Fuel is a highly inflammable substance and extremely toxic to the environment if not stored properly. Oil leaks lead to almost 15% of the pollution in the environment each year, harming plants, marine life, damaging rivers, groundwater and soil, natural habitats, and tampers with drinking water sources.

The design and construction of bulk oil tanks for storage are governed by API regulations and standards. The API Standard 650 is widely used for tanks that provide a framework for industries to follow when acquiring, installing, and maintaining tanks for the storage of petroleum, petroleum products, and other commodities.

The API 650 Standard was published by the American Petroleum Institute in 1961 and is one of the regulatory bodies for the design, construction, and maintenance of bulk oil storage tanks that can be applied globally.

The API 650 standard is not mandatory for purchasers, or manufacturers to comply with.

Instead, it is a set of guidelines meant to increase the safety, sustainability, and environmental impact of commercial oil and gas operations.

Does the API Standard 650 apply to all tanks?

The API 650 Standard mentions requirements for tank design, fabrication, welding, inspection, and erection of oil tanks. However, they do not apply uniformly to all types. These specifications apply to tanks that fall under the following category:

• Cylindrical, vertical, above ground, closed and open-top, welded, storage tanks irrespective of their sizes and capacities.

• The internal pressure of the tank is approximately atmospheric pressure.

• Higher pressures are allowed when there is a requirement for the same.

• The tank’s bottom is uniformly supported.

• Tanks in a non-refrigerated facility that has a maximum design temperature of 93 degrees Celsius or less.

  What does the API Standard 650 Specify?

Although this standard offers flexibility, it focuses on five key factors that can add to the safety of bulk oil storage tanks and translate into cost savings for operators in the long run.

1. Tank Material

The API Standard 650 recommends specifications for materials like alloys, minimum, and maximum design metal temperatures, including the lowest and highest temperatures that a plate can withstand with respect to the material and its thickness, impact properties and testing, toughness, etc.

Bulk oil storage companies usually prefer tanks of carbon steel or stainless steel construction for their business.

2. Quality of Welding

The welding holds the parts and components of the structure together. However, it must be compatible with the plate’s chemistry, strength, and quality.

The standards for welding, the method, and the material characteristics are mentioned in the standards along with aspects like corrosive properties, hardness, and overfill protection.

The design of other components like fixed and floating roofs, pipes and pipe couplings, manholes, flanges, gaskets, and nozzles are also mentioned in the API Standard 650.

3. Integrity of the Plate

The integrity of the plate is vital as it may lead to extensive financial losses and environmental damage in case of a natural or manmade disaster. For example, the materials must be protected from corrosion to ensure structural stability.

The plate must be strengthened by rolling or other metal forming techniques that keep the plate’s integrity intact.

Any lubricants, adhesives, or anti-weld spatter compounds should not contain sulfur and chloride compounds as they may react after coming into contact with stainless steel.

4. Installation 

The purchaser usually handles the foundation and grading of the site. The manufacturer examines the level tolerances and grade contours before installing the storage tanks. Once the installer approves the foundation and other parameters, the installer will retain the quality of the foundation provided by the purchaser during installation to ensure structural integrity throughout the oil tank’s lifespan.

The field welding is usually done using shielded metal arc, gas metal arc, gas tungsten arc, oxy fuel, flux-cored arc, submerged arc, electro slag, or electro gas.

The installer also ensures that welding is not performed in the presence of moisture due to rain, ice, or snow.

5. Inspection

Bulk oil tanks must be regularly examined to ensure structural integrity and prevent any leaks or evaporation of the liquids. These periodic inspections must be carried out with the help of an expert in the field.

A radiographic examination (X-Ray) of the shell welds, vacuum testing of floor welds, and other examinations must be carried to ensure safety.

Also remember to consider local and regional regulations, special conditions, and requirements of the industry while inspecting the tanks.

To Summarize

Complying with the API Standard 650 gives businesses the assurance that their facilities are safe and efficient. The guidelines are easy to follow and make decision-making for oil and gas businesses less of a burden. These regulations lay out the specifications for a broad range of commercial applications.

Engineering experts from Mechartes can help you adhere to API Standard 650 guidelines and design and construct state-of-the-art facilities.