Exempting Atmospheric Storage Tanks from Hydrostatic Testing
By: Devon Brendecke, Consulting Engineer, Quest Integrity GroupAs seen in the March 2013 issue of BIC Magazine - view the article as it was published.
to the widely growing acceptance of fitness-for-service methods, large
atmospheric storage tanks can now be exempt from hydrostatic testing following
repair. API 653 allows the use of a thorough fitness-for-service assessment in
lieu of hydrostatic testing. The exemption has been included in the past
several editions of API 653 and is becoming more widely used. In many cases,
the benefits of the hydrostatic test exemption greatly exceed the cost savings.
Although the data requirements for this type of assessment are extensive, the
exemption eliminates the time and logistics required to conduct a hydrostatic
test. Engineers with specialized consulting experience and software make
hydrostatic test exemption a viable option.
the benefits of the exemption go beyond fiscal savings, it is often one of the
motivating factors in decision making. For large tanks, the downtime required
for filling and emptying the tank is prohibitive. A large diameter tank can
take weeks to fill, hold and empty, whereas the analysis for the exemption can
take as little as a week. For many regions in North America, acquiring the
amount of water needed to conduct the test is nearly impossible. In other
regions, disposing of the water after testing is exorbitantly expensive and can
increase the emptying time based on disposal logistics alone. Cold weather
conditions can also make hydrostatic testing difficult. The hydrostatic test
exemption avoids all of these potential complications and costs and has been
successfully performed for more than 10 years.
exemption analysis requires little beyond that which API 653 requires following
a repair. Thorough inspection of all new welds is already a requirement;
however, evaluation of the weld procedures by a qualified engineer is also
necessary. To ensure all potentially problematic issues have been addressed,
the most recent API 653 out-of-service inspection report must be reviewed by
the engineer conducting the analysis.
is also necessary to ensure proper materials and repair design and procedures
were used. The last critical piece of information required by the
fitness-for-service standard is fracture toughness of the newly welded regions.
The fracture toughness is measured with a destructive test and can be performed
on a sample of material removed from the tank during the repair. The material
testing can often be completed in parallel with the majority of the analysis,
which contributes to the quick turnaround for the exemption.
Integrity Group provides hydrostatic test exemptions as part of its advanced
engineering services. The company’s background
in fitness-for-service makes it uniquely qualified to deliver advanced
engineering assessment solutions to terminal and production clients. Its team of
dedicated engineers has successfully completed hundreds of analyses, establishing
it as a leading tank assessment company.
more information, visit our storage tank integrity assessment page.