Insulation Pipe

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The heat-insulating pipe is a steel pipe that has undergone insulation treatment. It is mainly used to maintain stable temperature when transporting liquids, gases, etc., thereby reducing energy loss. Now, let's explain its various aspects in detail:

Thermal insulation pipe is an insulation pipeline used for the transportation of liquids, gases, etc. Through the insulation structure, it ensures that the temperature inside the working pipe and the surface temperature meet the usage requirements. It is suitable for transporting various media within the temperature range of -50℃ to 150℃.

Main application fields:
• Central heating and cooling systems
Hot oil transportation pipeline

• Greenhouse and cold storage projects
Insulation and cold protection projects in the coal mining, petroleum, and chemical industries
Municipal engineering, central air conditioning ventilation ducts

The insulation pipes vary in structure depending on their types:

1. Polyurethane insulation pipe (three-layer structure)

• First layer: Working Steel Tube Layer - Seamless steel tubes, spiral steel tubes or straight seam steel tubes are selected according to the design requirements.

• Second layer: Polyurethane insulation layer - This is formed by injecting the hard polyurethane foam plastic liquid directly into the cavity between the steel pipe and the outer protective layer using a high-pressure foaming machine (pipe-in-pipe foaming process)

• Third layer:High-density polyethylene protective layer - Pre-made black or yellow polyethylene plastic pipes with a certain wall thickness, which protects the insulation layer from mechanical damage and also provides anti-corrosion and waterproofing functions.

2. Steel Tube Steel Composite Insulation Pipe

Internal sliding structure (from inside to outside):

• Working pipe
Silica-alumina layer

• Drag-reducing layer
Microporous calcium silicate layer
Heat insulation layer
Stainless steel fastening steel belt
Aluminum foil reflective layer
Polyurethane insulation layer
Outer steel pipe
• External anti-corrosion coating

External sliding structure:
• Working pipe steel
Glass wool insulation layer
Aluminum foil reflective layer
Stainless steel fastening steel belt
Sliding guide bracket
Air insulation layer
Outer protective steel pipe
• External anti-corrosion coating

The production process of heat-insulating pipes mainly consists of three types:
1. Main production process

• One-step method: A one-time molding process, where the polyurethane insulation layer is wrapped around the outer surface of the working steel pipe. This method is suitable for steel pipes with a diameter of less than 500 millimeters.

• Tube-in-tube method (two-step method): The earliest method for forming pipe insulation, which involves first applying a foam plastic insulation layer on the outer wall of the working pipe, then covering it with a high-density polyethylene outer protective pipe, and finally conducting foaming treatment.

• Spray wrapping method: First, complete the anti-corrosion treatment of the steel pipe, and then, under high pressure, spray the foam polyurethane mixture onto the surface of the steel pipe.

2. Production Process

1. Raw material preparation: Use high-quality low-carbon steel or medium-carbon steel as the raw material for the steel pipes. The insulation materials include silica-alumina, glass fiber, rock wool, polyurethane, etc.
2. Pre-treatment of steel pipes: Perform surface shot blasting and rust removal treatment. The rust removal grade can reach Sa2.5 level.
3. Injection of insulation materials: Use quantitative or pressure injection methods to inject insulation materials into the cavity between the steel pipe and the outer protective layer.
4. Coating of insulation materials: Cover the insulation materials by winding, spraying, or adhering methods.
5. Epoxy layer coating: Conduct anti-corrosion and moisture-proof treatment on the exterior of the steel pipe.
6. Oven curing: Enhance the adhesion and hardness of the epoxy layer.
7. Quality inspection and packaging of finished products: Package and deliver after strict quality inspection.

1. Working steel pipe materials: seamless steel pipes, spiral steel pipes, straight seam steel pipes, double-sided submerged arc spiral welded steel pipes

2. Insulation layer materials: rigid polyurethane foam plastic (density 60-80 kg/m³), silicagel, glass wool, microporous silicacalcium, etc.

3. Protective layer materials: high-density polyethylene (HDPE), fiberglass reinforced plastic (FRP)

4. Other auxiliary materials: aluminum foil reflective layer, stainless steel fastening steel strip, anti-corrosion coating, etc.

