If all the re- excavation of pipeline corrosion, effort, and cost is enormous, only the implementation of the cathodic protection system is the most economical and easy solution , but because of pipeline construction without appropriate insulation measures and difficult to stop gas for insulation transformation, also difficult to obtain because there is no insulation and pipe -related parameters, so it can not be implemented before the relevant cathodic protection process calculation, which gives the cathodic protection system implementation has brought great difficulties. Cathodic protection methods are forced current law and the sacrificial anode protection laws, which force the current method due to the pipeline without insulation and building pipelines in multi- family area environment, technically feasible, it is difficult to use sacrificial anode cathodic protection law in the implementation of, since the anode at a certain distance pipelines laid in place, avoid other buildings and underground piping is protected against the impact of pipeline and technically feasible, so as to prevent the continuation of the development of corrosion, the use of sacrificial anode cathodic protection.
Soil environment in which the pipeline can not be changed, so we use the most simple way for family wings branch pipeline insulation insulation transform this transformation in the surge tank can be carried out at the flange, ie the surge tank flange screw plus insulating sleeve, the use of PTFE insulation pads, while the flange gasket without replacing the original asbestos mat, so stop making pipeline protection potential output has reached eleven, the realization will be, will be fully protected pipeline. To the factory area two parallel pipelines buried a short distance though, but after entering the factory overhead to each workshop, all of the overhead steel pipe support brackets, the number of overhead line length of about stents, each bracket is a ground point Meanwhile, the plant area electrolysis plant and other major electricity system grounding, causing stray current interference of the pipeline is also very obvious. This requires a large ground exclude exclude stray current interference impact of the pipeline. The best solution is in the pipeline overhead before installing insulation or insulating flange joints, were insulated transformation, then ground and stray interference issues have been resolved accordingly, but because of all gas production plant in the region, stop gas transformation will force production stopped, will lead to huge economic losses. Interference from stray current drain approaches can be taken to resolve the basic solution is buried pipeline overhead before installing zinc anodes with one hand, so that stray current through the zinc anode grounded to earth stray current row of people, partly because zinc anode has a more negative potential than steel, providing cathodic current can give pipeline, drainage and protection to achieve the dual purpose. But no matter what measures the exhaust stream draining grounding grounding resistance should be less than pipe body resistance, draining effect was obvious. However, due to high soil resistivity pipeline which should produce a ground resistance of less than pipe body resistance grounding is very difficult, but because the ground is used in zinc anode material is very expensive, can be installed to protect the pipeline, also Shangqie I do not know. In order to avoid blindness and unnecessary economic losses, we do not make any insulation transformation cases, an analog current cathodic protection test. To determine the case of non-insulated pipeline in the end require much cathode current cathodic protection system which re- determine the best solution embodiment.
Thursday, October 31, 2013
Discussion of the gas pipeline corrosion
Because the pipeline internal corrosion caused by gas leaks, explosions occupies a large proportion of the pipeline after doing inner coating can effectively suppress the occurrence of internal corrosion, thereby improving pipeline safety. The other hand, the level of efficiency of gas pipeline transmission and distribution projects in the pipeline is a measure put into operation one of the main symbol of good and bad, and pipeline efficiency and pipe wall roughness to some extent.
The organic coated steel pipes for the surface- coating with excellent corrosion resistance, chemical stability and good molding properties. Steel substrate with high mechanical strength, impact resistance, resistance to bending. The combination of organic coatings and steel focused on the advantages of both. Applications in the oil industry drill drilling organic coatings, containing hydrogen sulfide, salt, a very high temperature and pressure operating under poor working conditions, the actual use of the drill pipe is subsequently proved that organic coatings with good corrosion resistance, its service life than the non- coated with organic coatings increased by 2 to 3 times. Organic coating steel pipes are used than non- coated with organic coatings life of the pipeline increased by 3 to 4 times. When the organic coated steel pipes for laying in the ground, due to the presence of the coating, forms a good insulating layer, weakening the stray current corrosion. Organic coating smooth surface smooth, easy to breed bacteria and mold, wax effectively prevent corrosion, fouling, avoid bacterial corrosion, corrosion under the scale of production.
