Insulation steel pipe is a steel pipe that is processed by heat preservation technology, and under the action of different working environments and external media, the internal temperature and surface temperature of the working steel pipe are guaranteed to meet or meet the requirements of use. Insulation pipes are widely used in liquid and gas transportation pipe networks, chemical pipe insulation engineering petroleum, chemical industry, central heating heating network, central air conditioning ventilation pipes, municipal engineering, etc.
The classification of thermal insulation steel pipe mainly includes steel sleeve steel composite thermal insulation steel pipe and polyurethane thermal insulation steel pipe
Steel sleeve steel composite insulation steel pipe
Steel sleeve steel composite insulation steel pipe insulation structure can be divided into two categories according to different sliding methods:
1. Inner sliding type. The insulation structure is composed of working steel pipe, aluminum silicate, drag reducing layer, microporous calcium silicate, heat insulation layer, stainless steel fastening steel strip, aluminum foil reflective layer, polyurethane insulation layer, jacket steel pipe, and outer anti-corrosion layer. The inner sliding thermal insulation steel pipe is composed of steel pipe for conveying medium + composite silicate or microporous calcium silicate + rigid polyurethane foam + outer steel pipe + glass steel shell anti-corrosion protection layer structure. The thermal insulation treatment technology of various pipe fittings is mature and the quality is reliable.
2. External sliding type. The heat preservation structure is composed of working steel pipe, glass wool heat insulation layer, aluminum foil reflection layer, stainless steel fastening steel belt, sliding guide bracket, air insulation layer, outer protective steel pipe, and outer anti-corrosion layer.
Structural form of outer sliding thermal insulation steel pipe
1. Inner steel pipe
2. Zinc-rich primer
3. Sliding guide bracket
4. High temperature resistant glass wool
5. Aluminum foil reflective layer
6. Air insulation layer
7. Coat steel pipe
8. Coating steel pipe anti-corrosion layer
Steel-sheathed steel composite thermal insulation steel pipe is a kind of underground direct buried pipeline. The method of underground direct burial can be carried out without concrete structure, that is, the thermal expansion of the working steel pipe is carried out in the outer pipe, thereby reducing the material cost, shortening the construction date, and ensuring the safety of the heating pipeline. It can be used more safely in different temperature environments, especially for high-temperature steam pipeline projects. The use temperature can reach 150°C-450°C. Pipe ports are generally sealed with polyethylene film or three-layer PE cold wrap tape to prevent moisture or water from entering before installation or during construction. Multi-layer staggered seam wrapping of thermal insulation materials effectively reduces heat loss, and at the same time control measures are taken on the surface of the jacket to prevent the generation of cold bridges, thus ensuring the temperature control of the jacket's anti-corrosion layer. The multi-layer aluminum foil reflective layer is wrapped with thermal insulation material, which effectively reduces heat loss and makes the steam pipe more economical and reasonable. The hydrophobic system adopts a fully enclosed form, which is flexible in layout, reasonable in structure, safe and reliable. The moisture discharge pipe on the steel sleeve can not only discharge the humid gas in time, but also serve as an alarm signal pipe for daily operation. The thermal compensation of the pipeline adopts high-quality bellows compensator, which is installed in the casing and made into a direct-buried form. There is no need to set up an observation well, and the construction operation is convenient and the construction period is short. It is suitable for transporting steam or other media below 2.5MPa and 350 degrees Celsius. This product uses steel pipe as the outer protective layer, which has the advantages of high strength, not easy to damage, easy construction and maintenance, and long service life.
Polyurethane insulation steel pipe
On medium and small-diameter thermal crude oil or heating pipelines, in order to reduce the heat dissipation from the pipelines to the soil, an insulating composite layer is added to the outside of the pipelines. The commonly used insulation material is rigid polyurethane foam, and the applicable temperature is -185～120℃. This kind of material is soft in texture. In order to improve its strength, a layer of high-density polyethylene is applied outside the insulation layer to form a composite material structure to prevent groundwater from penetrating into the insulation layer. Use high-pressure polyurethane foaming equipment to carry out shot blasting and derusting treatment on the outer surface of the steel pipe and corona treatment on the inner surface of the outer protection pipe to improve the bonding performance of the insulation pipe. The material of the insulation layer is rigid polyurethane foam, which fully fills the gap between the steel pipe and the casing, and has a certain bonding strength, so that the steel pipe, the outer casing and the insulation layer form a firm whole. Polyurethane foam has good mechanical properties and thermal insulation properties. Usually, it can withstand a temperature of 120°C, and can withstand a temperature of 180°C through modification or combination with other insulation materials.
