Storage tanks typically contain large volumes of valuable but potentially hazardous fluids. Inspection is a key element of the integrity management of storage tanks. The objective of the inspection is to provide information on the tank condition. Opening storage tanks for internal inspection is a lengthy and difficult process, not only will the tank be unavailable during the internal inspection, but it must be drained and cleaned before entry is possible. There are also safety hazards associated with personnel entry for inspection. As such On-Line Inspection (OLI) methods offer an attractive alternative as they can be conducted whilst the tank is in-service and do not require vessel entry. Sonomatic's technicians are experienced in using a wide variety of inspection techniques on various assets in a multitude of environments.

    Inspection Techniques:

  • On-Line Inspection of Atmospheric Storage Tanks.
  • Critical Zone Weld and Lower Shell Plate Inspection.
  • Tank Wall/Shell Inspection.
  • Annular Plate Inspection and Applications.
  • Statistical Analysis of Tank Floor Inspection.
  • Out of Service Tank Floor Inspection.
  • In-Service Inspection of Atmospheric Storage Tank Floors.

Inspection Planning

Sonomatic works with clients to plan inspections of atmospheric storage tanks, considering both operational and integrity requirements:

  • Integrity: An approach similar to planning for pressure vessel NII is adopted. This entails developing a detailed understanding of the degradation threats and associated risks to define the most appropriate inspection strategy, e.g. Type A or Type B NII. Detailed inspection requirements, i.e. probability of detection, accuracy and coverage are then defined for each zone of the tank. Finally, inspection plans, defining the inspection technique(s), coverage and locations for inspection are developed.
  • Operational: Successful in-service inspection of tanks relies on comprehensive planning of all operational aspects. This relies on working closely with the tank owner/operator to establish critical design, operational and safety data relevant to carrying out the inspection. With this information, Sonomatic develops a detailed project plan. This covers logistics, equipment and manpower requirements as well as site requirements to facilitate the inspection.

Screening For Tank Floor Corrosion

Sonomatic’s inspection approach provides 100% coverage of the tank floor through acoustic emission (AE) testing, performed before the in-service ultrasonic inspection. The approach is aligned with the inspection strategy. In addition, a Short Range Ultrasonic Inspection (SRUT) is carried out on the external area of the annular plate, around the full circumference of the storage tank. Combining the results of these inspection technologies allows the following robotic in-service tank floor inspection to be focussed on specific areas of interest, highlighted by the AE and SRUT inspections.

    Inspection Types:

  • For tanks where a Type A strategy applies, the acoustic emission is used as confirmation that corrosion is not active. If evidence of corrosion activity is found at this stage, then the strategy is revised.
  • For tanks where a Type B strategy applies, the acoustic emission is used to identify areas of corrosion activity for prioritisation of coverage for the ultrasonic inspection. This ensures that the sample inspection includes representative areas of corrosion.

Tank Cleaning

Sonomatic have experience in cleaning all types of storage tanks and can treat sludge in several ways. With highly trained technicians, our cleaning methods meet and exceed the latest compliance and health and safety standards.

    Cleaning Methods:

  • The sludge can be locally disturbed to clear a space for the ultrasonic inspection.
  • The sludge can be marshalled into a particular location in the tank.
  • The sludge can be mixed in with the product higher up in the tank.
  • The sludge can be pumped from the floor to the roof manway and then into temporary tankage for treatment.
  • The sludge can be pumped from the floor to the roof manway and then into a neighbouring tank.