The organic coated steel pipes for the surface- coating with excellent corrosion resistance, chemical stability and good molding properties. Steel substrate with high mechanical strength, impact resistance, resistance to bending. The combination of organic coatings and steel focused on the advantages of both. Applications in the oil industry drill drilling organic coatings, containing hydrogen sulfide, salt, a very high temperature and pressure operating under poor working conditions, the actual use of the drill pipe is subsequently proved that organic coatings with good corrosion resistance, its service life than the non- coated with organic coatings increased by 2 to 3 times. Organic coating steel pipes are used than non- coated with organic coatings life of the pipeline increased by 3 to 4 times. When the organic coated steel pipes for laying in the ground, due to the presence of the coating, forms a good insulating layer, weakening the stray current corrosion. Organic coating smooth surface smooth, easy to breed bacteria and mold, wax effectively prevent corrosion, fouling, avoid bacterial corrosion, corrosion under the scale of production.
Monday, October 28, 2013
Large diameter steel pipe expanding proces
Because the large diameter seamless steel pipe diameter sizes is too large, in addition to the less efficient large hot extrusion unit and large pipe jacking machine outside, we can no longer use the familiar automatic pipe mill or continuous pipe mill and other models for direct production. Thus emerged pull Dial expanding, expanding top push and rotate the three main Seamless expanding expanding process. Currently most of the world are produced in large diameter seamless steel technology three and pull Dial and top push expanding process has been applied to some large -diameter welded steel pipe production, and become part of the composition of its processes.
Pull Dial expanding process
Pull Dial Flaring machine produced in the 1930s in Germany, then to Italy, France adopted and in Italy to perfect, which is currently the world's only six units and relatively obsolete technology. To 630 units, for example CSST; several thousand tons equipment, hundreds of millions of investment, annual output of 50,000 tons. The production process must first be heated thermal expansion material as the tube end valgus cone, for fixing the tubular body. Then the overall heating tube, with a chain pull has been set into the inner mold raw tube and fitted mandrel, complete flaring. Its characteristics: high production efficiency, longer processed finished products, equipment can be reduced flaring necking multi- wall, but the equipment weight of large infrastructure investment is large, deformed steel pipe flaring continues in tension, resulting in poor product quality, external Drive low precision steel surface is not smooth, as the removal of low end valgus cone timber defects caused more prominent.
Rotate expanding process
Expansion of the machine, also known as rotary disc flaring equipment. Its name comes from its cross- tilt placed two large-diameter disk-shaped rolls similar to the device once expansion ratio of up to 70 %, which is currently the world's largest amount of time expanded diameter pipe expansion models. The device is in a 1990s Italian oblique roller mill developed on the basis adapted from. So far only four sets of the world, only Italy Dalmine unit for the most successful cases, thousands of tons of equipment over a billion construction investment, sophisticated technology, despite its high production efficiency, deformation speed, a large flaring, so that the industry is still daunting . However, if the Department were equipped machine, sizing machine composed of expanding production lines, for a large number of large -diameter pipe production is not a good solution for the vector.
Pushing expanding process
This model was invented in Germany in the 1950s, the mid-1980s to elbow pushing machine models from Japan into China. To 1997 and renovated in China perfect obtaining intellectual property, and named two -step expansion of the machine hydraulic pusher, the device is simple in principle to the hydraulic push plate will cover only the fixed cone with expanding mandrel outside the hot feed pipe pushed through flaring cone will complete the expansion work. Expanding mandrel process only occurs in the raw material tube and associated fixed connections between stress lines therefore very short. And because of the fixed plate and cylinder mandrel mandrel tube billet between the forces, this device stiffness structure greatly simplified. Two step forward in turn reduce the length of the hydraulic cylinder nearly half, so a greater extent, reduce the equipment cost and mainly from the process solution to the cylinder machining length limit. The expanding device complete with frequency heating equipment, rapid and uniform heating of raw materials controllable, uniform propulsion deformed pipes are refined microstructure and mechanical properties of materials to improve the performance guarantee uniformity of the tube to create the conditions, although the device has less investment, short construction period, simple equipment, product quality, high geometric accuracy, finished product rate, etc.
Pull Dial expanding process
Pull Dial Flaring machine produced in the 1930s in Germany, then to Italy, France adopted and in Italy to perfect, which is currently the world's only six units and relatively obsolete technology. To 630 units, for example CSST; several thousand tons equipment, hundreds of millions of investment, annual output of 50,000 tons. The production process must first be heated thermal expansion material as the tube end valgus cone, for fixing the tubular body. Then the overall heating tube, with a chain pull has been set into the inner mold raw tube and fitted mandrel, complete flaring. Its characteristics: high production efficiency, longer processed finished products, equipment can be reduced flaring necking multi- wall, but the equipment weight of large infrastructure investment is large, deformed steel pipe flaring continues in tension, resulting in poor product quality, external Drive low precision steel surface is not smooth, as the removal of low end valgus cone timber defects caused more prominent.
