When considering whether to use heat shrinkable sleeve or heat shrinkable belt, we should pay attention to the following problems:
From the construction point of view, the heat shrinkable Belt should be selected, because the heat shrinkable belt does not need to be put on the pipe before installation, and it can be used for joint coating. It will not be lost or contaminated due to hanging on the pipe on site many days in advance, or the quality of the heat shrinkable sleeve will decline under other climatic conditions. However, from the perspective of quality, the heat shrinkable belt needs to be lapped into a sleeve on site, At the same time, the lap joint should be fixed with a fixed piece, which not only increases the bonding area and bonding edge, but also is more important because the lap joint is two layers higher, which is easy to be scratched or scraped off, especially when the construction personnel are not good enough, it is easy to produce quality problems, so the heat shrinkable sleeve should be selected as much as possible. However, at present, the quality of heat shrinkable tape has been continuously improved, the production cycle of large-diameter heat shrinkable belt is short, and the price is cheap, and other objective reasons, as well as the selection of heat shrinkable tape as joint coating material in large projects such as the second west to East Gas Pipeline Project, the heat shrinkable belt has become the main product in the pipeline anti-corrosion joint coating material market.
Therefore, in the selection of heat shrinkable sleeve and heat shrinkable belt, the following opinions can be referred to. (heat shrinkable joint tape)
(1) In the construction section with narrow working space, the installation of heat shrinkable sleeve is very inconvenient, so the heat shrinkable Belt should be selected;
(2) In case of frequent sandstorm on the construction site, and other climatic conditions will have a great impact on the quality of the heat shrinkable sleeve hanging on the pipe for a long time, such as the paper tape on the adhesive surface of the heat shrinkable sleeve is damaged and serious degumming occurs, the heat shrinkable Belt should be selected;
(3) the heat shrinkable sleeve is easy to be stolen or damaged. For example, the quality of residents in a certain place in the construction area is poor, so the heat shrinkable Belt should be selected.
(4) For the directional drilling crossing project, the heat shrinkable sleeve is used, and the thickness of the heat shrinkable sleeve is relatively thick. During the pull back process, the pipe section is dragged for a long distance. Even if the boreholes are in the fine soil layer, there may be hard materials such as concrete blocks, stones and tree roots in the surface layer near the excavation point and the soil entry point, which is easy to fall into the borehole from the excavation point. In the process of reaming, some hard materials may be squeezed onto the hole wall. Because the drag force is far greater than the edge adhesion force of the heat shrinkable sleeve and heat shrinkable band, the edges of the heat shrinkable sleeve and heat shrinkable band are easy to tear when encountering such hard objects. Compared with the two, because the self lap joint of the heat shrinkable belt is two layers higher (one layer higher when lapping itself, and another layer of fixing piece), the edge of this part is easier to tear off, especially the pipe section will rotate in a large range during the pull back process (there is a rotary joint between the drill pipe and the pipe. At present, there are no additional measures to prevent the pipe section from rotating during the pull back process in China, Some projects that do not allow the optical cable tube to be towed back together with the supervisor have also appeared. In the process of pipe rotation, the circumferential smooth surface of the heat shrinkable sleeve is not easy to tear off, but the fixed piece on the self lap part of the heat shrinkable belt is easy to be scraped off, and the lap joint of the heat shrinkable belt along the longitudinal direction of the pipe is also easy to be opened. The torn heat shrinkable belt will have a very adverse effect on the mud flow in the borehole. In some directional drilling crossing projects in the past, when the pipe section failed to pull back and was pulled out of the excavation point, there were scraped seal, lap and patch. Therefore, when the heat shrinkable sleeve or heat shrinkable belt can only be selected, the heat shrinkable sleeve or heat shrinkable belt with reliable quality and relevant engineering achievements should be selected as far as possible. For example, for the second west to east gas pipeline project, the heat shrinkable belt of manufacturer with good product quality is used as the joint coating material for pipeline crossing project.
(5) When the project cost is limited, the price of heat shrinkable sleeve or heat shrinkable tape is also taken as an important reference factor, because the price of heat shrinkable belt and heat shrinkable sleeve are different. Half of the large diameter heat shrinkable belt is cheaper. If the steel pipe diameter is less than 100, the heat shrinkable belt is not easy to produce. Even if it is done, the cost is relatively high. Therefore, the heat shrinkable sleeve can be selected or wrapped with heat shrinkable winding tape.
(6) When the project delivery time is urgent and the production of heat shrinkable sleeve is not as fast as that of heat shrinkable belt, the heat shrinkable Belt should be selected, and it does not need to be set on the pipe first, which will not affect the construction of other units, resulting in more idle personnel, waste of machines and delay of project delivery.
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