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ASME B31.3-2016 <br /> values of the short-term and working estimates of effec- considered in determining the need for flexibility in the <br /> tive moduli of elasticity for given conditions of loading branch pipe. <br /> and temperature may be obtainable from the manufac- <br /> turer. For materials and temperatures not listed, refer A319.7 Means of Increasing Flexibility <br /> to ASTM or PPI documents, or to manufacturer's data. Piping layout often provides adequate inherent flexi- <br /> (a) Because of their viscoelasticity,the effective mod- bility through changes in direction, wherein displace- <br /> uli of thermoplastics under actual conditions of use will ments produce chiefly bending and torsional strains of <br /> depend on both the specific course of the strain (or low magnitude. The amount of tension or compression <br /> load) with time and the specific characteristics of the strain (which can produce larger reactions) usually is <br /> thermoplastic. small. <br /> (b) The modulus may also vary with the orientation Where piping lacks inherent flexibility or is unbal- <br /> of the specimen. Because the reinforcement plays a sig- anced,additional flexibility shall be provided by one or <br /> nificant role in developing the physical properties for more of the following means: bends, loops, or offsets; <br /> RTR and RPM piping, the modulus may vary with the swivel or flexible joints;corrugated,bellows,or slip-joint <br /> type and orientation of the reinforcement. expansion joints; or other devices permitting angular, <br /> (16) A319.3.3 Poisson's Ratio. Poisson's ratio varies rotational,or axial movement. Suitable anchors,ties,or <br /> widely depending upon material and temperature. For other devices shall be provided as necessary to resist end <br /> that reason, simplified formulas used in stress analysis forces produced by fluid pressure,frictional resistance to <br /> for metals may not be valid for nonmetals.For RTR and movement, and other causes. <br /> RPM piping,Poisson's ratio varies with the orientation <br /> of the reinforcement. A321 PIPING SUPPORT <br /> A319.3.4 Dimensions. Nominal thicknesses and Paragraph 321 applies in its entirety. <br /> outside diameters of pipe and fittings shall be used in <br /> flexibility calculations. A321.5 Supports for Nonmetallic Piping <br /> A319.4 Analysis A321.5.1 General. In addition to other applicable <br /> requirements of para.321,supports,guides,and anchors <br /> A319.4.1 Formal Analysis Not Required. No formal shall be selected and applied to comply with the princi- <br /> analysis is required for a piping system that ples and requirements of para. A319 and the following: <br /> (a) duplicates,or replaces without significant change, (a) Piping shall be supported, guided,and anchored <br /> a system operating with a successful service record in such a manner as to prevent damage to the piping. <br /> (b) can readily be judged adequate by comparison Point loads and narrow areas of contact between piping <br /> with previously analyzed systems, or and supports shall be avoided. Suitable padding shall <br /> (c) is laid out with a conservative margin of inherent be placed between piping and supports where damage <br /> flexibility,or employs joining methods or expansion joint to piping may occur. <br /> devices, or a combination of these methods, in accor- (b) Valves and equipment that would transmit exces- <br /> dance with manufacturers' instructions sive loads to the piping shall be independently sup- <br /> A319.4.2 Formal Analysis Requirements. For a pip- ported to prevent such loads. <br /> in stem that does not meet the above criteria the (c) Consideration shall be given to mechanical guard- <br /> ing system ing in traffic areas. <br /> designer shall demonstrate adequate flexibility by sim- (d) Manufacturers' recommendations for support <br /> plified, approximate, or comprehensive stress analysis, shall be considered. <br /> using a method that can be shown to be valid for the <br /> specific case.If substantially elastic behavior can be dem- A321.5.2 Supports for Thermoplastic, RTR, and RPM <br /> onstrated for the piping system [see para. A319.2.2(a)], Piping. Supports shall be spaced to avoid excessive sag <br /> methods outlined in para. 319.4 may be applicable. or deformation at the design temperature and within <br /> the design life of the piping system. Decreases in the <br /> A319.5 Reactions modulus of elasticity with increasing temperature and <br /> Paragraph 319.5 may be applicable if a formal stress creep of material with time shall be considered when <br /> analysis can be shown to be valid for the specific case. applicable.The coefficient of thermal expansion shall be <br /> considered in the design and location of supports. <br /> A319.6 Movements A321.5.3 Supports for Brittle Piping. Brittle piping, <br /> Special attention shall be given to movement(displace- such as glass, shall be well supported but free of hin- <br /> ment or rotation)of piping with respect to supports and drance to expansion or other movement.Not more than <br /> points of close clearance. Movements of the run pipe one anchor shall be provided in any straight run without <br /> at the junction of a small branch connection shall be an expansion joint. <br />