NPFC - MIL-I-24092

INSULATING VARNISHES AND SOLVENTLESS RESINS FOR APPLICATION BY THE DIP PROCESS

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Organization:	NPFC
Publication Date:	21 September 1993
Status:	active
Page Count:	25

scope:

This specification covers clear solvent type varnishes and clear solventless resin systems used to insulate and bond electrical coils and windings.

Varnishes and resins are of the following grades, classes, and compositions as specified (see 6.2).

Grade Class Composition (see 1.2.1) (see 1.2.2) (see 1.2.3) CA - Clear, solvent, air-dry 130 and 155 I, II CB - Clear, solvent, baking, 130 to 180 I, II flexible CB - Clear, flexible, baking, 200 and 220 I, II varnish CBH - Clear, solvent, baking, 130 to 200 I, II semi-rigid CBS - Clear, solvent, baking, 180 to 220 I, II silicone

Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, SEA 03Q42, Naval Sea Systems Command, 2531 Jefferson Davis Hwy, Arlington, VA 22242-5160 by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.

Grade Class Composition (see 1.2.1) (see 1.2.2) (see 1.2.3) SF - Solventless flexible 130 to 180 IV SFT - Solventless flexible 130 to 180 IV thixotropic SH - Solventless semi-rigid 155 to 200 IV SHT - Solventless semi-rigid 155 to 200 IV thixotropic SS - Solventless silicone 180 to 220 IV WB - Water base flexible 130 to 200 III WBH - Water base semi-rigid 130 to 200 III PK - Patching kit 130 and 155 IV

Grades of material are classified according to composition and function (see 3.1).

Classes are designated in degrees Celsius (°C) according to the maximum continuous operating temperature.

Compositions are classified according to the type of solvent or monomer in the varnish or resin, as follows:

I - Organic solvent system.

II - Organic system in accordance with Rule 442(66).

III - Water reducible.

IV - Organic monomer or diluent.

This specification may require the use of hazardous material, operations, and equipment. It is the responsibility of the user to establish appropriate safety practices and to determine the applicability of regulatory limitations prior to use.

intended Use:

The insulating products covered by this specification are intended for impregnation or coating of all types of electrical coils and windings. They are rated for continuous operation at the maximum operating temperature specified for each class. Products may also be used at temperatures lower than the thermal class. Products covered by this specification are intended for use in the dip process except for brush applied patching materials and coatings applied over identification markings. The primary purpose of the varnish is to protect the coils from the operating environment.

Grade CA varnishes are clear, air-drying varnishes which are used for spot patching and emergency repairs where baking facilities are not available. This category includes certain coatings such as lacquers which are used as environmental protection for identification markings.

Grade CB varnishes are clear, flexible, baking varnishes which are for application on stationary coils and windings and satisfy the requirements of ASTM D 1932.

Grade CBH varnishes are clear, semi-rigid, baking varnishes/resin which have higher bond strengths at elevated temperatures than the CB grades. They are not intended to satisfy the requirements of ASTM D 1932 as required for CB grade (see 6.1.2). They are primarily used for rotating windings such as armatures, rotors, and similar constructions.

Grade CBS varnishes/resin are clear, silicone, baking varnishes/resin primarily used for insulating equipment operating at temperatures in excess of 180°C. These varnishes can usually satisfy the requirements of ASTM D 1932. They do not have high bond strengths at their designated classes of 200 and 220°C, and are, therefore, used for stationary windings which operate continuously at these temperatures.

Grade SF varnishes/resin are clear, flexible, solventless, baking varnishes which are used for impregnating and coating stationary coils and windings. These varnishes meet the requirements of ASTM D 1932.

Grade SFT varnishes/resin are clear, flexible, solventless, thixotropic, baking varnishes/resin which are similar to grade SF except they yield heavier coatings per varnish/resin. Since they normally contain powdered mineral fillers to obtain thixotropy, heavy coatings of these materials are usually translucent.

Grade SH varnishes/resin are clear, solventless, semi-rigid, baking varnishes/resin which have higher bond strengths than grade SF and are not intended to meet the requirements of ASTM D 1932. These materials are used on rotary windings.

Grade SHT varnishes/resin are clear, solventless, semi-rigid, thixotropic, baking varnishes/resin used on rotary windings because of high elevated temperature bond strengths. Since they normally contain powdered mineral fillers to obtain thixotropy, heavy coatings are usually translucent.

Grade SS varnishes/resin are clear, solvent-less, silicone, baking varnishes/resin used primarily for high temperature impregnation and coating applications.

Grade WB varnishes/resin are clear, flexible, baking varnishes/resin which are for application on stationary coils and windings and satisfy the requirements of ASTM D 1932.

Grade WBH varnishes/resin are clear, semi-rigid, baking varnishes/resin which offer high bond strengths at elevated temperatures and are not intended to satisfy the requirements of ASTM D 1932. They are primarily used for rotation windings such as armatures, rotors, and similar constructions.

Grade PK varnishes/resin are clear, room temperature cure varnishes/resin, used for spot patching and emergency repairs where baking facilities are not available. The final properties can be improved through the careful application of local heat, for example, by heat gun or heat lamp.

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