A complete guide to formal tank inspections: Ensure compliance and minimize downtime

As a fleet owner, you may have a tank that is in need of a formal inspection but are unsure about the process. Questions swirling around in your mind may be:

Will my tanks need to be emptied?
How much downtime will my tanks have?
How will the inspection impact my operations?

I aim to ease your concerns and remove the mystery of formal tank inspections so you can be prepared and confident in your plan to get the inspection done on time, in budget, and know you received good service.

When do you need to schedule an inspection?

Refer to your on-site spill prevention, control, and countermeasure (SPCC) plan, and of course you have one if you have over 1,320 gallons in containers or aboveground storage tanks (ASTs) 55 gallons and larger at your facility. Your plan will indicate whether your tank needs to be inspected as per American Petroleum Institute 653 or Steel Tank Institute SP001 standards. Both standards require regular visual inspections, usually monthly and annual, and periodic integrity testing done every year to every 20 years. As an STI SP001 certified inspector, I will be focusing on the formal periodic inspections required by STI SP001.

Types of inspections under STI SP001

Under the STI SP001 standard, the periodic integrity testing comes in three flavors: formal external inspection (FEI), leak test, and formal internal inspection (FII). Most formal inspections fall under the FEI category, and that’s good news since the FEI can be conducted while your tank is filled and in service. Leak tests and FII will require the tank to be temporarily out of service, but some leak tests can be done without emptying the tank. If your tank has only an earthen dike, no secondary containment, no overflow protection, or any damage noted during a formal inspection, a leak test or internal inspection may be necessary. For this article, I will be focusing on the FEI, with subsequent articles covering leak tests and FIIs.

Choosing the right inspector

Whether you employ the inspector directly or use a consultant, your selected inspector will need to be certified under either STI SP001 or API 653. If you decide to go with a consultant, send a picture of your tank or tanks to be inspected so the inspector can properly prepare and give you an accurate proposal.

Preparing for the inspection

Once you've selected your properly certified inspector, it's time to get your tank ready. Have your past three years of monthly and annual inspections ready, along with a copy of the AST schematics and any repair documentation. If you have secondary containment, have it drained, and consider cleaning your tank, as the inspector will end up cleaning small areas anyway, leaving clean spots after the inspection.

The inspector should arrive prepared with the proper equipment and materials to complete the FEI. If your tank's top is over 6 feet off the ground, arrangements for a ladder should be made with your SP001 inspector. The inspector will also bring a notebook and/or a camera, an ultrasonic thickness gauge and couplant gel, towels to clean areas of the tank, and the appropriate PPE required at your facility. They will also be dressed to get dirty or have a set of coveralls and work boots.

The inspection process

On the day of the inspection, your site representative will only need to check in or greet the inspector, provide the requested records, guide them to the tank, and check them out after the inspection. Unless your facility requires guests to be always escorted, the inspector can handle most of the inspection without someone from your facility.

The inspector will conduct a records review and initial walk around, followed by a detailed inspection of your tank’s important features:

Secondary containment
Continuous release detection methods
The tank shell
Information plate
Supports, saddles, or foundation
Normal vents
Emergency vents
Level gauge and alarm,
Filling port, bucket, hose, and valve
Dispensing pump, hose, and valve
Block/isolation valves
Anti-siphon valve
Line leak detector
Expansion relief valve
Impact shear valve
Fire valves for tanks with pipe penetrations below liquid level
Interstitial monitor for double-walled tanks

The inspector will then conduct the ultrasonic thickness testing on accessible areas of the tank shell, focusing on places where corrosion is most likely to be found. This non-destructive testing method assesses tank integrity by bouncing high-frequency sound waves off the opposite side of the tank shell to measure its wall thickness. The spot where a reading is collected will be cleaned and marked. Personally, I use a No. 2 pencil or carpenter pencil to draw a circle where I took the UT reading and what the gauge result was at that location. For a 3,000-gallon AST, expect the inspector to collect 60 to 100 readings and 100 to 200 readings for a 10,000-gallon horizontal AST. If you have multiple tanks, the tank inspector should be able to complete two to four tanks in a day, depending on the size, nature, and surroundings of your ASTs.

Please note, if previous issues are found, a more comprehensive UT scan may be needed. This scan covers the entire surface of the AST and creates many more data points, requiring much longer to complete and may require a team of two or more. Additionally, UTT is not possible for the main shell if your tanks are insulated or encased in concrete, so these ASTs are reviewed for signs of corrosion to the underlying steel tanks. If signs of corrosion are observed, the inspector will let you know and discuss how to proceed.

After the FEI is done, the inspector will give you or your facility representative a preliminary summary of findings and recommendations, if any.

The tank assessment report

After the FEI is completed, the inspector will create a tank assessment report for you, which is usually delivered within 1 to 2 weeks after the FEI. The tank assessment report will include an executive summary, narrative of the FEI, the inspector’s findings, recommendations, figures, photographs, and the inspector’s current STI certification. The executive summary is there to provide a quick overview of what tank was inspected and the inspector’s findings and recommendations. The narrative goes into detail about the tank description, features, associated equipment, and the inspector’s observations and inspection process. The findings are where the inspector will state if your tank is “fit for continued use” or not, and this section should not be a surprise since this should have been discussed during the discussion about preliminary findings at the end of the FEI.

The figures will include a facility layout indicating what tank was inspected and a diagram of where the UTT readings were collected and the results. The photographs will show what was inspected to support the findings and recommendations. The tank assessment report should be included with your other tank inspection records.

A formal external tank inspection is a necessary and critical process for maintaining the safety and integrity of your storage tanks. Understanding the formal inspection process will help you prepare effectively, minimize future operational downtime, and give you confidence that your tank meets the necessary standards. Your inspection will be efficient and thorough if you choose a certified inspector and prepare your tank and necessary documents in advance.

After the inspection, the detailed tank assessment report will provide you with a comprehensive overview of your tank's condition and any necessary recommendations. By understanding the inspection process and using it to your advantage, you can ensure the longevity of your tanks, the safety of your team and operations, and your compliance with your local, state, and federal regulations.