Roadway (Jacket Insulation Pipe) A new patchwork technology developed and developed successfully by the defect and deficiency of the polyethylene protective layer patching method. The core material of the technology is a composite patch that consists of a variety of different materials. Through electric heating, the filling mouthband and the polyethylene protective layer are mutually melted to form an organic whole body, the strength at the patch mouth is higher than the strength of the polyethylene protective layer base material, and the sealing property is good, and the filling mouthband is smooth and smooth in appearance. A number of engineering applications have proved that this technology is worth pushing cracks or crevices at the melt-cure point of composite materials, causing groundwater to invade into the inner layer and destroying the thermal insulation properties of polyurethane foam. What is more, water can dissolve the soluble H+ ions in the insulation layer (urethane foam) to form an acidic corrosion environment, thereby further accelerating the corrosion rate of the pipeline, and seriously affecting the safe operation and service life of the pipeline.
At present, in the filling method of the rigid polyurethane foam anticorrosive insulation pipe polyethylene layer, the following three are commonly used: (1) heat shrink (sheet or sleeve) method. In this method, the heat-shrink sleeve or sheet is flame-baked to make it shrink by heat, and it is tightly bonded to the polyethylene protective layer of the prefabricated pipe section at both ends. The advantage is that the structure is simple and the construction is convenient; the disadvantage is that the quality of the filling mouth is not easy to guarantee and the strength of the mouth is low.
(2) hot melt method. This method is usually used to clamp the patch (polyethylene sheet) and polyethylene protective layer compression, and then * Zhao Qixin graduated from the Chongqing University in 1987, mechanical manufacturing process and equipment professional, has been engaged in design work many times to obtain the province. The municipal excellent design award is currently the deputy manager of Jidong Oilfield Design Engineering Co., Ltd. He has organized and participated in the research and promotion of electrothermal shrinkage compound patch technology. Mailing address: Guangli Xili, Tangshan, Hebei Province, China Post code: 063004 Key words Pipeline insulation Corrosion-resisting rigid polyurethane foam Anti-corrosion insulation pipe (commonly known as jacket insulation pipe) is widely used in domestic and foreign oils for its excellent anti-corrosion and thermal insulation properties. Chemicals, urban thermal supply and other industries. The reason for this is that rigid polyurethane foams have excellent thermal insulation properties (the thermal conductivity is 0.03 lbs./o.) and high-density polyethylene plastic pipes have high strength (tensile, shear strengths can reach 18 ~ 22 MPa, and very The large elasticity, the organic combination of the two, is ideally a method of insulation.
Since the protection, heat preservation and anticorrosion of the pipe body are prefabricated in the factory by special equipment, the quality of the protective layer and insulation coating is generally reliable. Therefore, the key to determining the final anti-corrosion and thermal insulation performance of the pipeline is the quality of the protective layer filling (ie, the outer polyethylene plastic pipe interface). If the quality of the mouthpiece is not good (such as loose seal at the mouthpiece and low strength at the patch mouth, etc.), heat deformation occurs in the lower trench of the pipeline or during use, supplement the heating wire heating method to make up the mouth patch and polyethylene The shields are welded together. The advantage is that the strength of the mouthpiece is improved compared with the heat shrinkage method; the disadvantage is that the mouthpiece does not have contractility, and the flexible jig used for the pressurization is inferior in flexibility and the sealing performance is affected.
(3) plastic welding method. The plastic welding method uses a plastic welding rod to weld the patch (or cuff) and the polyethylene protective layer together. The advantage is that the construction process is simple; the disadvantage is that it is greatly affected by the weather during construction, welding quality is not easy to guarantee, at the same time, due to its small welding area, the strength of the welding part is much lower than the hot melt method.
