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Development of a Component Head Injury Criteria (HIC ... - FAA

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in figure 6. The regulator is a card-mounted device that does not require gas flow to maintain<br />

pressure. This design eliminates the discharge <strong>of</strong> vented nitrogen while maintaining constant<br />

pressure in the accumulator, thus ensuring that no nitrogen is lost during the process. The low,<br />

minimum-control volume <strong>of</strong> 1 in 3 ensures a smooth buildup <strong>of</strong> pressure and allows fine<br />

adjustments to be made.<br />

Figure 6. Electronic Pressure Regulator<br />

A silencer was added to the EPR primarily to prevent dust from entering the solenoid spool. A<br />

bursting disc (figure 7) was included upstream <strong>of</strong> the solenoid valve to protect the low-pressure<br />

components <strong>of</strong> the gas supply system from the high-side (gas bottle) pressure <strong>of</strong> up to 3000 psi.<br />

Bursting Disc<br />

Solenoid Supply<br />

Valve<br />

Figure 7. Solenoid Supply Valve and Bursting Disc<br />

The accumulator was instrumented with a pressure sensor (figure 8) that provided the computer<br />

with a feedback loop created using the pressure sensor, computer, and the EPR to obtain<br />

repeatable accumulator pressures.<br />

6

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