To keep storage tanks working safely and efficiently, the Environmental Protection Agency (EPA) and/or state statutes require tank owners to maintain a system or program of regular inspections and maintenance activities to ensure the environment is protected against a preventable release of hazardous liquids.
Steel aboveground storage tanks (ASTs), like those used in oil and gas midstream and downstream operations, chemical terminals, and tank farms, are especially vulnerable to wind, heat, cold temperatures, rain, salt, and snow. Inspections and periodic maintenance are especially important as ASTs are continuously exposed to wind, ultraviolet radiation, airborne debris, and salt microparticles.
Frequency of Inspections
The American Petroleum Institute (API) and the Steel Tank Institute (STI) define inspection standards for steel ASTs used in the petroleum and chemical industries. These standards, known as API 653 and the STI SP001 are the leaders in preventive maintenance standards. The inspection models are based on risk. The larger the tank, the more frequent the internal inspection will be.
These inspections are directed towards the formal inspection as they are performed based on historically documented corrosion rates in the industry. In some instances (thermoplastic and insulated tanks) the frequencies to remove potential heavy corrosion areas under the insulation for inspection can and should be done more frequently.
How to Determine Facility-Specific Requirements
Your facility’s SPCC Plan identifies the requirements for the plan “the Plan has been prepared in accordance with good engineering practice, including consideration of applicable industry standards, and with the requirements of this part;” to be followed for maintenance and inspection [§ 112.3 (d)(1)(iii)]. What this means is that your Plan must identify the inspection standard your Facility will use, either API, STI, or a hybrid of the two.
Each AST inspection offers unique challenges for inspection technicians. Entry into confined spaces to inspect and evaluate floor thickness and highlight repair areas is especially challenging when technicians relied on more traditional methods for performing inspections. Bulky equipment and ventilation systems made it tough for the technician to conduct a successful inspection and analysis of the inner spaces. The introduction of external Non-destructive Testing (NDT) units that are designed to be used from the external portion of the AST removes most hazards. However, the floor inspection still requires many companies to enter tanks where the hazards persist.
The introduction of robotic inspection units has taken off over the past few years. These units scour the floor of the tank and record steel thickness to the outside operator. This new technology allows the technician to be completely outside of the tank. This saves the client time and resources associated with the technician entering the tank (i.e., developing permits, providing oversight, and developing a rescue plan). This new technology creates a safer work area.
These challenges for ASTs are equaled by their importance. Without the periodic inspections prescribed in the facility SPCC Plan, even the smallest amounts of damage, if left undetected, can turn into costly future repairs and potential tank failures. Leaks from ASTs that go unseen can lead to regulatory and compliance enforcement issues, as well as cause downtime to operations.
The solution to these issues is to have an AST tank inspection integrity program that is flexible and brings in successful companies to evaluate the facility ASTs and lower the risk of failure due to corrosion. EHS Support has STI-certified AST inspectors that can successfully evaluate your ASTs and provide you with the details to lower the overall risk of an unforeseen release from the lack of formal inspections. Let us provide the oversight and conduct your annual visual inspections and STI interval inspections – providing you with confidence that your tanks are in proper working order for years to come.
For more information, please reach out to James Dodd, EHS Support’s Certified STI tank inspector, and Sr. Health and Safety Specialist.
 API. 2014. Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction. Fifth edition. November.
 STI. 2018. Standard for the Inspection of Aboveground Storage Tanks. SP001. Sixth edition. January.