American Safe Room manufactures these pre-hung blast resistant double leaf doors that are engineered to protect your shelter from the high pressure blast waves produced by a large conventional or nuclear detonation.
A double leaf blast resistant door has two swinging door leaves mounted on one frame that usually ships in two parts. It is designed to allow vehicles to pass through while carrying the same pressure rating as our single leaf blast door. If your shelter has the ability to house a vehicle, you need this door. Please measure the height and width of your vehicle before ordering.
Sizes - standard and custom
This door comes in two standard sizes - and customs sizes can be built. The standard sizes are 72 inches wide by 80 inches tall and 96 inches wide by 80 inches tall. The free opening when installed is nominally one half inch under the rated size. Please see the manual for more information. We have built many custom sized doors. If you have an existing opening that needs a blast door, please contact us.
This is a custom 12 foot high double leaf blast door with no top frame rail and a flat threshold. It is used in a blast containment room in a foundry where crucibles can be either rolled over the flat threshold or hoisted through the open top with a bridge crane.
These doors are also designed to protect against malicious people and fires. The door features four inches of concrete that resists structural fires, cutting torches, and has a UL level 8 ballistic rating - multiple hits with a 7.62 NATO round with no penetration.
Certified load rating
These doors are certified by a professional engineer to withstand a 50 PSI (3 bar) blast load in the seated condition and 14.5 PSI (1 bar) rebound load in the unseated condition.
The door has been engineered to withstand the "negative pressure" force (less than atmospheric) that sucks the door outward right after the blast wave passes over. A detonation blasts all the atmosphere outward, leaving little or no atmosphere for a very short amount of time. This "negative pressure" has energy and can be as deadly as the high-pressure blast wave. That is why our blast doors have the rebound load rating and our automatic blast valves are double acting for both pressure and vacuum.
How blast doors stop detonations
The energy from a detonation must first overcome the static inertia of the mass of the concrete. Once this inertia is overcome and the door begins to move, it flexes inward, acting as a bridge between the frame from side to side. The blast load puts the concrete fill under a compression load that transfers the blast load to the inside skin. The inside steel skin is put under a tension load as it stretches. Engineers use concrete for applications that require a high compression strength and steel for applications that require a high tensile strength.
Steel envelope construction
We put the steel right where it does the most to resist blast pressures. The concrete is contained inside the steel envelope where it cannot escape. Even if it cracks or disintegrates, it's mass stays inside the door leaf where it transfers the blast load to the inside steel skin.
Install before filling
The 3/16 inch steel envelope is filled with concrete after you hang it in place. This keeps the door relatively light for installation, but puts a lot of dense mass between you and whatever threats are outside your shelter.
The massive hinges have one and a half inch shafts captured by bronze bushings that are press fit into steel blocks and are packed with grease - and they feature grease zerks so that you can keep them lubricated for smooth, effortless opening. The hinges alone weigh 30 pounds per leaf.
The cam latches are rotating handles on the inside of the door leaf that engage a cam welded on the top and bottom frame rail. They are fabricated from plasma cut and formed quarter inch steel plate. They operate in opposite directions in case the door is moved in a blast - one may loosen, but the other one will tighten, holding the door in place. They feature adjustable tension bolts that keeps the handle in whatever position you leave it.
A lot of our double leaf blast doors are installed in industrial applications that require the door latches to be operated from either side of the door. As an option, we install outside cam latch operators that feature a shaft that goes through the door leaf with a handle on the other side that rotates the cam latches. This door has four outside operators and two pull handles on the outside. Outside operators are not suitable for shelters or other high security installations.
Double leaf doors do not have an airtight seal between the leaves. They allow more air leakage than single leaf doors, but they do feature a synthetic rubber seal between the door and the frame allowing for the use of a positive pressure NBC filtration system inside the shelter. The inside cam latches draw the door into the seal as they are rotated. This puts the seal under compression between the door leaf and the frame. The strict tolerances we hold allow us to use a closed cell EPDM foam seal - not the bulb (automotive type) seal commonly used when manufacturers can't hold the tolerance necessary for a solid seal. This seal is expertly applied without stretching it and the corners are cleanly chamfered to seal out airborne toxins. As an option, you can get a second, fire rated seal applied outside of this primary one. Any fires outside your shelter will have to burn through the fire seal before they get to the primary seal.
Double leaf blast doors latch on the top and bottom, not the side like a single leaf door. The standard threshold is a three inch step over frame.
This picture shows a double leaf inward swinging blast door with a flat threshold. It requires that a socket be installed in the floor for bolt latches be installed behind the door leaves.
This door also features adjustable sweeps on the bottom of the leaves that help seal the door.
Inward swinging blast doors
Blast doors normally open outward to carry the load in the seated condition. The blast load transfers directly from the door leaf to the frame and wall, not through the hinges and latches.
Certain installations require an inward swinging door and we offer it as an option. This is one of our cam latches secured shut on an inward swinging door. We mount the cams on risers and widen the face flange of the frame. This picture shows an inward swinging double leaf blast door ready to be shipped. It also features inset pull handles. It was shipped in one piece on a flatbed truck. Most double doors are shipped in two pieces:
We can specify that the delivery truck has a drop gate so the delivery is on the ground exactly where you want it. You must ensure that there is adequate turn around room.
We've placed a lot of these doors in industrial applications: chemical plants, foundries, ordnance storage magazines, ordnance testing ranges, refuge chambers, and even a rhinoceros enclosure at a zoo. If you have an application that needs to protect from, or to contain a detonation, please contact our Sales Manager at 541-459-1806 or sales@AmericanSafeRoom.com
Telephone 541-459-1806 or e-mail
Gallery of double doors
click to enlarge