Rotate expanding process
Expansion of the machine, also known as rotary disc flaring equipment. Its name comes from its cross- tilt placed two large-diameter disk-shaped rolls similar to the device once expansion ratio of up to 70 %, which is currently the world's largest amount of time expanded diameter pipe expansion models. The device is in a 1990s Italian oblique roller mill developed on the basis adapted from. So far only four sets of the world, only Italy Dalmine unit for the most successful cases, thousands of tons of equipment over a billion construction investment, sophisticated technology, despite its high production efficiency, deformation speed, a large flaring, so that the industry is still daunting . However, if the Department were equipped machine, sizing machine composed of expanding production lines, for a large number of large -diameter pipe production is not a good solution for the vector.
Pushing expanding process
This model was invented in Germany in the 1950s, the mid-1980s to elbow pushing machine models from Japan into China. To 1997 and renovated in China perfect obtaining intellectual property, and named two -step expansion of the machine hydraulic pusher, the device is simple in principle to the hydraulic push plate will cover only the fixed cone with expanding mandrel outside the hot feed pipe pushed through flaring cone will complete the expansion work. Expanding mandrel process only occurs in the raw material tube and associated fixed connections between stress lines therefore very short. And because of the fixed plate and cylinder mandrel mandrel tube billet between the forces, this device stiffness structure greatly simplified. Two step forward in turn reduce the length of the hydraulic cylinder nearly half, so a greater extent, reduce the equipment cost and mainly from the process solution to the cylinder machining length limit. The expanding device complete with frequency heating equipment, rapid and uniform heating of raw materials controllable, uniform propulsion deformed pipes are refined microstructure and mechanical properties of materials to improve the performance guarantee uniformity of the tube to create the conditions, although the device has less investment, short construction period, simple equipment, product quality, high geometric accuracy, finished product rate, etc.
Welding stress elimination
For the high-rise buildings, the component of the residual stress in particular the control of welding residual stresses is quite strict, the welding process of welding residual stress and stress will reduce the capacity and lifetime of the structure, but also the direct cause of cracks caused. After completion of the processing components must adopt appropriate measures to eliminate stress, while the economic costs are very high, the mechanical properties of the component will have a greater damage.
VSR substantive principle is based on mechanical vibration modes impose additional stress on the workpiece, when the additional stress and residual stress superimposed upon the total stress reaches or exceeds a certain value, the stress concentration at the site of more than metallic material yield strength occurs within the workpiece macroscopic and microscopic plastic deformation - Bauschinger effect, thereby reducing the residual stress of the peak point, the stress uniform, improved resistance to deformation of metals. Meanwhile, the dynamic stress and vibration superposition of macroscopic residual stress, combined stress caused yield greater than the elastic limit, the high stress drop, stress uniformity, improved dimensional stability. Particularly in the stress concentration are likely to form a larger tensile stress yield zone, formed after the stress unloading stress protected areas, improve the stability of the structure; early in the VSR effect plays a major role in this.
VSR substantive principle is based on mechanical vibration modes impose additional stress on the workpiece, when the additional stress and residual stress superimposed upon the total stress reaches or exceeds a certain value, the stress concentration at the site of more than metallic material yield strength occurs within the workpiece macroscopic and microscopic plastic deformation - Bauschinger effect, thereby reducing the residual stress of the peak point, the stress uniform, improved resistance to deformation of metals. Meanwhile, the dynamic stress and vibration superposition of macroscopic residual stress, combined stress caused yield greater than the elastic limit, the high stress drop, stress uniformity, improved dimensional stability. Particularly in the stress concentration are likely to form a larger tensile stress yield zone, formed after the stress unloading stress protected areas, improve the stability of the structure; early in the VSR effect plays a major role in this.
Sunday, October 27, 2013
Pipeline corrosion protection measures
At present, domestic and international long- distance pipelines for corrosion-resistant coatings are mainly coal tar enamel, two layer structure of PE, three-layer structure of PE, FBE (FBE), double-layer fusion bonded epoxy powder ( FBE layer ) covering layer.
