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Structure and characteristics of thermal insulation large-diameter spiral welded pipe

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Structure and characteristics of thermal insulation large-diameter spiral welded pipe

1. Features of heat preservation large-diameter spiral welded pipe:

Polyurethane foam has good mechanical properties and thermal insulation properties. Under normal circumstances, it can withstand a temperature of 120°C. The large-diameter spiral tube can withstand a temperature of 180°C through modification or combination with other thermal insulation materials.


The spiral tube has strong thermal insulation performance, which can ensure that the temperature of the internal transportation material is not changed from the outside, and has good cold resistance in winter. The sound insulation performance of the spiral tube is very good, avoiding the noise of liquid flowing through the pipeline during transportation. At the same time, the spiral welded pipe can be anti-corrosion and does not absorb water, so that the installation position of the pipe is not restricted and can be used in various places. The spiral welded pipe is simple and quick to construct, has high efficiency, and reduces capital cost. The spiral tube is used for low heat loss and can save energy.


Dual-pipe heating pipes can generally reduce the project cost by about 25% (using FRP as a protective layer) and 10% (using high-density polyethylene as a protective layer).


2. Large diameter spiral tube

The thermal conductivity of the spiral welded pipe is λ=0.013-0.03kcal/m•h•oC, which is much lower than other commonly used pipe insulation materials in the past, and the thermal insulation effect is increased by 4 to 9 times. Moreover, its water absorption rate is very low, about 0.2kg/m2. The reason for the low water absorption rate is that the closed cell rate of polyurethane foam is as high as about 92%. Low thermal conductivity and low water absorption, coupled with high-density polyethylene or glass fiber reinforced plastic protective shell with a good insulation layer and external waterproof performance, has changed the traditional trench-layed heating pipeline "wearing a wet padded jacket" and greatly reduced the heating pipeline The overall heat loss, the heat loss of the heating network is 2%, which is less than the international standard requirement of 10%.



3. Insulation large diameter spiral welded pipe structure:

(A) Core pipe: working steel pipe used to transport steam.

The core tube material performance, outer diameter size, dimensional tolerance, and minimum wall thickness meet the relevant national or industry standards. The surface of the core tube removes rust, grease, moisture, and other contaminants.


(B) Protective cushion: the interlayer between the core tube and the insulation layer to prevent damage to the inorganic insulation layer due to core tube displacement. When the core pipe adopts a spiral welded steel pipe and the inorganic insulation layer is a hard material, a protective cushion layer is provided. The protective cushion layer is generally made of aluminum silicate felt, the density is ≤192kg/m3, the thermal conductivity at room temperature is ≤0.056w/(m•k); the shrinkage of the heating line is ≤4%.


(C) Organic thermal insulation layer: thermal insulation layer made of organic thermal insulation material. Using polyurethane rigid foam plastic, density 55-65kg/m3, compressive strength ≥0.2MPa, normal temperature thermal conductivity ≤0.027w/(m•k), water absorption ≤3%, applicable temperature ≤140℃.


(D) Inorganic insulation layer: an insulation layer made of high-temperature resistant inorganic insulation materials. Thermal conductivity at room temperature ≤0.055w (m•k) According to different structures, microporous calcium silicate (density ≤220kg/m3), magnesium silicate, rock wool (density ≥110kg/m3) can be selected. At the same time, the material's moisture content and resistance Indexes such as temperature resistance and compressive strength can also meet relevant requirements.


(E) Outer protective pipe: An outer protective layer that protects the insulation layer from groundwater erosion, supports the core pipe, and can withstand a certain pressure. According to different materials, it is generally divided into steel outer protective tube, high-density polyethylene plastic outer protective tube, glass fiber reinforced plastic outer protective tube, composite outer protective tube, etc. This product generally uses high-density polyethylene (PE) as the outer protective pipe, but in areas with high water levels or rich surface water, steel outer protective pipes must be used. The performance and tolerance dimensions of the steel outer protective pipe material comply with relevant national or industry standards. The outer surface of the steel pipe is treated with shot blasting and rust removal.