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API RP 1111 Pipeline Ovality

Calculate API RP 1111 limit state pipeline out of roundness and ovality from tolerances, or from maximum and minimum diameter.

Out of roundness is equal to the maximum diameter minus the minimum diameter measured at the same cross section. Out of roundness ratio equals the out of roundness divided by either the nominal diameter or the mean diameter. DNV or ISO ovality is equal to the out of roundness ratio. API ovality is equal to half the DNV ovality (DNV or ISO ovality is equal to 2 x API ovality).

`Davg = (Dmax + Dmin) / 2 `
`OOR = (Dmax - Dmin) `
`ro = (OOR) / (Davg) `
`fa = (Dmax - Dmin) / (Dmax + Dmin) = (OOR) / (2.Davg) = (ro) / 2 `
`fd = 2.(Dmax - Dmin) / (Dmax + Dmin) = (OOR) / (Davg) = 2.fa = ro `

where :

OOR = out of roundness
ro = out of roundness ratio
Dmax = maximum diameter
Dmin = minimum diameter
Davg = average or mean diameter
fa = API ovality
fd = DNVGL or ISO ovality

Reference : API RP 1111 : Design, Construction, Operation, and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design) (2011)

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CALCULATOR : API RP 1111 Section 4.3.2 Pipeline Ovality [FREE]   ±

Calculate pipeline ovality (API RP 1111 section 4.3.2).

Out of roundness is the difference between the maximum and minimum diameter of the pipe. DNV ovality is equal to 2 x API ovality. All tolerances should be entered as positive values.

For line pipe with diameter D < 0.0603 [ m ] the out of roundness is included with the diameter tolerance. For line pipe with diameter D ≥ 0.2191 [ m] the out of roundness may also be calculated from the inside diameter.

Reference : API 5L : Specification for Line Pipe : Annex J.6 Offshore Pipeline : Table J.3 Out Of Roundness Tolerance

Tool Input

  • schdtype : Schedule Type
  • diamtype : Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
  • dntype : Pipe OD Or Pipe ID
  • pipetype : Line Pipe Type
  • toltyped : Out Of Roundness Tolerance Type
    • Dxu : User Defined Out Of Roundness Ratio
    • Dau : User Defined Out Of Roundness
    • Dmaxu : User Defined Maximum Diameter
    • Dminu : User Defined Minimum Diameter

Tool Output

  • D : Nominal Pipe Diameter
  • D/tn : Diameter Over Wall Thickness Ratio
  • Dmax : Maximum Diameter
  • Dmin : Minimum Diameter
  • ID : Nominal Inside Diameter
  • OD : Nominal Outside Diameter
  • OOR : Out Of Roundness
  • fapi : API Ovality
  • fdnv : Out Of Roundness Ratio And DNV Ovality
  • tn : Nominal Wall Thickness

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