There are several methods to cast polyurethane foam for polyurethane directly buried insulation pipe. These methods each have their own advantages and disadvantages.

1. Tilt foaming. Inject foam onto a tilted foam platform. Using the injection pressure of the polyurethane foaming machine and the fluidity of the polyurethane mixture after emulsification, and utilizing the inclination angle of the hydraulic foaming platform, the opening is sealed and injected from one side. Simultaneously fill the insulation space of the prefabricated buried insulation pipe with polyurethane mixture, and design the parameters of the polyurethane mixture through a foaming machine to achieve the expected density of the polyurethane rigid foam in the prefabricated buried insulation pipe.

This foaming methodThe advantage is that there are almost no pores or long bubbles in the polyurethane rigid foam. Pour materials under inclined pouring, and spray the mixed polyurethane black and white materials back in the insulation space with the help of high-pressure polyurethane foaming equipment, but the polyurethane flows to the nozzle after the emulsification reaction. In fact, the polyurethane foam is foamed from bottom to top. The viscosity of the polyurethane after emulsification increases, and the foaming resistance increases. Although the pores and long bubbles of the polyurethane rigid foam are overcome, it is difficult to make the density of the polyurethane rigid foam of the prefabricated directly buried insulation pipe uniformhighWhen the density of the polyurethane rigid foam at the position meets the design requirements, the difference between the low-end density and the density can reach 10%.

2. Horizontal foaming, pouring with holes in the middle, and injecting material in the middle to foam at both ends. The density of polyurethane rigid foam shall be the same on both sides. The injection parameters of polyurethane foaming machine can also be controlled to make the density of polyurethane foam meet the expected requirements. The disadvantage is that the polyurethane rigid foam insulation layer has bubbles and long holes. If the injection hole seal is unqualified, the tensile strength of 19Mpa and the elongation at break of more than 450% cannot be met.

3. Spray wrapping insulation pipe spray foaming is a new process for producing polyurethane prefabricated buried insulation pipes. The use of this process solves the problems of pores and long bubbles in polyurethane rigid foam, and there is no need to worry about uneven density of polyurethane rigid foam. The density can reach the requirement of 60kg/m. The disadvantage is that this process is continuous production. On the continuous production equipment, if the polyurethane rigid foam is compressed, deformed or crushed, the subsequent polyethylene winding process cannot be realized.