Test Details
Test Purpose
This test determines whether an operational shield is adequate for protecting personnel from a maximum credible incident (accidental) plus a 25 percent overcharge based on the following acceptance criteria as outlined in MIL-STD-398:
- Blast Attenuation: Shields shall be designed to prevent exposure of operating personnel to peak positive incident pressures above 2.3 psig.
- Fragmentation Confinement: Shields shall be designed to (a) contain all fragmentation or direct fragmentation away from areas requiring protection; (b) prevent generation of secondary fragmentation within areas requiring protection; and (c) prevent movement, overturning, or structural deflections which could result in injury.
- Thermal Effects Attenuation: Shields shall be designed to limit exposure of personnel to a critical heat flux value based on total time of exposure. The critical heat flux equation is as follows: Q = 0.62t^(-0.7423), where Q is the heat flux in cal/(sec cm^2) and t is the total time in seconds that a person is exposed to the radiant heat.
Blast overpressure and heat flux are measured at the center of probable head locations of each operator. For standing locations, the gauges are positioned 65 inches above the floor. For sitting locations, the gauges are positioned 31.5 inches above the seat.
Note that whether or not shielding is required depends on the process hazards analysis which incorporates the likelihood of an initiation event, quantity of material, personnel exposure, etc.
Key Parameters
| Key Parameter | Objective | Origin | Specs |
|---|---|---|---|
| Configuration of substance or article | Simulate a specific in-process configuration or a worst-case configuration (confined, random orientation) as identified in the process hazards analysis | In-process configuration | Articles placed in a worst-case configuration (e.g. side-by-side, end-to-end, and/or in a pile) as observed or possibly observed in process with a 25% overcharge according to MIL-STD-398. |
| Quantity of articles | Simulate the in-process configuration with a 25% overcharge according to MIL-STD-398 | 25% overcharge of worst-case in-process configuration | |
| Initiation method | Initiate the substance or article in the most likely way it could be initiated in the process as identified in the process hazards analysis | ||
| Operational shielding | Provide necessary shielding to protect personnel and as necessary comply with MIL-STD-398 requirments | Shield specifics and implementation verified by test data |
Indicators
| Indicators | Detection Method | Assessment |
|---|---|---|
| Pressure experienced by operator(s) | Pressure probe recorded data | Pressure should be below 2.3 psig per MIL-STD-398 |
| Fragmentation | Video and visual evidence | Shield should contain all fragments, prevent generation of secondary fragments, and prevent deflections that could cause injury per MIL-STD-398 |
| Heat flux experienced by operator(s) | Heat flux recorded data | Heat flux should not result in personnel injury as per the requirements in MIL-STD-398 |