Code of practice for design, fabrication, testing and installation of underground/above-ground horizontalcylindrical storage tanks for petroleum products

IS 10987 - Scope: Key Specifications & Tables

Scope:
IS 10987 guides design, fabrication, and inspection of horizontal underground and above-ground storage tanks with flat ends.

Key Specifications:

• Tank Sizes: No fixed sizes; assists purchaser in selecting tank size per need.
• Material Thickness (mm):
  • Wear Plate: 6-8 mm
  • Shell Plate: 5-6 mm (8 mm optional)
  • End Plate: 6-10 mm depending on capacity
• Steel Grade: Yield strength ~250 MPa (minimum)
• Corrosion Protection: Required for underground tanks (e.g., asphalt doping - Annex C)
• Welding: Continuous fillet welds for joints (shell, coupling, manhole, nozzle, lifting lug)
• Calibration: May be certified by independent authority (Clause 16.2)

Table: Dimensions & Capacities (Excerpt)

Welding Joint Details (Fig. 3 Summary):

• Shell Joints: Continuous fillet welds (longitudinal & circumferential)
• **Shell to Coupling

IS 10987 - Referenced Indian Standards Summary

Clause 16.2 and Annex A list key Indian Standards referenced for materials, welding, and construction related to steel tanks and vessels. These include:

Key Notes:

• Materials and welding consumables must conform to relevant IS codes.
• Calibration of equipment can

IS 10987: Welding Terminology & Symbols Summary

1. Welding Terms (Clause 4.2.1)

• As per IS 812:1957 — Glossary of welding and cutting terms.
• Defines standard welding terminology for uniform understanding.

2. Welding Symbols on Drawings (Clause 4.2.2)

• Follow IS 813:1986 — Scheme of symbols for welding.
• Symbols indicate weld type, size, length, and other details on plans.

3. Key Notations (Fig. 1 - Typical Horizontal Tank Arrangement)

4. Typical Weld Joint Details (Fig. 3)

• Continuous fillet welds for longitudinal/circumferential joints.
• Fillet welds all around manhole/nozzle necks.
• Stiffening details for end plates and lifting lugs.

5. Related IS Standards (Annex A)

• IS 812: Glossary of welding terms.
• IS 813: Welding symbols.
• IS 816: Code of practice for metal arc welding.
• IS 814: Covered electrodes for arc welding.
• IS 9595: Recommendations for metal arc welding carbon steels.

Welding Symbol Example (IS 813)

graph LR
A[Arrow Line] --> B[Reference Line]
B --> C[Basic Weld Symbol]
B --> D[Tail (Optional)]
D --> E[Supplementary Symbols]

Basic weld symbols include:

• Fillet weld: Triangle
• Groove weld: Various groove shapes (V,

IS 10987: Materials & Steel Specifications Summary

1. Steel Material Specifications (Clause 7.1.1)

Steel plates and sections for tank construction must conform to one of the following IS standards:

• IS 226:1975 – Structural steel (Standard quality)
• IS 961:1975 – Structural steel (High tensile)
• IS 2002:1982 – Steel plates for pressure vessels (moderate/low temp)
• IS 2041:1982 – Steel plates for pressure vessels (intermediate/high temp)
• IS 2062:1984 – Weldable structural steel
• IS 8500:1977 – Weldable structural steel (medium & high strength)

Note: Plates per 7.1.1 can be used without impact testing for design metal temperatures down to -10°C.

2. Other Materials (Clause 7.7)

Materials associated with steelwork must conform to relevant Indian Standards when available.

3. Relevant IS Codes for Steel & Welding

4. Key Notes on Welding

• Typical weld joints (longitudinal, circumferential, shell to coupling, manhole/nozzle neck) use continuous fillet welds.
• Lifting lugs: 12mm thick with fillet weld all around.
• Stiffening details for end plates are specified in Fig. 3 of the code.

5. Permissible Stresses (Clause 8)

Refer IS 800:1984 for permissible stresses in structural steel.

