Texas is home to more than 1,000 chemical plants, the bulk of them located near the coast. When Hurricane Harvey hammered Houston and the surrounding area in August 2017, the power went out and floodwaters rose — a potent recipe for disaster when you mix in explosive chemicals. 

Hundreds of plants had to be shut down in the aftermath of Harvey.  Workers at the Arkema chemical plant in Crosby, Texas scrambled to keep organic peroxides cold, even transferring the chemicals into refrigerated trucks with their own generators.

Alas, those failed as the floodwaters rose. The organic peroxides caught fire and set off a series of explosions. Residents and first responders have since filed lawsuits against the chemical company, alleging that the plant failed to take the proper precautions to prevent the fire.

Regulations for storing chemical or oils are a lot stricter than for water storage — for obvious reasons.  After all, water is not going to catch fire and explode, potentially releasing toxins into the environment. 

The government has been regulating chemical and oil storage for several decades, but the public became increasingly aware of the environmental and economic devastation caused by oil spills following several high-profile incidences in the 1980s like the Ashland oil spill.  On Jan. 2, 1988, a tank owned by Ashland Oil Company collapsed, spilling nearly one million gallons of oil that ended up in the nearby Monongahela River in Pennsylvania. Spills like this propelled new legislation and standards to be passed.  

Established in 1991 and updated regularly, API 653 addresses tank inspection, repair, alteration, and reconstruction of steel above ground storage tanks used in the petroleum and chemical industries. It applies to tanks built to the standards of API 650, which has been around since the 1960s and API 12C, which dates back to the 1930s when welding began overtaking riveted as the preferred construction method for steel tanks.

The API 653 standard covers the minimum requirements for maintaining the integrity of riveted or welded, non-refrigerated and refrigerated, atmospheric pressure, above ground storage tanks after they have been placed in service.

Above ground oil storage tanks can last between 20 to 40 years, though the life expectancies for some tanks are shorter or longer depending on a variety of factors. The more tanks age and deteriorate, the greater the chance is that there will be leaks or spills.

Tanks that aren’t well maintained or repaired are more prone to leakage and spills. Corrosion, where rust eats away at metals, is one of the most common causes of leaks and spills.  Poorly designed tanks, such as ones that for instance don’t factor in a cold or harsh climate, also leak more often. But, if a tank is well designed, maintained, and inspected regularly, it can remain in service for decades.

API 650 tanks are used to store crude oil, chemicals, gasoline and other liquid products.  API 653 addresses how to inspect, repair, and maintain field-erected aboveground steel storage tanks that are built to API 650 or API 12 C standards. 

Mandatory API 653 inspections are required at one month, five-year, and 10-year intervals. Without taking it out of service, the tank owner or operator should thoroughly evaluate the tank monthly to ensure structural integrity. Owners and operators are required to keep construction documents, inspection reports, and any details about repairs or alterations that have been made to the tank.

Cathodic protection records should be held onto for five years. Keeping thorough records provides a reference point for inspectors and for anyone whom will be performing maintenance or repairs on the tank.

A certified API 653 inspector should evaluate the tank every five years at the minimum. More frequent inspections might be necessary depending on the type of product stored, tank location, local or state requirements, and how badly the tank is corroding.  Sometimes the tank can remain in service, and the inspector doesn’t need to enter the tank. 

Heated storage tanks are often insulated. Inspecting an insulated tank can be difficult because signs of leaks or deterioration or corrosion may be hidden underneath the insulation. To eliminate this problem, the insulation can be partially removed, or inspection parts can be installed in the insulation to the extent that’s necessary to allow inspectors to carry out their examinations. 

A certified EPA inspector will often be required to conduct API 653 inspections. These inspections are in accordance with EPA standards for tanks that store petroleum and other liquid products. Tanks that contain flammable or combustible liquids must be inspected according to NFPA standards. Hazardous liquids can seep into the ground and wreak havoc on the environment, so inspectors scrutinize leak protection and monitoring systems.

The Spill Prevention Control and Countermeasures rule, set by the Environmental Protection Agency, tries to prevent hazardous chemicals from discharging into navigable U.S. waters. Primary containers can sometimes fail, so secondary containers are required.  Facility owners have flexibility with how they address preventing oil spillages, but the SPCC rule requires that they have a plan in place. Facilities must also be able to respond to oil discharges if all their safeguards fail.

Secondary containment can be either active or passive. Active secondary containment involves a person or people who help contain the spill like a response team or someone who uses a spill kit once oil has been discharged. Passive secondary containment involves a system like containment dikes, double walls, or double bottoms, to prevent spillage.

Internal API Inspections are required every 10 years, although some tanks might warrant more frequent inspections.  Tanks must be emptied and cleaned so a certified inspector can assess the lower tank shell courses and floor plates. Internal inspections of above-ground storage tanks reveal whether the tank bottom is severely corroded.

The inspections also allow inspectors to gather data on the minimum bottom and shell thickness. Tests performed at this time might include visual, ultrasonic, liquid penetrant, magnetic particle, magnetic flux scan, penetrating oil, vacuum box, radiography, and tracer gas.

The certified tank company that performs the inspection is required to provide a detailed report for any in-service or out-of-service inspections. The detailed report lists the conditions of the tank parts that were inspected, along with what methods were used to conduct the inspection. Photographs, data, and recommendations for repairs and maintenance in compliance with API 653 will be included.

Inspection reports include recommendations for tank maintenance and repairs. It’s up to the tank owner to decide when and if to address any deficiencies. Ignoring the recommendations altogether is a gamble that could be costly.

Erin Schmitt is the media director and technical writer for Pittsburg Tank & Tower Group, which was founded in 1919. Schmitt also has a bachelor’s degree in journalism from the University of Kentucky.