CN105276336A - Internal anti-corrosion method of welded pipeline and pipeline used for said method - Google Patents

Abstract

The invention provides an internal anti-corrosion method of a welded pipeline and a pipeline used in the method. The sequence of the anti-corrosion method in the welded pipeline includes the following steps: welding stainless steel joints (1) at both ends of the pipeline body (2), the pipeline body (2) and the stainless steel joint (1) are connected through joint welds (A), and the stainless steel The joint (1) is made of 00Cr19Ni10 or 0Cr17Ni12Mo2 stainless steel; the pipe body (2) is lined with anti-corrosion, and the inner liner (3) completely covers the pipe body (2) and the joint weld (A) to obtain a welded pipe For pipes with internal anti-corrosion method, the material of the inner lining layer (3) is the same as that of the stainless steel joint (1), and the thickness is not greater than 2.0mm; the pipes used for the internal anti-corrosion method of the welded pipes are counter-welded, and the outer end surface of the stainless steel joint (C ) and the end surface (B) of the inner lining layer is sufficient so that the butt welding process will not damage the inner lining layer (3).

Description

Internal anti-corrosion method of welded pipeline and pipeline used for said method

technical field

The invention relates to an internal anti-corrosion method of a welded pipeline and a pipeline used in the method.

Background technique

The corrosion of oil and gas pipelines seriously affects the reliability and service life of the pipeline system. With the development of oilfields and the increase of water content, the corrosion in pipelines is becoming more and more serious, which is the main cause of pipeline accidents. Internal anti-corrosion coating or lining treatment on the inner wall of the pipeline is the most convenient and effective method to solve the internal corrosion of various conveying medium pipelines. High temperature often causes a certain range of inner coating or inner lining on both sides of the weld to be scorched and damaged. If the joint is not repaired, the inner anti-corrosion coating or inner lining will lose its protective effect on the pipeline. Therefore, the problem of filling the inner anti-corrosion layer is the main bottleneck affecting the development of the inner wall coating technology of the pipeline.

According to the sequence of on-site welding of pipelines and filling of inner anti-corrosion layer, the filling methods mainly include:

(1) Welding first and repairing later:

For pipelines that have undergone internal anti-corrosion treatment, they shall be welded first at the installation site, and then the internal anti-corrosion coating shall be repaired on the damaged part of the internal anti-corrosion coating at the weld position. When repairing the joint, it is necessary to send a high-pressure airless sprayer into the weld seam in the pipe for spraying operations. This repairing method is also the mainstream form of anti-corrosion repairing in the current pipeline.

However, due to the influence of factors such as the limitation of the internal space of the pipe and the degree of drying and curing of the paint, problems such as uneven coating thickness, weak bonding, and inability to fill joints with small pipe diameters and elbows will result.

(2) Welding after repairing technology:

For pipelines that have undergone internal anti-corrosion treatment, before installation, high-temperature-resistant internal anti-corrosion measures should be taken for the pipe section near the weld position of the pipe joint, such as: spraying aluminum layer on the inner wall of the pipe end, high-temperature melting materials, and lining with heat insulation protection sets, etc., and then welded on site.

This kind of jointing method also has many limitations in use, and the quality of the jointing is difficult to guarantee, and there are still some hidden dangers for later use, for example: the inner diameter of the inner protective sleeve of the lining heat insulation layer will have the hidden danger of inconsistent inner diameter of the pipe, and the high-temperature molten material will be welded and melted. It may not be possible to completely cover the weld.

Contents of the invention

purpose of invention

An object of the present invention is to provide an internal anti-corrosion method for welded pipelines, which does not need to be filled with an internal anti-corrosion layer, is simple to operate, basically has the same inner diameter of the pipelines, and has good internal anti-corrosion effects.

Another object of the present invention is to provide a pipe used in the above-mentioned internal anti-corrosion method for welded pipes.

Summary of the invention

The sequence of the anti-corrosion method in the welded pipeline includes the following steps:

Stainless steel joints are welded at both ends of the pipe body, and the pipe body and the stainless steel joint are connected by joint welds. The material of the stainless steel joint is 00Cr19Ni10 (hereinafter referred to as 304L) or 0Cr17Ni12Mo2 (hereinafter referred to as 316) stainless steel;

Carrying out internal anti-corrosion lining to the pipeline body, the inner lining layer completely covers the pipeline body and joint weld seam, and obtains the pipeline used for the internal anti-corrosion method of the welded pipeline, the material of the inner lining layer is the same as that of the stainless steel joint, and the thickness is not more than 2.0mm;

Butt welding is carried out on the pipes used in the internal anticorrosion method of the welded pipes, and the distance between the outer end face of the stainless steel joint and the end face of the inner lining is sufficient so that the butt welding process will not damage the inner lining.

