maintenance check results
• Corrosion rates and allowance
• Previous inspection conditions
• Construction and repair methods/materials
• Tank location and environment (acidic atmospheres, high-risk areas)

Summary:

• External ultrasonic thickness measurement: Generally every 5 years for most products.
• Internal inspection: Varies from 5 to 10 years depending on product corrosiveness and tank type.
• Use inspection planning sheets (Appendix B & C) for scheduling.
• Inspection reports should document observations and repairs (Appendix D).

Practical Note:

Adjust inspection frequency based on corrosion rates and operational conditions to ensure safety and integrity.

flowchart TD
    A[Tank in Service] --> B{Inspection Due?}
    B -- Yes --> C[External Ultrasonic Measurement]
    C --> D{Corrosion Rate Acceptable?}
    D -- Yes --> E[Schedule

IS 9964 Part 2 - Planning of Inspection & Record Keeping

Key Documents for Inspection Planning (Clause 6.1)

• Long Term Planning Sheet (Appendix B): Tracks internal tank inspections over multiple years.
• Yearly Planning Sheet (Appendix C): Schedules inspections month-wise for each tank.
• Inspection & Repair Report (Appendix D): Records detailed observations and repairs.

Typical Long-Term Planning Sheet (Appendix B)

Inspection & Repair Report Format (Appendix D)

• Includes date of inspection, year of construction, previous inspections, type of inspection (internal/external).
• Recommended next inspection date and expected repairs are noted.

Additional Notes

• Visual Inspections are mandated by Factories Act 1948 (Section 31).
• Records must include extent of inspection, findings, and recommendations.
• Inspection must be by a competent person with certification (Appendix A format).

flowchart TD
    A[Start: Inspection Planning] --> B[Use Long-Term Planning Sheet]
    B --> C[Schedule Yearly Inspections]
    C --> D[Conduct Inspection]
    D --> E[Record Observations & Repairs]
    E --> F[Prepare Inspection Report]
    F --> G[Plan Next Inspection]

Summary:
Use Appendices B, C, D for systematic planning, scheduling, and recording tank inspections and repairs. Maintain certified records as per

IS 9964 Part 2 — Inspection of Tank Bottom: Key Points

Inspection Procedure (Clause 7.2)

• Visual check: Look for pitting, scale, and rivet condition (for riveted tanks).
• Thickness measurement: Use ultrasonic thickness gauge.
• Measurement locations:
  • 1 at bottom center
  • 5 towards outer periphery
  • 4 in intermediate areas
• Purpose: Assess corrosion and wear for maintenance planning.

Inspection Report Format (Clause 5.2, Appendix A)

Planning Sheets (Appendix B & C)

• Long-term and yearly inspection planning sheets help schedule inspections based on tank type, dimensions, and product stored.
• Enables systematic record-keeping and maintenance forecasting.

Summary Table for Thickness Measurement Locations

Recommendations

• Maintain detailed records including painting, product stored, and previous repairs (Clause 6.2).
• Use inspection data to schedule repairs and next inspection dates.

flowchart TD
    A[Visual Inspection] --> B[Ultrasonic Thickness Measurement]
    B --> C{Thickness OK?}
    C -- Yes --> D[Record Data, Schedule Next Inspection]
    C -- No --> E[Plan Repairs]
    E --> D

Summary: IS 9964 Part 2 emphasizes systematic visual and ultrasonic inspection of tank bottoms, with specified measurement points and detailed reporting formats to ensure safe and reliable

Leak Testing of Tank Bottom (IS 9964 Part 2 - Clause 8)

Key Specifications & Procedure:

• Pneumatic Leak Test (Clause 8.3 & Appendix E):

  • Install air connections at at least 5 points under the tank bottom.
  • Build a dam of clay or bitumen-sand mixture ~20 cm high around the tank near the shell wall.
  • Maintain an air pressure of 10 cm water column beneath the tank bottom.
  • Fill space between dam and tank wall with fresh water to create a seal.
  • Apply soap suds on all joints to visually detect leaks.

• Vacuum Box Test (Clause 8.1):

  • Used after repairs on bottom plates.
  • Detects leaks by visual examination.
  • Performed before surface coating and hydrotesting.

