Like all physical assets and equipment, the longevity and safe optimum operation of the tank is based on the condition of the asset. Scheduling regular inspections every (3-5) years and performing subsequent repairs can help identify and mitigate several potential hazards, so they can be corrected early with much less downtime and lower cost. This will also help these assets reach their designed useful life and improve their safety and performance. When considering the performance of a steel bolted tank for dry bulk plastics storage needs, there are four key drivers behind why inspections should be performed:

Structural Issues – Identification of metal loss or thinning of steel

There are several factors that contribute to metal loss in a steel tank, such as corrosion or wear from abrasion.  Often it is not obvious or visible from the outside of the tank and an internal inspection or ultrasonic thickness (UT) testing may be required.  Metal loss or reduced metal thickness may impact the structural integrity of the tank and in many cases can lead to dents, buckling, or bulges in the tank. Metal loss can also lead to holes in the tank which threatens product contamination, reduced product quality, product loss, or even loss of profits. Holes also lead to moisture ingress into the tank, which may accelerate corrosion, further reducing the integrity of the hardware or welds. At its most dangerous, substantial metal loss will impact the structural integrity of the entire tank and may lead to catastrophic silo failure and jeopardize personal safety of employees or other individuals. A proper inspection will identify at-risk areas in your tank to avoid aggressive metal loss.

Ensuring Best Operational Performance

The performance of your tank relies on proper operational procedures.  While that seems obvious, there are often overlooked indicators that the tank is not operating efficiently.  Proper venting is the most critical element because a tank needs to maintain the ability to “breath” as product goes in and out of the tank.  Pressure relieve valves, bag houses, bin vents or other ventilation equipment that are not properly cleaned or maintained can become plugged up and lead to over-pressure or excess vacuum on a tank during normal operations and deposit product on the roof around the vent.  Abnormal pressures can cause structural damage such as cracks in the steel, settlement of the roof, denting or severe buckling of the sidewall.  Ultimately, if not corrected, this may lead to excessive build-up of product on the roof or an accumulation of water which further overloads the tank, and ultimately may lead to structural failure. 

Improper flow of the stored product can also cause damage to a steel tank due to sudden changes in internal pressures due to rat-holing, bridging, arching or other abnormal conditions.  An indicator of potential flow issues is often hammer marks on the hopper.  When product is not flowing out of the tank properly, the tendency is to attempt to knock the material free at the hopper, but this is an indication that your tank is not performing efficiently.  The root cause is usually one of two things: the product has a high moisture content and is caking or not flowing properly, or the hopper angle is not sufficient for the product stored in the tank.  Proper inspection may identify these operational risks and determine scope of work needed, so it can be corrected before it becomes a problem.  However, in some scenarios it may be necessary to consult with a flow expert to correct the problem.

Increased Safety for Employees and Community – Regulatory requirements

There are three primary drivers for regulatory requirements: regulatory agencies, national codes and local jurisdictions.  Many regulatory agencies (OSHA, MSHA, etc.) require that owners inspect and maintain equipment in a safe condition to protect personnel and the community.  Codes (NFPA, FM, AWWA, etc.) also have minimum requirements for safe operation and compliance. Finally, in many cases local jurisdictions have adopted similar safety requirements.  In all cases, building owners are required to both know and meet the safety regulations related to the proper maintenance of their assets.  Regular inspections and maintenance can prevent incidents.

Extend Life of Your Tank with Preventive Maintenance

Inspections proactively identify signs of reduced metal thickness or improper operation conditions.  With proper and timely inspection and preventive maintenance, your tank will operate safely, and you will extend the life of your tank and avoid extensive and expensive rework later. A competent professional will see the warning signs through a thorough visual inspection. Also, always insist on a documented inspection report including a full summary of the tanks current condition with photographs and recommendations and cost estimates for any maintenance or work the tank may require. This will help with long-term budgetary planning.

When you have such a valuable and costly investment, there is no reason to allow less reliable sources to compromise your storage tanks integrity. In order to maintain the true integrity of your storage system, it is important to utilize OEM parts and services. As the original equipment manufacturer, we have your best interest, always. Companies like CST have always serviced tanks and domes upon request but have also advanced their maintenance program to ensure all customers receive OEM-quality parts and services from CST and CST authorized professionals, such as the CST Authorized Dealer Network. Utilizing OEM parts and services significantly simplifies the proper care and maintenance process, because their services will strictly match the quality that you would expect from a competent professional.

Other Reasons

There are other reasons to perform an inspection as well. Some additional considerations include:

  • To determine the suitability of the tank for continued or expanded service
  • To lower overall life cycle cost
  • To determine if a tank is suitable for a change in service (type of product stored, different flow characteristics, etc.)
  • Determined if a tank should be replaced
  • Perform Ultrasonic Thickness testing (UT) or other thickness testing to set baseline steel thicknesses

If you have numerous tanks across many facilities and regional operations, CST can also help you assess and prioritize all assets so you are focused on assessing and spending your maintenance budgets on the most critical needs in a timely manner. This starts with an initial assessment of the condition of all of your storage assets and ends with complete plan for you to implement that will guide you in budgeting and planning management of your assets for the next several years. If you do not know where to start with your tanks, we can help with that also.

CST Industries is the global leader in the manufacture and construction of factory coated metal storage tanks, aluminum domes and specialty covers. CST’s global network includes manufacturing facilities and technical design centers and multiple regional sales offices that are located throughout North America and the United Kingdom. International offices are in Argentina, Australia, Brazil, India, Japan, Mexico, Panama, Singapore, United Kingdom, United Arab Emirates and Vietnam. Currently, more than 350,000 storage tanks and 19,000 covers have been installed in 125 countries throughout the world.