Pipelines for the above-mentioned method of internal corrosion protection of welded pipelines include

pipe body;

The stainless steel joints at both ends of the pipe body are welded by joint welds, and the material of the stainless steel joints is 304L or 316 stainless steel;

The inner anti-corrosion lining layer that completely covers the pipe body and joint welds, the material of the lining layer is the same as that of the stainless steel joint, and the thickness is not greater than 2.0mm;

The distance between the outer end surface of the stainless steel joint and the end surface of the inner lining layer is sufficient so that the butt welding process of the pipeline used for the internal anticorrosion method of the welded pipeline will not damage the inner lining layer.

When the distance between the outer end surface of the stainless steel joint and the end surface of the inner lining layer is not less than 100mm, the butt welding process can effectively avoid damage to the inner lining layer.

In order to ensure that the inner liner completely covers the pipe body and joint welds, the end face of the inner liner should not coincide with the joint welds, but should extend to the stainless steel joints. Preferably, the distance between the end face of the inner lining layer and the joint weld is not greater than 50 mm.

The stainless steel joint needs to pass the corrosion rate test to confirm that its material meets the corrosion resistance performance requirements of oil and gas pipelines. The corrosion rate test method can be carried out in accordance with the standard SYT5329-2012 "Injection water quality indicators and analysis methods for clastic reservoirs". Of course, as common knowledge in the field, the selection of stainless steel joints should also meet other general performance requirements of pipeline welded joints, such as strength, size, etc. pressure.

The method of lining the pipeline body with anti-corrosion is the prior art. The stainless steel inner lining is not only economical and effective, but also because it is made of the same material as the stainless steel joint, the welding difficulty is low, no special process is required, as long as the relevant welding technical specifications are followed, the inner lining is not easy to fall off, and the weld quality is good. The weld seam is the weak link in the performance of the pipeline, so good weld seam quality is conducive to ensuring the corrosion resistance of the entire pipeline. Preferably, the thickness of the inner lining layer is 0.7-1.0 mm, and a smaller thickness of the inner lining layer can avoid large inconsistencies in pipe diameters.

The welding in the present invention only needs to be carried out according to the conventional requirements of the existing technical specifications according to the material of the welded pipe.

Using the above-mentioned anti-corrosion method and pipeline in the welded pipeline, since the parts to be welded are all corrosion-resistant stainless steel joints, there is a certain heat dissipation distance from the heat source of the weld seam to the anti-corrosion inner lining layer in the pipe, and the welding process will not burn the inner lining layer of the pipeline, and the welding is completed Finally, there is no need for internal anti-corrosion repairing, the operation is simple, and the anti-corrosion effect is obvious. Even if the stainless steel material with a small thickness is used as the inner lining, it can fully meet the anti-corrosion requirements of oil and gas pipelines, and solve the problem of conventional internal anti-corrosion layer jointing in oil and gas pipeline construction. The quality of the method cannot be guaranteed, the small pipe diameter and the bend pipe cannot be repaired, and the pipe diameter can be kept basically the same.

Description of drawings

Fig. 1 is the pipeline sectional schematic diagram that the present invention is used in described welded pipeline internal anti-corrosion method, wherein

1—stainless steel joint, 2—pipe body, 3—inner lining, A—joint weld, B—end face of inner lining, C—outer end face of stainless steel joint.

Fig. 2 is a structural schematic diagram after butt-to-port welding of two pipes used in the internal anti-corrosion method of the welded pipes.

detailed description

The present invention is easy to implement, simple to operate, specifically as follows:

①According to the general requirements for the selection of pipeline welded joints, the caliber and strength of the stainless steel joint 1 are determined according to the caliber and strength of the pipeline body 2, and the material of the stainless steel joint 1 is selected according to the corrosion of the pipeline transport medium through corrosion rate testing, and finally determined for processing stainless steel joints 1, the diameter, strength and grade of the pipe; ②Cut the pipe into a stainless steel joint 1 of not less than 150mm, and then process the corresponding weld chamfer according to the welding technology requirements; ③The stainless steel joint 1 and the pipe body 2 are welded according to the welding technology Welding is required, and necessary protective measures such as argon filling are taken according to conventional requirements during the welding process; ④ After the welding of the stainless steel joint 1 and the pipeline body 2 is completed, sand blasting and rust removal and internal anti-corrosion lining ( According to the design, it can also be determined whether external anti-corrosion is required. According to anti-corrosion requirements, only the pipe body 2 can be externally anti-corrosion. The stainless steel joint 1 itself is a corrosion-resistant material, and generally no external anti-corrosion is required), and the inner liner 3 completely covers the pipe body 2 and Joint weld A; ⑤ When the pipeline is installed on site, it only needs to be welded in accordance with the stainless steel joint 1 pipe welding technical requirements, and it can be landfilled and put into production after welding. Among them, the corrosion rate test method is carried out in accordance with the standard SYT5329-2012 "Injection water quality indicators and analysis methods for clastic rock reservoirs".

