In the fire safety system of public buildings,steel fire doors are a key line of defense for evacuation routes.The combination of normally closed door closers and automatic reset functions makes this line of defense more reliable and efficient in daily use.
Normally Closed Design:A Balance of Safety and Convenience
Steel fire doors using a normally closed design keep the door leaf always closed,achieving automatic reset through a door closer.This design does not rely on an external power supply or control system;it relies solely on the hydraulic or spring mechanism of the door closer to automatically close the door within 5-7 seconds after it is pushed open.For example,the steel fire doors in the inpatient department of a hospital use double-cylinder door closers with adjustable closing force levels of 3-5,ensuring complete door closure while preventing pedestrian injury,and simultaneously meeting the requirement in the”Code for Fire Protection Design of Buildings”that”fire doors should have an automatic closing function.”
Door Closer:The”Closing Commander”for Double-Leaf Doors
For double-leaf steel fire doors,the door closer is the core device ensuring airtightness.Its working principle is similar to a mechanical latch:when the door is pushed open,the gears or spring mechanism inside the sequential door releases energy;when closing,it first releases the lock on the secondary door,allowing it to close first.Once the secondary door is fully closed,it triggers the unlocking of the main door,which then closes accordingly.In one commercial complex project,the lack of sequential door installation caused double fire doors to”collide”when closing,creating gaps large enough to fit a finger,allowing dense smoke to penetrate within seconds during a fire.After replacing the doors with stainless steel I-beam sequential door units,the door closure error was controlled within±1mm,and smoke isolation performance was significantly improved.
Application Scenarios:From Public Spaces to Core Corridors
Escape Stairwells:Normally closed steel fire doors,combined with sequential locators,prevent smoke from entering the stairwell during a fire,providing a clear view for evacuees;
Equipment Rooms:Protect critical facilities such as power distribution rooms and air conditioning rooms;automatic reset function prevents equipment damage due to human error in leaving doors open;
Commercial Venues:Fire compartments in shopping mall atriums,pedestrian streets,and other areas;transparent steel fire doors maintain visual continuity while meeting fire safety regulations.
Through a combination of”normally closed design+sequential locator+automatic reset,”steel fire doors achieve fire and smoke isolation functions with a low-cost,high-reliability solution,providing a solid guarantee for building fire safety.