Method of replacing defective section of main line

FIELD: construction engineering.

SUBSTANCE: invention relates to pipeline transport and it can be used at repairs of main lines. Prior to replacing defective section of main line transporting combustible or explosive liquids and gases, section to be repaired is emptied, defective spool is cut out with provision of isolation of combustible and explosive gases and liquids from welding site by placing overlapping members at ends of pins adjoining section under repair, and new spool is welded in place. Prior to welding new spool placed between overlapping members, inert gas is fed into space of new spool and pressure in built exceeding pressure in adjoining sections of pipeline under repair.

EFFECT: improved safety at repairs.

2 dwg

 

The invention relates to the field of pipeline transportation of liquid products, in particular oil products, and can be used in case of emergency and planned repair of pipelines replacement of the defective area.

There is a method of replacing a defective section of the main pipeline, pumping flammable and explosive liquids and gases, which consists in emptying the repair area, cutting the defective coil, cleaning the surface of the free ends of the pipeline; in this case, the sealing defective area provide coverage of the free ends of the pipeline mechanized jaw gripper with outlets through which produce the emptying of the pipeline from the product to the level of the bottom of the pipe, further emptying of the pipeline from residues and stains product produced by a mechanized filing clays that are pressed into the ends of the pipe to length, ensuring sealing and submission of clay in the branches carry with removable, pre-filled containers; subsequent welding of the new coil [1].

Currently known methods of replacement of defective pipeline by insertion of new coils, replacement of pipes and whips used in the detection of large cracks and mechanical damage, such as dents, bumps, if the x dimensions exceed the allowable construction norms and rules [2].

There is also known a method of replacing the defective area of the pipeline, pumping flammable or explosive liquids and gases, which includes the tenderloin defective area of the coil, the preparation of the ends of the pipe for installation and welding, preparation of a new coil (insert), fit the new coil in place of welding, tack and weld the new coil in the pipeline and control held welding and Assembly works [3].

There is also known a method of replacing defective pipe section by cutting the defective coil or section of pipeline damage and welding a new coil or pipe [4].

However, the known methods of replacement of defective pipeline section[1, 2, 3, 4], includes clipping defective coils and welded the new coil should be applied depending on the specific conditions, in the presence of appropriate technical means using the technology of disaster recovery operations, there are strict fire safety requirements applicable to the conduct of hot work in hazardous conditions.

A disadvantage of known methods [1, 2, 3, 4] is the inability to ensure full integrity of overlapping pipeline, resulting gases pass to the place of welding to contact "pipe - overlapping element" or most lane is kryvusha element, as well as the disadvantages of the known methods [1, 2, 3, 4] are low fire safety and explosive situations when performing welding operations.

The closest technical solution in its essence, is selected as a prototype, is a way to replace the defective section of the main pipeline, pumping flammable or explosive liquids or gases [3, p.51], which consists in emptying from the product of the repair area, cutting the defective area of the coil, ensuring isolation of flammable and explosive liquids and gases from welding, installation on both ends of the tube overlying the cavity of the pipe elements, for example, is installed mechanical swab sealer (construction JSC MN "Friendship"), approved for application in the prescribed manner or are the wads of clay or composite materials such as swabs from urea composition.

The disadvantage of this method of replacement of defective pipeline section, selected as a prototype [3 p.51], is the inability to create a perfect sealing of the overlap of the pipeline due to the fact that the gases pass through the contact tube - overlapping element, as well as on the most overlapping element, and, consequently, lower the fire safety and h is the existence of explosive situations when performing welding operations.

The technical objective of the proposed method of replacement of defective pipeline section is to provide a reliable air-tightness of the overlap of the pipeline, improving fire safety and exception explosive situations carried out welding by providing isolation of flammable and explosive liquids and gases from welding by creating in the cavity of the new coil more pressure injection of inert gas.

The technical problem is solved in that in the method of replacing the defective section of the main pipeline, pumping flammable or explosive liquids and gases, which consists in emptying the repair area, cutting the defective coil, ensuring isolation of flammable and explosive gases and liquids from the welding installation on both ends of the pipe adjacent areas of the repaired pipeline pumping elements, welding a new coil, unlike the prototype to ensure reliable isolation of the welding places from combustible and explosive gases and liquids in the cavity of the new coil creates a pressure greater than in adjacent areas of the repaired pipeline for pumping elements by injection into the cavity of the new coil inert gas.

Figure 1 shows the method for replacing the defective area of the main drobopro is Yes emptied with a repaired area, welded a new coil and overlapping elements. Gases from the cavities I and II of the pipeline are received in the cavity of the new coil, ie,

R<P1or R<R2,

where P is the pressure in the cavity of the new coil

P1and R2- pressure in the first and second cavities of the pipeline.

