Piping allowable stress

There is an NPS 8 branch at right angles to an NPS 12 header (Fig. E-l). Both run and branch are of aluminum alloy Schedule 80 ASTM B 241 6061-T6 seamless pipe. The connection is reinforced by a ring 14 in. O.D. (measured along the run) cut from a piece of NPS 12 Schedule 80 ASTM B 241 6063-T6 seamless pipe and opened slightly to fit over the run pipe. Allowable stresses for welded construction apply in accordance with Mandatory Appendix IX, Table IX-1A, Note (28). The fillet welds have the minimum dimensions permitted in para. IP-3.4. A zero corrosion allowance is specified. What is the maximum permissible design pressure if the design temperature is -320°F ... 

For the case in which the pipe contribution in canying the load is considered, ASME PCC-2 suggests an equation similar to that of ISO 24817 (Eqn (10.4)) with two differences the substitution of the term pipe allowable stress by Specific Minimum Yield Stress , which... 

In Eqn (11.1), Puve is the internal pressure in the pipe at the time of the repair application, Ec and Eg are the composite and the steel module of elasticity, is the remaining pipe wall thickness, tmin is the minimum required thickness of the composite layer, D is the pipe diameter, P is the design pressure and finally is the composite allowable strain. The only difference between the two codes is the definition of s—ASME PCC-2 identifies it as the specific minimum yield stress while ISO 24,817 recognizes it as the pipe allowable stress. 

The live pressure does not influence the hoop strain in the repair laminate at the design pressure. A correct estimate for the composite repair thickness is calculated by ignoring the live pressure and using the yield stress as pipe allowable stress in the repair equation. 

Supports. The spaciag of supports is governed by the hot allowable stress of the piping materials stabiUty, ia the case of large-diameter thin-wall pipe deflection to avoid sagging or pocketing and the natural frequency of the unsupported length to avoid susceptibiUty to undesirable vibration. 

Plastic Pipe In contrast to other piping materials, plastic pipe is free from internal and external corrosion, is easily cut and joined, and does not cause galvanic corrosion when coupled to other materials. Allowable stresses and upper temperature limits are low. Normal operation is in the creep range. Fluids for which a plastic is not suited penetrate and soften it rather than dissolve surface layers. Coefficients... 

Support spacing must be much closer than for carbon steel. As temperature increases, the allowable stress for many plastic pipes decreases very rapidly, and heat from sunhght or adjacent hot uninsulated equipment nas a marked effec t. Successful economical underground use of plastic pipe does not necessarily indicate similar economies outdoors aboveground. 

To assure that a system meets these requirements, the computed displacement-stress range Se shall not exceed the allowable stress range [Eqs. (10-93) and (10-94)], the reaction forces [Eq. (10-105)] shall not be detrimental to supports or connected equipment, and movement of the piping shall be within any prescribed hmits. 

Special note for the sixth edition At diis time, metric equivalents have not been provided for the allowable-stress tables of the piping code B31.3. Tliey may be computed by the following rela-tionsliips ( F - 32) x 9 = C Ibf/iir (stress) x 6.S9.5 x 10 = MPa. 

For use in code piping at the stated allowable stresses, the tensile and yield strengths listed in these tables must be verified by tensile tests at the mill such tests shall be specified in the purchase order. 

SE values shown in tliis table for welded pipe include the joint quality factor E, for the longitudinal weld as required by Fig. 10-164 and, when applicable, the structural-grade quality factor Es of 0.92. For some code computations, particularly with regard to expansion, dexibility, structural attachments, supports, and restraints, the longihidinal-joint quality factor E, need not be considered. To determine the allowable stress S for use in code computations not ntdizing the joint quality factor E, divide the value SF shown in tliis table by the longitudinal-joint quality factor E, tabulated in Fig. 10-164. 

The allowable stress range for displacement stresses and permissible additive stresses shall be as specified in Eqs. (10-93) and (10-94) for systems primarily stressed in bending and/or torsion. For pipe or piping components containing longitudinal welds the basic allowable stress S may be used to determine S. (See Table 10-49, Note 13.)... 

IX Allowable Stresses and Quality Factors for Metallic Piping, Pipeline,... 

Some of the standards for components in Table IP-8.1 (e.g., ASME B16.9 and ASME B16.ll) state that pressure-temperature ratings are based on straight seamless pipe. Except as limited in the standard or elsewhere in this Code, such a component, made of a material having the same allowable stress as the pipe, shall be rated using not more than 87.5% of the nominal thickness of seamless pipe corresponding to the schedule, weight, or pressure class of the fitting, less all allowances applied to the pipe (e.g., thread depth and/or corrosion allowance). 

If the allowable stress for the branch pipe wall is less than that for the run pipe, its calculated area must be reduced in the ratio of allowable stress values of the branch to the run in determining its contributions to area A3. 

No additional credit may be taken for a material having higher allowable stress value than the rim pipe. 

Allowable stresses for materials used for pipe supporting elements, except springs, shall be in accordance with para. IP-2.2.6. However, the following factors need not be applied to the allowable stresses for welded piping components that are to be used for pipe-supporting elements ... 

ALLOWABLE STRESSES AND QUALITY FACTORS FOR METALLIC PIPING, PIPELINE, AND BOLTING MATERIALS... 

This table is split into two tables by usage Table IX-l A, Basic Allowable Stresses in Tension for Metal Piping Materials and Table IX-1B, Specified Minimum Yield Strength for Steel Pipe Commonly Used in Pipeline Systems. 

Table IX-1A Basic Allowable Stresses in Tension for Metal Piping Materials...

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