The prefabricated polyurethane insulation steel pipe is divided into three layers from the inside to the outside:
1. The first layer: working steel pipe layer
According to the design and customer requirements, seamless pipes, spiral steel pipes(SSAW pipe) and straight seam steel pipes(ERW pipe) are generally used. After the surface of the steel pipe is treated by the advanced shot blasting derusting process, the derusting grade of the steel pipe can reach Sa2 level, and the surface roughness can reach R=12.5 microns.
2. The second layer: Polyurethane insulation layer:
It is formed by injecting rigid polyurethane foam stock solution into the cavity formed between the steel pipe and the outer sheath with a high-pressure foaming machine at one time.
3. The third layer: HDPE protective layer:
Prefabricated black or yellow polyethylene plastic pipes with a certain wall thickness. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance, and the lowest operating temperature can reach -70~-100°C. Good chemical stability, resistant to most acids and alkalis (not resistant to acids with oxidizing properties). It is insoluble in general solvents at room temperature and has low water absorption, but because it is a linear molecule, it can slowly dissolve in some organic solvents without swelling and has excellent electrical insulation properties. One of its functions is to protect the polyurethane insulation layer from being damaged by mechanical hard objects, and the other is to prevent corrosion and waterproof.
Advantages and features of polyurethane thermal insulation steel pipe:
1. Reduce project cost
According to the calculation of relevant departments, in general, polyurethane insulation steel pipe can reduce the project cost by about 25% (using FRP as the protective layer) and 10% (using high-density polyethylene as the protective layer).
2. Low heat loss, saving energy
The thermal conductivity of polyurethane is much lower than that of other pipe insulation materials commonly used in the past, and the thermal insulation effect is increased by 4 to 9 times. Furthermore, its water absorption is very low, about 0.2kg/m2. The overall heat loss of the heating pipeline is greatly reduced, and the heat loss of the heating network is 2%.
3. Anti-corrosion, good insulation performance, long service life
Since the polyurethane rigid foam insulation layer is tightly bonded to the outer skin of the steel pipe, the infiltration of air and water is isolated, and it can play a good anti-corrosion effect. At the same time, its foam cells are closed, and its water absorption is very small. Both the high-density polyethylene shell and the glass fiber reinforced plastic shell have good anti-corrosion, insulation and mechanical properties, and the service life can reach more than 50 years, which is 3~4 times longer than the traditional trench laying and overhead laying.
The classification of thermal insulation steel pipe mainly includes steel sleeve steel composite thermal insulation steel pipe and polyurethane thermal insulation steel pipe
Steel sleeve steel composite insulation steel pipe
Steel sleeve steel composite insulation steel pipe insulation structure can be divided into two categories according to different sliding methods:
1. Inner sliding type. The insulation structure is composed of working steel pipe, aluminum silicate, drag reducing layer, microporous calcium silicate, heat insulation layer, stainless steel fastening steel strip, aluminum foil reflective layer, polyurethane insulation layer, jacket steel pipe, and outer anti-corrosion layer. The inner sliding thermal insulation steel pipe is composed of steel pipe for conveying medium + composite silicate or microporous calcium silicate + rigid polyurethane foam + outer steel pipe + glass steel shell anti-corrosion protection layer structure. The thermal insulation treatment technology of various pipe fittings is mature and the quality is reliable.
2. External sliding type. The heat preservation structure is composed of working steel pipe, glass wool heat insulation layer, aluminum foil reflection layer, stainless steel fastening steel belt, sliding guide bracket, air insulation layer, outer protective steel pipe, and outer anti-corrosion layer.