Pneumatic Test Setup (Appendix E):

flowchart LR
    A[Air Supply Line] --> B[Air Connections (5 points)]
    B --> C[Space under tank bottom]
    C --> D[Dam of clay/bitumen-sand ~20 cm high]
    D --> E[Water seal between dam and tank wall]
    C --> F[Maintain 10 cm water pressure]
    F --> G[Apply soap suds on joints for leak detection]

Important Notes:

• Testing must be done immediately after welding repairs.
• Ensure no surface coating or water filling before leak testing.
• Rivet heads should be checked per Clause 7.5 (reject if head thickness/diameter < 50%).

This ensures early detection of leaks preventing costly failures.

Inspection of Tank Shell as per IS 9964 Part 2 (1981)

Key Specifications & Tables

• Ultrasonic Thickness Measurement (Appendix E, Clause 8.3):
  • Shell thickness measured externally (inside if insulated).
  • Welding efficiency, E = 0.95 (butt welded).
  • Minimum allowable thickness values are tabulated per shell course, e.g.:

• Pneumatic Test Setup (Fig. 3, Appendix E):
  • Use U-tube pressure indicator and air supply line to check shell integrity.

Inspection Reporting (Appendix F & D)

• Record shell thickness, welding type, and efficiency.
• Note all observations and repairs executed on shell components (manholes, nozzles, ladders, insulation, etc.).
• Maintain reports for future reference.

Recommended Practices

• Use ultrasonic testing for shell thickness.
• Follow rejection limits based on minimum allowable thickness.
• Plan inspections using long-term and yearly planning sheets (Appendices B & C).

flowchart TD
    A[Start Inspection] --> B[Visual Inspection]
    B --> C[Ultrasonic Thickness Measurement]
    C --> D{Thickness ≥ Min Allowable?}
    D -- Yes --> E[Record & Monitor]
    D -- No --> F[Plan Repairs]
    F --> G[Execute Repairs]
    G --> H[Update Inspection Report]
    E --> H
    H --> I[Schedule Next Inspection]

Summary: Use ultrasonic testing to measure shell thickness against min allowable values, perform pneumatic tests for shell integrity, document all findings and repairs, and plan inspections systematically.

IS 9964 Part 2: Inspection of Welded and Riveted Tanks

Key Specifications & Tables

1. Ultrasonic Thickness Measurement (Clause 8.3, Appendix E)

• Welded Joint Efficiency, E = 0.95
• Shell thickness measurement from outside (inside if insulated).
• Minimum allowable thickness based on original nominal thickness and steel grade (S=200 MPa).

(Refer to Appendix E Table for detailed values)

2. Pneumatic Test Setup (Clause 8.3, Appendix E)

• Use U-tube pressure indicator and air supply line.
• Ensure space between bottom and base is monitored for deformation.
• Test pressure and duration as per design and safety guidelines.

3. Inspection Reports & Planning

• Appendix A (Clause 5.2): External inspection report format includes tank type, size, date, and recommendations.
• Appendix B (Clause 6.1): Long-term internal inspection planning sheet (year-wise).
• Appendix D (Clause 6.1): Detailed inspection and repair report including roof, shell, nozzles, insulation, and fittings.

Important Notes:

• For riveted tanks (Clause 10.3), inspection focuses on rivet condition, corrosion, and joint tightness.
• Ultrasonic thickness testing is critical for assessing corrosion and remaining life.
• Pneumatic testing is preferred for leak detection without liquid.

flowchart LR
    A[Start Inspection] --> B{Tank Type}
    B -->|Welded| C[Ultrasonic Thickness Test]
    B -->|Riveted| D[Visual & Rivet Tightness Check]
    C --> E[Pneumatic Test Setup]
    D --> E
    E

Inspection of Roof and Roof-Supporting Structures (IS 9964 Part 2, Clause 11)

Key Points & Specifications:

• Visual Inspection:

  • Usually done from tank bottom using binoculars.
  • For cone roofs, detailed inspection requires scaffolding and cutting a hole in the roof.

• Measurement & Acceptance Criteria:

  • When corrosion/distortion is observed, measure thickness and dimensions.
  • Reject supporting members if material loss > 25%.
  • Examine welds and bolts for damage.