In short, over the years, domestic and foreign scientific and technological workers have never interrupted the research on the technology and methods of filling rigid polyurethane foam anticorrosive and thermal insulation pipes. The first is to corona the jacket tube in the prefabrication process of the “tube-in-tube†method and to increase the polarity of the polyethylene jacket tube so that the foam layer and the jacket tube can be tightly bonded together, followed by the increase at both ends of each tube segment. Shaped waterproof caps, however, this is only a passive measure to prevent water vapor from eroding from the filler to the middle of the pipe; the second is to increase the temperature-sensitive line on the surface of the heat-shrinking material, that is, to change the color when the heating temperature reaches the specified temperature, so as to avoid The unevenness of the heating temperature is too high or too low to ensure the shrinkage molding quality of the heat shrinkable material. However, these improvements cannot fundamentally overcome the shortcomings of the general patching technology.
2 Electrothermal shrinkage compound joint technology In view of the existing defects and deficiencies of various commonly used patching methods, Jidong Oilfield Design Engineering Co., Ltd. and China Petroleum Engineering Technology Research Institute jointly developed a rigid polyurethane foam anticorrosion and thermal insulation pipe electric hot melt. Shrinking and compounding technology, at the same time, successfully developed the JDD-1 electric heat-shrinking compound patch with which it has been applied, and has already applied for a national patent.
The filling method integrates welding and shrinking functions.
It effectively solves the problems that the tightness and high strength of the rigid polyurethane foam anticorrosive and heat-insulating pipeline can't be taken into consideration during the construction of the joint.
The principle is to use a dedicated power source to heat the electric heat shrinkable composite patch cord, so that the compound patch cord is welded with the polyethylene protective layer under the effect of the hoop hoop force formed by the special elastic fixture and the heat shrink of the patch cord. A whole.
Due to the special heating and fusion-bonding materials used in the cuff, a change in the line contact of the hot-melt melting interface is a surface contact, which increases the fusing area, and enhances the connection strength between the cuff and the protective layer, and thus enables fusion. The tensile and shear strength of the part is greater than or equal to the strength of the substrate, so that the composite patch will not be destroyed prior to the PE sheath when subjected to damaging external forces (see Table 1 for random sampling test data and results).
Table 1 Test results of weld strength of composite joints Test number Specimen number Tensile and shear strength test results (Reference GB7124-86) PE Pipe diameter 21.2 MPa PE Jacket pipe Substrate destruction 20.6 MPa PE Sleeve tube Substrate destruction 22.7 MPa PE jacket tube Substrate Damage 20.8MPa PE Jacket Tube Substrate Damage 20.2MPa PE Sleeve Tube Substrate Destruction 21.5MPa PE Jacket Tube Substrate Damage 19.2MPa PE Sleeve Sleeve Substrate Destruction 20.3MPa PE Sleeve Sleeve Substrate Destruction 21.9MPa PE Sleeve Sleeve Substrate Damage 22.7MPa PE Jacket Tube Base Destruction of wood It is worth mentioning that during the heating, cooling and normal use of the pipeline, the shrinkage force of the patch is not affected, so while ensuring the strength of the patch, it also ensures a stable and reliable sealing quality.
In the field construction, the composite patch belt is always subjected to the uniform pressing force of the axis of the pipe caused by the joint action of the elastic fixture and the composite patch, and the pressing force at any point of the fusion area is basically the same. The welding effect of the entire welding layer is almost exactly the same, the uneven fusion defects of the hot melt method are abandoned, and the appearance of the entire joint tape is smooth and flat.
3Materials, structure and features of composite joints To reduce the cost of filling mouths, the technology uses a combination of polyethylene sleeve sleeves and composite joint tapes. The joint uses a non-shaft of the same material as the polyethylene protective layer. Integral sleeve sleeve to incision. On the one hand, the overall stiffness at the mouthpiece is increased, and the resistance to damage is increased. On the other hand, the use area of ​​the compound patch cord is reduced (the compound patch cord is much more expensive than the sleeve sleeve), thus saving the cost of patching.
Style see). The JDD-1 type composite patch tape is the core of this technology. It is a composite structure composed of a variety of different materials, mainly consisting of a heat shrink layer, a heating layer, and a fusion layer. It is manufactured in the workshop using special equipment and transported to the construction site for use. Because of its unique technological advancement, the quality and strength of the fusion of the polyethylene protective layer of the patch cords and pipes are much higher than other commonly used patching methods.
