MIL-DTL-18182F
ends. The style B union shall be threaded with NPT male on one end and female on the other, and shall
be applicable only to class 1 and class 2 unions.
3.2 Manufacture. Unions shall either be hot-formed, cold-formed or machined from wrought bars.
Swaged-end unions manufactured by swaging or upsetting pipe ends do not meet the requirements of
this specification.
3.3 Materials. Materials used shall be free from defects, which would adversely affect the performance
or maintainability of individual components or of the overall assembly. Materials not specified herein shall
be of the same quality used for the intended purpose in commercial practice. Unless otherwise specified
herein, all equipment, material, and articles incorporated in the work covered by this specification are to
be new and fabricated using materials produced from recovered materials to the maximum extent
possible without jeopardizing the intended use. The term "recovered materials" means materials that
have been collected or recovered from solid waste and reprocessed to become a source of raw materials,
as opposed to virgin raw materials. Unless otherwise specified, none of the above shall be interpreted to
mean that the use of used or rebuilt products are allowed under this specification.
3.3.1 Carbon steel. The unions shall be manufactured from carbon steel conforming to
ASTM-A181/A181M, Class 70, or ASTM-A105/A105M.
3.4 Standard commercial product. Each union of the same classification shall, as a minimum, be in
accordance with the requirements of this specification and shall be the manufacturer's standard
commercial product. Additional or better features which are not specifically prohibited by this
specification, but which are a part of the manufacturer's standard commercial product, shall be included in
the unions being furnished. Standard commercial product is a product, which has been sold or is
currently being offered for sale on the commercial market through advertisement, manufacturer's
catalogs, or brochures, and represents the latest production model.
3.5 Identical items. All unions of the same classification, furnished under any specific contract, shall be
physically and mechanically identical. This requirement includes parts, assemblies, components, and
accessories.
3.6 Design. The design of the unions shall be in accordance with the manufacturer's standard product
and Class 2 unions shall be in compliance with paragraphs 8 and 10 of MSS SP-83.
3.7 Size. The size of the union shall be the nominal pipe size of the pipe with which it is intended for use.
The size required shall be as specified (see 6.2), in accordance with the following nominal pipe size range
for each class of union:
Class 1 0.125 through 3 inches.
Class 2 0.125 through 3 inches.
Class 3 0.250 through 2 inches.
3.8 Union joint. Unions shall be furnished with either a ball-to-ball or ball-to-cone joint.
3.8.1 Seats. Union joint seats shall be integral or inserted.
3.8.1.1 Integral seats. Integral seats shall be machined directly in the parent metal of the union end
pieces.
3.8.1.2 Inserted seats. Inserted seats may be either single or double. Single-insert seats shall consist of
a seat ring secured to the union thread-piece and machined to the contour of the female seat to form a
bearing surface for the male joint surface of the nut-piece. Double-insert seats shall consist of separate
seat rings secured to each end piece. Insert seat rings shall be secured to the applicable end piece in
such a manner as to become an integral part of the union.
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