• Roof Plate Condition & Repair:

  • If average thickness is above minimum and only scattered holes exist, patching is allowed.
  • Renewed plates must be tested per subsequent clauses.

Appendix G:

• Provides a template for recording measurements on sag members, tie members, and main rafters.
• These records must be filed with the inspection report.

Summary Table for Member Rejection Criteria

Inspection Flow (Mermaid Diagram)

flowchart TD
    A[Visual Inspection from Tank Bottom] --> B{Corrosion or Distortion Observed?}
    B -- No --> C[Record and File Inspection Report]
    B -- Yes --> D[Measure Thickness & Dimensions]
    D --> E{Material Loss > 25%?}
    E -- Yes --> F[Reject Member]
    E -- No --> G[Examine Welds and Bolts]
    G --> H{Damage Found?}
    H -- Yes --> F
    H -- No --> I{Roof Plate Condition}
    I -- Above Minimum Thickness & Scattered Holes --> J[Patch Roof]
    I -- Below Minimum Thickness or Extensive Damage --> K[Renew Roof Plates & Test]
    J --> C
    K --> C

This ensures structural integrity and safe operation of tank roofs per IS 9964 Part 2.

Inspection of Tank Fittings as per IS 9964 Part 2 (1981) includes:

Key Specifications & Tests:

• Roof Drain (Clause 11.3.4):
  • Hydrostatic test at 3.5 kg/cm² gauge pressure
  • Check carefully for leakage

Inspection Reporting (Appendix A & D):

• Use Atmospheric Tank Inspection Report including:

  • Tank No., Type (Cone/Floating/Welded/Insulated)
  • Diameter, Date of Inspection, Last Inspection
  • Condition & remarks on fittings such as nozzles, level indicators, roof water pipes, etc.

• Tank Inspection & Repairs Report (Appendix D) covers:

  • Roof structure, ladders, vents, valves, manholes, nozzles, heating coils, insulation painting, etc.
  • Columns for Inspection Observations and Repairs Executed

Ultrasonic Thickness Measurement (Appendix F):

• Shell thickness measured externally (or internally if insulated)
• Minimum allowable thickness based on nominal thickness and steel grade (S=200 MPa, welding efficiency E=0.95)
• Example thickness table (in mm):

Pneumatic Test (Appendix E):

• Use U-tube pressure indicator and air supply line
• Observe space between bottom and base under air pressure to detect leaks

Summary Table: Inspection Tests for Tank Fittings

This structured inspection ensures tank fittings integrity and safety compliance per IS 9964 Part

Inspection of Tank Foundation per IS 9964 Part 2 (1981)

Key Formula for Maximum Allowable Sag (Clause 3.75)

[ f = \sqrt{(100 f_0)^2 + 3.75 D} ]

• f = Maximum allowable sag in tank bottom (cm)
• f₀ = Deflection at bottom center relative to bottom curb (cm), can be positive, zero, or negative
• D = Diameter of tank (cm)

If sag exceeds f, stresses at the bottom-shell joint may become excessive. Remedy: lift tank and re-pack foundation.

Tilting Limits (Clause 3.75 & Fig. 2)

• Maximum allowable tilting increases hoop stress by 2%.
• Exceeding tilting limits requires lifting tank and re-leveling foundation.
• Floating roofs may become inoperable before these limits.

Inspection Guidelines (Clauses 13.1 & 13.2)

• Settlement: Inspect regularly for even/uneven settlement; continuous settlement signals subsoil weakness.
• Erosion: Protect raised foundations with sand-bitumen sealing; repair damage promptly.
• Remedial Actions: Jack up low parts and repack with clean sand or lift tank for foundation leveling.

