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API 650 refers to a standard published by the American Petroleum Institute (API)

API 650 Cone Roof Storage Tank design — classic vertical tanks with a fixed cone roof, often used for storing petroleum products like, water, acids, oils, diesel, crude oil, fuel oil, etc., under atmospheric pressure.

Let's break this down into a structured, engineering-oriented summary for API 650 cone roof tank system design:

🛢️ API 650 Cone Roof Storage Tank – Design Overview

📘 Standard Reference

API 650 – Welded Tanks for Oil Storage
Latest Edition (check if your project needs the 13th or latest addendum)
Applicable for: vertical, cylindrical, above-ground, atmospheric storage tanks

📐 1. Tank Configuration

Type: Fixed cone roof, self-supporting or column-supported
Orientation: Vertical, flat-bottom
Typical use: Crude oil, diesel, gasoline, chemical products
Volume Range: 10 m³ to >100,000 m³

🔍 2. Key Design Inputs

Design InputDescription

Tank Diameter (D)Usually ranges from 3 m to 60+ m

Tank Height (H)Dependent on required volume

Design Liquid LevelMaximum operating liquid height

Design Specific Gravity (SG)Affects hydrostatic pressure on shell

Design TemperatureNormally < 93°C (200°F) for API 650

Corrosion AllowanceTypically 1.5 mm (can vary)

Wind & Seismic LoadsBased on site location

Roof TypeCone roof angle typically 1:6 to 1:12 (approx. 5°–10° slope)

🔧 3. Shell Design

Hydrostatic Pressure-Based Shell Thickness

t=(2.6⋅H⋅SG⋅D)(SE−1)t = \frac{(2.6 \cdot H \cdot SG \cdot D)}{(SE - 1)}t=(SE−1)(2.6⋅H⋅SG⋅D)

Where:
- HHH: Liquid height
- SGSGSG: Specific gravity
- DDD: Tank diameter
- SSS: Allowable stress
- EEE: Weld efficiency
Courses: Shells are designed in courses (rings), and thickness reduces upward
Lap or butt welded, usually with full penetration

🏗️ 4. Roof Design (Cone Roof)

Slope: Typically 1:6 to 1:12 (5°–10°)
Self-supporting or column-supported
Roof Plates: Often designed as flat steel plates
Central compression ring at the apex
Roof-to-shell joint: Often a fillet weld; can include a knuckle (radius)

🧱 5. Bottom Design

Flat bottom, made from multiple steel plates
Annular ring (thicker plate ring around perimeter) recommended for:
- Diameter > 36 m
- High loading or settlement zones

🛠️ 6. Appurtenances & Components

Component Purpose

Manways Entry/access (shell and roof manways)

Vents Pressure/vacuum relief (per API 2000)

Nozzles For inlet/outlet, sampling, drains

Gauge Hatch For dipstick/manual level gauge

Overflow Pipe Prevents overfilling

Ladders, Platforms Maintenance access

Roof Drain System For external rainwater collection (if needed)

🧪 7. Testing & Inspection

Hydrostatic Testing: Tank is filled with water to test structural integrity
NDE (Non-Destructive Exams):
- RT (radiographic) on selected welds
- MT (magnetic particle), PT (penetrant) for surface flaws
- UT (ultrasonic) thickness gauging

BS EN 14015. This is the British and European standard

BS EN 14015: Specification for the design and manufacture of site-built, vertical, cylindrical, flat-bottomed, above-ground, welded steel tanks for the storage of liquids at ambient temperature and above

📌 Key Features

FeatureDescription

📅 First Published2004 (current version may be updated – let me know if you want latest via web)

🌍 RegionUK & Europe (based on EN standards)

🏗️ ApplicationSimilar to API 650 — for atmospheric or low-pressure liquid storage

⚙️ Tank TypeCylindrical, vertical, welded, above-ground, flat-bottomed tanks

🌡️ TemperatureAmbient to slightly elevated temps

🔧 Key Design Topics

1. Materials

Includes both carbon steel and stainless steel
More aligned with European steel grades (e.g., S235, S355)

2. Design Loads

Wind, snow, seismic, and internal pressures
Seismic per Eurocode 8
Wind per EN 1991-1-4

3. Tank Bottom & Shell Design

Includes guidance on annular plates, corrosion allowances, etc.
Bottom can be single plate or annular ring-based depending on diameter

4. Welding and NDT

Strict welding procedures
Requires Welding Procedure Specification (WPS), PQRs, and welder qualifications
NDT: Radiographic, ultrasonic, magnetic particle, and dye penetrant testing as applicable

5. Inspection and Testing

Hydrostatic testing required
Includes leak testing of bottom plates
Visual and dimensional inspections

🇯🇵 Storage Tank Design Standards in Japan

🏗️ Primary Japanese Standard:

🔹 JIS B 8501 – "Welded Steel Tanks for Oil Storage"

This is the closest equivalent to API 650 in Japan.

