The insulation elbow is one of the pipe insulation, which is composed of high-density polyethylene outer sleeve, polyurethane foam insulation layer and inner working steel pipe. Insulated elbows are mainly used for the turning of insulated straight pipes and are generally used in conjunction with insulated pipelines. They are used for compensation in the design of insulation engineering pipelines, so that the elbow area can also have sufficient insulation performance. Standard elbow angles are 30 degrees, 45 degrees, 60 degrees, and 90 degrees.

Insulated elbows are widely used in liquid and gas transportation pipelines, chemical pipeline insulation engineering, petroleum, chemical, central heating networks, central air conditioning ventilation pipelines, and municipal engineering pipeline bends. Insulation pipes (including elbows, tees, and tees) are a type of directly buried prefabricated insulation pipe with good insulation performance, safety and reliability, and low engineering cost. Effectively solved the insulation of insulation pipes, insulation of bends, sliding lubrication, waterproofing and anti-corrosion of exposed pipe ends and eight bends in various pipeline projects such as heating, cooling, heating, power, and chemical engineering. Not only does it have advanced technology and practical performance that traditional trench and overhead pipeline laying cannot match, but it also has significant social and economic benefits, energy conservation and environmental protection benefits.

Insulated elbow

2、 Execution standards:

CJ/T200-2004 Technical Conditions for Prefabricated Directly Buried Steam Insulation Pipes for Urban Heating

CJ/T104--2005 Technical Specification for Directly Buried Steam Pipelines for Urban Heating

SY/T114-2000, SY/T115-2001 High density polyethylene polyurethane foam insulated steel pipes

One type is composed of elbows for conveying media, anti-corrosion coated steel pipes, and polyurethane filled between elbows and coated steel pipes. The principle of insulated elbow is the same as that of directly buried insulated pipe. It is a new buried technology that is waterproof, leak proof, impermeable, compressive, and fully enclosed. It is a major breakthrough in the use of directly buried laying technology in areas with high groundwater levels. The primary problem of the protective pipe of the directly buried pipeline is the reliability of tight waterproof. In addition, it should have good mechanical strength. Because of its high strength, the insulation elbow uses the high-density polyethylene outer pipe closely combined with the polyurethane foam insulation layer and the inner working steel pipe, so the reliability of waterproof sealing performance is very high. In addition, its high temperature resistance performance is also unmatched by other external protective pipes.

3、 Structural mechanism

1. High density polyethylene anti-corrosion coating: High density polyethylene pipes protect elbows from corrosive substances and plant corrosion, extending the service life of pipe fittings. 

Support the work pipe and be able to withstand certain external loads to ensure its normal operation. 

2. Polyurethane foam layer: resistant to high temperature, ensuring medium temperature, ensuring normal temperature on the surface of external protection pipe, and thermal insulation of internal working pipe fittings,

Ensure that foam is not carbonized. 

3. Working steel pipe: Ensure the normal flow of the conveying medium.

4、 Construction precautions:

1. During construction, it is necessary to avoid soaking in groundwater and rainwater. If the end is accidentally submerged, it should be dried before connecting the jacket. 

2. The pipes should be stored in a flat area, neatly stacked, and the stacking height should be less than 1.5 meters. 

3. Pipe hoisting should be carried out with care, collision and throwing are prohibited, and steel wire rope should not be used to directly lift the pipe body. 

4. The insulation layer and anti-corrosion layer should avoid direct contact with flames. On site installation, please follow the following procedures: trench excavation - foundation treatment (drainage, sand padding) - pipe laying - steel pipe welding - inspection (water pressure) - installation (pressure testing) - foaming - sealing foam holes. Installation of elbows and joints: Hebei Juqing Pipeline Company can dispatch personnel to the engineering site to carry out insulation work for joints, including the installation of joint sleeves, connection and sealing between joint sleeves and main pipes, and foaming work for on-site joints. However, this does not include welding work for the steel pipes in the joint section.

(1) In this method of sleeve joint, the joint sleeve is made of polyethylene sleeve with the same material and density as the prefabricated insulation pipeline sleeve. The polyethylene joint sleeve and the main pipe are connected and sealed with heat shrink tape to ensure the water tightness of the joint. Then, the foam holes on the joint sleeve are subjected to joint foaming. After foaming is completed, high-density polyethylene is used for sealing, and the foam holes are sealed by patching or hot melt welding.

(2) Heat shrink tape, in the joint method using heat shrink tape, is a material that plays a crucial role in the lifespan and sealing of the joint. The company only uses heat shrink band products recognized by the European Heating Association. The existing suppliers of heat shrink band products are Xiankan Company in the United States or CANUSA Company in Canada. The adhesive layer and hot melt temperature of the heat shrink tape specially designed for prefabricated insulation pipeline joints in regional centralized heating are suitable for this purpose.

(3) Electric fusion sleeve is a welding method that uses a sleeve with pre embedded resistance wires. The hot melt sleeve is tightly tied to the outer sleeve with a binding strap, and then the power is turned on to start welding. The welding time is pre-set, and the welding is completed after automatic power off. After the sleeve is completely cooled, the binding strap is removed. By using this method of joint, the construction is simple and the welding joint is firm. This pipeline system can be applied to all known installation methods of buried pipeline systems. In addition to the usual compensated laying method, its advantages can be better demonstrated in the following three uncompensated laying methods. The pipeline temperature during the cold installation method of welding the pipeline as a whole is equal to the ambient temperature during backfilling. Cold installation is the most economical and efficient installation method. The pipeline can be backfilled in a timely manner during construction, which minimizes or even eliminates the need for compensators and fixed brackets, thus saving a lot of money. Due to the increase in axial stress of the pipeline, it is sometimes necessary to strengthen the tee or increase the burial depth.

5、 Service life

The polyurethane rigid foam material in the insulated elbow has a stable porosity structure and is basically closed cell. This not only provides excellent insulation performance, but also has good freeze-thaw resistance and sound absorption. The average lifespan of on-site cast polyurethane rigid foam insulation structures can reach over 30 years under normal use and maintenance conditions. All materials, through protective treatment, can withstand normal usage conditions during the lifespan of the structure, without causing damage due to dryness, humidity, electrochemical corrosion, as well as various invasions such as insect, fungal or algal growth, or damage from rodents. All materials of this product are compatible with each other and meet the quality requirements of relevant national standards.

6、 Application scope

Polyurethane foam insulation has been rapidly developing as an excellent insulation material since the birth of polyurethane synthetic materials in the 1930s. Its application range is also becoming more and more extensive, and it is widely used in various pipelines such as heating, cooling, oil and gas transportation due to its simple construction, significant energy-saving and anti-corrosion effects. Widely used in various pipelines such as heating, cooling, oil and gas transportation. Product main engineering: petroleum and gas pipeline engineering, natural gas pipeline engineering, chemical plants, power plants, shipyards, pharmaceuticals, dairy products, beer, beverages, water conservancy and other engineering.