Johnson Window Films - Bomb Blast Test

Bomb Blast Testing

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ANTI-GRAFFITI / VANDALISM

BOMB BLAST / TERRORISM

ANCHORING SYSTEMS

Open arena bomb blast testing is commonly carried out in accordance with one of 2 accepted standards, ISO 16933 and ASTM F 1642 (GSA Blast Standard). Both standards involve a live explosion against a series of windows mounted within test cubicles. The cubicles are arranged around the explosive at measured distances which will give the test windows sufficient blast pressure to meet test standards. Pressure gauges are mounted on the test cubicles as well as an independent structure to confirm pressures during the test.

Typical Blast Test Site Configuration

The basic test procedure is to set off the explosion and measure the pressures along with the performance of the glazing unit. There are two types of pressure measurements:

1) PSI/kPa Pressure – peak pressure of the explosive measured in pounds per square inch (PSI for the GSA test) or kilopascal (kPa for the ISO test).
2) PSI Millisecond /kPa Millisecond Impulse – measures the total duration of the explosion.

Blast Cubicle Interior

For Security films, minimum pressure requirements has been established by the GSA and ISO depending on the glazing product being tested. For example: the GSA minimum pressure required for a window containing 8 mil. Security film with an attachment system is 4 PSI and 28 psi-millisecond. The minimum pressure requirement to pass the ISO test is 50 kPa and 250 kPa-millisecond.

After the explosion occurs, a post blast inspection is performed and the amount of glass (if any) that has been blown into the test chamber enclosure is measured to determine the performance of the film and glazing unit.

Glass Blown Outside of Test Container

It's interesting to note there are 2 phases to a test blast wave. The first is known as the positive phase or reflected pressure load. It's the pressure that expands outwards from the blast origin. A negative phase is then experienced immediately after when the rapid outward movement of the blast wave creates a vacuum in the air. This vacuum is rapidly filled by the surrounding atmosphere being drawn back into the evacuated space. This rapid “re-filling” of air causesdrag or suction on the face of the test container and can cause windows to blow outside of the test container.

Performance ratings are determined by the amount of and area in which the glass (if any) falls within the test chamber. Each performance rating includes the level of protection, hazard level and a brief description of the window glazing response. Below is both the GSA and ISO Performance Rating charts:

GSA Criteria for Test Specimen Performance Conditions

PROTECTION LEVEL	PROTECTION LEVEL	HAZARD LEVEL	DESCRIPTION OF WINDOW GLAZING RESPONSE
1	safe	none	Glazing does not break. No visible damage to glazing or frame.
2	very high	none	Glazing cracks, but is retained by the frame. Dusting or very small fragments near still on floor acceptable.
3a	high	very low	Glazing cracks. Fragments enter space and land on floor no further than 3.3ft. from the window.
3b	high	low	Glazing cracks. Fragments enter space and land on floor no further than 10ft. from the window.
4	medium	medium	Glazing cracks. Fragments enter space and land on floor and impact a vertical witness panel at a distance of no more than 10ft. from the window at a height no greater than 2ft. above the floor.
5	low	high	Glazing cracks and window system fails catastrophically. Fragments enter space impacting a vertical witness panel at a distance of no more than 10ft. from the window at a height greater than 2ft. above the floor.

ISO Performance Chart

HAZARD RATING	HAZARD RATING DESCRIPTION	DEFINITION
A	No Break	The glazing is observed not to fracture and there is no visible damage to the glazing system.
B	No Hazard	The glazing is observed to fracture, but is fully retained in the facility test frame or glazing system with no breach and no materials is lost from the interior surface.
C	Minimal Hazard	The glazing is observed to fracture and the total length of tears in the glazing plus the total length of pullout from the edge of the frame is less than 20% of the glazing sight perimeter. Also, there are no more than 3 perforations or indents anywhere in the vertical witness panel and any fragments on the floor between 1m and 3m from the interior face of the specimen have a sum total united dimension of 250mm or less. Glazing dust and slivers are not accounted for in the hazard rating. If by design intent there is more than 20% pullout, but the glazing remains firmly anchored by purpose designed fittings a rating of C (minimal hazard) may be awarded provided the other fragment limitations are complied with. The survival condition and anchoring provisions shall be described in the test report.
D	Very Low Hazard	The glazing is observed to fracture and is located 1m behind the original location. Also, there are no more than 3 perforations or indents anywhere in the vertical witness panel and any fragments on the floor between 1m and 3m from the interior face of the specimen have a sum total united dimension of 250mm or less. Glazing dust and slivers are not accounted for in the rating.
E	Low Hazard	The glazing is observed to fracture, but glazing fragments fall beyond 1m and up to 3m behind the interior face of the specimen and not more than 0.5m above the floor at the vertical witness panel. Also, there are 10 or fewer perforations in the area of the vertical witness panel and higher than 0.5m above the floor and none of the perforations penetrate more than 12mm through the thickness of the foil backed insulation board layer of the witness panel as defined in paragraph 3.14
F	High Hazard	Glazing is observed to fracture and there are more than 10 perforations in the area of the vertical witness panel and higher than 0.5m above the floor or there are one or more perforations in the same witness panel area with fragment penetration more than 12mm through the thickness of the foil backed insulation board layer of the witness panel.

Click to view the PDFs: ISO GSA Report 4664-1 / ISO GSA Report 4667-1