Polyurethane direct buried thermal insulation pipe is suitable for thermal insulation and cold insulation projects of various media in the range of -50℃~150℃. It is widely used in thermal insulation and cold insulation projects in urban central heating, warm room, cold storage, coal mine, petroleum port, chemical industry and other industries. Knowledge of the application and precautions of polyurethane thermal insulation steel pipe

Compared with traditional various types of thermal insulation pipes, directly buried prefabricated thermal insulation pipes have very prominent advantages and applications: the application of polyurethane thermal insulation steel pipes and knowledge of matters needing attention

1. Reduce the project cost.
According to the calculations of the relevant departments, the double-pipe heating pipeline can generally reduce the project cost by about 25% (using glass fiber reinforced plastic as the protective layer) and 10% (using high-density polyethylene as the protective layer).
2. Low heat loss and energy saving.
It is much lower than other commonly used pipe insulation materials in the past, and the insulation effect is increased by 4 to 9 times. Furthermore, its water absorption rate is very low, about 0.2kg/m2. The reason for the low water absorption is due to the closed cell rate of polyurethane foam as high as about 92%. Low thermal conductivity and low water absorption, coupled with thermal insulation layer and high-density polyethylene or glass fiber reinforced plastic protective shell with good waterproof performance on the outside, changed the situation of “wearing wet cotton jacket” in traditional trench laying heating pipes, and greatly reduced the heat supply. The overall heat loss of the pipeline, the heat loss of the heat network is 2%, which is less than the international standard requirement of 10%.
3. Anti-corrosion, good insulation performance and long service life.
Since the polyurethane rigid foam insulation layer is tightly bonded to the outer skin of the steel pipe, it can isolate the infiltration of air and water, and can play a good anti-corrosion effect. At the same time, its foam cells are closed, and the water absorption is very small. High-density polyethylene shell, glass fiber reinforced plastic shell have good anti-corrosion, insulation and mechanical properties. Therefore, the outer skin of the working steel pipe is difficult to be eroded by the outside air and water. As long as the internal water quality of the pipeline is well treated, according to foreign materials, the service life can reach more than 50 years, which is 3 to 4 times longer than that of traditional trench laying and overhead laying.
4. Small footprint, fast construction, and favorable environmental protection.
Directly buried heating pipes do not need to build huge trenches, only need to bury the insulation pipes underground, thus greatly reducing the land occupation of the project, reducing the amount of earthwork excavation by more than 50%, and reducing the amount of civil masonry and concrete by 90%. At the same time, the processing of the insulation pipe and the on-site trenching are carried out in parallel, and only on-site joints are required, which can shorten the construction period by more than 50%.
Matters needing attention in the construction of polyurethane thermal insulation steel pipe
Process confirmation
1. Determine the foaming process: the foam water 141B is still cyclopentane. Be sure to use it according to the manufacturer’s directions and instructions. Knowledge of the application and precautions of polyurethane thermal insulation steel pipe
2. First, clarify the process details of the target production line: the type of foaming machine, the perfusion flow, the temperature control value before infusion, the temperature control value of the kang road insulation temperature and the insulation time, where the box injection port is and the foaming material flow through the route itinerary , The operation process of mold clamping and hole sealing after pouring.
3. Changes in temperature and humidity of the construction environment.
4. Ask the on-site operators and quality inspectors for the defects of the current process and raw materials, and ask them to put forward any other specific requirements.

Specific test of polyurethane thermal insulation steel pipe
1. Compatibility: (1) Add silicone oil, catalyst and water, stir well, and see if it is transparent. (2) Add physical foaming agent and stir well to see if it is transparent (note that the volatilized physical foaming agent should be replenished after stirring). (3) The pre-prepared composite material samples should be stored for at least 3 days to be transparent and not delaminated. (4) When the composite material samples are stored at 35 and 15 °C for 24 hours to see if they are transparent and conditional, it is necessary to measure the viscosity of the composite material in the design (25 °C and the temperature under normal production conditions) to see if the viscosity changes with temperature. large fluctuations.
2. Anti-shrinkage: cut the free foaming sample into regular squares after 1hr, measure the fixed edge size, put it in a -20℃ freezer for 24hrs to see the size change, the linear shrinkage within 2% is acceptable.
3. Free foaming: Free foaming is performed according to the designed black and white material ratio and temperature control, paying attention to material speed, core density and drawing traces.
4. Fluidity of polyurethane thermal insulation steel pipe: After the density and speed of free foam are determined, a fluidity test must be carried out. The simple method is: after mixing the quantitative foaming material (usually 200g), immediately put a slightly larger long plastic bag on the mouth of the foaming cup, straighten it vertically and let the foaming material grow upward until it is shaped (two people are required to operate it). ).

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