Beamed pipeline crossings
BEAMED PIPELINE CROSSINGS (EN: cross-over beam of pipelines; DE: Balken-Zahnungen der Rohrleitungen; FR: transitions des conduites fixees aux poutres; ES: puente de vigas para tuberias; RU: балочные переходы трубопроводов) are constructed on the supports at the intersection of the water and other obstacles, during the laying of the pipelines onto the swamped, waterlogged, permafrost soils. The construction of the above-ground crossings. They make the beamed pipeline crossings according to the two design schemes, namely, without the compensation, and with the compensation of the longitudinal deformations.
They place the beamed pipeline crossings without the compensation of the longitudinal deformations (Figure # 1) onto the intermediate pile or monolithic supports with the longitudinally movable support parts, which permit the movement of the pipeline only along the axis.
They cover with soil the ends of the open parts of the beamed pipeline crossings (within the soft soils, they underlay the reinforced concrete plates under the pipes). The absence of the movements causes the emergence of the longitudinal stresses, which are increasing with the increase of the temperature of the walls of the pipes, and with the increase of the internal pressure within the pipeline. They construct such beamed pipeline crossings during the crossing of the mountain rivers, gorges, ravines, and other obstacles.
The beamed pipeline crossings with compensation of the longitudinal deformations have the special devices (compensators), which are installed at the ends of the above-ground parts of the pipelines with the length of up to 200-300 metres, and with the greater length also additionally at each 100-300 metres.
During the construction of such beamed pipeline crossings, they use the supports with the fixed, freely movable, and longitudinally movable support parts of the various modifications (with small rollers, with big rollers, sliding, and others). The middle supports between the compensators have the non-movable support parts; the supports, which are near to the compensators, have the freely movable support parts, which permit the transverse and longitudinal movements; the remaining supports are longitudinally movable. They use for the compensation of the longitudinal deformations also the laying of the beamed pipeline crossings with curvature (kink) of the individual parts of the pipeline within the horizontal plane. They made the curvature or kink with the help of the curved bends or lateral inserts, which have been made under the factory conditions, or by the method of the cold bending on the place of the construction of the pipeline. The distance between the supports within the systems of the beamed pipeline crossings with compensation depends on the diameter of the pipes, quantity of the spans, adopted scheme of the laying, and natural conditions. At the gas pipelines with the diameter of the pipes of 700-1400 millimetres, the distance between the supports is usually 30-50 metres; at the pipelines for the petroleum and petroleum products, the distance between the supports is usually 25-40 metres. With the necessity of taking into account of the resonant vibrations within the wind flow within the multi-span beamed pipeline crossings with the diameter of the pipes of 700-1400 millimetres, the distance between the supports is 25-40 metres. They lay the beamed pipeline crossings with compensation of the longitudinal deformations within the regions with waterlogged, swamped, and permafrost soils.
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