Mounting the installation trunk
The installation trunk must be mounted so that it remains vertical during normal operating conditions.
Prerequisites
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This task must take place in dry dock. The shipyard must provide all necessary tools and manpower.
Illustration:
The centre line of the trunk (!) must be parallel with the vessel’s centre line.
The installation trunk is heavy. Always use appropriate lifting equipment to minimize risk of personnel injury or equipment damages. Only certified equipment must be used.
Context
Only the basic steps of the task are offered. Additional procedures with more information and/or details must be provided by the installation shipyard to fit the vessel properties.
The top mating surface of the installation trunk must be protected with a blind flange or wooden cover at all times until the hull unit is installed.
Note
The quality of the welding is critical to the safety of the vessel. Welding must only be done by a certified welder. Always wear the personal protective equipment. Observe and obey the relevant safety instructions.
The final installation work must be approved by the vessel’s national registry, the corresponding maritime authority and/or classification society.
Procedure
1 Define the physical location of the installation trunk.
This location must be carefully selected. The decision must be based on the general principles outlined in chapter Preparations and all relevant knowledge about the vessel construction.
Note
All information related to practical and theoretical noise patterns along the hull must be taken into consideration.
2 Note the orientation of the centre line of the installation trunk with regards to the mounting bolts.
3 Remove the rubber gasket from the top of the installation trunk to protect it from the heat.
4 Cut out a hole in the vessel’s hull with a diameter large enough to accommodate the installation trunk.
The exact size of the hole must be determined by the installation shipyard.
5 Orientate the installation trunk correctly, and then weld it into position.
Observe the installation examples to select the height from the top of the trunk flange and down to the underside of the protection blister.
Important
In order to obtain optimal CS90 performance, the total height of the installation trunk must be as close as possible to its stated minimum height.
The top flange must be parallel to the water line in both the fore-and-aft and athwartship directions.
6 Make sure that the upper surface of the installation trunk is level, undamaged and clean.
7 Cover the upper surface of the installation trunk with a blind flange or wooden plate to protect it.
8 Brace the installation trunk to the hull plating and the surrounding hull frames by adding several strengthening plates.
The plates must be at least 1.5 times as thick as the surrounding shell plating. The final dimensions of the doubling plate must be defined in the approved installation drawings supplied by the shipyard.
9 Stiffen the installation trunk in both the fore-and-aft and athwartship directions by welding strengthening knee-plates both to the trunk and to the doubling plate.
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A Strengthening knee-plates (stiffereners)
B Installation trunk
10 Depending on the shape of the hull, we recommend that you fit a steel blister for protection.
The blister must be designed by the installation shipyard. It must be welded to the shell plating. The blister may be an open type, or it can be filled with oil to prevent corrosion. This last method provides excellent protection, and simplifies maintenance.
Note
Make sure that the hull plating surrounding the trunk is even and smooth without protruding objects that can cause noise. Objects protruding from the hull will generate turbulence and flow noise. This will reduce the CS90 performance. If necessary, grind and polish all surfaces.
11 As soon as all installation, welding and grinding has been done, prime or paint the trunk and the surrounding area using a high quality protective coating.
You must also apply the protective coating to the inside of the installation trunk.
12 Inspect the installation of the installation trunk, the blister, hull plating and all surfaces thoroughly.