The pipeline network in the southern oilfield of Dagang Oilfield, Cangzhou City, Hebei Province has high temperature and strong corrosiveness, and the corrosion resistance of steel pipelines is poor. (mm/year). In order to solve the corrosion problem, repeated tests were carried out, and it was concluded that 304L austenitic stainless steel has good corrosion resistance in the medium environment of the oil field. The second treatment leakage accident caused a large area to stop production. In 2007, according to the present invention, the following modification was carried out on the 200m line of the incoming liquid manifold: the pipeline body 2 is 20# carbon steel conforming to the GB-8163 standard, the pipe diameter is Ф325*8mm, and the design pressure is 2.5MPa; the stainless steel joint 1 is made of 304L stainless steel , Ф325*8mm, design pressure 2.5MPa; lining layer 3 is made of 304L stainless steel, thickness 0.8mm. The specific steps are:

Stainless steel joints 1 are welded at both ends of the pipe body 2, and the pipe body 2 and the stainless steel joint 1 are connected through joint welds A;

Carry out sandblasting and derusting according to the internal anti-corrosion technical requirements of steel pipelines, crimp and weld 304L stainless steel plates with a thickness of 0.8mm into pipes with the same inner diameter and length as the pipe body, line them into the inner wall of the pipe body 2, and then connect the two ends with stainless steel The joint 1 is welded to form an inner liner 3, the inner liner 3 completely covers the pipe body 2 and the joint weld A, and the distance between the end surface B of the inner liner and the joint weld A is 50mm, and the pipe for welding is obtained as shown in Figure 1 The pipeline of the internal anti-corrosion method, the pipeline used for the internal anti-corrosion method of the welded pipeline includes a pipeline body 2, a stainless steel joint 1 welded by the joint weld seam A at both ends of the pipeline body 2, and an inner joint that completely covers the pipeline body 2 and the joint weld seam A. For the lining layer 3, the distance between the outer end surface C of the stainless steel joint and the end surface B of the inner lining layer is not less than 100mm, which is enough to prevent the inner lining layer 3 from being damaged during the butt welding process of the pipeline used for the internal anticorrosion method of the welded pipeline;

The pipe with joints welded at both ends is butt-welded, and the schematic diagram of the pipe structure after butt-welding is shown in Figure 2.

Before the weldment is assembled, the oil, paint, scale, rust and burrs on the groove and its inner and outer surfaces shall be cleaned up within a range of not less than 10mm, and there shall be no cracks, interlayers and other defects. The welding process needs to be protected by argon filling. Argon purity should not be lower than 99.9%.

According to the above steps of construction, it has been applied for nearly 8 years without any leakage.

Claims (5)

1. a welded pipe line inner anticorrosive method, is characterized in that order comprises following steps:

At pipeline body (2) two ends soldering stainless steel joint (1), pipeline body (2) is connected by joint welding (A) with stainless joint (1), and the material of described stainless joint (1) is 00Cr19Ni10 or 0Cr17Ni12Mo2 stainless steel;

Interior corrosion-proof lining is carried out to pipeline body (2), inside liner (3) covers pipeline body (2) and joint welding (A) completely, obtain the pipeline for welded pipe line inner anticorrosive method, the material of described inside liner (3) is identical with stainless joint (1), and thickness is not more than 2.0mm;

The pipeline being used for welded pipe line inner anticorrosive method is carried out butt welding, and the distance between stainless joint exterior edge face (C) and inside liner end face (B) is enough to make described butt welding process can not destroy described inside liner (3).

2. welded pipe line inner anticorrosive method as claimed in claim 1, it is characterized in that, the distance between described stainless joint exterior edge face (C) and inside liner end face (B) is not less than 100mm.

3. welded pipe line inner anticorrosive method as claimed in claim 1, it is characterized in that, the distance between the end face (B) of described inside liner and joint welding (A) is not more than 50mm.

4. welded pipe line inner anticorrosive method as claimed in claim 1, it is characterized in that, the thickness of described inside liner (3) is 0.7 ~ 1.0mm.

5., for a pipeline for the welded pipe line inner anticorrosive method according to any one of Claims 1 to 4, it is characterized in that, comprise

Pipeline body (2);

The stainless joint (1) that pipeline body (2) two ends are welded by joint welding (A), the material of described stainless joint (1) is 00Cr19Ni10 or 0Cr17Ni12Mo2 stainless steel;

Cover the inside liner (3) of pipeline body (2) and joint welding (A) completely, described inside liner (3) thickness is not more than 2.0mm;

Distance between stainless joint exterior edge face (C) and inside liner end face (B) is enough to make describedly can not destroy described inside liner (3) for the butt welding process of the pipeline of welded pipe line inner anticorrosive method.