In the construction industry, insulation at the joints of PPU pipes is a primary task. With the right procedure, the life of the pipeline can be extended due to reliable protection from negative environmental influences. However, you first need to find out what the design of the HDPE pipe is.
Foamed plastic using polymeric materials is called polyurethane. Depending on the type of plastic used, hard and soft are distinguished. This consistency is dominated by air at a concentration of 90%.
Why is it necessary
Among the main areas of activity of insulation for modern PPU pipes are:
- Thermal insulation of walls of residential buildings in industrial and civil construction.
- The process of manufacturing sandwich panels and prefabricated structures.
- Production of refrigeration equipment: refrigerators, cold stores and special chambers.
- Decorative finishing of pieces of furniture.
- Thermal insulation made of durable polyurethane foam for pipeline structures.
- Production of synthetic materials, including leather.
- Radio engineering and electronics.
No less popular is the household scope: in the manufacture of sponges, washcloths, furniture fillers as foam rubber.
It is customary to distinguish between two types of PPU: hard and soft. The second option — foam rubber, does not differ in strength characteristics. However, other advantages can be distinguished: flexibility and softness. Its use is very limited and most often it is used for the manufacture of soft toys, clothing, and furniture.
The material has good adhesion, because after application the foam dries quickly and adheres strongly to other materials, regardless of which type is used: brick, concrete, plastic, wood or glass. During processing, additional fasteners are not required.
The insulating material is able to take any shape and fill the empty space, regardless of the complexity of the configuration. Therefore, it is often used in the construction of complex structures and for any weight of the pipe. The processing process involves the creation of a continuous layer, where there are no joints, slots and bridges. Operation is allowed at a temperature regime of -200 + 200 degrees. It is an excellent insulating material that dampens noise and vibration.
The material has a foamy consistency that is easy to transport. It is also used in soil conditions or high humidity. For industrial production, it is transported in two forms. It is important to take into account that the solid version does not allow moisture to pass through, does not contribute to the spread of decay, and also shows inertness with respect to many alkaline and acidic compounds. It is classified as a material that is difficult to ignite.
However, before using it, you need to know one caveat: it negatively tolerates exposure to ultraviolet rays. To maintain positive properties, you need to cover with a casing or opaque structures.
When using PPU, the joints with an internal diameter in the range of 40-1420 mm are insulated. As a rule, a large length of pipelines is used for the assembly of oil and gas pipelines. The thickness of the insulation is in the range of 40-100mm, sometimes there is an indicator of 20mm.
Shells are found:
- Two-segment with an angle of 180 degrees, if the pipe diameter is up to 530 mm.
- Three-segment designs with a diameter of up to 820mm with an angle of 120 degrees.
- Systems with four segments of 1420mm with an angle of 90 degrees.
Advantages and disadvantages
PPU insulation is used:
- Many areas of operation as a foamed consistency or foam insulation.
- It makes it possible to lower the soil as a pipeline without using it. additional fasteners.
- The speed of work is carried out twice as fast, and the construction process is greatly simplified.
- When creating a sealed layer in the factory, maximum sealing is achieved, as well as reliable protection against the spread of corrosion.
- Thanks to the built-in copper indicators, areas with a high percentage of moisture can be detected, which saves time on repairs.
- The service life is calculated for 30 years without additional replacement of elements. Often the top is covered with special varnishes, polymers and paints.
However, there are a number of disadvantages that you should pay attention to:
- The ignition temperature is 550-600 degrees.
- After the end of their service life, the pipes need to be completely replaced.
- Low strength provided by the outer coating.
- In case of damage due to high humidity, you will have to completely change the design.
Types of foam insulation
Polyurethane foam insulation is carried out using the method of insulated joints or shell mounting. The main material for the work is polyurethane. Previously, most of the heat was lost due to high humidity. With the use of the shell, this problem was solved.
The shell has the following advantages:
- It can be used in areas where the temperature drops sharply in winter. The maximum temperature mode of operation is -190 + 150 degrees.
- Possesses high characteristics of moisture resistance. The indicator is no more than 2%.
- Light weight. It is enough to dock the fasteners with grooves. If a certain area is deformed, it is easy to replace, the insulation is reused for dismantling.
- Not exposed to chemicals.
- Density — 40-60kg / m.
- Resistant to mechanical damage.
The protective shell can be made of any materials: galvanized steel, foil, fiberglass, paper.
During the construction process, it is important to select high quality materials for joint insulation. With high-quality sealing of fasteners, the service life of the structure increases. One of the actual methods is the use of a heat-shrink sleeve.
To carry out the insulating installation of joints, it is necessary to take care of the preparatory operations. To do this, you will need to attach a special coupling to one of the ends of the pipe with the choice of the optimal diameter. It is important to carry out all operations carefully so as not to cause mechanical damage to the structure and not reduce waterproofing. Next, do the welding.
Next, you need to check the result and remotely control the state of the conductors of the connections. If no errors are found, it is allowed to proceed with the installation of heat-insulating joints.
How to attach a heat shrink sleeve
First you need to prepare the following tools:
- Connections with joints made of polyurethane foam;
- gas burner;
- Soap solution;
- PPU liquid substance;
First of all, the coupling must be attached to one end of the pipe. After bonding, it’s time to remove the protective layer from the surface. Turn on the gas burner and heat the sleeve until it shrinks completely. As a result, visually its shape resembles an ordinary barrel.
The next step is to check the sealing in the inner surface of the coupling. A plug is inserted into the hole and air is injected with a volume of 0.5 atmospheres. The pressure indicator is checked after 5 minutes. If everything is in order, the indicator should not change. If the result decreases, it is recommended to check how tightly the coupling fits. To check, you must use a soapy solution.
If the shrinkage is insufficient, you will have to re-install more tightly. In the case of a stable pressure indicator, the process is done in accordance with all the rules and nothing will have to be finalized. It remains to pull out the cork and pour polyurethane. It should become solid, fill the empty space. The ends of the pipe are closed with polyethylene plugs. For strength, welded to the coupling. This method helps to effectively protect fasteners from negative external influences: strong wind, temperature changes, frost.
The production of liquid consistency polyurethane foam is carried out in a foam pack, which contains polyol and polyisocyanate. When mixed, a liquid consistency is obtained, which is foamed. As a result, its volume increases and begins to harden. Builders do not have to spend time mixing mortar. Foam packs are presented in various diameters depending on the size of the pipe.
In a situation where it is impossible to use the fill as a mounting, it is better to use shells. Actual when using waterproofing fasteners. They have a long service life, and due to the rigidity there is no structural shift.
PPU pipe insulation is used in many areas of activity, due to the versatility of the material. The material helps to save money, as well as to realize the tasks in production or construction.