API RP Code Compliance web-application

API RP 1102 Code Check User Guide

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Introduction

The web-application performs stress calculation for Steel Pipelines crossing Railroads and Highways as per API RP 1102. This design methodology relates to steel pipelines installed using trenchless construction methods, in particular auger boring, with the crossing perpendicular to the railroad or highway. The design performed by the web-application for the steel pipeline crossing is applicable in all scenarios where provisions of API RP 1102 code are applicable (refer clause 1.2 of API RP 1102) except the following:

  • Two types of unit systems i.e. SI Unit & Customary Unit system can be selected for performing the calculation.
  • The design methodology used in the program is such the pipelines having diameters of D = 2.375 to 48 inches (60.3 to 1219 mm) can be analysed. Values from various graphs of API RP 1102 for pipe diameter greater than 42 inch (1067 mm) is obtained by extra-plotting the graphs.
  • The wall thickness to diameter ratios must be within the range of tw/ D = 0.010 to 0.080.
  • Railroad crossings can be analysed for depths of cover H = 6 to 14 ft (1.8 to 4.3 m). Highway crossings can be analysed for depth of cover H = 3 to 10 ft (0.9 to 3.0 m).
  • The loading condition for railroads if based for four axle distributed to the track surface, and would develop from the trailing and leading axle sets form sequential cars. Highway loadings are based on both single and tandem-axle truck loading configurations.

Design Methodology

The methodology is broadly divided into four parts for designing railway or highway crossing of steel pipelines as per API RP 1102:

  1. Calculation of circumferential stress due to internal pressure by "Barlow formula" and check against allowable.
  2. Calculation of stresses due to external loads such as:
     a)   Stresses due to Earth Load
     b)   Stresses due to live load
          - Surface Live Load
          - Impact Factor
     c)   Railroad Cyclic Stresses
     d)   Highway Cyclic Stresses
  3. Calculation of principal stresses, effective stress and check against allowable
  4. Check for fatigue

List of Symbols/ Terms

 Bd
Bored diameter of crossing
 Be
Burial factor for circumferential stress from earth load
 D
Pipe outside diameter
 E
Longitudinal joint factor
 E'
Modulus of soil reaction
 Ee
Excavation factor for circumferential stress from earth load
 Er
Resilient modulus of soil
 Es
Young’s modulus of steel
 F
Design factor (barlow stress & fatigue check)
 Fa
Allowable design factor (equivalent stress check)
 Fi
Impact factor
 GHh
Geometry factor for cyclic circumferential stress from highway vehicular load
 GHr
Geometry factor for cyclic circumferential stress from rail load
 GLh
Geometry factor for cyclic longitudinal stress from highway vehicular load
 GLr
Geometry factor for cyclic longitudinal stress from rail load
 H
Depth to the top of the pipe
 KHe
Stiffness factor for circumferential stress from earth load
 KHh
Stiffness factor for cyclic circumferential stress from highway vehicular load
 KHr
Stiffness factor for cyclic circumferential stress from rail load
 KLh
Stiffness factor for cyclic longitudinal stress from highway vehicular load
 KLr
Stiffness factor for cyclic longitudinal stress from rail load
 L
Highway axle configuration factor
 LG
Distance of girth weld from centerline
 p
Maximum allowable operating pressure
 NH
Double track factor for cyclic circumferential stress
 NL
Double track factor for cyclic longitudinal stress
 Nt
Number of tracks at railroad crossing
 Ps
Single axle wheel load
 Pt
Tandem axle wheel load
 R
Highway pavement type factor
 RF
Longitudinal stress reduction factor for fatigue
 Seff
Total effective stress
 SFG
Fatigue resistance of girth weld
 SFL
Fatigue resistance of longitudinal weld
 SHe
Circumferential stress from earth load
 SHi
Circumferential stress from internal pressure
 SHi(Barlow)
Circumferential stress from internal pressure calculated using the Barlow formula
 S1
Maximum circumferential stress
 S2
Maximum longitudinal stress
 S3
Maximum radial stress
 SMYS
Specified minimum yield strength
 T
Temperature derating factor
 T1
Installation temperature
 T2
Operating temperature
 tw
Pipe wall thickness
 w
Applied design surface pressure
 αT
Coefficient of thermal expansion
 γT
Unit weight of soil
 SHh
Cyclic circumferential stress from highway vehicular load
 SHr
Cyclic circumferential stress from rail load
 SLh
Cyclic longitudinal stress from highway vehicular load
 SLr
Cyclic longitudinal stress from rail load
 νs
Poisson’s ratio of steel