API RP 1111 pdf free download
API RP 1111 pdf free download.Design, Construction, Operation, and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design).
4.1.2 Design for Internal and External Pressures 4.1.2.1 Design for Internal Pressure Pipeline components at any point in a pipeline system should be designed for or selected to withstand the maximum differential pressure between internal and external pressures to which the components will be exposed during construction and under operating conditions. NOTE Design equations in this section using differential pressure apply to pipe or other round cylindrical shells only and may not be suitable for valves and similar components. For such components, more detailed analysis is required to assess the combined effect of internal and external pressure, which is beyond the scope of this RP. The maximum differential pressure for a flowline may be due to a shut-in pressure condition. This condition may result from closure of a valve at the production facility without closing the valves at the tree, manifold, or downhole safety valve. The condition may also occur due to leakage of these same valves or due to plugging of the flowline. The shut-in pressure condition should be considered unless an overpressure protection device or system is installed (refer to API 14C). 4.1.2.2 Design for External Pressure An important consideration in offshore pipeline design is external pressure on all undersea pipeline systems. The significance of external pressure has been demonstrated by the buckling of large pipelines subjected to severe bending and external pressure.4.1.3 Thermal Influences The design should consider the effects of thermal expansion and contraction of the pipeline system. When temperature changes are anticipated, the pipeline approach to a platform or subsea junction should have additional flexibility for expansion and contraction using measures such as slack curves, pipeline bends, and thermal expansion devices. Adequate measures should be taken to prevent excessive strains or fatigue damage due to thermally induced upheaval buckling of buried pipelines or lateral buckling of non-buried pipelines. Design considerations for upheaval and lateral buckling should account for fatigue, longitudinal, and combined loads as described in 4.5 and 4.6.5 (more information can be found in the reference paper OTC 6335 [5] ). High production temperatures may lead to thermal expansion of production casing and elevation increases of subsea wellheads. Such elevation changes will induce displacements and loads in attached equipment such as jumpers and flowlines. Thermal expansion of subsea flowlines may result in the movement of mat foundations supporting piping and valve equipment. The mat foundation should be designed to accommodate repeated expansion movements and prevent excessive rotation or settlement as a result of soil being displaced from beneath it.4.1.4 Static Loads The design should consider static loads imposed on the pipeline. These include the weight of the pipe, coating, appurtenances, and attachments; external and internal hydrostatic pressure and thermal expansion loads; and the static forces due to bottom subsidence and differential settlement. The weight-related forces are of special concern where the pipeline is not continuously supported, that is, where spans are expected to occur. Spans are also of concern where seismic liquefaction of the supporting bottom could occur, and where mudslides could occur, such as some areas around the Mississippi River delta. The weight of the submerged pipeline can be controlled through the combination of the pipe wall thickness and the density and thickness of the external (concrete) weight coating. Weight calculations should consider stability when empty (the usual as-laid condition), full of the fluid to be transported, and flooded with seawater. Consideration should be given to preventing unacceptably long unsupported lengths by use of dumped gravel, anchor supports, concrete mattresses, sand bagging, or other suitable means.API RP 1111 pdf download.