Advantages:

1. Excellent thermal insulation performance: The thermal conductivity is low (0.013 - 0.03 kcal/m·h·℃), and the heat loss is only 25% of that of traditional pipes.
2. Good corrosion resistance: The polyurethane insulation layer is closely bonded to the steel pipe, preventing the penetration of air and water.
3. Convenient and fast construction: Prefabricated in the factory, easy on-site installation, reducing the excavation volume by more than 50%, and reducing the amount of civil engineering work by 90%.
4. Economical and energy-saving: Reduces project costs, significantly reduces heat loss, saves energy and operating costs.
5. Long service life: With correct installation and use, it can last for 30 - 50 years.
6. High safety performance: Some products are equipped with leakage alarm lines, which can detect leaks in time.

Disadvantages:

1. Higher cost: Compared to other insulation materials, the price of polyurethane insulation pipes is higher.
2. High installation requirements: There are certain restrictions on the space of the construction site and the installation process.
3. Difficult maintenance and replacement: The insulation layer and the outer protective layer are usually integrated, and during maintenance, the entire pipeline needs to be dismantled.
4. Large space occupation: The thick insulation layer results in a relatively larger outer diameter of the pipeline.
5. Limited waterproof performance: Waterproof measures need to be strengthened during the construction process.

Installation Specifications:

1. Selection of laying method: Differentiate between compensated direct burial and uncompensated direct burial methods. Select the appropriate method based on parameters such as soil thermal resistance and pipeline length.
2. Transportation and handling: Handle with care to avoid scratches or tears on the polyethylene outer protective pipe.
3. Angle handling: If the pipeline needs to be bent during installation, the design unit should recalculate the stress and reinforce it.
4. Signal line layout: The signal line should be placed above the pipeline. Before welding, test the continuity and resistance value.
5. Winter construction: When the ambient temperature is below 10℃, preheat the working steel pipe, outer protective pipe, and foaming material to 30-60℃.
6. Joint handling: The overlap length of the outer protective pipe should be ≥ 100mm. The welding area must be completely adhered and undergo 100% airtightness testing.
7. Burial depth standard: The buried depth of the water supply pipeline should be ≥ 1.5m, and that of the hot water pipeline should be ≥ 1.2m.

Maintenance Requirements:

1. Daily cleaning: Clean the surface dust and debris of the insulation layer every quarter. In humid environments, increase the cleaning frequency.
2. Integrity inspection: Monthly visual inspection to check if the insulation layer is cracked or blistered. If any damage is found, use polyurethane foaming agent for repair.
3. Sealing test: Check the sealing performance of pipeline interfaces every half year using the soap water testing method.
4. Anti-corrosion treatment: Apply anti-corrosion paint to the outer protective pipe every 3 years. In coastal areas, the cycle should be shortened to 1-2 years.
5. Fire prevention measures: Wrap high-temperature pipelines with fireproof coatings. Clear combustible materials within 1 meter of the pipeline.

Common Issues Handling:
• Foaming speed is slow: When the ambient temperature is low, raise the black material to 30-60℃, and heat the environment to 20-30℃.
• Foam is soft and pliable: Adjust the ratio of black and white materials to 1:1.05 to prevent excessive black material.
•Cracking of the outer protective pipe: Use a dedicated cutting tool and leave a 200mm non-insulation zone as a buffer.
• Joint leakage: Re-weld the outer protective pipe and increase the lap length to 150mm.

Storage and Transportation:
When storing, avoid placing it together with chemical substances and keep it in a dry and well-ventilated environment.

During transportation, cover it with a standard-sized cloth to prevent rainwater from seeping in.
During transportation, handle with care to avoid causing scratches or bruises.

Insulation pipes, as an important material in modern pipeline engineering, play a crucial role in centralized heating, petrochemical industries, and other fields. Correct selection, installation, and maintenance of insulation pipes can significantly enhance energy utilization efficiency, extend the service life of pipelines, and reduce operating costs.