**Summary Table

IS 10987 Design Requirements - Key Specifications & Table Summary

1. Tank Dimensions & Thickness (Clause 13.4, Table 9.5)

• Tanks have flat ends, horizontal orientation (underground/above-ground).
• Thicknesses include corrosion allowance; minimum steel yield strength = 250 MPa.
• Thickness varies by nominal capacity (K liters), e.g.:
  • Shell plate thickness (tg): 5-10 mm
  • End plate thickness (te): 6-10 mm
  • Wear plate thickness (tw): 6-8 mm
• Saddle support dimensions and stiffener sizes are specified per capacity.

2. Design Considerations

• Thickness must be checked for soil pressure, fluid pressure, and external loads.
• End plates should preferably be without joints; welded joints must be horizontal.
• Stiffeners are mandatory on end plates (see Fig. 3E in code).
• Corrosion protection mandatory for underground tanks (e.g., asphalt doping per Annex C).
• Design temperature range: **-10°C to

IS 10987: General Arrangements and Dimensions for Storage Tanks

Key Table: Dimensions & Capacities of Horizontal Tanks (Flat Ends)

• UG: Underground tank thickness; AG: Above-ground tank thickness.
• Thickness values include corrosion allowance (steel yield = 250 MPa).
• End plates must have stiffeners as per Fig. 3E (welds horizontal if multiple plates).

Important Notes:

• Actual thickness must consider soil pressure, fluid pressure, and external loads.
• Corrosion

IS 10987: Fabrication and Welding Key Points

Welding Terms & Symbols

• Refer IS 812:1957 for welding terminology.
• Welding symbols per IS 813:1986.

Typical Weld Joint Details (Clause 13.5 & Fig. 3)

• Longitudinal & Circumferential Joints: Continuous fillet welds for shell plates (ts = 5, 6, 8, 10 mm).
• Shell to Coupling Joints: Continuous fillet welds all around.
• Manhole & Nozzle Necks: Fillet welds all around with lifting lugs (12 mm thick).
• Flat Ends & Lifting Lugs: Fillet welds with stiffening details on end plates.

Calibration (Clause 16.2)

• Calibration of welding equipment may be certified by an independent authority if required.

Referenced IS Codes for Welding & Fabrication

Example: Fillet Weld Size for Shell Joints

Summary Diagram of Typical Weld Joint (Fig. 3)

graph TD
A[Shell Plate] -->|Continuous Fillet Weld| B[Longitudinal Joint]
A -->|Continuous Fillet Weld| C[Circumferential Joint]
A -->|Fillet Weld All Around| D[Manhole/Nozzle Neck]
D -->|Attached| E[Lifting Lug (12 mm thick)]
F[Flat End Plate] -->|Fillet Weld + Stiffening| G[End Plate Joint]

For detailed welding procedures, electrode selection, and welder qualification,

IS 10987: Structural Design and Stresses - Key Points

• Permissible Stresses:

  • Maximum stresses in shells and structural members must comply with clauses 8.1.1 to 8.1.3.
  • For stresses in compression, buckling, shear, bearing, etc., refer to IS 800:1984.
  • Steel grades per IS 2002:1982 and IS 2041:1982 are equivalent to IS 226:1975 or IS 2062:1984 for design purposes.
  • Type 2 steel of IS 2041:1982 is equivalent to IS 961:1975.

• Design & Fabrication:

  • Follow IS 800:1984 for permissible stresses, design, fabrication, and erection unless otherwise specified.

Key References from IS 800:1984 (for stresses)

Summary Diagram

flowchart TD
    A[IS 10987 Structural Design] --> B[Permissible Stresses]
    B --> C[Shell & Structural Members (8.1.1-8.1.3)]
    B --> D[Compression, Buckling, Shear (IS 800:1984)]
    D --> E[Steel Grades Equivalence]
    E --> F[IS 2002, IS 2041 ≈ IS 226, IS 2062]
    E --> G[Type 2 Steel (IS 2041) ≈ IS 961]

Note: Always cross-check steel grade equivalence and permissible stresses with the latest IS codes and amendments.

