MIL-DTL-16356E
3.12.11 Illuminators and vision hoods. Gauges shall be furnished complete with illuminators operating on
110 volts alternating current (AC). Illuminator boxes and vision hoods (if used) shall be easy to remove and to
maintain and depth of box shall be held to the minimum possible. Mercury vapor type lamps shall not be permitted.
Illuminators and hoods shall not be adversely affected by externally imposed vibrations through 33 hertz (Hz).
Illuminators and hoods shall be shockproof (see 4.4.1.1 and 4.4.1.2). Hoods, when used, shall allow a minimum
angle of 90 degrees visibility. Where LED light units are supplied, they must be mounted so that adequate cooling
is provided and quick replacement can be achieved in the event of a unit failure. Where two units are provided for
18-inch visibility gauge they shall be interchangeable; they should also be interchangeable with the spares provided.
Since there is no illuminator housing on LED illuminators for the installation of emergency back-up lighting, an
uninterruptable power supply (UPS) shall be used with LED systems.
3.12.12 Shock and vibration.
3.12.12.1 Shock. Gauges shall withstand the test for Grade A and Type A equipment as specified in
MIL-S-901. Gauges shall not be damaged or caused to malfunction by the shock loadings encountered aboard ship,
such as those resulting from non-contact underwater explosion, when tested as specified in 4.4.1.1.
3.12.12.2 Vibration. Gauges shall withstand the Type I vibration test in accordance with MIL-STD-167-1
through 33 Hertz (Hz). Gauges shall not be adversely affected by externally imposed vibrations when tested as
specified in 4.4.1.2.
3.12.13 Pressure.
3.12.13.1 Class I. Class I gauges shall accommodate a designed pressure to 750 psig (600 psig nominal).
These gauges shall be for installation on boilers with up to and including 750 psig design pressure.
3.12.13.2 Class II. Class II gauges shall be for designed pressure to 1050 psig (900 psig nominal). These
gauges shall be for installation on boilers with between 700 and 1050 psig design pressure.
3.12.13.3 Class IV. Class IV gauges shall be for designed pressure to 2550 psig (2500 psig nominal). These
gauges shall be for installation on 1200 psig boilers and catapult accumulators.
3.12.14 Life. Boiler-water gauge assemblies, except for glass set insets, shall have a life of 40,000 hours of
operation at saturated steam pressures corresponding to applicable boiler design pressure. Glass set inserts shall
have a minimum life of 5,000 hours of operation at saturated steam pressures corresponding to applicable boiler
design pressure. Bulbs for illuminators shall operate for a minimum of 2,500 hours of service. LED illuminator
assemblies shall be designed for minimum life of 10,000 hours of service.
3.13 Type B.
3.13.1 Configuration. The Type B gauges shall be furnished with reflex glasses. Sizes and visibility range of
gauge glass shall be as specified (see 6.2). A shut-off valve with lever pull and chain shall be furnished for main
boiler and catapult accumulator applications (see 3.10.2).
3.13.1.1 Reflex glass. The reflex glass shall be made of a tempered borosilicate glass for use with steam up to
300 psig pressure. The steam or water face of the glass shall have molded or cast prismatic serration extending the
full length of the inner or exposed surface of glass. There shall be ample margin on the inner surface to receive the
gasket. The glass shall be 15/16+3/64, -1/64 inches wide and 11/16+0, -1/32 inch thick. Length shall be in accordance with size
shown in table IV as specified. Both ends shall be rounded to a semicircle of a radius equal to one half of the width.
The front and back faces of the glass shall be parallel within 0.010 inch.
3.13.1.2 Gaskets. Two gaskets 1/16 inch thick made of MIL-DTL-24696, Type I reinforced graphite gasket
material shall be furnished with each glass. The outside dimensions of the gaskets shall be the same as those of the
glass for which they are intended. The bearing surface of the gasket shall have a uniform width of not more than
/8 inch and not less than 5/16 inch.
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