What regulations need to be followed in the construction and installation of prefabricated directly

1. Engineering surveying and earthwork shall comply with the provisions of CJJ28 "Code for Construction and Acceptance of Urban Heating Pipe Network Engineering" and CJJ T81 "Technical Regulations for Urban Direct Buried Heating Pipeline Engineering".

2. Pipeline connection.

1.Before pipeline installation, check whether the elevation, slope and substrate treatment of the bottom of the trench meet the design requirements. Debris and sand in the pipeline should be removed.

2.Prefabricated insulation pipes with different specifications and different properties of different manufacturers should not be used in the equal diameter straight pipe section, and the consent of the design department should be obtained when it is unavoidable.

3.Between the working pipes, the nominal outer diameter less than DN90 is connected by electric fusion pipe fittings, and the nominal outer diameter greater than or equal to DN90 is connected by hot melt butt connection or electric fusion pipe fittings. The connection between the working pipe and the metal pipe can be connected by flange connection or steel-plastic conversion joint.

4.The connection between the working pipe and the metal pipe or valve, flow meter, pressure gauge and other pipe fittings can be flanged connection. The flange connection operation can refer to the provisions of CJJ 63 "Technical Regulations for Polyethylene Gas Pipeline Engineering".

5.Regardless of whether it is an electric fusion connection or a hot melt connection, each weld should be visually inspected; The main means of pipeline welding inspection is non-destructive inspection, which is used for on-site quality control and operator self-inspection through visual inspection and special tools.

6.The interface insulation shall comply with the provisions of CJJ T81-1998 "Technical Regulations for Urban Direct Buried Heating Pipelines".

3. Inspection of working pipeline joints.

1.After the pipe joint is connected, it should be left for 24 hours, and the pipe purge, strength test and tightness test should be carried out sequentially. When leakage is found during the test, it should not be treated under pressure.

If repairs or additional piping elements are added after the test, the affected piping should be retested.

2.During the test, the test record should be made for each pipeline system, which is as follows:

1) The date of the trial.

2) The logo of the piping system under test.

3) Test fluids.

4) Test pressure.

5) Certificate of inspection results issued by the inspector.

3.Preparation for a stress test.

1) Joints are exposed, except for joints that have been tested for leakage in advance, which can be coated with an insulation layer, all joints should be exposed so that they can be checked during the leak test.

2) Limitation of the test pipeline The equipment that is not intended to be tested should be separated from the pipeline during the pressure test, or separated from the pipeline by a plug plate or other method (a valve suitable for the test pressure can be used).

3) The safety valve and instrument on the pipeline to be tested have been removed or isolated.

4 .Hydraulic test.

1) The fluid used in the hydraulic test should be clean water. Unless there is a risk of damage to the pipeline due to freezing or water that has an adverse effect on the pipeline or process, other suitable non-toxic liquids may be used.

2) Before the test, the air in the channel system should be discharged when the liquid is injected.

3) When the ambient temperature is lower than 5 C, antifreeze measures should be taken.

4) The test pressure should be times of the working pressure, and should not be less than.

5) Under the test pressure, the pressure is stabilized for 1h, and the pressure drop should not be greater than and there is no seepage or leakage.

The prefabricated directly buried insulation pipe PE-RT LL type adopts a trinity structure of working pipe, insulation layer and outer protection pipe, which is the same as that of steel pipe insulation pipe, but because the plastic material is a poor conductor of heat, the thermal conductivity of the inner pipe of the solid insulation composite plastic pipe is only 1% of that of the steel pipe, that is, the pipe itself has a certain thermal insulation performance, and the thermal expansion coefficient of the pertll pipe, insulation layer and outer protection pipe is basically the same, and the three layers will become an organic whole, which is not easy to produce delamination problems. Therefore, the insulation effect of pipes is better than that of steel pipes.

Performance characteristics of prefabricated directly buried insulation pipe PE-RTLL type.

1. Reduce the cost of the project. According to the calculations of relevant departments, the use of high-density polyhexene as a protective layer can generally reduce the cost of the project by about 220%. 2. Low heat loss and energy saving.

Prefabricated directly buried insulation pipe PE-RTLL type, the insulation layer is polyurethane foam, compared with other insulation materials, the insulation effect is 4-9 times higher. In addition, its water absorption rate is very low, and the closed cell rate is as high as about 92%, which greatly reduces the overall heat loss of the heating pipeline, and the heat loss of the heating network is 2%, which is less than the international standard requirement of 10%.

3. Anti-corrosion, good insulation performance and long service life. Prefabricated directly buried insulation pipe PE-RTLL type, because the polyurethane rigid foam insulation layer is tightly bonded to the PE-RT outer skin, isolating the penetration of air and water, which can play a good anti-corrosion role. At the same time, its foam pores are closed, and the water absorption is very small.