📌 Key Features of JIS B 8501

Feature Details

📘 Title Welded Steel Tanks for Oil Storage

🏗️ Type Field-erected, vertical, cylindrical, flat-bottomed steel tanks

🌡️ Temperature Ambient or slightly elevated

📏 Pressure Low-pressure, atmospheric tanks

🧯 Applications Crude oil, petroleum products, chemicals

🔧 Design Elements in JIS B 8501

Tank Shell & Bottom
- Design stresses and allowable stress similar to API 650
- Plate thickness, welding joints, corrosion allowance
Seismic Design
- Japan is highly seismic, so this is critical
- Earthquake design must follow Japan’s Building Standards Law and Notification No. 593 (Ministry of Construction)
Wind Loads
- Based on Japan Meteorological Agency data
- Specific formulas for design wind speed & pressures
Materials
- Japanese steel grades (e.g., SS400, SM490, similar to ASTM A36 or A516)
- Material testing & certification required
Roof Types
- Cone, dome, and floating roofs are supported
- Design of internal and external floating roofs follows similar logic to API 650, but with Japanese safety codes
Welding & NDT
- Detailed requirements for welding procedures and testing
- Radiographic testing, ultrasonic testing, visual inspections
Testing & Inspection
- Hydrostatic testing is mandatory
- Includes leak testing of bottom plates
- Seismic safety inspections may be required post-installation

Japanese Industrial Standards (JIS).

Storage Tank Design Standards – China

he main standard for aboveground welded steel tanks in China is:

🔹 GB 50128 – "Code for Construction and Acceptance of Vertical Cylindrical Welded Steel Oil Tanks"

This standard is often used alongside GB 50341 – Code for Design of Vertical Cylindrical Welded Steel Oil Tanks.

These two together cover the design, fabrication, construction, inspection, and testing of oil storage tanks, much like API 650 or BS EN 14015.

🏗️ Key Chinese Standards for Storage Tanks

Standard Title Description

GB 50341Design Code for Vertical Cylindrical Welded Steel Oil Tanks Main design standard (similar to API 650)

GB 50128Code for Construction and Acceptance Covers fabrication, welding, inspection, and testing

GB 50009Load Code for the Design of Building Structures Wind and snow load

GB 50011Code for Seismic Design of Buildings Seismic design (very important in high-risk areas)

GB 12348Emission Standard for Noise at Boundary of Industrial Enterprises May be referenced for operational compliance

HG/T 20570.1~3Floating Roof Tank Accessories Specifics on floating roof seals, vents, etc. (from chemical industry standards)

🔧 Design Scope of GB 50341

Vertical, cylindrical, aboveground, flat-bottomed, welded steel tanks
Diameter range: Generally from 5 meters to over 100 meters
Fluid: Oil and oil products (can be extended to chemicals with similar properties)
Temperature: Ambient to mildly elevated
Pressure: Atmospheric or very low pressure

🛢️ Floating Roof Tank Design (Internal & External)

Chinese standards recognize both internal and external floating roof tanks, but like BS EN 14015, they're less prescriptive than API 650.

🔄 Floating Roof Design Coverage (GB Standards)

Roof Type Included in GB? Notes

External Floating Roof (EFR)✅ Yes Common in large oil depots

Internal Floating Roof (IFR)✅ Yes Increasingly used for emission control

Fixed Roof✅ Yes Cone or dome style, often with IFR below

👇 Design Based on:

HG/T 20570 (Part 1-3) – Chemical industry standard, used for:
- Floating roof accessories (vents, manways, seals)
- Pontoon vs full-contact IFRs
Enterprise standards or project-specific specs often supplement with API 650 Appendix H principles

🧪 Construction & Testing (GB 50128)

Hydrostatic testing
Radiographic, ultrasonic, and magnetic particle testing for welds
Dimensional tolerance checks
Foundation settlement checks
Welding qualification procedures per GB/T 3323 or GB/T 11345

⚖️

Wisdom is one of the leading design Service provider for oil & Gas, Petrochemical & process Industries

If you’re planning a new facility or upgrading existing infrastructure, Wisdom Design Consultancy is here to provide cutting-edge design services for your Cone roof storage tank systems.

With over 22 years of specialized experience in Cone roof storage tank design,

Wisdom Design Consultancy is a trusted name in the industry for delivering high-quality, efficient, and code-compliant solutions tailored to your project needs

22+ Years of Expertise in Cone roof Tank Design
One-Point Contact for the Entire Project.
All engineers and draftsmen on our team have over 15 years of experience in Cone roof tanks design
Every design document is thoroughly reviewed and approved by a Senior Design Manager to ensure technical accuracy and quality before delivery.
We strictly follow agreed schedules, ensuring on-time delivery without compromising on quality.
Compliance with International Codes & Standards, API 650, ASME, EN, ISO, and other applicable global standards.
From concept to commissioning, we ensure complete coordination with the client, consultants, and stakeholders at every stage
Our solutions strike the right balance between cost-efficiency and safety, without compromising long-term reliability

(HFO, LFO, FURNACE OIL, CRUDE OIL)

(Vegetable oil, Edible oil, Canola Oil, Soybean Oil:, Coconut Oil: Peanut Oil )

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