The determination of the ratio of the thickness of the double-layer insulation material in the pipeline anti-corrosion and heat preservation You Yong (Huainan Chemical Engineering School, Huainan 207) The temperature is an important operating parameter in the chemical production process. In order to maintain the working temperature of the materials, prevent the loss of heat, and to prevent the corrosion of pipelines, in the design and construction, the pipelines that are not operated at room temperature shall be considered for anti-corrosion and insulation measures, and the appropriate insulation materials shall be selected to determine the thickness of the insulation layer. Calculate the amount of insulation material, etc.

In the determination of insulation thickness, the calculation is more complicated. Especially for high-temperature pipelines, double-layer insulation materials are generally used. How to reasonably and effectively select inner and outer layer materials and determine the thickness of each layer is more complicated.

1 Reasonable use of double-layer insulation material 1.1 The heat loss of the double-layer insulation material outside the pipe is different from that of the general pipeline with double-layer insulation measures. The structure is shown in Figure 1.

For the radius of the outer wall of the pipe, the thermal conductivity coefficients of the two types of insulation materials (A and B) are respectively λ and λ2, and the thicknesses of the inner and outer layers are respectively b and b. The temperature difference between the outer wall of the pipe and the outermost layer of the insulation layer is t.

If the material A is placed in the inner layer, the heat loss is the other way around. If the material B is placed in the inner layer, the heat loss is). Then there is a relationship between the 1.2X value and the heat loss ratio. Therefore, the X value range When the value of Y is different from 0.3 to 3.25, the amount of heat loss is shown in Table 1.

1 .3 Reasonable use of the two kinds of insulation materials can be seen from Table 1: Value 1, heat loss ratio of 1, that is to say good insulation properties (small value of λ) material on the inner layer, the heat loss is relatively small.

A value of 1, the heat loss ratio of 1 that is at this time the poor thermal insulation properties (λ value) of the material placed in the inner layer, the heat loss is relatively small.

2 When determining the thickness ratio of the two kinds of heat-insulating materials, when the double-layer material is used for heat preservation, the heat-resistance performance of the inner layer material should be considered first. Therefore, after determining the internal and external materials (known as X values), how to ensure that the amount of heat loss is small is related to the Y value.

In order to minimize the amount of heat loss, when the X value is 1, the Y value should be less than 1. When the X value is 1, the Y value should be greater than 1.

2.1 Relationship between Y value and thickness ratio) Assuming that the thickness of the inner layer material is b1, the thickness ratio of the outer and inner layer thermal insulation material is substituted into the Y value formula, and the equation above can be known: When β2 .2Y=1, the thickness ratio The numerical value assumes that the Y value is 1 and β=1 is used to obtain the thickness ratio of the outer and inner thermal insulation materials under different pipe diameters after the inner layer thickness is selected. If the inner diameter of the pipe diameter is 2.3, the example assumes that the pipe diameter is 150mm, the outside temperature is 447°C, the thermal conductivity of the thermal insulation material is 0.07, the heat-resistant temperature is 800°C, and the thermal conductivity of the thermal insulation material B is 0.104 , Heat-resistant temperature 300 °C.

From the above conditions, it can be known that: (1) The inner layer thermal insulation material should be selected as A = 0.67. According to Table 1, the Y value should be selected to be 1.

(3) Assume that the thickness of the inner layer material is selected as 50mm. According to Table 2, the thickness ratio of the outer inner layer material should be less than 1.67.

3 Conclusion Using the above two tables, you can quickly determine the thickness ratio of double insulation materials, and then calculate the heat loss according to the formula Q, and then verify with the requirements of the process conditions, for the actual production of pipelines to take anti-corrosion insulation measures, The selection of a double-layer insulation material provides a scientific and rational method to improve the production efficiency.

Reference 1 Department of Chemical Engineering, Tianjin University, Principles of Chemical Engineering, Tianjin Science and Technology Press, 2 Tang Shishi, “Chemical Engineering Principles Design”, Chemical Industry Press, 1989.

(Continued from page 28) 3.2 The height of the plant's prefabricated column is 17m, and the unit grid is bulky. When hoisting, a 40t crane should be used. The crane is supported on the north side of the plant, and the winders in the four corners of the hoisting are respectively to facilitate the adjustment of the direction. After the completion of the preparation work, the cranes shall be hoisted ※ hoisted and hoisted and placed on a slip track.

3.3 The grid is grounded on the track by means of a traction sheave. The flight crew should follow the commands and traction on the rack. The traction speed should not be greater than 1.0 m min. Traverse the fulcrum in place according to the requirements of the drawings and the production sequence.

3.4 When the unit grid is in place, use 4 groups of inverted chain brackets to support the 16.5m ring beam, gently lift the grid frame, pull out the scroll wheel and taxiway, and slowly place it. Put the leveling instrument on the surface of the original compression house and correct whether the height of the arching accords with the requirements of the drawings. Finally, fix the bearing bolts. The unit racks are fixed in the same way in turn.

3.5 erect partial scaffolding, adjacent two units close together.

Practice has proved that the use of high-altitude sliding construction network structure reduces the danger of high-altitude operations, saving scaffolding costs compared to high-altitude assembly, and can guarantee the assembly quality of the grid. The construction can be intersected with the three-dimensional construction of the civil works and the three-dimensional construction, shortening the construction period of the entire project. There is no need for large-scale lifting and installation of equipment, reducing construction costs and achieving good results.

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