It’s been a challenging year, but finally it is vacation time and you are boarding on your cruise around the islands. It is a luxury cruise ship with all facilities for water sports, pampering clubs and exciting night life. The best part is your lovely cabin with a balcony that’s overseeing the ocean. The night comes and you look forward to a long, peaceful sleep, when you hear the subtle rattling on the wall…
As a passenger enjoying the hotel facilities, it is easy to overlook the reality of a ship’s structure, which is an assembly of panels making of the finished interior, while behind the scenes there is the supporting structure and systems that are interconnected, creating a bridge between your cabin and the reciprocating engine or the rotating propeller shaft. These are merely an example of many excitation forces, causing vibrations that are projected as tremor or noise in the accommodation spaces.There are a number of measures taken to limit the phenomenon, among which I will concentrate only on the insulation.
It should be noted that insulation has a dual purpose, with setting fire boundaries being the primary. The ship is subdivided in fire zones, that can create efficient shelters from one space to the next and protect the persons onboard. It is applied on the structure, piping and ducting, as prescribed from regulations and comfort studies.
In the present market, the most common materials are glass wool and stone wool for the structure and ducting, while for piping closed cell foam materials, like armaflex, are more popular. Glass and stone wool are produced as ceramics, with their fabrication being practically unchanged for the past 30 years, as you can see in the references below that describe the method, despite a long chronological gap.
Core materials for glass wool are sand and limestone, with additions of soda-ash and organic or acrylic binding agents, while stone wool is based on basalt and slag. As the aforementioned diagrams illustrate, the process is very straight forward, they materials are weighed, mixed with the proper ratios and then lead into a furnace that heats up to around 1400°. Next comes the fiberizing stage, following by the curing stage, with the end product being cut into prescribed dimensions, ready for delivery.
The references offer a very detailed description of this procedure, therefore I prefer not to expand on it. I’ve only wished to outline it, so I can stress the sore points regarding the environment.
- Sand is a material used in so many different applications and we are constantly depleting its resources, with some people speaking of a global sand crisis. The best response to this fact is the use of recycled materials like old windows or the excess of the material itself during production and application. Recycled glass laterally reduces energy consumption, as melting is accomplished in lower temperatures;
- Basalt is the most popular rock under earth’s surface, sourced from volcanoes eruptions, so perhaps its resources are not in so much strain, but it has gone under scrutiny for its mining and transport GHG emissions.
- Focusing on the furnace, it can be powered by gas or electricity. Gas option is tangled with SOx, NOx, and CO emissions, which are measured to be 10x more than the respective ones generated from the electric furnace, when electric power is sourced through renewable energy. Indeed there are measures taken to limit the GHG emissions from the gas furnace, such as heat recovery systems resulting to lower energy consumption;
- Another form of waste is particle matter, that is generated in different stages of the production, with unloading, gas furnace and oven curing being the main contributors;
Manufacturers claim that for every ton of CO2 produced during manufacture, we are spared 200ton for the product’s lifetime application. It is difficult to validate this claim without independent data, yet it is worth thinking what would require to heat up and maintain a comfortable temperature inside a steel structure without insulation. Then think what it would take to chill it…
Off course composite structure, considering mainly sandwich panels, have their own insulation, very similar to the armaflex piping insulation, yet they have higher requirements for fire divisions, so the need for insulation is still present and at a higher quantity.
Historically the industry has been marred by use of asbestos, which has excellent fireproofing and insulation properties and carcinogenic side effects, that many applicators had to pay the heavy price with their lives. Asbestos has been very popular the better half of the 20th century, with building and ships still covered with it, but has been excluded from the market since the early nineties. The market has since created the aforementioned alternatives, equal to asbestos, free of health concerns for the applicators and residents. Another great example of what is possible when the market hits a wall and has to reinvent itself with higher standards.