SU1756718A1 - Method of laying underwater pipe line - Google Patents

Abstract

Summary of the invention: mount the pipeline (TP), install the plugs at its ends, equip it with pontoons. Place the TP at the underwater crossing, give it a negative uniformly distributed buoyancy, immerse it at the bottom, fix it in the design position and pontoon offsets. Negative buoyancy is imparted by injecting gas under pressure into the TP cavity. Pressure is relieved after the TP is fixed. 3 il.

Description

The invention relates to the construction and can be used in the construction of offshore pipelines and underwater pipelines crossing water obstacles: rivers, lakes, reservoirs and deep marshes.

The purpose of the invention is to simplify the installation of the subsea pipeline.

FIG. Figure 1 shows the layout of a pipeline with floating pontoons; in fig. 2 - the position of the pipeline during its immersion to the bottom; in fig. 3 is a diagram of the separation of the pontoons after laying the pipeline to the bottom.

Laying of the pipeline is implemented as follows. Onshore, installation of pipeline 1 with installation of plugs at its ends and equipment of pontoons 2 is performed. Pipeline 1, equipped with pontoons 2, is installed afloat on the surface of water 3 in a given alignment (Fig. 1). With the help of a compressor installed on the watercraft or ashore (not shown in the drawings),

through the hose create inside the pipeline 1, the pressure of gas, such as air. With increasing pressure, the gas density increases and, accordingly, the mass of pipeline 1 increases, the buoyancy of which changes from positive to negative, and pipeline 1 from the surface of water 3 sinks to bottom 4 as a rigid body (Fig. 2) without experiencing stress from bending. After laying on the bottom 4, the pipeline 1 is fixed in the design position by separating the pontoons 2 (Fig. 3) and relieves the gas pressure in the pipeline 1,

A different order of implementation of the method is also possible. For example, pipeline 1, having positive buoyancy without pontoons, is installed afloat in a given range. Gas (air) is injected into the pipeline 1, and under the effect of increasing the density of the gas, pipeline 1 changes its buoyancy from evenly distributed positive to negative and sinks to the bottom. After laying to the bottom

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pipeline 1 is fixed in the design position by additional ballasting or underwater anchors, and then the gas pressure in the pipeline 1 is relieved.

As an example, the calculation of laying an underwater pipeline with a diameter of D 1.42 m, a wall thickness of 3 0.014 m and a positive buoyancy q 300 n / m is given.

The relationship between the weight of the compressed gas and the pressure P is determined by the formula

P qi-R; T P

where R 8.31 J / mol K is universal gas;

1.1 - 0.029 kg / mol — molar mass of air;

T - absolute temperature of compressed air .. K;

at a temperature of compressed air 12 ° С Т-273-112 285;

/ volume of the internal cavity of the pipeline with a length of 1 m

., lSR-26) 2, (1.42-20.014) 2,

v. 4 l41

1,522m3.

To ensure that the pipeline is immersed from the surface of the water to the bottom, it is necessary that the weight of the compressed gas in a pipeline 1 m long be equal to 6 kgf. Substituting in (1) the values of the initial parameters, we obtain

P - Fp fclffis H5 1642 1 ° 6 kgf / s 2 When R 16 kgf / cm2 the pipeline acquires uniformly distributed negative buoyancy and is lowered from the surface of the water to the bottom of the water barrier. In this method, the maximum possible laying depth of the pipeline can reach hundreds of meters, since the pipeline sinks to the bottom like a rigid body without experiencing a bending moment in the process of immersion.

Claims (1)

Invention Formula The method of laying the underwater pipeline, which consists in installing the pipeline, installing plugs at its ends, equipping with pontoons, placing the pipeline in the submerged passage, giving it a negative uniformly distributed buoyancy, diving to the bottom, fixing in the design position and detaching the pontoons, characterized in that, in order to simplify the laying technology, the pipeline is given negative buoyancy by pressurizing a gas into its cavity, which is removed after the pipeline is fixed to the bottom in project position. ЖЖ / ЖЖЖх ЖЖЖЖЖЖ Phia.1 V / //////////////////////////////////// FIG. 2