CN114192935A - Ultra-low temperature high pressure stainless steel pipeline welding method in closed space - Google Patents

Abstract

The invention relates to a method for welding ultralow temperature and high pressure stainless steel pipelines in a closed space; the method comprises the following steps of groove processing: a groove is cut by adopting a mechanical processing method, and the groove is V-shaped; degreasing and cleaning the pipeline; inflating and aligning the pipeline; manufacturing a plug; the plugs are numbered during manufacturing and managed uniformly, so that the plugs are prevented from falling into a pipeline; the plug is taken out after the welding line is completely cooled, so that the influence on the cleanliness in the pipeline caused by the fact that the non-woven fabric is stuck on the pipeline after being heated and cannot fall off is avoided; the butt joint is fixed by a web plate, and the pipeline components with the same wall thickness are assembled; and setting welding parameters, wherein the welding material is welded by using a 308L welding wire. The cold box is a shell with the periphery sealed, the cold box is closed in the pipeline installation process and belongs to a sealed space, personnel suffocation accidents are easily caused due to the fact that the content of argon and nitrogen in the sealed space is too high, the volume of gas filled in the pipe can be reduced by the method, the accidents can be greatly reduced on the premise that the requirement of cleanliness in the pipeline is met, and the construction cost is saved.

Description

Ultra-low temperature high pressure stainless steel pipeline welding method in closed space

Technical Field

The invention relates to the technical field of welding of special pipelines, in particular to a method for welding ultralow-temperature high-pressure stainless steel pipelines in a closed space.

Background

In a patent CN102601499A partial argon-filled protection welding method for a petrochemical stainless steel pipeline, a welding method for partial argon-filled protection of the petrochemical stainless steel pipeline is explained, and water-soluble paper is respectively pasted at positions 15mm-30mm away from a pipe orifice in two pipes to be welded, and the welding seam is inflated by using a flat pipe. However, this method is not suitable for the pipeline welding with high requirement on the cleanliness of the inner wall and working pressure, because the water-soluble paper method is used for inflation, and the cleanliness cannot be ensured after the welding of the fixed port is completed.

Disclosure of Invention

The invention aims to overcome the defects and provides a method for welding ultralow-temperature high-pressure stainless steel pipelines in a closed space.

In order to achieve the above object, the present invention is realized by:

a method for welding ultralow-temperature high-pressure stainless steel pipelines in a closed space comprises

Step 1, groove preparation: a groove is cut by adopting a mechanical processing method, and the groove is V-shaped and should be kept neat and smooth;

step 2, preparing welding;

step 2.1, degreasing and cleaning the pipeline: the tools, measuring tools and instruments used for degreasing and mounting are required to be degreased firstly; sealing and protecting the pipeline qualified for degreasing in time; the inner wall of the tube is wiped by trichloroethylene for degreasing, and the content of solvent grease after degreasing is required to be not more than 125 mg/L;

step 2.2, inflating the pipeline and aligning: argon is filled into the tube by adopting a plug method, the plug is made of high-density sponge, the tube opening is completely sealed, the argon is prevented from leaking, in order to prevent the sponge from dropping slag, a layer of non-woven fabric is wrapped outside the sponge, the requirement of the non-woven fabric is not lower than 170 g of polyester fabric, and the non-woven fabric is prevented from being damaged or generating fragments to pollute the pipeline; a hose is adopted for inflation and clamped below a plug, the plug is used for placing two ends of a pipe to be welded, and the distance between the two ends of the pipe to be welded and a welding seam is more than 300 mm;

step 2.2.1, manufacturing a plug: the sponge is clamped by two slightly-small boards, a bolt is arranged between the boards, a nut is spot-welded on the bolt, so that the iron wire can be conveniently pulled out of the pipeline after the plug is used, the iron wire is made of stainless steel, and the phenomenon that the common iron wire or galvanized iron wire is contacted with the inner wall of the pipeline to cause carburization on the parent metal of the pipeline is avoided; the plugs are numbered during manufacturing and managed uniformly, so that the plugs are prevented from falling into a pipeline; the plug is taken out after the welding line is completely cooled, so that the influence on the cleanliness in the pipeline caused by the fact that the non-woven fabric is stuck on the pipeline after being heated and cannot fall off is avoided;

the butt joint is fixed by a web plate, and the pipeline components with the same wall thickness are assembled to ensure that the inner walls are flush, and the misalignment amount is less than or equal to 10% of the wall thickness and is not more than 2 mm; under the condition that the staggered joint cannot be avoided, the uniform staggered edges at two ends are controlled, and the rapid inflation of the welding line is realized by adopting the masking paper to paste the joint in the opposite joint;

step 3, setting welding parameters; in order to avoid welding beading, incomplete penetration and depression or other defects during welding as much as possible, the conditions of incomplete slag removal after welding and the like are adopted, and the welding is carried out by adopting a full argon arc welding mode no matter how much the wall thickness is, the welding parameters are as follows

