Blast Openings

When you have a project with blast requirements, consult your door manufacturer to help you get the information needed to quote and provide the correct products. After participating in a project or two, you will see it is not that difficult of a product to provide.

Security is a core responsibility of a door opening. The door, frame and hardware must work cohesively to provide security from not only people, but various intruders such as fire, noise, storms, radio waves and explosions. Protection from explosion requires high performance security. Blast openings are key in securing buildings for the gas & chemical industry, military, embassy and government buildings. Some hollow metal distributors will shy away from blast openings for fear of not knowing what type of products to supply. Other distributors feel this type of opening is too complicated and will not offer blast products.

The key to providing the correct products for blast is to know the pertinent information required and getting that to the correct people. The first question is what blast standard you are dealing with. Most specifications will reference UFC 4-010-01. This Unified Facilities Criteria (UFC) was established by the Department of Defense (DoD) as Minimum Antiterrorism Standards for Buildings. The latest version of the standard is UFC 4-010-01, 9 February 2012, change 1, 1 October 2013. The standard is a 111 page document covering the minimum test requirements and standards. The standard identified the performance level for the assembly, post blast. Since the standard does not identify the size of the blast or the distance the blast origin is from the assembly, the standard alone will not give you the details you need to provide the correct product for the opening.

Most projects will reference this standard with few other details. The key details needed are:

  • Copy of specification with blast criteria listed
  • Detailed take-off
  • Elevations
  • Section detail
  • Frame anchorage
  • Peak Pressure in psi (pounds per square inch)
  • Impulse Load in psi-ms (pounds per square inch-milliseconds)

Copy of the Specification with blast criteria details included is critical in determining the correct door construction required. The specification language will spell out the test standard and other details on blast size and standoff distance. A well written specification will also list the blast pressure and impulse load, both of which can be determined from the explosive weight and standoff distance, though a number of blast door specifications do not contain this information. The specification might also reference “Level of Protection”, “Damage Category” or “Hazard Level”. All of this information helps determine the door construction needed to contain the blast pressure.

Detailed Take-off will provide the door size along with hardware. This information is needed to confirm the door construction provided will be correct.

The Building Elevation provides the hand of the opening. It is very important to determine if the door is a seated (swings into the direction of the blast area) or unseated (swings away from the blast area) application. An opening that is seated has the advantage of using the frame to help support the door in a blast and does not require special hardware. In an unseated opening, the hardware is critical in keeping the opening secure because the frame only supports the door at the latch and hinge locations during a blast.

The Section Detail and Frame Anchorage show the wall construction.   The frame anchors and wall substrate are essential in keeping the frame intact. The frame provider has calculations that show how much pressure a particular anchor can withstand in various wall types.

Peak Pressure and Impulse Load is important for determining the door type needed to meet the particular building blast requirement. Both are calculated from the blast size (charge weight) and standoff distance (distance from the door to the blast origin). The blast size is referenced as Explosive Weight. The Explosive Weight is categorized as 1 or 2, with Explosive Weight 1 being a larger (vehicle type) explosive and Explosive Weight 2 a smaller (carried by a person) explosive charge. The standoff distance is the span in feet from where the explosive can go off in relation to the opening. The greater the standoff distance, the less force or pressure on the building or opening. The peak pressure is measured in Pounds per Square Inch (psi). The Impulse Load is also measured in psi along with Milliseconds (ms). The impulse load is the duration (length) of the blast load on the building or opening times the blast load (pressure) divided by 2. The peak pressure and impulse load are calculated by an engineer based on size of the explosive and the standoff distance.

Developing doors and frames that will stand up to the pressures needed to protect buildings from the force of an explosion is a challenging process. Independent test labs use a shock tube to test openings at predetermined blast pressures. Using the data from the shock tube test, engineers can calculate the maximum pressure an opening can withstand.

When you have a project with blast requirements, consult your door manufacturer to help you get the information needed to quote and provide the correct products. After participating in a project or two, you will see it is not that difficult of a product to provide.

If you have any questions on blast products feel free to leave a comment. I will get back to you quickly.