|
ASME B31.3-2016
<br /> the temperatures determined in para. 319.3.1(a) or (b). (c) is of uniform size, has no more than two points
<br /> For materials not included in Appendix C, reference of fixation, no intermediate restraints, and falls within
<br /> shall be made to authoritative source data, such as the limitations of empirical eq. (16)8
<br /> publications of the National Institute of Standards and
<br /> Technology. Dy 5 Ki (16)
<br /> 319.3.3 Poisson's Ratio. Poisson's ratio may be
<br /> taken as 0.3 at all temperatures for all metals. More where
<br /> accurate and authoritative data may be used if available. D = outside diameter of pipe, mm (in.)
<br /> 319.3.4 Allowable Stresses EQ = reference modulus of elasticity at 21°C (70°F),
<br /> (a) The allowable displacement stress range, SA, and MPa (ksi)
<br /> permissible additive stresses shall be as specified in Ki = 208 000 SA/EQ, (mm/m)�
<br /> para. 302.3.5(d)for systems primarily stressed in bend- = 30 SA/EQ, (in./ft)
<br /> ing and/or torsion. L = developed length of piping between anchors,
<br /> (b) The stress intensification factors in Appendix D in (ft)
<br /> have been developed from fatigue tests of representative SA = allowable displacement stress range in accor-
<br /> piping components and assemblies manufactured from dance with eq. (1a), MPa (ksi)
<br /> ductile ferrous materials. The allowable displacement U = anchor distance,straight line between anchors,
<br /> stress range is based on tests of carbon and austenitic in (ft)
<br /> stainless steels.Caution should be exercised when using y = resultant of total displacement strains,
<br /> eqs. (1a)and (1b) (para. 302.3.5)for allowable displace- mm (in.),to be absorbed by the piping system
<br /> ment stress range for some nonferrous materials (e.g., 319.4.2 Formal Analysis Requirements
<br /> certain copper and aluminum alloys)for other than low (a) Any piping system that does not meet the criteria
<br /> cycle applications. in para.319.4.1 shall be analyzed by a simplified,approx-
<br /> 319.3.5 Dimensions. Nominal thicknesses and out- imate, or comprehensive method of analysis, as
<br /> side diameters of pipe and fittings shall be used in flexi- appropriate.
<br /> bility calculations. (b) A simplified or approximate method may be
<br /> applied only if used within the range of configurations
<br /> 319.3.6 Flexibility and Stress Intensification for which its adequacy has been demonstrated.
<br /> Factors. The flexibility factors,k,and stress intensifica- (c) Acceptable comprehensive methods of analysis
<br /> tion factors,i,shall not be less than unity.In the absence include analytical and chart methods that provide an
<br /> of more directly applicable data,the flexibility factor,k, evaluation of the forces, moments, and stresses caused
<br /> and stress intensification factor,i,shown in Appendix D by displacement strains (see para. 319.2.1).
<br /> shall be used for flexibility calculations described in (d) Comprehensive analysis shall take into account
<br /> para. 319.4. stress intensification factors for any component other
<br /> Stress intensification factors may be developed in than straight pipe. Credit may be taken for the extra
<br /> accordance with ASME 1331J. flexibility of such a component.
<br /> For piping components or attachments(such as valves,
<br /> strainers, anchor rings, or bands) not covered in 319.4.3 Basic Assumptions and Requirements.
<br /> Table D300, suitable stress intensification factors may Standard assumptions specified in para. 319.3 shall be
<br /> be assumed by comparison of their significant geometry followed in all cases. In calculating the flexibility of a
<br /> with that of the components shown.The validity of any piping system between anchor points, the system shall
<br /> assumptions is the responsibility of the designer. If two be treated as a whole. The significance of all parts of
<br /> or more of the geometries shown in Appendix D are the line and of all restraints introduced for the purpose
<br /> combined,their combined k and i might be significantly of reducing moments and forces on equipment or small
<br /> different from the values shown.Examples include trun- branch lines, and also the restraint introduced by sup-
<br /> nions on elbows and branch connection fittings welded port friction,shall be recognized. Consider all displace-
<br /> to anything other than straight pipe. ments,as outlined in para.319.2.1,over the temperature
<br /> range defined by para. 319.3.1.
<br /> (16) 319.4 Flexibility Analysis
<br /> 319.4.1 Formal Analysis Not Required. No formal 8 WARNING:No general proof can be offered that this equation
<br /> analysis of adequate flexibility is required for a piping will yield accurate or consistently conservative results. It is not
<br /> applicable to systems used under severe cyclic conditions.It should
<br /> system that be used with caution in configurations such as unequal leg U-bends
<br /> (a) duplicates,or replaces without significant change, or near-straight"sawtooth"runs,or for large thin-wall pipe(i>_5),
<br /> a system operating with a successful service record or where extraneous displacements(not in the direction connecting
<br /> anchor points) constitute a large part of the total displacement.
<br /> (b) can readily be judged adequate by comparison There is no assurance that terminal reactions will be acceptably
<br /> with previously analyzed systems low,even if a piping system falls within the limitations of eq.(16).
<br />
|