4.3.1 General Notes:
1) The stress design requirements in this Standard are considered to be adequate under conditions usually encountered and for general stress design of conventional pipeline systems.
2) The design factors and stress limits in this Standard ensure that certain minimum resistances are not exceeded by the effects of the loadings specified in Clause 4.2. Such resistances are membrane strength, fatigue strength, and primary bending strength.
220.127.116.11 There is a commentary available for this Clause. The designer shall be responsible for determining supplemental local stress design criteria for structural discontinuities, high-temperature thermoelasticity, and fatigue evaluations; structural limits for denting, wrinkling, secondary tensile loading, and bending stresses in buried pipelines; and structural stability. Notes:
1) The design requirements of this Standard do not provide criteria for all design conditions.
2) For stress conditions not covered by Clause 4.3 and Clauses 4.6 to 4.10, reference should be made to Annex C or to the alternative rules in the ASME Boiler and Pressure Vessel Code (Section VIII, Division 2). Attention should be focused on the nonlinear nature of piping under certain loading conditions, and it should be recognized that linear elastic stress analysis methods used for the usual flexibility analysis might not be sufficient to analyze deformations and related failure or damage conditions.
3) This Standard does not provide criteria for nonlinear deformation conditions.
18.104.22.168 Designers shall provide adequate protection to prevent unacceptable damage to the piping from unusual or special external conditions. Note: Examples of such protection include increasing the pipe wall thickness, using additional cover, constructing revetments or other suitable mechanical protective devices, providing erosion protection, installing anchors, replacing potentially unstable soil with stable soil, using insulating materials, using refrigeration or heat tracing, using special construction procedures to reduce surface disturbance, and using right-of-way revegetation. Grade and above-grade installations are additional alternatives. 22.214.171.124 There is a commentary available for this Clause. Consideration shall be given to designing pipelines to accommodate the use of internal inspection devices. Items to be considered include the location and sizing of scraper barrels, full-opening mainline block valves, internal bore of components, bend radii, and scraper guide bars. 4.3.2 Class location assessment areas There is a commentary available for this Clause. 126.96.36.199 Class location assessment areas shall be 1.6 km long, except as follows: a) Undeveloped class location assessment areas may be any length not less than 400 m. b) Where the distance between successive undeveloped class location assessment areas is less than 1.6 km, that distance may be used as the length of the class location assessment area between such undeveloped class location assessment areas. 188.8.131.52 Class location assessment areas shall be used in a continuous sliding series of assessments to determine the class location designations, except that the sliding series of assessments may be discontinued on one end of any undeveloped class location assessment area and resumed on the other end of such an area.