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API 653 best practices for preventing bulk storage tank corrosion

Corrosion in a tank or its accessories is bad news for the facility owner. Corrosion reduces the reliability of the storage tanks and presents a threat to the integrity of the tanks. If corrosion is not dealt with in time, it can lead to catastrophes like fire, contamination, leakage, spill, and more. Moreover, the cost associated with cleaning up the spill is much more than conducting inspections. Thus, tank facility owners must hire API inspection companies for the regular upkeep of the tanks. 

In this blog, we will discuss some steps that tank owners can follow to mitigate the risks caused by corrosion. 

Regular and periodic inspection of tanks

Regular inspection of the facility is the first step towards ensuring there is no risk from corrosion. 

API 653 inspection standards are in place to help bulk storage tank operators extend the life of their equipment. In addition to five-year exterior inspections and ten-year interior inspections, API 653 proposes monthly inspections. Bulk storage tank operators should follow these guidelines as a best practice:

  • Check the insulation mechanism for any changes visually. 
  • Manually examine the chime region and the junction weld for oxidation and spills on a regular basis.
  • Keep track of all monthly, five-, ten-, and even twenty-year inspections.

Oxidation at the base of bulk storage tanks is caused by a variety of factors.

Corrosion is caused by three factors: long-term exposure of uncoated steel to humidity, moisture chemical composition, and surface temperature value between 32 and 212 degrees (F) that encourage steel corrosion. Continuous moisture infiltration into absorbent insulation in insulated bulk storage tanks contributes to this equation and reduces a tank’s energy efficiency.

Corrosion of a tank can be caused by a variety of factors, including:

  • Between the tank and the concrete ring wall foundation, there are a few empty spaces.
  • Underneath the insulation, waterlogged insulation causes localized and acute corrosion.
  • Sealants surrounding the chime have failed.
  • Around the chime, heated bituminous coatings crack and shrink.
  • Tank expansion and contraction cause sealant failure.
  • Water accumulates around the base of the tank.

The tank chime is commonly exposed by owners of bulk storage facilities. The tank chime is the intersection of the steel tank sidewall with the tank bottom at the bottom of bulk storage tanks. Because of this exposure, the crucial weld at the tank’s base should be inspected often by the API inspection services professionals. However, if this exposed region is not properly covered and protected, it will corrode due to exposure to the environment.

Possible reasons for corroded tank bases

The tank chime is often exposed by several feet by many tank facility operators. When the bulk container needs insulation, this causes issues. To keep the sheets from rolling down the tank, the shell insulation requires support at the bottom. Some proprietors use clips around the tank’s side to support the bottom of the panels. As the panels begin to fall downhill, the clips finally cause the insulating system to collapse due to gravity. The downward slide exposes the top of the tank and causes holes, enabling more water to enter. As a result, moisture infiltration in the insulating sheet and adds a substantial amount of weight to the insulation panels, hastening their failure.