Structural form of outer sliding thermal insulation steel pipe
1. Inner steel pipe
2. Zinc-rich primer
3. Sliding guide bracket
4. High temperature resistant glass wool
5. Aluminum foil reflective layer
6. Air insulation layer
7. Coat steel pipe
8. Coating steel pipe anti-corrosion layer
Steel-sheathed steel composite thermal insulation steel pipe is a kind of underground direct buried pipeline. The method of underground direct burial can be carried out without concrete structure, that is, the thermal expansion of the working steel pipe is carried out in the outer pipe, thereby reducing the material cost, shortening the construction date, and ensuring the safety of the heating pipeline. It can be used more safely in different temperature environments, especially for high-temperature steam pipeline projects. The use temperature can reach 150°C-450°C. Pipe ports are generally sealed with polyethylene film or three-layer PE cold wrap tape to prevent moisture or water from entering before installation or during construction. Multi-layer staggered seam wrapping of thermal insulation materials effectively reduces heat loss, and at the same time control measures are taken on the surface of the jacket to prevent the generation of cold bridges, thus ensuring the temperature control of the jacket's anti-corrosion layer. The multi-layer aluminum foil reflective layer is wrapped with thermal insulation material, which effectively reduces heat loss and makes the steam pipe more economical and reasonable. The hydrophobic system adopts a fully enclosed form, which is flexible in layout, reasonable in structure, safe and reliable. The moisture discharge pipe on the steel sleeve can not only discharge the humid gas in time, but also serve as an alarm signal pipe for daily operation. The thermal compensation of the pipeline adopts high-quality bellows compensator, which is installed in the casing and made into a direct-buried form. There is no need to set up an observation well, and the construction operation is convenient and the construction period is short. It is suitable for transporting steam or other media below 2.5MPa and 350 degrees Celsius. This product uses steel pipe as the outer protective layer, which has the advantages of high strength, not easy to damage, easy construction and maintenance, and long service life.
Polyurethane insulation steel pipe
On medium and small-diameter thermal crude oil or heating pipelines, in order to reduce the heat dissipation from the pipelines to the soil, an insulating composite layer is added to the outside of the pipelines. The commonly used insulation material is rigid polyurethane foam, and the applicable temperature is -185～120℃. This kind of material is soft in texture. In order to improve its strength, a layer of high-density polyethylene is applied outside the insulation layer to form a composite material structure to prevent groundwater from penetrating into the insulation layer. Use high-pressure polyurethane foaming equipment to carry out shot blasting and derusting treatment on the outer surface of the steel pipe and corona treatment on the inner surface of the outer protection pipe to improve the bonding performance of the insulation pipe. The material of the insulation layer is rigid polyurethane foam, which fully fills the gap between the steel pipe and the casing, and has a certain bonding strength, so that the steel pipe, the outer casing and the insulation layer form a firm whole. Polyurethane foam has good mechanical properties and thermal insulation properties. Usually, it can withstand a temperature of 120°C, and can withstand a temperature of 180°C through modification or combination with other insulation materials.
The prefabricated polyurethane insulation steel pipe is divided into three layers from the inside to the outside:
1. The first layer: working steel pipe layer
According to the design and customer requirements, seamless pipes, spiral steel pipes(SSAW pipe) and straight seam steel pipes(ERW pipe) are generally used. After the surface of the steel pipe is treated by the advanced shot blasting derusting process, the derusting grade of the steel pipe can reach Sa2 level, and the surface roughness can reach R=12.5 microns.
2. The second layer: Polyurethane insulation layer:
It is formed by injecting rigid polyurethane foam stock solution into the cavity formed between the steel pipe and the outer sheath with a high-pressure foaming machine at one time.
3. The third layer: HDPE protective layer:
Prefabricated black or yellow polyethylene plastic pipes with a certain wall thickness. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance, and the lowest operating temperature can reach -70~-100°C. Good chemical stability, resistant to most acids and alkalis (not resistant to acids with oxidizing properties). It is insoluble in general solvents at room temperature and has low water absorption, but because it is a linear molecule, it can slowly dissolve in some organic solvents without swelling and has excellent electrical insulation properties. One of its functions is to protect the polyurethane insulation layer from being damaged by mechanical hard objects, and the other is to prevent corrosion and waterproof.
Advantages and features of polyurethane thermal insulation steel pipe:
1. Reduce project cost
According to the calculation of relevant departments, in general, polyurethane insulation steel pipe can reduce the project cost by about 25% (using FRP as the protective layer) and 10% (using high-density polyethylene as the protective layer).
2. Low heat loss, saving energy
The thermal conductivity of polyurethane is much lower than that of other pipe insulation materials commonly used in the past, and the thermal insulation effect is increased by 4 to 9 times. Furthermore, its water absorption is very low, about 0.2kg/m2. The overall heat loss of the heating pipeline is greatly reduced, and the heat loss of the heating network is 2%.
3. Anti-corrosion, good insulation performance, long service life
Since the polyurethane rigid foam insulation layer is tightly bonded to the outer skin of the steel pipe, the infiltration of air and water is isolated, and it can play a good anti-corrosion effect. At the same time, its foam cells are closed, and its water absorption is very small. Both the high-density polyethylene shell and the glass fiber reinforced plastic shell have good anti-corrosion, insulation and mechanical properties, and the service life can reach more than 50 years, which is 3~4 times longer than the traditional trench laying and overhead laying.
