Polyurethane spraying polyethylene winding thermal insulation pipe production system and process

Abstract

The invention relates to a polyurethane spraying polyethylene winding thermal insulation pipe production system and process. The production process comprises the following steps: 1) spraying a layer of polyurethane foaming material on a working steel pipe, curing the foaming material to obtain a thermal insulation base layer, controlling the thickness of the thermal insulation base layer to be smaller than the design thickness of a thermal insulation layer, calculating the difference value between the thickness of the cured thermal insulation base layer and the design thickness of the thermal insulation layer, and taking the difference value as a reference value; 2) spraying a composite layer of a polyurethane foaming material and polyurethane solid particles on the surface of the cured thermal insulation base layer, winding a polyethylene outer protective layer before the composite layer is cured, and obtaining a polyurethane spraying polyethylene winding thermal insulation pipe after the composite layer is cured; wherein the particle size of the polyurethane solid particles is determined according to the reference value calculated in the step 1). The method can solve the problem of thickness control of the polyurethane thermal insulation layer, and can improve the bonding strength between the polyethylene outer protective layer and the polyurethane thermal insulation layer at the same time.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation pipe production technology, specifically relating to a polyurethane sprayed polyethylene spiral insulation pipe production system and process. Background Technology

[0002] Polyurethane sprayed polyethylene spiral wound insulated pipes are commonly used in petrochemical, heat transmission, and other fields. Their structure consists of a polyurethane insulation layer sprayed onto the outside of the main pipeline, followed by a polyethylene outer sheath wrapped around the cured polyurethane insulation layer. The polyurethane insulation layer plays a crucial role in thermal insulation, and its thickness is a key control indicator. If the cured insulation layer thickness is less than the design requirement, it can be corrected by re-spraying, but this requires another curing and waiting period, reducing efficiency. Excessive thickness increases material consumption and makes rework difficult. The polyurethane insulation layer undergoes foaming expansion and curing shrinkage after spraying. The thickness of the cured insulation layer is generally controlled by adjusting the spraying thickness empirically. Other methods exist to improve the accuracy of thickness control, such as the method for calculating the spraying thickness and density of sprayed spiral wound insulated pipes disclosed in patent CN202311705757.6. Furthermore, the bonding strength between the polyethylene outer sheath and the polyurethane insulation layer is also an important factor affecting the quality of the insulated pipe. For example, patent CN202011421267.X discloses a hot melt adhesive powder for bonding polyethylene / polyurethane foam, and patent CN201911385158.4 discloses a production process for high-performance spray-coated and wound insulation pipes. Both methods enhance the bonding strength by adding an adhesive medium between the polyethylene outer sheath and the polyurethane insulation layer, but these methods also increase the cost of raw materials. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention first proposes a production process for polyurethane sprayed polyethylene spiral insulation pipes, the specific solution of which is as follows:

[0004] A manufacturing process for polyurethane sprayed polyethylene spiral insulation pipe includes the following steps: 1) First, spray a layer of polyurethane foam onto the working steel pipe. After the polyurethane foam is cured, the insulation base layer is obtained. Control the thickness of the insulation base layer to be less than the design thickness of the insulation layer. Calculate the difference between the thickness of the cured insulation base layer and the design thickness of the insulation layer, and use the difference as a reference value. 2) After the insulation base layer has cured, a composite layer of polyurethane foam and polyurethane solid particles is sprayed onto the surface. Before the composite layer is cured, a polyethylene outer protective layer is wrapped around it. After the composite layer is cured, a polyurethane sprayed polyethylene wound insulation pipe is obtained. The particle size of the polyurethane solid particles is determined according to the reference value calculated in step 1).

[0005] In this invention, the insulation base layer formed by the first polyurethane spraying is controlled to be less than the designed thickness, and the second spraying ultimately increases the insulation layer thickness to the designed thickness. This method facilitates control over the insulation layer thickness. The second spraying uses a composite layer of polyurethane solid particles and polyurethane foam. The polyurethane solid particles themselves have a certain strength, which can provide support and prevent the compression of the second spraying layer during polyethylene winding from affecting the foaming and expansion of the polyurethane. Polyethylene winding can be performed directly after the second spraying, eliminating the curing waiting time after spraying.

[0006] In addition, the polyurethane foam applied in the second coat has good adhesion before curing, which can improve the connection strength between the polyethylene layer and the insulation base layer formed after the first coat has cured.

[0007] Furthermore, in step 1), the reference value is no greater than 1 / 5 of the design thickness.

