Torsional & Shaft Alignment
TecnoVeritas (Portugal & Singapore), uses TAS, Torsional Vibration Analysis system telemetry instrument from TecnoVeritas Engineering to perform true mechanical Torque & Power measurements on marine propeller shafts. Shown below is a recent case study.
TecnoVeritas was contracted by a United States shipowner to perform torsional vibration and shaft alignment measurements using strain gages technique on the main propulsion system, specifically on the propeller shaft of an oil tanker. The ship owner’s and classification society concern was related to the torsional vibration and possible shaft misalignment stresses on the intermediate shaft bolts that were found cracked. They needed to know if the originated torsional vibration stresses were within the shafting limits or not, therefore becoming a possible cause of the bolts failure.
TecnoVeritas was tasked with getting torsional vibration and shaft alignment measurements from the shaft line which would show the stresses magnitude and frequencies involved to compare with ship design data. They did so by using the TAS in conjunction with TecnoVeritas Torsional Vibration Software. This combination allowed TecnoVeritas to accurately measure the torsional vibrations and alignment stresses within the ship’s propulsion system and compare the measurements with the predicted values from the analysis carried out using the TecnoVeritas Torsional Vibration Software and respective ship design data.
Using this combination of TecnoVeritas Torsional Vibration Software, the ships design data and the measurements data, it was determined that the torsional vibration levels were acceptable to the classification society rules and that the cause of failure was related to defective tightening of the flange bolts.
Type of vessel: Crude Carrier
DWT: 182, 655 Ton
LOA: 274,26 meters
Main engine MCR power: 18, 620 kW
Main engine MCR speed: 91 RPM
Propeller type: 5 Bladed Fixed Pitch
Propeller weight on air: 44,281 Ton
Propeller diameter: 9,00 m