Guidance on the issue of a mini ROV for MoU Ballast Tank inspections

DNV GL Technical Update

DNV GL has issued technical update to outline the minimum requirements and conditions that must be met in order to accept the use of ROVs for ballast tank inspections. This includes the planning and preparation as well as conditions for acceptance and reporting.

Planning and preparation

1. The owner shall submit plans and procedures for an ROV survey of the tank(s) to DNV GL in advance of the survey and make these available on board
2. Pre-planning should include an agreement between DNV GL and the owner on the criteria for acceptance and crediting of the survey
3. Plans should be in place for how to handle the discovery of cracks and damage which may require repair at the yard or in dock.
4. Plans should include drawings or forms for identifying the areas to be surveyed, the extent of cleaning and NDT locations and methods, and provision for the reporting of any damage or deterioration found
5. A history of the previous defects found in the tank shall be made available
6. Use of ROVs may be considerably more time-consuming for the DNV GL sureyor compared to traditional inspection by tank entry. Extra time spent is expected to be compensated for.

Conditions for acceptance

1. Water clarity and visibility should be acceptable to the attending surveyor
2. Access to all areas of the tank must be possible using the ROV, and the ROV pilot must be capable of manoeuvring the ROV as directed by the surveyor.
3. The tank has to be suitably marked (frames, distance off CL, etc) such that the location of the mini ROV in the tank is easy to determine at any time (Alternative methods eg sonar, may be considered if they can be proved reliable)
4. Tank coating must be in good condition
5. The ROV inspection footage must be recorded on video media and the system should be able to record voice commentary along with the images
6. If the ROV is to be used for thickness measurements, the firm must be approved undeer approval programme 402A

Reporting

1. Upon completion of the survey, an inspection report, including pictures/ video recordings, shall be produced by the inspection company and presented to DNV GL for review. Reporting should include measurements of the cathodic protection system performance for the renewal survey.
2. In connection with the survey reporting, the criteria on which the tank survey has been credited shall be clearly stated, including any limitations identified.

Source: DNV GL Technical update