The reasons for the difference in thermal expansion include the difference in the thermal expansion coefficient of materials, the difference in the thermal load of parts and the difference in the constraint conditions of parts. For bare valves, if the working gap between valve parts is not designed accurately under the condition of cold flow, The possibility of abrasion and seizure during work is greater than that of mild and good words. Because in the process of thermal alternation, for the same valve, there are more times of hot state closing and lifting state opening when it is exposed than when it is well insulated. The cause of scratches and seizure is that when the hot fluid enters the cold valve, the valve disc is surrounded by the hot fluid. Since the heat dissipation of the valve disc is only carried out by the valve stem with smaller section connected to it, the whole valve disc can quickly reach the temperature of the pipeline fluid. The seat ring is almost heated at the same time as the valve disc. The heat dissipation condition of the seat drawing is better than that of the valve disc. However, the linear expansion of the valve body is often less than that of the seat ring, so the valve body limits the radial expansion of the seat ring. In this way, scratches may occur between the flap and the seat ring. For the valve body with good temperature, the overall average temperature of the valve body will be higher than the average temperature of the valve body without thermal insulation. Although the linear expansion of the valve body is correspondingly larger, the restriction on the linear expansion of the seat ring will be smaller, and the possibility of scratches between the valve disc and the valve seat will be smaller.

What is the waterproof effect of waterproof casing
The waterproof performance of B type flexible waterproof casing is better than that of ordinary casing. The steel flexible B type waterproof casing mainly refers to the new equipment consumed in the national standard 02S404 waterproof casing atlas. It is mainly used in various construction projects to maintain the pipeline when the pipeline passes through the wall of the building. Therefore, it is widely used in various erection projects
The machinery produced by B-type steel flexible waterproof casing products is mainly used to represent the repair works of ancient buildings in ancient sites, houses in ancient historical and cultural blocks, decoration of ancient shops, residential projects in ancient villages and towns, and renovation projects of modern buildings in ancient sites
In addition, it also includes green flagstone road and vehicle road projects, asphalt road projects, ancient water transport wharf restoration projects, water supply and drainage municipal reconstruction projects, strong and weak current reconstruction projects, green landscape projects, etc. In street reconstruction projects, B-type flexible waterproof shells are used. The pipes running through the streets have been effectively maintained, meeting the needs of the project
B flexible waterproof casing products mainly use the separation of water stop wing ring and seal ring to reach the pipeline of waterproof request passing through the building, especially B flexible waterproof casing consumption. Using the guide line of double wing ring, the waterproof effect is better