AS 1692 vs API 650: Which Standard Applies to Your Storage Tank?
Steel storage tanks are widely used across Australian mining, industrial, agricultural and infrastructure facilities for the storage of diesel, petroleum products and other liquids.
Two standards that may be encountered when designing or assessing these tanks are AS 1692 – Steel tanks for flammable and combustible liquids and API 650 – Welded Tanks for Oil Storage.
While both standards deal with steel storage tanks, they are not simply Australian and American versions of the same document. Their scope, tank configurations and typical applications differ.
Understanding which standard applies is an important first step when designing a new tank, assessing an existing tank, or planning modifications to a storage facility.
What is AS 1692?
AS 1692 – Steel tanks for flammable and combustible liquids is an Australian Standard covering the design and construction of steel tanks intended for the storage of flammable and combustible liquids.
It is particularly relevant to fuel storage installations commonly found throughout Australian industry, including:
diesel storage tanks
petroleum product tanks
mine-site fuel storage
industrial fuel facilities
transport and equipment depots
agricultural fuel storage
above-ground and other steel tank configurations within the scope of the Standard.
AS 1692 addresses requirements associated with the tank itself, including its materials, construction, welding, fittings, openings and testing.
For Australian installations, however, the tank cannot necessarily be considered in isolation.
How does AS 1940 relate to AS 1692?
Another important Australian Standard is AS 1940 – The storage and handling of flammable and combustible liquids.
A useful distinction is:
AS 1692 primarily addresses the steel tank, while AS 1940 addresses the broader storage and handling installation.
Depending on the facility and stored product, AS 1940 may introduce requirements relating to matters such as tank location, separation distances, spill containment and bunding, operational arrangements and fire safety.
As a result, an Australian fuel storage project may require consideration of both the tank design and the surrounding facility.
What is API 650?
API 650 – Welded Tanks for Oil Storage is an internationally recognised standard published by the American Petroleum Institute.
API 650 establishes requirements for the material selection, design, fabrication, erection and inspection of vertical, cylindrical, above-ground welded storage tanks.
These tanks are typically field-erected, have their bottoms uniformly supported and operate at or near atmospheric pressure.
API 650 tanks are extensively used throughout:
mining
oil and gas
mineral processing
refineries
chemical and process plants
fuel terminals
large industrial facilities.
Although its title refers to oil storage, API 650 is used for tanks storing a much broader range of suitable liquid products.
What is the difference between AS 1692 and API 650?
The most obvious difference is the range of tank configurations and applications addressed by each standard.
API 650 is specifically focused on vertical, cylindrical, above-ground welded tanks with uniformly supported bottoms.
AS 1692 covers steel tanks for flammable and combustible liquids and is commonly encountered in Australian fuel-storage applications, including tank configurations that may fall outside the typical API 650 arrangement.
This means that the appropriate standard cannot be determined simply by asking whether the tank contains diesel or another petroleum product.
The tank configuration, capacity, operating conditions, stored product, installation and client requirements all need to be considered.
Does AS 1692 allow API 650 tanks?
AS 1692 recognises that tanks may be designed and constructed in accordance with other recognised tank standards in appropriate circumstances.
This is particularly relevant in Australian mining and industrial facilities where API 650 is already widely specified by asset owners and EPCM organisations.
Consequently, AS 1692 and API 650 should not always be viewed as competing standards.
For some projects, the Australian regulatory and site requirements may establish the overall storage requirements, while API 650 provides the engineering basis for the tank itself.
The applicable standards should therefore be established at the beginning of the project rather than assumed from the tank's contents alone.
Which standard applies to a diesel storage tank?
There isn't a universal answer.
For a relatively small packaged or fabricated diesel tank in Australia, AS 1692 and AS 1940 may be central to determining the applicable requirements.
For a large vertical field-erected diesel storage tank at a mine, processing plant or fuel terminal, API 650 may be specified for the tank design, with Australian Standards and site requirements applying to the broader installation.
The appropriate design basis depends on factors including:
tank orientation and geometry
tank capacity
stored liquid
operating pressure and temperature
above-ground or underground installation
support arrangement
fabrication and erection method
client specifications
site requirements
applicable Australian Standards and regulatory obligations.
For this reason, identifying the applicable standard should form part of the engineering assessment rather than simply selecting a standard based on tank capacity.
What about existing storage tanks?
Determining the original design standard becomes particularly important when an existing tank is being inspected, repaired or modified.
Older industrial facilities may contain tanks designed to previous editions of Australian Standards, API standards, proprietary designs or engineering requirements that were applicable when the facility was constructed.
Before undertaking significant modifications, it may be necessary to establish:
the original design basis
available drawings and documentation
tank dimensions and configuration
material specifications
remaining wall and floor thicknesses
corrosion condition
weld details
nozzle and penetration arrangements
foundation and support condition
proposed changes to loading or service.
Where sufficient documentation is unavailable, inspection, dimensional surveying and engineering assessment can help establish the existing condition of the tank.
Where does API 653 fit?
For existing API 650 tanks, API 653 – Tank Inspection, Repair, Alteration, and Reconstruction is another important standard.
While API 650 primarily addresses the design and construction of tanks, API 653 provides requirements for maintaining the integrity of tanks once they are in service.
Engineering support for an existing storage tank can therefore involve several standards depending on its design, age, service and proposed modifications.
Storage tank engineering requires more than selecting a standard
Whether a tank falls under AS 1692, API 650 or another applicable standard, tank engineering involves considerably more than calculating shell thickness.
A complete assessment can involve consideration of:
hydrostatic loading
wind loading
seismic loading
shell stability and buckling
roof structures
tank floors
nozzles and penetrations
local shell stresses
supports and foundations
corrosion allowance
welding and fabrication
inspection and NDT requirements
access platforms and structural steelwork
modifications to existing tanks.
For brownfield facilities, the challenge is often greater because the engineer must understand both the original tank and the effect of the proposed modification.
Storage Tank Engineering Support in Regional NSW
Trang Imagineering provides mechanical, structural and civil engineering services for mining and industrial facilities throughout Orange, the Central West and regional NSW.
Our engineering capability includes support for steel storage tanks and associated infrastructure, including projects involving API 650, API 653, AS 1692 and AS 1940.
Services can include:
new tank engineering and design review
existing tank structural assessment
tank modifications and upgrades
nozzle and penetration modifications
inspection engineering support
preparation and modification of engineering drawings
brownfield engineering and site verification.
For existing facilities where drawings are incomplete or site conditions have changed, Trang can combine 3D laser scanning, mechanical engineering and structural engineering to establish existing geometry and develop practical modification designs.
Need help determining which tank standard applies?
The applicable standard for a storage tank depends on more than whether it stores diesel, oil or another combustible liquid.
AS 1692, AS 1940, API 650 and API 653 each address different aspects of storage tank design, installation and integrity.
Establishing the appropriate design basis early can help avoid unnecessary redesign and ensure that the tank, its supports and the surrounding installation are considered as an integrated system.
Trang Imagineering can assist asset owners, operators, fabricators and EPCM teams with the design, assessment and modification of steel storage tanks across regional NSW.