Importance of taking hull vibration measurements post scrubber installation.

The technology referred to as scrubbers cleans the Sulphur oxides (SOx) from the ship′s engine and boiler exhaust gases by scrubbing the emissions generated from burning fuel. With an exhaust gas cleaning system, it is therefore possible to continue operating on heavy fuel oil (HFO) after implementation of the IMO 2020 regulation. 

An exhaust gas cleaning system consists of one or several scrubber towers, installed onboard a vessel which change the stiffness and mass of the deck construction. This modification changes the resonance frequency of deck construction and can lead to excessive vibrations which can be harmful to the crew during work/rest time and even cause cracks in structure.

Therefore, it is important to perform measurements of hull before and after modification to check how the new installation influences the deck structure.

The measurements are made in cabins, recreation and working space according to ISO 20283-5 to indicate level of vibrations that influence Crew and passengers.

Other measurements are made on main deck structure, together with scrubber and its parts (pipes etc.) to check if in particular places there are noticed high vibrations that can produce cracks.

Below are examples of measurement places according to Crew comfort:

Fig.1 Navigation bridge – place where officers work

Fig.2 ENGINE ROOM -3rd floor -place where Engineers work

The example of structural measurements to check possibility of cracks is as below:

Fig. 3 Scrubber pipe located in Engine Room

For above examples the results are as follow:

Conclusion for above measurements:

Vibration levels of work places for Crew according to ISO 20283-5 is on low level for the measurements condition.

High vibrations which are observed on scrubber pipe can lead to cracks. Stiffness of scrubber pipe should be increased in location of points 1 and 2 (see pictures below).

Fig.4 Scrubber pipe