MIL-DTL-17813H
3.6.3 System alignment. Piping adjacent to the expansion joint shall be properly aligned and guided
so that the expansion joint is subjected to only those movements for which it is designed. On a universal
expansion joint incorporating tie-rods, the rods may be used to support the weight of the center section.
Joints aligned by internal guides shall have suitable means provided to prevent excessive annular
pressure between the guide and the bellows. (Note: The use of internally or externally guided expansion
joints does not eliminate the necessity of using adequate external pipe guides.)
3.6.4 Guiding. Expansion joints may have guides located both internally and externally or only
internally to the chamber, as specified (see 6.2). Guides shall be integral with the body or rigidly attached
to the tube. They shall be concentric with each other, with the body of the joint, and with the tube. Limit
stops shall be furnished in accordance with the manufacturer's standard practice.
3.6.5 Flow liners. Flow liners and material for these liners shall be specified for all expansion joints,
regardless of the metal of the bellows, in the following cases (see 6.2):
a.
When friction losses should be held to a minimum and smooth flow is desired.
b.
When flow velocities exceed those specified in the EJMA Standards.
c.
When there is a danger of pitting or erosion, as in lines carrying abrasive solid particles,
heavy sleeves are required.
d.
During high temperature service with an uninsulated bellows, when it is necessary to
decrease the temperature of the bellows and enable the metal to retain its higher
mechanical properties.
e.
When copper alloy bellows are used for high pressure drip, or superheated steam, hot
water, or condensate, or when there is any possibility of flashing.
When flow liners are used in "vertical up" sections, drain holes shall be provided to prevent fluid or
condensate accumulation. Flow liners should not be used when high viscosity fluids, such as tars, are
being transmitted, since these fluids could accumulate and cause premature expansion joint failure.
When the fluid is such that purging will effectively prevent accumulation, flow liners may be used in
conjunction with purging connections. Flow liners should not be considered as substitutes for internal
guides.
3.6.6 Shrouds. When specified (see 6.2), shrouds shall be provided which shall protect from external
damage, prevent foreign material from falling between the corrugations of the bellows, and permit
insulation of the expansion joint.
3.7 Bellows material.
3.7.1 Copper alloy bellows. Copper alloy bellows shall have their longitudinal seams joined by either
welding or brazing operations. The bellows (except for those fabricated of diaphragms welded or brazed
at inner and outer perimeters) shall be supplied in a stress relieved or annealed condition and shall be
pickled to remove the heat treating scale. The maximum working pressure rating shall not exceed 25
pounds per square inch gage (psig) for corrugated, unreinforced joints or 200 psig for corrugated,
reinforced joints.
3.7.2 Corrosion-resistant steel bellows. Corrosion-resistant steel bellows shall have their longitudinal
seams joined by welding. The bellows may be stress relieved or annealed at the discretion of the
manufacturer. When some form of heat-treating is employed, the bellows shall be pickled to remove the
resultant scale. (If iron or carbon steel forming tools are used with corrosion-resistant steel bellows, the
bellows shall be passivated after forming.)
3.7.3 Other bellow materials. If materials other than those mentioned previously are used, the
bellows shall be constructed in accordance with the manufacturer's standard practice.
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