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Difficulties in UL10B Testing
UL 10B Fire Resistance Test
The test specimen (door assembly) is installed within a test wall assembly, which typically consists of masonry, drywall, and stud structures. The entire test assembly is then mounted into the test furnace and exposed to a specified temperature for a designated period. The furnace temperature is measured by nine thermocouples evenly distributed throughout the furnace and controlled according to a prescribed time-temperature curve. The furnace pressure must be established within 5 minutes of the test start and maintained throughout the fire resistance test.
UL 10B is a neutral or negative pressure fire test, requiring the neutral pressure plane to be at the top of the test specimen. At this time, the areas below the neutral pressure plane will be affected by the negative furnace pressure, causing the ambient air on the unexposed side to be drawn into the furnace and flow into the interfaces between the door and the frame as well as within the components.
UL 10B Hose Stream Test
Within 3 minutes after the completion of the fire resistance test, the test assembly must immediately be subjected to the impact, erosion, and cooling effects of water flow. The water jet first sprays from the bottom center and then covers all parts of the exposed surface. The water flow should be applied to the test assembly in a steady manner, ensuring that all parts of the test assembly are affected by the water. The duration of the hose stream test depends on the size of the test specimen and the fire endurance period.
On the surface, the UL10B test doesn't seem overly complicated. However, many manufacturers get stuck at this testing stage. After summarizing, our laboratory has identified several reasons:
Inferior Materials, There's not much to elaborate on this. Low-quality door panel filling materials burn and decompose rapidly under high temperatures, truly unable to meet the required fire resistance duration.
Fragile Connectors and Frames, The door frame and the door leaf are connected by hardware. If the door frame lacks sufficient support and the quality of hinges, door locks, etc. is poor, under the impact of hot air currents and the spraying pressure of fire hoses, the door frame will distort, allowing fire to leak, the connections of fittings will become loose and deformed, the door will have problems with opening and closing, and may even fall off, completely undermining the integrity of the fire door as a barrier.
Poorly Designed Sealing Structures, Even if the door core board is of good quality, problems with the sealing structure can lead to fire leakage.
Since the UL 0B test simulates a realistic and harsh fire scenario, any minor product flaws will be magnified, causing manufacturers to fall short at the last moment. Therefore, it is advisable for manufacturers to conduct pre-tests before certification.
The structure of fire doors is complex, involving everything from door panels, filling materials, to hardware fittings and sealing components, all interconnected. During routine production inspections, manufacturers usually focus on conventional performance indicators and find it difficult to simulate the extreme fire scenarios like those in the UL10B test. By conducting pre-tests, manufacturers can identify and address weaknesses, while also avoiding the high costs of failed certification tests, subsequent rectifications, and so on.