Coal tar enamel with good insulation properties, low water absorption, corrosion-resistant bacteria and plant roots penetrate the material adequacy and long service life and low price. The main disadvantage is lower mechanical strength, suitable temperature range is narrow, low and easy brittle, production and construction process may escape of toxic gases, requires strict smog measures. Used abroad for more than 70 years of history, in recent years due to environmental restrictions gradually replaced by other coatings. 2 layer PE structure has good insulation properties, low water absorption, high mechanical strength, tough wear-resistant, acid salts and bacteria, corrosion resistance, temperature changes, sufficient material advantages, the price is lower. Drawback is poor resistance to ultraviolet radiation, exposure to sunlight for too long and easy to aging, poor adhesion with steel surface, anti- cathodic stripping poor performance. PE layer electrostatic shielding effect is not conducive impressed current cathodic protection. 3-layer PE anti-corrosion layer structure combines a high-density polyethylene coating, FBE advantages. It is an epoxy powder and firmly with the pipe surface, the use of high density polyethylene resistant to mechanical damage, a special layer between the two layers so that the three molecules bond to form a composite structure, to achieve corrosion properties, good combination of mechanical properties, is currently the leading pipeline engineering preferred coating. FBE (FBE) has a steel surface with a solid, good insulation properties, high mechanical strength, resistance to temperature changes, resistance to chemical corrosion, etc., suitable for a variety of harsh natural environment. The main disadvantage is poor resistance to ultraviolet radiation, since the covering layer is thin, scratch and bump performance is poor. Abroad from the 1960s began to be used pipeline corrosion, has developed rapidly and is currently used on the international pipeline corrosion largest amount of overburden. FBE layer ( layer FBE) and 3-layer PE structure is similar, with good overall performance, high mechanical properties. FJC also with double FBE, good compatibility, cladding surface smooth. In addition, the cathode shielding problems can be avoided with the cathodic protection system matching better than the three-layer structure of PE. It is internationally developed a new kind of coating, the most suitable for use across the mountain section and the stonework.
Coal tar enamel with good insulation properties, low water absorption, corrosion-resistant bacteria and plant roots penetrate the material adequacy and long service life and low price. The main disadvantage is lower mechanical strength, suitable temperature range is narrow, low and easy brittle, production and construction process may escape of toxic gases, requires strict smog measures. Used abroad for more than 70 years of history, in recent years due to environmental restrictions gradually replaced by other coatings. 2 layer PE structure has good insulation properties, low water absorption, high mechanical strength, tough wear-resistant, acid salts and bacteria, corrosion resistance, temperature changes, sufficient material advantages, the price is lower. Drawback is poor resistance to ultraviolet radiation, exposure to sunlight for too long and easy to aging, poor adhesion with steel surface, anti- cathodic stripping poor performance. PE layer electrostatic shielding effect is not conducive impressed current cathodic protection. 3-layer PE anti-corrosion layer structure combines a high-density polyethylene coating, FBE advantages. It is an epoxy powder and firmly with the pipe surface, the use of high density polyethylene resistant to mechanical damage, a special layer between the two layers so that the three molecules bond to form a composite structure, to achieve corrosion properties, good combination of mechanical properties, is currently the leading pipeline engineering preferred coating. FBE (FBE) has a steel surface with a solid, good insulation properties, high mechanical strength, resistance to temperature changes, resistance to chemical corrosion, etc., suitable for a variety of harsh natural environment. The main disadvantage is poor resistance to ultraviolet radiation, since the covering layer is thin, scratch and bump performance is poor. Abroad from the 1960s began to be used pipeline corrosion, has developed rapidly and is currently used on the international pipeline corrosion largest amount of overburden. FBE layer ( layer FBE) and 3-layer PE structure is similar, with good overall performance, high mechanical properties. FJC also with double FBE, good compatibility, cladding surface smooth. In addition, the cathode shielding problems can be avoided with the cathodic protection system matching better than the three-layer structure of PE. It is internationally developed a new kind of coating, the most suitable for use across the mountain section and the stonework.
Buried steel pipeline corrosion factor analysis
Buried pipelines in the working environment, mainly with soil erosion corrosion, bacteria, corrosion and stray current corrosion. Soil is a solid, liquid and gas -phase capillary porous gelatinous body, the soil voids is filled with air and water, the water contains a certain amount of salt, so that the soil has ionic conductivity, soil physical and chemical properties of heterogeneous and metal electrochemical inhomogeneity, constitute electrochemical corrosion of buried pipeline conditions, which will produce soil erosion. In some soil bacteria oxygen ( SRB ) participated in the etching process, the role of bacteria is to participate in the electrode reaction, the soluble iron sulfate to hydrogen sulfide, thus producing bacterial corrosion. Stray current is flowing in the ground outside the protection system design corrosive to metal pipes damaging effects of current. Stray current corrosion including DC and AC stray current corrosion stray current corrosion. DC stray current corrosion principles and electrolytic corrosion similar to AC stray current corrosion is a pipe near high voltage power lines generated by the second induction AC superimposed on the pipeline corrosion corrosion resulting electrochemical cell , the corrosion was smaller, but concentrated corrosion resistance.
