MIL-DTL-917 Electric Power Equipment, Basic Requirements ForThis specification covers the basic requirements applicable to the design, materials, and construction of naval shipboard electric power equipment \(exclusive of communication equipment, information technology \(IT\) equipment, and combat systems [fire control and weapons control equipment]\). Unless otherwise specified herein, the electric equipment developed for shipboard use under the requirements of this specification are limited to a maximum 450 volt \(V\) alternating current \(AC\) and a maximum 1,000 V direct current \(DC\). This equipment is intended for use on surface and submarine naval vessels \(see 6.2\).

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MIL-DTL-917F(SH)

3.3.1.8 Other prohibited materials. The following materials shall not be used, except as specified in the

individual equipment specification:

Linen

Cellulose acetate

Cellulose nitrate

Regenerate cellulose

Wood

Jute

Leather

Cork

Paper and cardboard

Organic fiberboard

Hair or wool felts

Plastic materials using cotton, linen, or wood flour as a filler

3.3.1.9 Flammable materials. Flammable materials include any material in a form which will ignite or explode

from an electric spark, flame, or from heating, and which, if so ignited, will independently support combustion in the

presence of air. As a guide, materials shall be selected on the basis of maximum resistance to burning when tested

in accordance with the methods in the applicable documents listed in table VI.

TABLE VI. Material resistance to burning.

Applicable

Materials 1/

Limit

document

Laminated plastics

DTIC AD 297457

Ignition � 95 sec. min.

Molded plastics

ASTM D5948

Burning � 120 sec. max.

Encapsulating compounds

DTIC AD 297457

Weight loss � 15% max. Ratio

B/I � 84% max.

All other flammable materials except

ASTM D635

Burning time � 10 sec. max.

those used internally in varnished coil

Self-support plastics

Extent of burning � 25 mm max.

structure, metal enclosed shock resilient

pads, and gaskets sealing metal surfaces

NOTE:

These are organic materials in the open atmosphere having insulating characteristics and used

for mechanical protection and structural support. Insulating materials used in the open

atmosphere in switchgear, control, regulating, and power applications are materials falling in

the category of table VI. Varnished coil structures are excluded from this category at present,

on the basis that flame resistant varnishes are not available and, in general, the heat sink

capabilities of equipment using varnished coil structures are such that flame propagation is

reduced.