![]() ![]() NL – Railroad Double Track Factor for Longitudinal Stress NH – Railroad Double Track Factor for Circumferential Stress Step 4: Impact Factor and Applied Design Surface Pressure (F-Flexible, R-Rigid, N-None) (Case 1,2,3)ĭetermine the Critical Load case and the applied surface design load. Step 3: Circumferential stress due to Earth Load Soil type – Default Value: (K μ= 0.165 for Soil Type A, K μ= 0.192 for Soil Type B) □ − Pipe Depth □ □ − Bored Diameter □ □□□□□ − Modulus of Soil Reaction □ □ − Resilient Module □ − Average unit weight of soil □ □ − Young′s Modulus of Elasticity (see External Link: Barlow’s Formula in ) The allowable range for the live load design curves is from 6ft wt d.Is used to establish the impact factor, F i used in the design methodology.The depth of the carrier pipe, H, is measured from the top of tie to the pipeline crown for railroads.The wall thickness to diameter ratios must be within the range of wt./D = 0.01 to 0.08.T 2 also is used with T 1 to determine thermal stress effects.The T 2 value is used to determine the temperature derating factor, T.The operating temperature, T 2 is give in degrees Fahrenheit (☏).The allowable range is from -20 to 450 ☏.This value is used with T 2 to determine thermal stress effects.The installation temperature, T 1 is given in degrees Fahrenheit (☏).The input screen limits E to either 0.60, 0.80, or 1.00, consistent with the values given in 49CFR192, Section 192.113.The longitudinal joint factor, E, depends on the type of pipe welds.The allowable range is from 0.10 to 1.00.Although 49 CFR 192 or 195, establishes a design factor, F, the user can input another F value.The SMYS is also used to establish the girth and longitudinal weld fatigue endurance limits.Has a range of allowable values covering steel grades A25 (SMYS = 25000 psi) to X-80 (SMYS = 80000 psi).Has units of pounds per square inch (psi).The specified minimum yield strength, SMYS,.The allowable range is from 0 to 5,000 psig.The maximum allowable operating pressure, MAOP, is used as the design internal pressure for calculating circumferential stress due to internal pressurization,.The allowable range is from 2.000 to 42.000 in.The diameter, D, is the outside pipe diameter.Variables and Boundary Conditions Pipe Properties DIAMETER. Develops from the trailing and leading axles sets form sequential cars.The loading condition for railroads is based for four axles distributed to the track surface.Railroad crossings can be analyzed for depths of cover of 6 to 14 feet (1.8 to 4.3 meters).The wall thickness to diameter ratios must be within the range of tw/D = 0.01 to 0.08.Pipelines having diameters 2 to 42 inches (51 to 1067 mm) can be analyzed.Steel pipelines installed using trenchless construction methods, in particular auger boring, with the crossing perpendicular to the railroad.API RP 1102 should be available to the user for additional documentation and preferences, and supplement the information provided by the program help and graphical display of the design curves. Concise summaries of the Cornell/GRI Guidelines are given in “Guidelines for Pipelines Crossing Beneath Railroads” (Stewart, et al., 1991b). ![]() The design methodology used in program follows directly the approach given in API RP 1102. The details of the full design methodology can be found in “Technical Summary and Database for Guidelines for Pipelines Crossing Beneath Railroads” (GRI91, Final Report) and should be read and understood. API 1102 – PC PISCES (Personal Computer Pipeline Soil Crossing Evaluation System) program is based on the design methodology resulting from the research and has been implemented in the program to aid pipeline designers in analyzing existing uncased pipelines and designing new uncased pipelines that cross beneath railroads. ![]()
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