If you’re going to be doing anything related to liquid fertilizer tanks, then you need to be familiar with the API 653 standard. What is that, exactly? Tank Inspection Protocol API 653 is what regulates the inspection, repair, alteration and reconstruction of steel above ground storage tanks used widely in the chemical and petroleum industries. First published in 1991, the API 653 standard was most recently updated in November, 2014 (its fifth edition).
What do you need to be doing to ensure your tanks are inspected to the standard? There are four general things you’ll need to keep in mind:
- The General Tank Information
In conjunction with an inspection, you’ll want to review the specifications and construction details of a tank, including its release detection measures and spill control measures.
- Bottom, Shell and Roof Inspection
The three major things that will be taken into account during the inspection regarding the tank’s structure are the minimum remaining thickness, the minimum required thickness, and the maximum corrosion rate. These apply to the bottom, shell and roof of the tank.
- Accepted Inspection Method
There’s quite a bit of flexibility allowed in how the components of an above ground tank are inspected. Visual, ultrasonic, liquid penetrant, penetrating oil, radiography, magnetic flux scan, magnetic particle, vacuum box and tracer gas methods may all be applicable.
- Tank Settlement Evaluation
It’s very important that a tank not tilt or settle improperly in the ground. Here’s what you don’t want to see: rigid body tilting, out of plane components, edge settlement, and localized dispersion. Any settling should be uniform.
Keep in mind that it’s recommended that a site’s owner and/or operator assesses the condition of a tank at least monthly. These inspections should be as thorough as possible, but the tank doesn’t need to be taken out of service. Since these inspections are just recommended, the person performing them needs to be knowledgeable but does not need to be certified.
Formal inspections of the external and internal components of the tank, on the other hand, must be performed at least every five and 10 years, respectively. It’s important to establish a regular schedule for these so as to avoid fines and other penalties.