Figure 2 shows the implementation of the proposed method with the creation of a new coil cavity pressure P greater than the pressure in the adjacent sections of the pipeline, i.e. R>R1and R>R2by injecting into the cavity a new coil inert gas, in this case, combustible or explosive gas or liquid fall into the welding point.

The inventive method is implemented in the following way.

In the defective pipeline section 1 (1), produce emptying from the product and cutting the defective coil, provide isolation of flammable and explosive gases and liquids in place of welding, for this set on both ends of the pipe overlapping elements 2, which can be made in the form of wads of clay or composite materials, for example, swabs of the urea composition.

In the defective pipeline section 1 installing a new coil 3.

When installed in a defective portion of the pipe 1 new coil 3, without changing its pressure P, in this case atmospheric pressure, it is possible p is khojdenie gases from the cavities I and II of the pipeline 1, adjacent to the new coil 3. Gases pass through the contact tube - overlapping element, as well as on the most overlapping element 2, as in this case, to ensure complete sealing of the overlap of the input gas is impossible.

The gases pass into the cavity of the new coil 3 (Fig 1) contact "pipe - overlapping element (arrow B in figure 1) or on the most overlapping element 2 (arrow a in figure 1). Gases pass into the cavity of the new coil 3, i.e. R2>P and P1>P, and I and II cavities pipeline for various reasons, for example, due to heating of pipelines, evaporation petroleum and petroleum products, flammable or explosive liquids and gases in the cavity of the piping and other pressure P1and R2increase.

The flow of gases through the overlapping elements 2 in the welding and in the cavity of the new coil 3 increases explosive situation.

In the present method (figure 2) in the defective portion of the pipe 1 is installed a new coil 3 and after welding the root pass creates a pressure P greater than the pressure P1and R2R>P1and R>R2.

The inner cavity of the new coil 3 through the hole in the wall is connected through a pressure gauge 4, valve 5, gear 6, the second valve 7 with a capacity of 8, containing a neutral gas under high pressure.

When turning on the valves 5 and 7 inert gas under high pressure is receiving from the tank 8 through the reduction gear 6 is fed into the cavity of the coil 3 and the welding point, ensuring the safe production of the weld seam 9.

Entering the cavity of the new coil 3 (2) inert gas, creating excess pressure P, i.e. P>P1and R>R2, nestles in the first and second hollow pipe 1 through the contact tube - overlapping element (arrow B in figure 2), as well as on the most overlapping element 2 (arrow a in figure 2), thereby eliminating the possibility of penetration in the weld areas of flammable and explosive gases.

When the supply of inert gas from the tank 8 through the gear 6 into the cavity of the new coil 3 must meet the condition:

1,1 (R-R2)≤ΔP and 1.1 (P-P1)≤ΔP

where ΔP - value of the differential pressure at which begins the shift of overlapping elements 2 in the pipe 1, as otherwise the blocking elements 2 can move in the cavity of the pipeline 1.

Value ΔR is determined by the formulawhere

τ ultimate shear stresses along the contact ‚Äúpipe - overlapping element;

L is the length along the longitudinal axis of the pipe in contact area between the pipe and blocking element (for clay tampons is the length of the tampon);

DNR- internal diameter of the pipeline.

As the inert gas in the present method can be used: nitrogen (N2), helium (He), argon (ar) andetc.

Sources of information

1. USSR author's certificate No. 1832879, IPC F 16 L 55/16, publ. 20.03.96. Bull. No. 8.

2. Guidance document "regulations for the safe conduct of welding in the repair of oil and pipelines under pressure." RD 39-0147103-360-89. IPTER, Ufa, 1989

3. Guidance document "instruction on the elimination of accidents and damage to oil pipelines". RD 39.-110.-91. IPTER, Ufa. 1992 (p.51 - prototype).

4. Guidance document "rules of liquidation of accidents and damage to oil pipelines". RD 153-39.4-114-01. IPTER, Ufa. 2001

How to replace a defective section of the main pipeline, pumping flammable or explosive liquids and gases, which consists in emptying the repair area, cutting the defective coil, ensuring isolation of flammable and explosive liquids and gases from welding, installation of the pipe ends adjacent areas of the repaired pipeline overlapping elements, welding a new coil, characterized in that the cavity of the new coil installed between the overlying elements, serves inert gas, for example nitrogen, creating a pressure slightly above the pressure in the adjacent areas of the repaired pipe, and carry out the welding process.



 

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