Tank Inspection
API 653 & MFL Floor Scanning Tank Inspections on 10yr Old Tank
BACKGROUND
A major natural gas and oil E&P producer in Erie, Colorado requires API 653 inspections on their crude oil storage tanks. The tank system was drained and cleaned prior to inspection in accordance with regulatory requirements. Tank dimensions were 100’ X 32’-6” with an overall fill capacity of 41,264 gallons. Tank construction was conducted in 2018 with no periodic condition inspections so a 5yr API 653 was required. The tank is coated steel with welded shell and bottom.
Scope of Work
What are API 653 inspections and what does it entail? The first step in ensuring that a tank is API 653 compliant is to perform external inspections at the recommended intervals. There are three main types: routine inspections, external visual or ultrasonic testing (UT) thickness inspections, and cathodic protection surveys.
Routine inspections are visual inspections of the outside of in-service tanks to look for leaks, corrosion, or shell distortions and to monitor the condition of the foundation, coatings, insulation, and appurtenances. This is the only tank inspection that does not require a certified API inspector. Tank owners/operators or trained personnel are permitted to perform routine inspections at intervals not exceeding one month.
External inspections are executed by an authorized API 653 inspector. The inspector will visually examine the roof, shell, and grounding systems and, if applicable, will remove insulation to the extent required to determine the condition of the base material. An external inspection should be performed every five years unless the owner/operator opts for a UT inspection, which may extend the interval. AUT thickness inspection of the tank’s shell is also performed by an authorized API inspector.
Floor Scanning: the tanks floor is inspected with Magnetic Flux Leakage (MFL) technology and verified with UT. NDE Level II technicians operate an MFL floor scanning unit which detects anomalies over a large surface area.
Lastly, for tank bottoms that are externally protected by cathodic protection, periodic cathodic protection surveys should be completed.
The SOLUTION
Tulsa Inspection Resources (TIR) provides specialized inspection and integrity services for all aspects of the energy industry. Specific to tank inspection, TIR utilizes a single API 653 inspector to condition asses the tank and provide recommendations for repair and/or reconditioning. Similarly, since TIR also employs NDE technicians all internal tank inspection including MFL floor scanning operations can also be executed by TIR. Typically, a single tank requires two (2) ASNT Level II NDE Technicians to conduct a full tank floor scanning operation. For the client in Colorado an additional helper was required as a “hole watch” to ensure anyone working inside the tank was safe from any external tank operations. Following project completion detailed reports were formulated and submitted to the client for use in repair operations as well as documented records to use for subsequent inspections.
RESULTS FROM THE PROJECT
Ultimately, the project manager expressed sincere appreciation of TIR’s ability to react quickly and provide a last-minute solution to their tank inspection requirements. The client is currently in the process of coordinating additional tank inspections and plans to contract TIR to conduct these operations.
