What Is the Difference Between API 650 and AS 1692?
When planning an atmospheric storage tank, one of the first engineering decisions is which design standard to adopt. In Australia, this often comes down to API 650 versus AS 1692.
While both standards govern the design and construction of welded steel tanks for liquid storage, they differ significantly in scope, flexibility, industry acceptance, and how engineering judgement is applied.
At Trang Imagineering, we regularly work with clients navigating this decision. The right choice depends on the application, regulatory environment, and long-term asset expectations — not just geography.
Overview of the Two Standards
API 650 — Welded Tanks for Oil Storage
API 650 is an internationally recognised standard published by the American Petroleum Institute. It is widely used across:
Oil and gas
Mining and resources
Industrial processing
Bulk liquids storage
Despite the name, API 650 is not limited to oil and is commonly applied to water, chemicals, and other liquid products stored at or near atmospheric pressure.
AS 1692 — Steel Tanks for Flammable and Combustible Liquids
AS 1692 is an Australian Standard primarily focused on tanks storing flammable and combustible liquids. It has traditionally been used in fuel storage applications and is often referenced in Australian regulatory frameworks.
Key Differences Between API 650 and AS 1692
1. Scope and Flexibility
API 650
Broad applicability across many liquid types
Multiple design methodologies
Extensive annexes covering seismic, wind, settlement, and special conditions
Commonly used for large-diameter tanks
AS 1692
Narrower scope, focused on flammable and combustible liquids
More prescriptive design rules
Limited flexibility for non-standard geometries
API 650 offers greater flexibility for bespoke or large-scale tanks, while AS 1692 is more constrained.
2. Engineering Methodology
API 650
Allows multiple shell design approaches (e.g. one-foot method, variable design point)
Encourages optimisation of shell courses and material usage
Explicit recognition of engineering judgement
AS 1692
More conservative and rule-based
Less opportunity to optimise steel tonnage
Fewer alternative calculation pathways
API 650 generally enables more efficient steel tank engineering, particularly for larger tanks.
3. Wind, Seismic, and Environmental Loading
API 650
Dedicated annexes for:
Seismic loading (Annex E)
Wind loading (Annex V)
Settlement considerations
Well suited to sites with challenging environmental conditions
AS 1692
Simpler treatment of environmental loads
Less detailed seismic provisions
Often requires supplementary analysis for complex sites
In Australia: API 650 is frequently preferred where seismic or wind effects are non-trivial.
4. Industry and Regulatory Acceptance
API 650
Globally recognised
Preferred by EPCs, insurers, and multinational operators
Commonly accepted by Australian regulators when supported by a competent engineer
AS 1692
Familiar to Australian authorities
Sometimes mandated for specific fuel storage scenarios
Less recognised internationally
API 650 is widely accepted in Australia, provided it is applied correctly and documented clearly.
5. Tank Size and Project Scale
API 650
Well suited to large-diameter, high-capacity tanks
Scales efficiently for industrial and mining projects
AS 1692
More common for small to medium fuel tanks
Less commonly used for very large installations
Which Standard Should You Use?
There is no universal answer — but some general guidance applies.
API 650 Is Often the Better Choice When:
Tanks are large or non-standard
Wind or seismic effects are significant
Material optimisation matters
International alignment is required
AS 1692 May Be Appropriate When:
The tank is small and fuel-specific
A regulator explicitly mandates AS 1692
The project is simple and conservative by design
In many Australian projects, API 650 is selected even for non-oil applications due to its robustness, flexibility, and widespread acceptance.
A Practical Engineering Perspective
The difference between API 650 and AS 1692 is less about nationality and more about engineering philosophy.
API 650:
Provides a framework
Relies on competent engineering judgement
Scales well with complexity
AS 1692:
Provides prescriptive rules
Limits interpretation
Can be restrictive for modern projects
Good outcomes depend less on the standard itself and more on how it is applied.
How Trang Imagineering Can Help
Trang Imagineering provides independent advice and detailed design for tanks designed to API 650 or AS 1692, including:
Standard selection and regulatory justification
Atmospheric storage tank design
Steel tank engineering and optimisation
Design verification and peer review
Construction support and technical clarification
We work with clients early to select the most appropriate standard — reducing risk, cost, and downstream redesign.
Need Advice on API 650 vs AS 1692?
If you’re unsure which standard best suits your project, or need support defending a design approach to regulators or stakeholders, get in touch with Trang Imagineering.
Clear engineering decisions early in a tank project save time, money, and headaches later.