[0008] Furthermore, in step 2), the polyurethane solid particles are obtained by crushing and screening recycled polyurethane waste.

[0009] Furthermore, in step 2), the particle size of the polyurethane solid particles is 1.0-1.5 times the reference value.

[0010] To achieve the method of the present invention, a polyurethane sprayed polyethylene wound insulation pipe production system is further proposed, including a polyurethane spraying area and a polyethylene winding area, and also including a polyurethane waste recycling area. The polyurethane waste recycling area is equipped with a polyurethane waste crusher, a screening machine, a storage bin and a conveying mechanism. The conveying mechanism is connected to a polyurethane solid particle feeding mechanism. The discharge port of the feeding mechanism is used to add polyurethane solid particles to the outside of the working steel pipe. A polyurethane nozzle is provided on the upstream side of the discharge port along the rotation direction of the working steel pipe.

[0011] Furthermore, both the polyurethane spraying area and the polyethylene winding area use spiral conveyor lines, and the feeding mechanism is located in the polyurethane spraying area.

[0012] Furthermore, the polyurethane spraying area uses a mobile trolley for conveying, the polyethylene winding area uses a spiral conveyor line, the feeding mechanism is set in the polyethylene winding area, and a polyurethane nozzle is set at the inlet end of the polyethylene winding area.

[0013] The advantages of this invention are: 1. By controlling the thickness of the polyurethane insulation layer through secondary spraying, the problem of controlling the thickness of the polyurethane insulation layer can be solved; 2. A portion of the polyurethane waste can be recycled, reducing raw material costs; 3. The bonding strength between the polyethylene outer sheath and the polyurethane insulation layer can be improved. Attached Figure Description

[0014] Figure 1 Design drawing for thermal insulation pipe.

[0015] Figure 2 Image of recycled polyurethane solid particles.

[0016] Figure 3 This is a schematic diagram of the polyethylene winding area in Example 1.

[0017] Figure 4 This is a schematic diagram of the polyurethane spraying area and the polyethylene winding area in Example 2. Detailed Implementation

[0018] Example 1 like Figure 1 The insulated pipe consists of a working steel pipe 1, an outer protective layer 2, and an insulation layer 3. Taking a φ500mm working steel pipe as an example, the required thickness of the insulation layer 3 is... mm, the density of polyurethane foam in the insulation layer is not less than 60 kg / m³ 3 .

[0019] The production process is as follows: 1. The overhead crane places the working steel pipe onto the loading platform, the hydraulic rocker arm moves the steel pipe from the loading platform onto the conveyor line, the spiral conveyor line transports the steel pipe, the outer wall of the steel pipe is shot-blasted to remove rust, and the hydraulic rocker arm transports the steel pipe from the conveyor line to the storage platform.

[0020] 2. The pipe transport vehicle places the steel pipes from the loading platform onto the rotary spraying vehicle, which then transports the steel pipes. The intermediate frequency device heats the outer surface of the steel pipes to above 25°C.

[0021] 3. The nozzle of the polyurethane spraying machine is fixed on an industrial robot. The speed of the production line movement and the rotation speed of the steel pipe are automatically adjusted by a computer to match the polyurethane spraying volume with the production line speed.

[0022] 4. A rotating trolley is used to carry the steel pipes. During spraying, the rotating rollers on the trolley drive the steel pipes to rotate, with the rotation speed controlled by frequency conversion. The rotating spraying trolley transports the steel pipes forward at a constant speed, and the spray gun evenly sprays the polyurethane raw material onto the advancing steel pipes in an umbrella-shaped, mist-like, and uniformly mixed form. The polyurethane raw material ferments within a certain time, reaching a certain compressive strength and thickness, completing the first layer of insulation. The thickness of the insulation base layer formed after the first spraying is measured using a probe method, controlling the thickness to 40-45mm, with a difference of 5-10mm from the design thickness requirement of 50mm. The pipe transport trolley then moves the polyurethane sprayed pipes from the rotating spraying trolley to the unloading platform, where the steel pipes are stored.

[0023] 5. The collected waste polyurethane material is crushed using a twin-shaft crusher and screened by a vibrating screen, then stored in different storage bins according to particle size. A hydraulic rocker arm feeds the steel pipes from the feeding platform onto the conveyor line, which then transports the pipes to the polyethylene winding area. A spiral conveyor line is used for the spiral advance of the steel pipes, employing smooth, solid rubber tires to support the pipes; the conveying speed is frequency-controlled.