IS 10987: Corrosion Allowance & Protection Summary

Corrosion Allowance (Clause 9.3 & 1.5)

• Minimum corrosion allowance: 1.5 mm on all tank plates (shell, end plates).
• This allowance accounts for corrosion due to environment and stored product.
• Design thickness = Structural thickness + 1.5 mm corrosion allowance.

Thickness & Dimensions (Clause 6.2 & Table 9.5)

• Thickness values in Table 9.5 include the 1.5 mm corrosion allowance.
• Example for 10 KL tank:
  • Shell plate thickness (tg) = 5.0 mm (includes corrosion allowance)
  • End plate thickness (te) = 8.0 mm
• Stiffener sizes and saddle support dimensions are specified for different capacities.

Corrosion Protection (Clause 10)

• Underground tanks must be protected against soil corrosion.
• Protection methods include asphalt coating (Annex C) or other purchaser-specified methods.
• Proper anchorage and coating prevent soil and moisture-related corrosion.

Key Formula for Design Thickness:

[ t_{design} = t_{required} + t_{corrosion\ allowance} ] Where:

• (t_{corrosion\ allowance} = 1.5 \text{ mm (minimum)})

Excerpt from Table 9.5 (Thickness for 10 KL tank):

flowchart LR
    A[Corrosion Allowance: 1.5 mm] --> B[Add to Structural Thickness]
    B --> C[Total Plate Thickness]
    C --> D[Fabrication & Installation]
    D --> E[Corrosion Protection (e.g., Asphalt Coating)]
    E --> F[Long-term Durability of Tank]

Note: Always verify thickness considering soil pressure, fluid pressure, and external loading as per Clause 6.2 Note 2.

IS 10987: Tank Accessories and Mountings – Key Specifications

1. Tank Dimensions & Thickness (Clause 13.4, Table 1)

• Thickness includes corrosion allowance (1.5 mm).
• Actual thickness must consider soil, fluid pressure, and external loads.
• End plates should preferably be without joints; if welded, welds must be horizontal.

2. Corrosion Protection

IS 10987 Installation Requirements: Key Specifications & Table Summary

1. Foundation & Support (Clause 13.4 & Table 9.5)

• Tanks (horizontal, underground/above-ground, flat ends) dimensions & capacities are standardized.
• Thicknesses include corrosion allowance; minimum yield strength = 250 MPa.
• Thicknesses to be verified for soil pressure, fluid pressure & external loads.

2. Corrosion Protection (Clause 10)

• Underground tanks must have corrosion protection (e.g., asphalt coating).
• Purchaser specifies protection type.

3. Tank Anchorage & Inspection (Clause 11 & 15.2)

• Manufacturer supplies all gauges/templates for inspection.
• Calibration can be certified by independent authority (Clause 16.2).

4. Welding & Joint Details (Fig. 3)

• Continuous fillet welds for shell joints.
• Horizontal weld joints for flat ends.
• Stiffeners on end plates per Fig. 3E.

Summary Table Excerpt (Nominal Capacity 5 KL to 50 KL)

| Nominal Capacity (KL) | D (mm) | L (mm) | E (mm) | tw (mm) | tg (mm) | ts (mm) | te (mm) | Stiffener (mm) | B (mm) | C (mm) | Ullage (%) | |----------------------|---------|---------|---------|---------|

IS 10987 Calibration and Measurement - Key Points

• Clause 16.1:

  • Tanks can be calibrated mathematically unless purchaser specifies physical calibration.
  • Physical calibration must follow IS 2009:1975 with certified water.
  • Calibration tables must show volume for every 0.5 cm of filling height.

• Clause 16.2:

  • Calibration certification can be done by an independent authority if required.

• Dip Rod (Clause 12.5.2.1):

  • Use a non-sparking material dip rod, e.g., 12 mm square brass rod.

• Inspection Tools (Clause 15.2):

  • Manufacturer supplies all gauges/templates needed for inspection.

Calibration Table Format (per IS 2009:1975)

Volume values (Vx) are determined by physical measurement or mathematical calculation.

