Polyurethane insulated steel pipe

Since direct buried heating technology started late in our country, Manager Wang
The above conditions still need to be continuously improved. Judging from the quality problems that arise in engineering practice, special attention should be paid to the following issues in design and construction
1. In design and construction, it is necessary to truly understand that the direct burial laying method of heating pipes is divided into compensated direct burial methods. There are two methods of buried laying and uncompensated direct buried laying. We must truly understand the working principles, characteristics and application situations of the two methods, so as to make reasonable selection in design and safe, reliable and economical construction.
We must first grasp the concept of compensated direct buried laying method, which solves the thermal elongation of pipelines through natural compensation of pipelines and compensators such as square and bellows compensators, thereby minimizing thermal stress during uncompensated direct buried laying. , simply put, the pipe does not have any compensation measures when it is heated, but relies on the strength of the pipe itself to absorb thermal stress.
The basic principle of the compensation laying method is that when installing a pipeline, the pipeline is first heated to a certain temperature, and then the pipeline is welded and fixed. When the pipeline returns to the installation temperature, the temperature decreases and the pipeline withstands a certain tensile stress in advance. When the pipeline is heated and working, as the temperature rises, the stress of the pipeline is zero. When the temperature continues to rise, the compressive stress of the pipeline increases. When the temperature rises to the operating temperature, the compressive stress and thermal stress of the pipeline are still less than the allowable stress. In this way, the pipeline can operate normally without a compensation device. This non-compensation method applies the fourth strength theory, which requires preheating the pipeline during construction, making the construction more troublesome. However, there have been a large number of engineering practices at home and abroad, and the theoretical calculations are reliable and can ensure safety. Another non-compensation method is the calculation method and stress classification proposed by my country's Beijing Gas Thermal Design Institute in recent years, using stability analysis and applying the third strength theory. This method fully utilizes the plastic potential of steel and is easy to construct without preheating.