Atmospheric Testing the Tank Interior

Posted On: February 6, 2018
In the Know: Underground Storage Tank

Atmospheric Storage Tanks

Atmospheric testing of tank interiors is a requirement of the petroleum industry. The reason for this is related to tank design. Atmospheric storage tanks are designed to operate with vapor and gas spaces that are close to atmospheric pressure. Atmospheric storage tanks are usually fabricated from alloy or carbon steel, aluminum and other metals, depending on storage use. In the petroleum industry, atmospheric storage tanks may be used for heavy or crude oil, furnace oils, gasoline, gas oil, naphtha as well as other non volatile chemicals. Atmospheric storage tanks are operated and used to meet API (American Petroleum Institute) standards for vapor pressure. These tanks are protected tanks are "protected by pressure vacuum vents that limit the pressure difference between the tank vapor space and the outside atmosphere to a few ounces per square inch."

Management of Atmospheric Storage Tanks

With each new loading of materials into an atmospheric storage tank, tank inspectors are required to follow OSHA, API and NFPA guidelines to prevent worker injury and also cross contamination of materials to be stored. Maintaining tank specifications for vapor pressure in confined spaces of the tanks and ensures pressure vacuum vents are operating properly.

Atmospheric Testing the Tank Interior

Before atmospheric testing of the tank interior is performed, an employer must make certain entry into the tank is safe for workers. As atmospheric testing begins, the order of testing includes:
  • Test first for oxygen
  • Next, test for combustible gases and vapors
  • Test for toxic gases and vapors

The objective of atmospheric testing the tank interior is to monitor and document the condition of the tank floor and walls and check valves for leakage.   Click To Tweet

The objective of atmospheric testing the tank interior is to monitor and document the condition of the tank floor and walls and check valves for leakage. Inspections are done using various types of "mapping" and risk assessment programs to determine if corrosion or other damage to the tank interior has occurred. For atmospheric tanks specifically, it is important the inspection of the interior detail components of corrosion, as well as operating temperature, pressure, process chemistry condition of construction materials when applicable.

Texas Class C Operator Job Specifications

The Oil and Gas Industry in Texas considers workplace safety imperative, given the nature of the work and materials of storage. Thus, when hiring workers, there is a checklist for the hiring company to complete to document that employees they hire have completed Texas UST Class C Operator training. It's easy to see why this is a requirement for workers who perform the duties of their jobs in confined spaces like atmospheric storage tanks and other underground storage tanks. The training courses highlight safety for entry and exit of USTs, as well as proper safety gear, understanding safety alarms and alarm failures, hazard identification and also emergency response. A UST Class C training course for Texas operators are offered online at and is comprised of seven chapters, each with a quiz that reinforces students’ chapter instruction. The course is convenient and especially valuable for Class C operators responsible to inspect, monitor and maintain atmospheric storage tanks as part of their jobs. More information on how to enroll in the Class C operator training course can be found at

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