Summary Diagram: Calibration Process

flowchart TD
    A[Tank Fabrication] --> B{Calibration Type?}
    B -->|Mathematical| C[Calculate Volume vs Height]
    B -->|Physical| D[Fill with Certified Water]
    D --> E[Measure Volume at 0.5 cm intervals]
    E --> F[Prepare Calibration Table]
    C --> F
    F --> G{Certification Required?}
    G -->|Yes| H[Independent Authority Certification]
    G -->|No| I[Use Calibration Table]

References:

• IS 10987 Clause 16, 15.2, 12.5.2.1
• IS 2009:1975 (Calibration method for tanks)

IS 10987: Inspection and Testing - Key Points

1. Tolerance on Overall Length (Clause 14.3)

• Maximum permissible deviation: ±0.5% of overall length (from Table 1).

2. Inspection Tools (Clause 15.2)

• Manufacturer must supply all gauges and templates required for inspection.
• Inspection must satisfy the inspector.

3. Calibration (Clause 16.2)

• Calibration of measuring instruments may be certified by an independent authority if requested by purchaser.

4. Table 1: Dimensions & Capacities (Summary)

5. Welding & Joint Inspection

• Continuous fillet welds for longitudinal, circumferential, shell-to-coupling, manhole, nozzle neck joints.
• Welds must comply with IS welding codes (refer IS 813, 814, 816).

Summary Diagram: Inspection Flow

flowchart TD
    A[Manufacture Tank] --> B[Supply Gauges & Templates]
    B --> C[Inspection by Inspector]
    C --> D{Acceptable?}
    D -- Yes --> E[Calibration Certificate (if required)]
    D -- No --> F[Rework & Retest]
    E --> G[Final Approval]

Note: Refer to IS 10987 Table 1 for detailed dimensional tolerances and thicknesses. Calibration and inspection tools are critical for quality assurance.

IS 10987 Tolerances Summary

Key Formulas

• Diameter Tolerance: [ D_{actual} = D_{specified} \pm 0.35% \times D_{specified} ]

• Circularity Tolerance: [ D_{max} - D_{min} \leq 0.01 \times D_{nominal} ]

• Length Tolerance: [ L_{actual} = L_{specified} \pm 0.5% \times L_{specified} ]

Notes:

• Measurements for diameter tolerance are based on external circumferential measurements.
• Circularity tolerance applies to internal shell diameter variations.
• Length tolerance is relative to values in Table 1 (refer IS 10987 for exact lengths).
• Calibration of measuring instruments should be certified if required (Clause 16.2).

flowchart LR
    A[Specified Dimensions] --> B{Tolerance Limits}
    B --> C[Diameter ±0.35%]
    B --> D[Circularity ≤1% of nominal diameter]
    B --> E[Length ±0.5%]
    C --> F[External Measurement]
    D --> G[Internal Diameter Variation]
    E --> H[Overall Length per Table 1]

This ensures dimensional accuracy and structural integrity of tanks as per IS 10987.

IS 10987 - Earthing and Safety Provisions (Clause 12.5.4 & Annex D)

Key Specifications for Earthing Connections:

• Number of connections: Minimum 2 separate and distinct earthing connections at opposite extremities of the tank.
• Connection quality: Joints must be riveted, welded, or bolted and soldered for mechanical and electrical soundness.
• Resistance limits:
  • Resistance to earth ≤ 70 ohms
  • Resistance to earth plate or any fitting ≤ 20 ohms

Earthing Connection Details:

• For above-ground tanks: Two earthing bosses welded to the saddle supports.
• For underground tanks: Two earthing bosses welded to the end plates.

Guidelines Summary (Table D-1 excerpt):

Additional Notes:

• Earthing eliminates static charge accumulation from atmospheric electricity or product flow.
• Connections should minimize joints to reduce resistance and improve durability.

graph LR
A[Tank] --> B[Earthing Boss 1]
A --> C[Earthing Boss 2]
B & C --> D[Earth Electrode]
D --> E[Earth Ground]

This diagram shows two earthing bosses connected to earth electrodes at opposite ends of the tank for effective static dissipation.

For detailed fabrication and dimensions of tanks, refer to Table 1 in Clause 13.4 for shell diameter, thickness, and saddle support sizes.