[0024] Based on a reference value of 5-10mm, select polyurethane solid particles with a particle size of 10-15mm, such as... Figure 2 Solid polyurethane granules are conveyed to a vibrating feeder via a screw conveyor. For example... Figure 3 A vibrating feeder 4 is installed at the inlet end of the polyethylene winding area 5, and another polyurethane spray gun head 6 is also installed at the inlet end. The spray gun head of the polyurethane spraying machine performs a secondary spraying on the exterior of the insulation base layer, while polyurethane solid particles are added using the vibrating feeder. Because the sprayed polyurethane foam has good adhesion, the polyurethane solid particles can be adsorbed onto the surface of the insulation base layer.

[0025] 4. Polyethylene winding area After the second coating is completed, the steel pipe is conveyed by a spiral conveyor, and the polyethylene winding is extruded by an extruder. The polyurethane foam material can enhance the bonding strength between the polyethylene layer and the cured insulation base layer. Water spray cooling is applied, the PE outer protective layer is cut by an online cutting machine, the polyurethane steel pipe is conveyed by the spiral conveyor, and the polyethylene winding pipe is transported from the spiral conveyor to the finished pipe rack by a hydraulic rocker arm. Finally, the pipe is transported by a pipe transport vehicle.

[0026] Example 2 like Figure 4 The continuous spraying production line uses a spiral conveyor for polyurethane spraying. The polyethylene winding zone 5 and the polyurethane spraying zone 7 are set on the same spiral conveyor. The vibrating feeder 4 can be directly placed in the polyurethane spraying zone 7. After the first spraying, the working steel pipe is moved back onto the conveyor from the loading platform and enters the polyurethane spraying zone for a second spraying, where polyurethane solid particles are added using the vibrating feeder. After the second spraying, the steel pipe directly enters the polyethylene winding zone for polyethylene winding.

[0027] In addition, when the polyurethane spraying area is equipped with dual nozzles, the vibrating feeder is positioned between the two nozzles.

Claims

1. A production process for polyurethane sprayed polyethylene spiral insulation pipe, characterized in that, Includes the following steps: 1) First, spray a layer of polyurethane foam onto the working steel pipe. After the polyurethane foam is cured, the insulation base layer is obtained. Control the thickness of the insulation base layer to be less than the design thickness of the insulation layer. Calculate the difference between the thickness of the cured insulation base layer and the design thickness of the insulation layer, and use the difference as a reference value. 2) After the insulation base layer has cured, a composite layer of polyurethane foam and polyurethane solid particles is sprayed onto the surface. Before the composite layer is cured, a polyethylene outer protective layer is wrapped around it. After the composite layer is cured, a polyurethane sprayed polyethylene wound insulation pipe is obtained. The particle size of the polyurethane solid particles is determined according to the reference value calculated in step 1).

2. The production process of polyurethane sprayed polyethylene spiral insulation pipe according to claim 1, characterized in that, In step 1), the reference value is no greater than 1 / 5 of the design thickness.

3. The production process of polyurethane sprayed polyethylene spiral insulation pipe according to claim 1, characterized in that, In step 2), the polyurethane solid particles are obtained by crushing and screening recycled polyurethane waste.

4. The production process of polyurethane sprayed polyethylene spiral insulation pipe according to claim 3, characterized in that, In step 2), the particle size of the polyurethane solid particles is 1.0-1.5 times the reference value.

5. A polyurethane spraying and polyethylene winding insulation pipe production system, comprising a polyurethane spraying area and a polyethylene winding area, characterized in that, It also includes a polyurethane waste recycling area, which is equipped with a polyurethane waste crusher, a screening machine, a storage bin and a conveying mechanism. The conveying mechanism is connected to a polyurethane solid particle feeding mechanism. The discharge port of the feeding mechanism is used to add polyurethane solid particles to the outside of the working steel pipe. A polyurethane nozzle is provided on the upstream side of the discharge port along the rotation direction of the working steel pipe.

6. The polyurethane sprayed polyethylene spiral wound insulation pipe production system according to claim 5, characterized in that, Both the polyurethane spraying area and the polyethylene winding area use spiral conveyor lines, and the feeding mechanism is located in the polyurethane spraying area.

7. The polyurethane sprayed polyethylene spiral wound insulation pipe production system according to claim 5, characterized in that, The polyurethane spraying area uses a mobile trolley for conveying, the polyethylene winding area uses a spiral conveyor line, the feeding mechanism is set in the polyethylene winding area, and a polyurethane nozzle is set at the inlet end of the polyethylene winding area.

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