Inspection Reporting (Appendix A & B)

• Use Atmospheric Tank Inspection Report (Clause 5.2) to record:
  • Tank type, diameter, inspection dates
  • Foundation, nozzles, pipes, coatings status
• Use Long-term Planning Sheet (Appendix B) for periodic internal inspections.

flowchart TD
    A[Inspect Tank Foundation] --> B{Check Sag (f)}
    B -->|f ≤ allowable| C[Continue Monitoring]
    B -->|f > allowable| D[Lift Tank & Repack Foundation]
    A --> E{Check Tilting}
    E -->|Within Limits| C
    E -->|Exceeds Limits| D
    A --> F{Check Settlement and Erosion}
    F -->|Minor| C
    F -->|Major| D

Summary: Regular inspection of sag, tilting, settlement, and erosion per IS 9964 Part 2 is critical. Use formula for max sag, monitor tilting limits, and take timely remedial action to ensure tank

IS 9964 Part 2: Inspection of Tank Insulation - Key Points

• Clause 14.1:

  • Inspect waterproof sealing of tank insulation annually and after rainy season.
  • Moisture ingress reduces insulation efficiency and causes hidden corrosion of tank plates.
  • If moisture is suspected, uncover a small plate area to check for corrosion.

• Inspection Report (Appendix A, Clause 5.2):
  Use the Atmospheric Tank Inspection Report format including:

  • Tank No., Type (Cone/Floating/Welded/Insulated)
  • Date inspected, last inspection date
  • Size (Diameter)
  • Condition of bottom, foundation, nozzles, pipe connections, insulation, etc.
  • Recommendations

• Planning Sheets (Appendices B & C):

  • Long-term and yearly planning sheets for internal and external inspections to schedule and record inspections systematically.

• Inspection Observations & Repairs (Appendix D):

  • Detailed checklist for roof, shell, insulation, nozzles, valves, ladders, painting, and other components.
  • Record repairs executed and recommendations for next inspection.

Summary Table: Inspection Frequency & Actions

Important Formula for Tank Bottom Sag (Clause 3.75)

[ f = (100 f_0)^2 + 3.75 D ]

• (f) = max allowable sag (cm)
• (D) = tank diameter (cm)
• (f_0) = deflection of bottom center (cm) relative to bottom curb

If sag exceeds (f), foundation repacking or tank lifting is needed.

flowchart TD
    A[Annual Inspection] --> B{Waterproof Sealing Intact?}
    B -- Yes --> C[Continue with Routine Checks]
    B

IS 9964 Part 2 – Long Term Planning Sheet for Internal Tank Inspection

Key Documents (Clause 6.1)

• Appendix B: Long Term Planning Sheet (multi-year schedule)
• Appendix C: Yearly Planning Sheet (detailed monthly plan)
• Appendix D: Inspection & Repair Report format

Long Term Planning Sheet (Appendix B)

• DXH: Diameter (D) and Height (H) in meters.
• Tracks inspection years and schedules future inspections.
• Helps plan internal inspections over long periods (e.g., 10 years).

Inspection & Repair Report (Appendix D)

• Detailed checklist for all tank components.
• Records condition and maintenance actions.
• Includes recommended date for next inspection.

Ultrasonic Thickness Measurement (Appendix F)

• Used to monitor corrosion and thinning.
• Measurements mostly external; internal if insulated.

Summary

• Use Appendix B for multi-year inspection planning.
• Use Appendix C for detailed monthly scheduling.
• Use Appendix D for documenting inspection results and repairs.
• Ultrasonic thickness checks to

IS 9964 Part 2 (1981) — Yearly Planning Sheet for Internal Tank Inspection

Key Documents (Clause 6.1)

• Appendix B: Long-term planning sheet for internal inspections.
• Appendix C: Yearly planning sheet (typical example).
• Appendix D: Report format for tank inspections and repairs.

Yearly Planning Sheet (Appendix C)

• Columns include:
  • Tank No., Type, Dimensions (Diameter DX, Height H)
  • Product stored
  • Monthly inspection schedule (Jan to Dec)
  • Remarks for each tank

Inspection Frequency (Clause 4.3)

Inspection & Repair Report (Appendix D)

• Details to record:
  • Inspection date, year of construction, previous inspections
  • Type of inspection (internal/external)
  • Observations & repairs on components like roof, nozzles, insulation, ladders, valves, etc.
  • Recommended next inspection date and expected repairs

Summary

• Use Appendix C yearly planning sheet for scheduling internal inspections.
• Follow frequencies in Clause 4.3 based on tank type and product.
• Document findings and repairs as per Appendix D.

flowchart TD
    A[Start: Tank Inventory] --> B[Fill Yearly Planning Sheet (Appx C)]
    B