The high-density polyethylene shell has good room erosion, and the service life of PE-RTII prefabricated directly buried insulation pipe can reach more than 50 years, which is 3-4 times higher than the service life of traditional trench laying and overhead laying.

1) Hygienic performance.

The hygienic performance of pipes for domestic hot water transmission shall comply with the provisions of GB T17219.

2) Thermal insulation composite plastic pipe.

a.Appearance: The appearance of the insulation composite pipe should be clean, and the visible surface should not have defects such as grooves, cracks, depressions, impurities, and uneven color that affect its performance.

b.Verticality of pipe end: The outer protective pipe of the pipe end of the thermal insulation composite plastic pipe should be flush with the insulation layer of polyurethane foam, and should be perpendicular to the axis of the working pipe, and the angle error should be small and flat.

c.Extrusion deformation and scratches: When the insulation layer is extruded and deformed, the radial deformation should not be greater than 15% of the thickness of the designed insulation layer.

The scratch depth of the outer hose should not be greater than 10% of the minimum wall thickness of the outer hose and should not be greater than 1mm.

d.Length and deviation of reserved section at the end of the pipe:

The length of the non-insulation reserved section at both ends of the working pipe should meet the requirements of the insulation composite plastic pipe connection, and the difference between the reserved lengths at the two ends should not be greater than 20mm.

e.Foam delamination at the end of the pipe: The insulation layer should be tightly bonded with the working pipe and the outer protection pipe, the radial size of the foam delamination of the pipe section should not be greater than 2mm, the depth along the axial direction should not exceed 70mm, and the cumulative length of the circumference should not be greater than 1 3 of the circumference.

3) Surface temperature of the outer protection tube.

Under operating conditions, the temperature of the surface of the outer protective tube should be less than 50.

4) The increase rate of the outer diameter of the outer protection tube.

Before and after foaming of the insulation composite plastic pipe, the increase rate of the outer diameter of the same section at any position of the outer protection pipe should not be more than 2%.

5) Maximum axis eccentricity.

When the outer diameter of the outer protective tube is not greater than 160mm, the axis eccentricity should not be greater than; When the outer diameter of the outer guard tube is greater than.

When 160mm, the axis eccentricity should not be greater than.

6) Axial shear strength.

Under the condition of 23, the axial shear strength of the insulated composite plastic pipe should not be.

7) Ring stiffness.

The stiffness of the insulation composite plastic in the ring should not be less than 4kn.

8) Impact resistance.

Under -20° conditions, with a drop weight from 2m

Falling from a high place to impact the outer protective pipe, the outer protective pipe should not have visible cracks.

9) Flexibility.

It is suitable for PUPE and PUPB insulation composite plastic pipes with a nominal outer diameter of no more than 50mm. When the minimum bending radius of the outer protective pipe is not greater than 30 times of the nominal outer diameter of the outer protective pipe, the insulation layer and the outer protective pipe should not be broken, the roundness of the outer protective pipe should not be more than 30%, and the crack width of the thermal insulation layer connecting with the outer protective pipe should not be greater than 5mm.

10) Creep performance.

The creep ratio should be less than 5.

Foster introduces you.

PE-RT pipes, insulation and outer protective layers. The prefabricated insulation pipe is to process and install the insulation layer for the special pipe that needs it before installation.

Answer: Li Xing's case]: a, c, e

This question examines the installation of directly buried insulation pipes. The same construction section of the same diameter straight pipe section should be closed with prefabricated insulation pipes, pipe fittings and insulation joints of the same manufacturer, the same specifications and performance. When it cannot be satisfied, the consent of the design unit should be obtained.

Directly buried steam pipelines should be provided with tide discharge pipes; The steel outer protection pipe should be externally anti-corrosion. The air tightness test should be done before the anti-corrosion layer at the interface of the outer protection pipe, and the test pressure should be .

As a new type of heat-resistant polyethylene (Pert II) insulation composite plastic pipe, PE-RT II prefabricated directly buried insulation pipe has the characteristics of corrosion resistance and long service life. PE-RT II prefabricated directly buried insulation pipe adopts hot melt connection, which has low construction cost, corrosion resistance and low maintenance cost. The service life of the PE-RT II type prefabricated directly buried insulation pipe is up to 50 years.

PE-RT II prefabricated direct buried insulation pipe consists of three parts:

The outer layer is HDPE high-density polyethylene pipe;

The middle layer is a polyurethane foam insulation layer;

The inner layer is a working pipe PE-RT type II tube.

