The PPH pipeline adopts spray cooling in the vacuum tank

Both ends of the vacuum box are open, so flexible gaskets can be installed, and the extruded PPH pipes are led out of the water tank through the gaskets at both ends. When the PPH pipeline starts to pull the production, the vacuum degree is quickly established, and the vacuum tank with the sizing element should be shorter. After the vacuum sizing tank is set, the so-called double-chamber vacuum tank is used immediately after the vacuum sizing tank is set. Moreover, it is quite flexible when the degree of vacuum needs to be changed to adjust the friction force between the tube and the sizing sleeve, and the requirement for the degree of vacuum in different stages of cooling can also be fully considered.

For the through-type gasket attached to the double-chamber vacuum tank, the subsequent vacuum chambers are separated from the sizing chamber, and the vacuum chambers are also isolated from each other. Each chamber has an adjustable air release valve to adjust its own vacuum degree, and the degree of vacuum degree should be adapted to the pipe requirements of the cooling section. The vacuum chambers are regulated, but they can share a single vacuum source, which can be provided by several vacuum units for the sizing chamber and subsequent cooling chambers. Most vacuum box gaskets are made of flexible rubber with a hole slightly smaller than the diameter of the extruded pipe to ensure vacuum tightness between the vacuum box end and the different vacuum chambers in the box.

In order to completely stop the air leakage, the rubber gasket is usually made quite thick. The gasket material must be flexible enough to seal tightly around the extrusion tube without excessive frictional resistance. The lower the temperature of the cooling medium in the vacuum tank, the higher the suction capacity of the vacuum pump, and part of the working medium will be discharged with the gas, so the working medium is continuously replenished, but the water ring vacuum pump cannot be started without water. There are two cooling methods for PPH pipes, one is immersion cooling and the other is spray cooling. The immersion bath type is usually used for small diameter pipes, and pipes with a diameter greater than 110mm tend to use spray cooling.

There are 4-6 gears in the immersion cooling water tank, each gear is 2-3 meters long to maintain the temperature gradient and adjust the cooling speed. The cooling water should maintain a certain water level in the tank, and the cooling temperature can be adjusted by adjusting the cooling water flow into the tank. The main problem with immersion bath cooling is that the vertical temperature difference in the tank and the buoyancy of the water can deform the pipe, especially for larger diameter pipes. The spray cooling of the sprinkler heads evenly arranged around the circumference of the PPH pipeline can significantly improve the cooling intensity, because the water flow will impact the outer wall of the PPH pipeline at a relatively high speed, preventing the formation of the interface warm water layer.