Corrosion protection control pipe corrosion damage is a key factor. Currently, the pipeline corrosion protection using a double measures, namely anti-corrosion coating and cathodic protection ( impressed current or sacrificial anode exhaust stream ). Anti-corrosion coating can withstand corrosive environment of the scene to ensure that the pipe firmly bonded, does not appear possible cause cathodic protection cathodic stripping and dead. In the event of partial peeling, you must adjust the impressed current cathodic protection system operating parameters, in order to effectively control the dead corrosion achieve the protective effect. Tube material and manufacturing factors are internal pipeline corrosion, especially steel chemical composition and crystalline structure, high content of non-metallic components ( such as S and P) prone to corrosion, C and Si could easily lead to brittle cracking. Microcrystalline fineness of low-grade, cracks along the grain expansion , prone to cracking. In the manufacturing process, the surface defects ( such as scratches , pits, micro-crack , etc. ), also cause pipe corrosion cracking. Pipeline operation is running, delivery pressure and pressure fluctuations are an important factor in stress corrosion cracking. Excessive pressure to the wall using excessive stress corrosion crack easy to make, easy to make pressure cycle fluctuations crack.
Corrosion protection control pipe corrosion damage is a key factor. Currently, the pipeline corrosion protection using a double measures, namely anti-corrosion coating and cathodic protection ( impressed current or sacrificial anode exhaust stream ). Anti-corrosion coating can withstand corrosive environment of the scene to ensure that the pipe firmly bonded, does not appear possible cause cathodic protection cathodic stripping and dead. In the event of partial peeling, you must adjust the impressed current cathodic protection system operating parameters, in order to effectively control the dead corrosion achieve the protective effect. Tube material and manufacturing factors are internal pipeline corrosion, especially steel chemical composition and crystalline structure, high content of non-metallic components ( such as S and P) prone to corrosion, C and Si could easily lead to brittle cracking. Microcrystalline fineness of low-grade, cracks along the grain expansion , prone to cracking. In the manufacturing process, the surface defects ( such as scratches , pits, micro-crack , etc. ), also cause pipe corrosion cracking. Pipeline operation is running, delivery pressure and pressure fluctuations are an important factor in stress corrosion cracking. Excessive pressure to the wall using excessive stress corrosion crack easy to make, easy to make pressure cycle fluctuations crack.
Friday, October 25, 2013
Development and application of thick wall straight seam steel five-wire submerged arc process
In the thick wall LSAW steel pipe production process, five -wire submerged arc welding process has been a hot research. Currently, only a few countries in the world to master this advanced production technology. Five power wire submerged arc welding using five were arranged longitudinally along the welding wire five separate power supply, the wire solder layer in the pool under a total combustion, enabling the pipe welding. Since more than five arc welding wire, current, pool length, and therefore has a large heat input, high deposition efficiency, metallurgical reaction fully, welding speed, etc. In five wire submerged arc welding process development projects, there is significant electromagnetic interference between AC arc, multi- adjustable parameters, process control and so demanding and difficult. Specifically in the configuration of the welding power source and connection of the wire set spatial position welding parameter selection, the combination of wire diameter and the selection of solder and so on. Where welding power supply configuration, wire spatial position and the welding parameters design choice is the focus of the development process, which is the key technical problems choose reasonable power connections as well as many rational combination of variable parameters.
Introduction of virtual manufacturing technology for non- mandrel -drawn steel production process modeling and simulation, cold drawn steel pipe can operate virtual machines, draft and draft seats, the virtual deformation and bending the material, and for the metal in the deformation process generated in the longitudinal extension and lateral flow causes the inner wall of uneven metal flow problems for the overall coordination and dynamic process optimization; while the material hardness, bending springback, outline size , aspect ratio and other issues simulation. Through this virtual computer model to observe the deformation process of the metal vertical extension and lateral flow, pipe wall thickness changes, and adjust draft and draft seat size, pipe wall thickness of the original with the original diameter ratio, each parameters such as reducing the amount of times, improve product quality.
Introduction of virtual manufacturing technology for non- mandrel -drawn steel production process modeling and simulation, cold drawn steel pipe can operate virtual machines, draft and draft seats, the virtual deformation and bending the material, and for the metal in the deformation process generated in the longitudinal extension and lateral flow causes the inner wall of uneven metal flow problems for the overall coordination and dynamic process optimization; while the material hardness, bending springback, outline size , aspect ratio and other issues simulation. Through this virtual computer model to observe the deformation process of the metal vertical extension and lateral flow, pipe wall thickness changes, and adjust draft and draft seat size, pipe wall thickness of the original with the original diameter ratio, each parameters such as reducing the amount of times, improve product quality.
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