PE-RT II Prefabricated Direct Buried Insulation Pipe Application Project:

urban central heating secondary pipe network, hot spring water insulation pipeline;

Hotel and guesthouse air energy heat pump hot water project Hotel and guesthouse solar water heating project;

School Air Energy Heat Pump Hot Water Project School Solar Water Heating Project;

Hospital Air Energy Heat Pump Hot Water Project, Hospital Solar Water Heating Project;

Villas, resorts, leisure centers air energy heat pump hot water project Villas, resorts, leisure centers solar water heating project.

The application fields of PE-RT II prefabricated directly buried insulation pipe are:

1) Urban central heating secondary pipe network, hot spring water insulation pipeline.

2) Factory Air Energy Heat Pump Hot Water Project Factory Solar Water Heating Project 3) Hotel and Guesthouse Air Energy Heat Pump Hot Water Project Hotel and Guesthouse Solar Water Heating Project 4) Hotel and Salon Air Energy Heat Pump Hot Water Project Hotel and Hair Salon Solar Water Heating Project 5) School Air Energy Heat Pump Hot Water Project School Solar Water Heating Project 6) Hospital Air Energy Heat Pump Hot Water Project Hospital Solar Water Heating Project 7) Sauna and Foot Bathing Air Energy Heat Pump Hot Water Project Sana and Foot Solar Water Heating Project 8) Apartment Air Energy Heat Pump Hot Water Project Apartment solar water heating project 9) Villas, resorts, leisure centers air energy heat pump hot water projects Villas, resorts, leisure centers solar water heating projects.

10) Building Energy Saving Air Energy Heat Pump Hot Water Engineering Building Solar Water Heating Engineering Building Hot Water Engineering.

PE-RT II prefabricated directly buried insulation pipe has a three-layer structure: 1Outer sheath pipe HDPE 2The middle layer is polyurethane foam insulation layer 3The inner layer is a working core PE-RT II tube.

PE-RT working tubesBearing the pressure and temperature of the system, the outer protection pipe plays the role of protecting the insulation layer. The bracket between the PE-RT working tube and the outer guard tube mainly plays the role of support, ensuring the coaxiality of the PE-RT working tube and the outer guard tube. In terms of structure, it is the same as the steel pipe insulation composite pipe, but the difference is that the plastic pipe is used as the working pipe, and the stability requirements of the structure are not so strict, because the thermal conductivity of the PE-RT working pipe is about , which is a poor conductor of heat, and the air gap between the insulation layer does not have a significant impact on the thermal insulation of the system as much as that of the steel pipe composite insulation pipe; In Europe, there are also monolithic non-bonded composite pipes in which the plastic working pipe is completely separated from the insulation.

1) The nominal outer diameter and wall thickness of PE-RT working pipe refer to GB T10798-2001 "General Wall Thickness Table for Thermoplastic Pipes", and the size of the outer protection pipe refers to GB T29047-2012 "High-density polyethylene outer protection pipe rigid polyurethane foam prefabricated directly buried insulation pipe and pipe fittings".

2) For the color of PE-RT working pipes in different countries have different regulations and management methods, generally speaking, industrial plastic pipes are mostly black or gray (such as the international standard ISO 15494), and the color of plastic pipes for domestic hot and cold water is usually not specified, but there are requirements for opacity, so most of them are dark colors such as gray. For PE-RT working pipes, due to the protection of black outer protection pipe and buried installation, the color can be determined according to market conditions, and other colors are determined by negotiation between the supply and demand parties.

3) The performance of raw materials for PE-RT working pipes and pipe fittings is the most basic guarantee to ensure the long-term performance of pipelines, so the performance of raw materials is specified in detail, among which the long-term hydrostatic reference curve, density, full-incision creep performance, and thermal stability under 110 hydrostatic conditions are the theoretical basis and basis for ensuring the long-term use of PE-RT working pipes.

Insulation

Between the working pipe and the outer protection pipe, the insulation material layer is set up to maintain the temperature of the pipeline conveying medium. The insulation structure shall comply with the relevant provisions of the current national standards "General Principles for Equipment and Pipeline Insulation Technology" GB T4272, "Equipment and Pipeline Insulation Design Guidelines" GB T8175 and "Design Code for Industrial Equipment and Pipeline Insulation Engineering" GB50264.

When calculating pipeline insulation, it should be carried out with reference to the provisions of the current national standard "Design Guidelines for Equipment and Pipeline Insulation" GB T8175, and in accordance with the provisions of "Technical Regulations for Urban Direct Buried Heating Pipelines" CJJ T81. The thermal conductivity of PE-RT working pipe is , and the thermal conductivity of polyurethane foam is .

Outer protective tube

PrimallyTo block the damage and influence of environmental factors such as external force and water on the insulation layer, it is necessary to have sufficient mechanical strength and reliable waterproof performance of the casing.