Three-layer structure and technical parameters of polyurethane thermal insulation steel pipe

Polyurethane thermal insulation steel pipe has become a relatively mature and advanced technology in some developed countries abroad. In recent years, Chinese heating engineering technicians have been promoting the development of domestic pipe network laying technology to a higher level through digesting and absorbing this advanced technology.

The practical achievements in the past few years have fully proved that the laying method of the polyurethane thermal insulation direct buried pipe has many advantages compared with the traditional trench and overhead laying. This is also the internal driving force for the rapid development of polyurethane heat insulation directly buried pipes in China's heating engineering.

Three layers of polyurethane thermal insulation steel product oil, among which are:

The first layer: working steel pipe layer

According to the design and customer requirements, generally choose seamless pipe (GB8163-87) spiral welded pipe (GB9711-88; SY / T5038-92) and straight seam welded pipe (GB3092-93). After the surface of the steel pipe is processed by the advanced shot blasting derusting process, the derusting grade of the steel pipe can reach Sa2 grade in the GB8923-1988 standard, and the surface roughness can reach R = 12.5 microns in the GB6060.5-88 standard.

The second layer: polyurethane insulation layer

The high-pressure foaming machine is used to inject the rigid polyurethane foam plastic liquid into the cavity formed between the polyurethane thermal insulation steel pipe and the outer sheath at one time. It is commonly known as "tube-in-tube foaming process". Its function is to waterproof, the second is to keep warm, and the third is to support the weight of the heating network. When the temperature of the conveying medium is: -50 ℃ -120 ℃, rigid polyurethane foam is selected as the heat preservation layer.

Third layer: high-density polyethylene protective layer

Pre-made black (yellow) plastic pipes with a certain wall thickness. Its function is to protect the polyurethane insulation layer from mechanical hard objects and to prevent corrosion.

  Technical Parameters:

Polyurethane unit index FRP unit index

Capacity kg / m240-60 Compressive strength MPa120-220

Thermal conductivity W / mk <0.025 Compressive strength MPa210-355

Heat resistance ℃ ≤120 Surface hardness MPa <320

Cold resistance ℃ ≥-50 Breakdown voltage KV> 25

Bonding strength KPa ≥ 200 Surface layer glue content> 45%

Compressive strength KPa≥200 Ammonia coagulation KPa400-900

Water absorption rate kg / m2≤0.2 Service life 30-50 years