API 1102:2017 pdf free download.Steel Pipelines Crossing Railroads and Highways
Pipe stresses induced by temperature fluctuations can be included. All other loads are a result of special conditions. Loads of this nature must be evaluated on a site-specific basis and, therefore, are outside the scope of this recommended practice. Ingraffea et al. [4] describe how pipeline stresses can be influenced by longitudinal bends and tees in the vicinity of the crossing, and they give equations to evaluate such effects.
4.6.2 External Loads
4.6.2.1 Earth Load The earth load is the force resulting from the weight of the overlying soil that is conveyed to the top of pipe. The earth load is calculated according to the procedures widely adopted in practice for ditch conduits [1 0]. Such procedures have been used in pipeline design for many years and have been included in specifications adopted by various professional organizations [11 , 1 2, 13].
4.6.2.2 Live Load 4.6.2.2.1 Railroad Crossing It is assumed that the pipeline is subjected to the load from a single train as would be applied on either track shown in Figure 1. For simultaneous loading of both tracks, stress increment factors for the cyclic longitudinal and cyclic circumferential stress are used. The crossing is assumed to be oriented at 90 degrees with respect to the railroad and is an embankment-type crossing as illustrated in Figure 1 . This type of orientation generally is preferred in new pipeline construction and is likely to result in pipeline stresses larger than those associated with pipelines crossing at oblique angles to the railroad.
4.6.2.2.2 Highway Crossing It is assumed that the pipeline is subjected to the loads from two trucks traveling in adjacent lanes, such that there are two sets of tandem or single axles in line with each other. The crossing is assumed to be oriented at 90 degrees with respect to the highway and is an embankment-type crossing, as shown in Figure 1 . This type of orientation generally is preferred in new pipeline construction and is likely to result in pipeline stresses larger than those associated with pipelines crossing at oblique angles to the highway.
4.6.3 Internal Load The internal load is produced by internal pressure, p, in pounds per square inch (psi) or kilopascals (kPa). The maximum allowable operating pressure, MAOP or maximum operating pressure, MOP should be used in the design.
4.7 Stresses
4.7.1 General For detailed information on the methods used to develop the design approaches and design curves for determining stresses, see Ingraffea et al. [4].
4.7.2 Stresses Due to External Loads External loading on the carrier pipe will produce both circumferential and longitudinal stresses. Recommended procedures for calculating each component of these stresses follow. It is assumed that all external loads are conveyed vertically across a 90 degree arc centered on the pipe crown and resisted by a vertical reaction distributed across a 90 degree arc centered on the pipe invert.
It is recommended that γ be taken as 1 20 lb/ft 3 (1 8.9 kN/m 3 ) (equivalent to 0.069 lb/in. 3 ) for most soil types unless a higher value is justified on the basis of field or laboratory data.
The earth load stiffness factor, K He , accounts for the interaction between the soil and pipe and depends on the pipe wall thickness to diameter ratio, t w /D, and modulus of soil reaction, E’. Figure 3 shows K He plotted for various E’, as a function of t w /D. Values of E’ appropriate for auger borer construction may range from 0.2 to 2.0 kips/in. 2 (1.4 to 13.8 mPa). It is recommended that E’ be chosen as 0.5 kips/in. 2 (3.4 mPa), unless a higher value is judged more appropriate by the designer.
Table A-1 in Annex A gives typical values for E’. The burial factor, B e , is presented as a function of the ratio of pipe depth to bored diameter, H/B d for various soil conditions in Figure 4. If the bored diameter is unknown or uncertain at the time of design, it is recommended that B d be taken as D + 2 in. (51 mm). For trenched construction and new structures constructed over existing pipelines, B d = D can be assumed, recognizing that soil compaction in the trench would lead to higher E’ values than those for auger bored installations.
The excavation factor, E e , is presented as a function of the ratio of bored diameter to pipe diameter, B d /D in Figure 5. If the bored diameter is unknown or uncertain at the time of design, E e should be assumed equal to 1 .0. For trenched construction and new structures constructed over existing pipelines, E e can be assumed equal to 1 .0.API 1102 pdf download.API 1102:2017 pdf free download