3.1, because the working medium is low-temperature liquid and the working temperature is-196 ℃, when the process evaluation is carried out in the early stage of welding, besides necessary tensile test and bending test, low-temperature impact test needs to be carried out in a welding seam area and a heat affected area;

step 3.2, using 308L welding wires as welding materials;

3.3, when the air is inflated, whether the air is completely exhausted or not and whether the welding condition is met or not can be known, an oxygen measuring instrument or a burning incense head is placed at the welding seam, and when the oxygen measuring instrument gives an alarm or the incense head is extinguished, the welding condition is met;

and 4, welding.

Because the interior pipeline of the cold box is mostly connected with the tower, if the whole pipeline is filled with protective gas, not only time is consumed, but also argon is expensive, and the welding cost is increased. The requirements of degreasing and cleanliness in the cold box are extremely high, and a welding method of a flux-cored wire and water-soluble paper is not allowed. The cold box is a shell with the periphery sealed, the cold box is closed in the pipeline installation process and belongs to a sealed space, personnel suffocation accidents are easily caused due to the fact that the content of argon and nitrogen in the sealed space is too high, the volume of gas filled in the pipe can be reduced by the method, the accidents can be greatly reduced on the premise that the requirement of cleanliness in the pipeline is met, and the construction cost is saved.

Drawings

FIG. 1 is a design drawing of a pipe groove in the method.

Detailed Description

The invention is further illustrated by the following specific examples.

As shown in figure 1, the method for welding ultralow temperature and high pressure stainless steel pipelines in the closed space comprises

Step 1, groove preparation: a groove is cut by adopting a mechanical processing method, and the groove is V-shaped and should be kept neat and smooth;

step 2, preparing welding;

step 2.1, degreasing and cleaning the pipeline: the tools, measuring tools and instruments used for degreasing and mounting are required to be degreased firstly; sealing and protecting the pipeline qualified for degreasing in time; the inner wall of the tube is wiped by trichloroethylene for degreasing, and the content of solvent grease after degreasing is required to be not more than 125 mg/L;

step 2.2, inflating the pipeline and aligning: argon is filled into the tube by adopting a plug method, the plug is made of high-density sponge, the tube opening is completely sealed, the argon is prevented from leaking, in order to prevent the sponge from dropping slag, a layer of non-woven fabric is wrapped outside the sponge, the requirement of the non-woven fabric is not lower than 170 g of polyester fabric, and the non-woven fabric is prevented from being damaged or generating fragments to pollute the pipeline; a hose is adopted for inflation and clamped below a plug, the plug is used for placing two ends of a pipe to be welded, and the distance between the two ends of the pipe to be welded and a welding seam is more than 300 mm;

step 2.2.1, manufacturing a plug: the sponge is clamped by two slightly-small boards, a bolt is arranged between the boards, a nut is spot-welded on the bolt, so that the iron wire can be conveniently pulled out of the pipeline after the plug is used, the iron wire is made of stainless steel, and the phenomenon that the common iron wire or galvanized iron wire is contacted with the inner wall of the pipeline to cause carburization on the parent metal of the pipeline is avoided; the plugs are numbered during manufacturing and managed uniformly, so that the plugs are prevented from falling into a pipeline; the plug is taken out after the welding line is completely cooled, so that the influence on the cleanliness in the pipeline caused by the fact that the non-woven fabric is stuck on the pipeline after being heated and cannot fall off is avoided;

the butt joint is fixed by a web plate, and the pipeline components with the same wall thickness are assembled to ensure that the inner walls are flush, and the misalignment amount is less than or equal to 10% of the wall thickness and is not more than 2 mm; under the condition that the staggered joint cannot be avoided, the uniform staggered edges at two ends are controlled, and the rapid inflation of the welding line is realized by adopting the masking paper to paste the joint in the opposite joint;

step 3, setting welding parameters; in order to avoid welding beading, incomplete penetration and depression or other defects during welding as much as possible, the conditions of incomplete slag removal after welding and the like are adopted, and the welding is carried out by adopting a full argon arc welding mode no matter how much the wall thickness is, the welding parameters are as follows

3.1, because the working medium is low-temperature liquid and the working temperature is-196 ℃, when the process evaluation is carried out in the early stage of welding, besides necessary tensile test and bending test, low-temperature impact test needs to be carried out in a welding seam area and a heat affected area;

step 3.2, using 308L welding wires as welding materials;

3.3, when the air is inflated, whether the air is completely exhausted or not and whether the welding condition is met or not can be known, an oxygen measuring instrument or a burning incense head is placed at the welding seam, and when the oxygen measuring instrument gives an alarm or the incense head is extinguished, the welding condition is met;

and 4, welding.

