SYSTEM DETAILING AND FINAL FLOW ANALYSIS

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SE = maximum allowable stress in material due to internal pressure

and joint efficiency at the design temperature, in psi (kPa).

The value of SE shall not exceed the value given in Appendix A

of the B 31.1 Code. For materials to be brazed, a joint

efficiency of 0.8 shall be used.

A = an additional thickness in inches (millimeters).

1. To compensate for material removed in threading, grooving,

etc.,

2. To provide for mechanical strength of the pipe for extreme

conditions of misapplied external loads or for mechanical

abuse.

3. To provide for corrosion and/or erosion.

(2) Additional Wall Thickness, Threaded Pipe. While the

thicknesses determined from Formula (4) or (4A) are theoretically ample for

both bursting pressure and material removed in threading, the following

minimum requirements are mandatory to furnish added mechanical strength.

(a) Where steel or stainless steel pipe is threaded the pipe

shall have a minimum ultimate tensile strength of 48,000 psi (330 MPA) and a

weight at least equal to Schedule 80 of ANSI B 36.10.

(b) Where threaded brass or copper pipe is used for the

services described in (2) (a) above, it shall have a wall thickness at least

equal to that specified above for steel pipe of corresponding size.

Minimum Wall Thickness, Straight Pipe Under External Pressure.

For determining wall thickness and stiffening requirements for straight pipe

under external pressure the procedures outlined in Para UG-28, UG-29, and

UG-30 of Section VIII, Division 1, of the ASME Boiler and Pressure Vessel

Code shall be followed.

Allowances.

(1) Corrosion or Erosion. When corrosion or erosion is expected,

an increase in wall thickness of the piping shall be provided over that

required by other design requirements. This allowance in the judgement of

the designer shall be consistent with the expected life of the piping.

(2) Threading and Grooving. The calculated minimum thickness of

piping (or tubing) which is to be threaded shall be increased by an allowance

equal to thread depth; dimension h of ANSI B 2.1 or equivalent shall apply.

For machined surfaces or grooves, where the tolerance is not specified, the

tolerance shall be assumed to be 1/64 inch (0.40 mm) in addition to the

SYSTEM DETAILING AND FINAL FLOW ANALYSIS. For any category I, II, III,

or IV piping system, a detailed system layout, consisting of a complete

physical description of the piping system and its supports and anchors, is

necessary. The preparation of a system layout is discussed in the following

paragraphs.