One of the most common questions we hear from tank owners is, "How often does my liquid fertilizer storage tank need to be inspected?"
The answer depends on several factors, including API 653 inspection guidelines, state regulations, insurance requirements, and the condition of the tank itself. While there are no federal regulations governing liquid fertilizer storage tank inspections, industry standards and state requirements help establish inspection schedules that protect both your investment and your operation.
This guide explains the different types of inspections, when they are typically required, and how Heartland Tank Services helps customers stay compliant.
What Determines Inspection Frequency?
Several organizations and requirements influence how often a liquid fertilizer storage tank should be inspected:
- API 653, the industry standard for inspecting aboveground storage tanks
- The Fertilizer Institute (TFI), which provides inspection recommendations for fertilizer storage
- State laws and regulations, which vary from state to state
- Insurance companies, which may establish their own inspection requirements
Because these requirements can overlap, inspection schedules are not always straightforward. Understanding which standards apply to your facility is the first step in maintaining a safe, compliant storage system.
Understanding the Three Types of Tank Inspections
Monthly Routine External Inspections
Routine "walk-around" inspections are typically performed by the tank owner or operator. These inspections focus on identifying visible issues such as leaks, corrosion, settlement, or damage that could indicate developing problems.
Because every facility is different, the timing and procedures for routine inspections are determined by the needs of the operation.
Formal External API 653 Inspections
Formal external inspections are performed by an API 653 Certified Aboveground Storage Tank Inspector while the tank remains in service.
According to API 653, these inspections are generally recommended every five years, or at an interval determined by corrosion-rate calculations, whichever is less. The inspection evaluates the condition of the tank shell, roof, foundation, and other structural components to identify issues before they become significant problems.
Formal Internal Inspections
Internal inspections require the tank to be removed from service so the interior can be thoroughly evaluated.
Because liquid fertilizer products are more corrosive than many petroleum products, The Fertilizer Institute recommends more frequent internal inspections than the general API 653 guidelines for petroleum storage tanks.
For tanks equipped with an internal PVC liner or protective coating, TFI recommends an internal inspection at least every five years. For unlined tanks, inspection intervals are based on measured corrosion rates but generally should not exceed ten years.
An initial API 653 inspection within the first ten years of service helps establish corrosion rates that determine future inspection intervals.
State Regulations and Insurance Requirements
While API 653 provides industry guidance, many inspection schedules are ultimately determined by state regulations and insurance providers.
Most states have inspection requirements tied to operating permits or licensing, although those requirements vary considerably. Some states require inspections at specific intervals, while others have few or no formal inspection requirements.
Insurance companies may also require tanks to be built to API 650 standards and inspected according to API 653 before issuing or renewing coverage.
Whenever possible, it is important to coordinate state-required inspections with insurance requirements so a single inspection satisfies both obligations and eliminates unnecessary duplication.
Why Ultrasonic Thickness Testing Matters
A critical component of both formal external and internal inspections is Ultrasonic Thickness (UT) Testing.
UT testing measures the remaining thickness of the tank's shell, floor, and roof plates using high-frequency sound waves. These measurements are compared to the minimum thickness requirements established by API 653 based on the tank's size, construction, and the specific gravity of the stored product.
Each measurement location is carefully documented so future inspections can evaluate corrosion over time and identify changes before they threaten the structural integrity of the tank.
Preparing a Tank for Inspection
A successful API 653 inspection requires more than simply emptying the tank.
Inspectors must have clear access to the steel surfaces they are evaluating. Tanks without internal liners or coatings often require thorough power washing and, in some cases, abrasive cleaning to remove hardened deposits that may conceal corrosion.
Every area inside the tank should be accessible so inspectors can evaluate the entire structure, not just the lower shell courses.
Typical Inspection Schedule
While every facility is different, a typical inspection program includes:
|
Inspection Type |
Typical Frequency* |
|
Routine external walk-around |
Monthly |
|
Formal external API 653 inspection |
Approximately every 5 years |
|
Ultrasonic Thickness (UT) Testing |
Typically every 5 years or as determined by corrosion calculations |
|
Formal internal inspection |
Every 5 to 10 years depending on tank condition, corrosion rates, and liner/coating system |
*Actual inspection intervals may vary based on API 653 calculations, state regulations, insurance requirements, and the condition of the tank.
Let Heartland Help You Stay on Schedule
Determining when inspections are required can be challenging, especially when balancing API recommendations, state regulations, and insurance requirements.
Heartland Tank Services helps customers simplify that process. We stay current with inspection requirements across the country, assist customers in coordinating inspection schedules, and automatically track inspection dates so you'll receive reminders when your next inspection is due.
Whether you need an API 653 inspection, guidance on your state's requirements, or help developing an inspection schedule, our experienced team is ready to help you protect your storage tank investment for years to come.