Because the interior pipeline of the cold box is mostly connected with the tower, if the whole pipeline is filled with protective gas, not only time is consumed, but also argon is expensive, and the welding cost is increased. The requirements of degreasing and cleanliness in the cold box are extremely high, and a welding method of a flux-cored wire and water-soluble paper is not allowed. The cold box is a shell with the periphery sealed, the cold box is closed in the pipeline installation process and belongs to a sealed space, personnel suffocation accidents are easily caused due to the fact that the content of argon and nitrogen in the sealed space is too high, the volume of gas filled in the pipe can be reduced by the method, the accidents can be greatly reduced on the premise that the requirement of cleanliness in the pipeline is met, and the construction cost is saved.

Claims (1)

1. A method for welding ultralow-temperature high-pressure stainless steel pipelines in a closed space is characterized by comprising the following steps of: comprises that

Step 1, groove preparation: a groove is cut by adopting a mechanical processing method, and the groove is V-shaped and should be kept neat and smooth;

step 2, preparing welding;

step 2.1, degreasing and cleaning the pipeline: the tools, measuring tools and instruments used for degreasing and mounting are required to be degreased firstly; sealing and protecting the pipeline qualified for degreasing in time; the inner wall of the tube is wiped by trichloroethylene for degreasing, and the content of solvent grease after degreasing is required to be not more than 125 mg/L;

step 2.2, inflating the pipeline and aligning: argon is filled into the tube by adopting a plug method, the plug is made of high-density sponge, the tube opening is completely sealed, the argon is prevented from leaking, in order to prevent the sponge from dropping slag, a layer of non-woven fabric is wrapped outside the sponge, the requirement of the non-woven fabric is not lower than 170 g of polyester fabric, and the non-woven fabric is prevented from being damaged or generating fragments to pollute the pipeline; a hose is adopted for inflation and clamped below a plug, the plug is used for placing two ends of a pipe to be welded, and the distance between the two ends of the pipe to be welded and a welding seam is more than 300 mm;

step 2.2.1, manufacturing a plug: the sponge is clamped by two slightly-small boards, a bolt is arranged between the boards, a nut is spot-welded on the bolt, so that the iron wire can be conveniently pulled out of the pipeline after the plug is used, the iron wire is made of stainless steel, and the phenomenon that the common iron wire or galvanized iron wire is contacted with the inner wall of the pipeline to cause carburization on the parent metal of the pipeline is avoided; the plugs are numbered during manufacturing and managed uniformly, so that the plugs are prevented from falling into a pipeline; the plug is taken out after the welding line is completely cooled, so that the influence on the cleanliness in the pipeline caused by the fact that the non-woven fabric is stuck on the pipeline after being heated and cannot fall off is avoided;

the butt joint is fixed by a web plate, and the pipeline components with the same wall thickness are assembled to ensure that the inner walls are flush, and the misalignment amount is less than or equal to 10% of the wall thickness and is not more than 2 mm; under the condition that the staggered joint cannot be avoided, the uniform staggered edges at two ends are controlled, and the rapid inflation of the welding line is realized by adopting the masking paper to paste the joint in the opposite joint;

step 3, setting welding parameters; in order to avoid welding beading, incomplete penetration and depression or other defects during welding as much as possible, the conditions of incomplete slag removal after welding and the like are adopted, and the welding is carried out by adopting a full argon arc welding mode no matter how much the wall thickness is, the welding parameters are as follows

3.1, because the working medium is low-temperature liquid and the working temperature is-196 ℃, when the process evaluation is carried out in the early stage of welding, besides necessary tensile test and bending test, low-temperature impact test needs to be carried out in a welding seam area and a heat affected area;

step 3.2, using 308L welding wires as welding materials;

3.3, when the air is inflated, whether the air is completely exhausted or not and whether the welding condition is met or not can be known, an oxygen measuring instrument or a burning incense head is placed at the welding seam, and when the oxygen measuring instrument gives an alarm or the incense head is extinguished, the welding condition is met;

and 4, welding.

Images