MIL-DTL-62545E
3.2.1 Dissimilar metals. Except where necessary to complete an electrical circuit, contact between dissimilar
metals, which could encourage galvanic action, shall be avoided. Separation of dissimilar metals shall be
accomplished by providing approved protective finishes, coatings, or insulation between the mating materials and
shall be in accordance with provisions of MIL-STD-171 which address reduction of corrosion at intermetallic contact
points. Corrosion-resistant materials shall be used whenever possible (see 4.6.1).
3.2.2 Encapsulation. Encapsulation (if used) shall be silicone rubber compound to permit removal for repair
(see 4.6.1).
3.2.3 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally
preferable materials should be used to the maximum extent possible provided that the material meets or exceeds the
operational and maintenance requirements and promotes economically advantageous life cycle costs. All
components supplied shall be new and unused.
3.2.4 Pure tin. The use of pure tin as an underplate or final finish is prohibited both internally and externally. Tin
content of the standard electronic control module components and solder shall not exceed 97 percent, by mass. Tin
shall be alloyed with a minimum of 3 percent lead, by mass (see 6.8).
3.3 Design and construction. The MSEC shall be designed to monitor and control fire extinguishing systems
consisting of the following components:
a.
One MSEC.
b.
One to four Halon 1301 fire extinguishers in accordance with MIL-DTL-62547.
c.
One to four optical fire sensor assemblies (OFSA) in accordance with MIL-PRF-62546.
d.
Built-in-test-equipment (BITE) (integral with above components).
e.
Test and alarm panel.
f.
Interconnecting electrical harnesses.
The MSEC shall issue signals upon receipt of the following data:
a.
Report of system condition from the BITE.
b.
Report of extinguisher availability.
c.
A fire signal from an OFSA or from the test and alarm panel.
A large fire signal, which may originate from an OFSA or the test and alarm panel, shall cause the MSEC to drive
extinguisher discharge, activate visible and audible fire warnings, and power a ventilation fan relay. In response to a
small fire signal from an OFSA(s), the MSEC shall only activate warnings. Loss of continuity in extinguisher circuits
shall cause the MSEC to activate extinguisher status lamps. The MSEC shall not be involved in OFSA decisions
respecting the nature and origin of fires and false alarms. The MSEC shall communicate system condition between
BITE and the test and alarm panel. Operating temperature range shall be -51 to +71°C (-60 to +160°F) (see 4.6.1).
3.3.1 Activation sequence The MSEC shall monitor the availability of, and shall activate, extinguishers as
specified herein. The order of priority of the extinguishers shall be 1 (highest), 2, 3, and 4. Extinguishers shall be
considered available when pressure/flow switch and solenoid continuities are sensed by the MSEC (see 3.4.5 and
table I). Within 2 milliseconds (ms) of receipt of a large fire signal from an OFSA or an electrical-manual activation
signal, the MSEC shall apply extinguisher drive signals to the two highest priority available extinguishers. An
extinguisher shall not be considered available for 8 to 10 second(s) after the MSEC has supplied a drive signal to it.
If flow indications are not received within 38 ms of the start of the drive signal for either or both of the extinguishers
chosen initially, the MSEC shall provide automatic back-up (see 6.4.3) to select and apply drive signals to the next
highest priority extinguisher(s) and check its flow in turn. After the MSEC begins extinguisher activation, it shall
ignore OFSA large fire signals for 0.5 second and electrical-manual activation signals for 4 to 6 seconds. If the
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