Underwater Clearance Measurements

During the underwater inspection BEVALDIA, uses a two-way communication system between diver and surveyor and real-time monitoring  ( CCTV ) in order to achieve the best possible results including tailshaft wear down measurements. The whole underwater inspection process is videotaped and photographed , then delivered to the client and the inspector on DVD along with a detailed written report. BEVALDIA has been approved by all Classification Societies (IACS: DNV, ABS, LR, BV, CLASSNK, RINA, KR, CCS, RS, IRS, CRS, PRS, TL) and the INSB for in water class surveys. In this way decisively contributing to ships dry dock extension. It performs underwater clearance measurements of rudder pintles and tail – end shaft wear down.

Ships under the regulations , it is necessary to measure the rudder clearances and the tail-end shaft wear down clearance measurements in order to ensure that they are seaworthy and safe for the cargo and the crew that mans it.

For the underwater clearance measurements of the tail – end shaft wear down , the measuring tool is provided by the ship , which is unique for each ship and approved by the respective classification society. For the tail-end shafts , four measurements are taken in the strut and stern tube (Fore, aft, port, starboard).

In the tail-end shaft the distance between the shaft and its bearing is measured. For measurements of the wear down of the rudder underwater clearance measurements are taken of the rudder shaft and the bearing , as well as the pegs if any. This clearance should not exceed 2% of the diameter of the shaft.

If the ship observes vibrations then most often the cause lies in the axis system. It may be due to excessive clearances, or misalignment of the axial systems or propeller defects and cannot be detected without specific measurements and controls, such as pitch unevenness, imbalance etc.

If the reported vibrations are accompanied by overheating of the bearings, then the bearing should be replaced even if clearances are less than 2% of the diameter.