- Schematic description of the structure of the composite layer of the welding layer of the heating layer 4 On-site construction process According to the principle of the electric heat shrinkable composite joint technology of the rigid polyurethane foam anticorrosion and thermal insulation pipeline, after many years of experiments and on-site construction experience summary, a standardized and unified structure has been formed. The construction process, the specific construction steps are as follows: () According to the outer diameter of the pipe, the corresponding sleeve diameter sleeve tube and elastic fixture are manufactured.
(2) Prior to the welding of the pipeline interface, the sleeve tube is placed on the process pipe in advance.
For special parts such as cathodic protection system cable lead treatment method is: the cable leads from the process pipe polyethylene protective layer and sleeve sleeve tube gap, and its surrounding with hot melt adhesive seal.
5 Field application effects In early 1999, this technology formally passed the field test and expert appraisal and acceptance. It was highly praised by the expert group, and it was fully promoted in the Jidong oilfield in the second half of the same year, and was repeatedly destructively tested by the quality supervision department. , The quality of each project's patch meets and exceeds the national and industry standards. The main project examples are shown in Table 2. Table 2 Field application examples of compound patching technology Project name Construction pipe specifications Length of pipe length (pieces) Date Diameter Thickness Gao Shangbao Laoye Temple oil pipeline L21 oil transfer station Crude oil pipeline G17 Oil Station Crude Oil Pipeline G29 Oil Transfer Station Crude Oil Pipeline G37 Oil Transfer Station Crude Oil Pipeline L103 Oil Transfer Station Crude Oil Pipeline Liuzanyi Gaoshangbao Oil Pipeline Due to Increased Sintering Area (Sinter Width Width > 50mm), not only makes the strength of the filling site higher than that of the protective layer, but also enhances the sealing performance of the bonding surface.
Due to the use of a special heating electrode of the same size as the patch mouth, the temperature rise and welding process is very uniform, making it more stringent than the commonly used patching method. For example, the crude oil temperature drop of the Gaoshangbao Yi Lao Miao oil pipeline is 5°C lower than that of the original pipeline. Therefore, the No. 2 heating point among the original three heating points is shut down, and only two heating points are operated, which reduces energy consumption.
6 Problems and Future Directions After several years of use, rigid polyurethane foam anti-corrosion and thermal insulation pipes have the following problems: () The construction cost is slightly higher. The compound filling technique integrates heat fusion and shrinkage functions. Although it guarantees the quality of the mouthpiece and improves the service life, its price is much higher than that of the hot melt method and the heat shrink method. In the future, it is necessary to make improvements in the production of composite patch tapes and on-site construction techniques in order to reduce the cost of filling mouths.
(2) The processing technology for some special pipe sections is not perfect. In the pipeline tees, elbow bends, and reducer joints and other parts, due to its complex structure, electric heating and shrinking composite joints have not yet been used. At present, only the finished parts of the manufacturers can be selected.
In summary, although there are some areas that need to be improved in the electric heat shrinkable composite patching technology, the quality of its patch is indeed superior to other patching methods in view of its technical principle and practical use effect. it is good. It is believed that in the near future, the electric heat shrinkable composite patching technology will be fully promoted in the construction of rigid polyurethane foam anticorrosion and thermal insulation pipelines, and will play a role in improving the investment efficiency of the pipeline construction unit and extending the service life of the pipeline.
(Editor Tian Zhe 2001―04―(Continued from page 25)) Welding, pressure testing are performed GB50235-97, GB50236-98 standards, the selection of materials to be consistent with the parent material and implementation of GB9711 standard.
(2) With the principle of short construction period and easy dismantling, combined with the site environment and location, the direction of the temporary diversion bypass pipe can be flexibly selected, such as the culvert that can pass through the railway; the threading road and ditches can bypass or be used for temporary protection measures. And according to the relevant traffic regulations.
6 Safety and environmental protection measures (2) Special tools and supporting equipment shall be provided for clean oil.
(4) Construction workers must strictly abide by the operating procedures and wear labor protection.
(edited by Tian Zhe 2000-
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