Due to a rapid decrease in the volume of shipbuilding orders amid the ongoing global economic downturn, the sluggish performance of the domestic shipbuilding industry has been continued. However, the volume of the orders of high value-added offshore plants such as special ships resulting from the development of energy resources has been on the rise. Accordingly, domestic shipyards and related material companies have been developing the materials of offshore plants with great interest.
Yet, the technology of making such materials in Korea is still at the stage where the development of class H materials of offshore plants has been limited to only a few items including vertical and horizontal partition members and fireproof doors. And most materials are just classes B & A those are fire protection ratings for general ships.
Outbreaks of fire at sea are one of the most risky factors posing a threat to safety and, therefore, it is essential to prevent fire from spreading to other areas. Besides, when a fire breaks out, toxic gas and flames move quickly through ducts penetrating the fireproof divisions. Thus, in order to protect against damages from flames and the spread of fire to nearby areas, the installation of fire dampers was made mandatory.
Depending on fire ratings of the fireproof divisions penetrated by ducts, fire dampers of class A-0 ~ A-60 must be installed when ducts penetrate class A divisions and class H-0 ~ H-120 fire dampers have to be installed when ducts penetrate class H divisions. However, as for the current domestic technology relating to the development of fire dampers, only class A-0 fire dampers have been developed and the development of class A-60 fire dampers has been completed only recently. As class H fire dampers required for offshore plants have not been developed yet, they are all being imported from overseas.
The need to develop such fire dampers made the present research aim to secure class H-120 thermal insulation of fire dampers. To this end, 3 types of specimens were created depending on the thickness of coaming insulation and on the presence or absence of damper blade insulation and fire resistance tests were carried out to measure the surface temperatures of the unexposed sides of insulation materials and coaming.
The test results showed that specimen-1(88 mm) and specimen-2(126 mm) of an uninsulated damper blade exceeded thermal insulation performance acceptance criteria at 21 minutes and 46 minutes, respectively, but specimen-3(126 mm) of an insulated damper blade met the 120 minute insulation performance criteria. It was confirmed based on the fire resistance tests that at the minimum protruded length of 500 mm of the unexposed side of coaming according to the fire resistance test criteria of fire dampers, the insulation of the damper blade is an important factor in the fireproof performance of fire dampers.
In addition, fire resistance tests on the specimen-4 and -5 were conducted with the changes in the thickness of the insulation of the exposed and unexposed sides of the coaming as variables in order to identify optimal coaming insulation conditions that can secure class H-120 insulation for the specimen-3 (blade insulated & coaming 126 mm) which secured the class H-120 fireproof performance in the previous experiment.
The test results revealed that the specimen-4 (88 mm) whose exposed side of coaming insulation was 38 mm shorter than the specimen-3 (126 mm) satisfied the class H-120 insulation criteria, but the specimen-5 (50 mm) that was 76 mm shorter exceeded thermal insulation performance acceptance criteria at 110 minutes with 181℃. These findings indicate that the optimal insulation conditions that are lighter than the specimen-3 include 88 mm of thickness of the exposed side of coaming insulation, 50 mm thickness of the unexposed side of coaming insulation, and 324 mm length of insulation.
According to the comparisons of the temperature increases, it appears that a reduction in the thickness of the exposed side of coaming insulation causes the surface temperatures of insulation materials to be greatly influenced by the conductive heat from the bulkhead. And the surface temperatures of coaming seem to be largely affected by radiant heat emitted by blade and the exposed side of coaming.