Measurements

Global Vibration Measurements
A low vibration level of the superstructure is the prerequisite for a convenient accommodation and effective working condition on board ships. By global measurements the vibrational behaviour of the ship hull and the deckhouse are investigated during the ship's operation. Synchronous multi-channel data registration allows not only for an identification of excitation sources but additionally reveals the corresponding mode shapes of the hull and the deckhouse. In case the structural vibrations are suspected to be mainly induced by the propeller the global vibration measurement can be combined with propeller pressure pulse measurements.
The yard's target of a low vibration level can effectively be supported by local and global vibration analyses conducted during design phase. Exciter measurements help to validate and check the design during the building phase. We offer you a GL expertise in successful trouble shooting since several decades, a combination of calculations and measurements as well as large data base for comparison and assessment.

Local Vibration Measurements
Local vibration measurements target mechanical vibration on structural components as well as comfort and habitability aspects in accommodation areas and working spaces. Assessment is done according to relevant rules as required by the client (e.g. specific contract conditions, GL rules, ISO 6954, IMO requirements, VDI 2057, BV440, etc). The yard's target of a low vibration level can effectively be supported by local and global vibration analyses conducted during design phase. Impact measurements help to validate and check the design during the building phase. GL offers expertise in sea trial measurements and determines low vibration levels for the proof of comfort on yachts. GL provides measurements of large vibration amplitudes at machinery parts.

Machinery Vibration Measurements
To ensure the long life of main engines and all machinery components conformance with required limits given in different vibration standards is checked. Since all rotating or oscillating machinery is subject to vibration, machinery vibration measurements are the right tool for collecting detailed information about the individual or typical vibration behaviour of a machine component. Local vibration measurements can be carried out using mobile equipment delivering the vibrational load and spectra at specific engine parts. For troubleshooting purposes a full-scale multi-channel measurement can be carried out using modal analysis methods for advanced investigations. GL offers checking of contract conditions on newbuildings, the quantification of vibrations and the identification of machinery vibrations and inadequate designs entailing operational risks.

Contact: Vibration Measurements

Nautical Manoeuvres
Nautical Manoeuvres assess the manoeuvrability of your vessel and the conformance to the related IMO requirements. Based on independent DGPS-equipment this service provides on-line information of the manoeuvring capacity of the vessel during sea trials for instance. Apart from the installation of the antenna no preparation work need to be accounted for. The system can be combined with analogous data like rudder angles or propeller pitch. This service determines the diameters of turning circles to ps and sb,  stop ways (normal or crash stop), Williamson turn or rate of turn. Moreover zig zag tests with the relevant overshoot angles (in connections with rudder angles) are performed. The crabbing capability of your vessel can be investigated as well. GL offers detailed control of ship speed and course track during Mile Runs and the data basis of manoeuvring capability for the wheelhouse poster.

Contact: Nautical Measurements

Long Term Data Acquisition
This tool solves tricky problems in the trouble shooting domain, gathers and selects valuable data for operational decisions. GL's service comprises measuring concept, installation on site and the service during the campaign as well as the analysis and the evaluation of data. The data collection is performed with a multi channel, microprocessor controlled acquisition system. Data reduction as FFT, rainflow analysis and different class counting methods is realized by individually adapted software to meet the requirements of the client's individual task. The crew only periodically needs to send a data disk back to GL.

The client receives both statistical data and triggered time records. Rare and stochastic events can be registered and documented; the triggered time series even provide a pre- and post-history of the event. This long term investigation may reveal the following aspects:

• How does the structure or machinery component perform over a long period?
• What normal load level does it face?
• What are the influences of operating parameters and ambient conditions?
• Which irregularities and short-term loads occur during operation?
• Why do these irregularities occur?

Long term measurements often include GL SeaScout installation.

Shaft Power Measurements
This basic tool verifies the speed performance with regard to contract conditions or when investigating short comings of the propulsion plant. The shaft power is determined by strain gauge techniques. The signal is transferred by an FM-system to a data acquisition system controlled by a laptop. The monitor continuously displays the actual values of shaft torques, speed and powers. A general check of power trains, engine performance and basic aspects for trouble shooting cases are provided. This standard sea trial measurement service was successfully carried out for more than 15 years; technical problems and contractual conflicts have been solved this way on different types of vessels.

The power and speed results gained during the sea trials can, if desired, be transformed to contractual conditions. In case of 2 or more power trains the correct power distribution and performance is checked. When the ship speed is too low it can be decided whether the engine power or the resistance of the vessel is to blame. This tool is needed to control the adequate fuel oil consumption.

Contact: Shaft Power Measurement