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ajarb
ajarb
Magnetically Sealed Doors: A ticking Bomb
May 18 2010, 5:12 AM EDT | Post edited: May 18 2010, 5:12 AM EDT
"All doors are magnetically sealed and only accessible with a valid security pass. Internally each building is connected by indoor corridoors which can also be sealed and isolated by giant magnetically sealed fire doors. These doors are not powered and thus would remain sealed even in the event of no mains power."
Firstly they are sealed by electro-magnets not magnets.These doors will have a backup suply for when the mains fails this will only last for about 24hours then the batteries will die and the doors will release. This is a security system designed to prefent intruders and as such is NOT fail safe it relies on police being somoned , if the power is cut, and them ariving long before the batrerries die. 1  out of 1 found this valuable. Do you?    
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hayden0103
1. RE: Magnetically Sealed Doors: A ticking Bomb
Jul 13 2010, 11:41 PM EDT | Post edited: Jul 13 2010, 11:41 PM EDT
This.

Basically, there are two types of electromagnet doors: Plate locks and latch locks.

Plate locks are the most common. A large metal plate is mounted to a door that contacts a solenoid mounted on the frame. Thus, when the door is shut, the metal plate is magnetically attached to the frame. WHEN THE MAINS FAIL, THESE WILL OPEN. This is both a safety feature and a design quirk. It's physically impossible to 'turn off' permanent magnets so these doors require mains power to run.

The other type, the latching lock, I'm not really sure how it works (magnetically/electrically, I mean. It's really just a latch). The most important thing about latch locks are what type of latch the lock uses. There are two: FAIL-SAFE/FAIL-OPEN AND FAIL-LOCK. When the mains go out, FAIL-OPENS OPEN. Therefore, fail-locks do the opposite: they remain shut when the mains fail. Problem is that they will only ever be able to be opened from the outside without power and that most latch locks are mounted to glass doors, defeating the purpose.

Moral of the story: Stick with 2x4 and rebar. Do you find this valuable?    
ajarb
ajarb
2. RE: Magnetically Sealed Doors: A ticking Bomb
Jul 15 2010, 1:18 PM EDT | Post edited: Jul 15 2010, 1:18 PM EDT
I was assuming as it said fire doors that they would be set to fail-safe open. I was also assuming plate locks. and I quite agree wit your last coment Do you find this valuable?