We performed API 579 / ASME FFS-1 Fitness for Service on steel tanks for a brewery – after one of their tanks had failed. Because of the age of this and other tanks, they were concerned about tank structural integrity. Each glass-lined tank is 12 feet in diameter by 12′ 6″ in length with two semi-elliptical heads on the ends. They all had multiple penetrations and are supported by a total of six vertical posts along the length of the shell. The tanks are constructed of carbon steel and the insides of the tanks are glass lined.
The tanks were inspected in accordance with API 510. The findings determined:
- The presence of oxidation scale, as well as minor pitting was found on tank exteriors
- Inactive pitting corrosion was found on the inside of the tanks
- The structural supports did not show any conditions of concern
The evaluation included effect of the supports on the tank shell and head, the effects of penetration area replacement, Maximum Allowable Working Pressure (MAWP), and Remaining Life Assessment.
While the MAWP of the tanks is greater than 15.0 psig, operating the tanks at 15 psig or greater will result in the tanks designated as pressure vessels. The Commonwealth of Pennsylvania has specific laws governing the inspection and maintenance requirements of pressure vessels.
The results determined that the tanks had an expected life of 20+ years, provided they are properly maintained.
We Perform Engineering Analysis to Various Codes including AWS, ASME and API – on Equipment for Clients in Health and Food/Beverage.
– Introduction to API 579 / ASME FFS-1 Fitness for Service
– (PDF) “Weld Defects and Failures: Quantifying Fitness For Service – How Finite Element Mathematical Simulations can Mitigate Risk, Cut Costs and Improve Overall Safety”