Construction Scheme of Precast Directly Buried Insulation Pipe

Prefabricated directly buried thermal insulation pipe has good thermal insulation performance, high safety and low engineering cost, and is widely used in liquid and gas transportation pipe network. Chemical pipeline insulation engineering oil. , it can also effectively solve the waterproof problem, and at the same time, it occupies less land and is fast in construction, which is conducive to protecting the replacement machine and reducing the impact on surrounding residents. Next, let's learn more about the construction scheme of precast directly buried insulation pipe.

Construction Scheme of Precast Directly Buried Insulation Pipe

First, the construction preparation

(1) Operators must receive professional training and hold relevant certificates.

(2) The materials used for joint coating shall have quality certificates, and the products shall meet the requirements of design and relevant technical standards and specifications.

(3) The accuracy of the instruments used to monitor the joint filling process shall be inspected, and the next working procedure can be carried out only after passing the inspection.

(4) The factors affecting the quality of joint coating and the determined key parameters of joint coating process shall be documented and applied in the process of joint coating.

(5) Before patching, the matching between the steel pipes used in this project and the patching raw materials shall be tested to verify that the raw materials are well matched with the patching process and can meet the construction requirements of this project.

Second, the pipeline joint construction technology

(A) the construction process

(2) Process preparation

After the pipeline welding nondestructive testing is qualified, after receiving the notice of joint repair, the pipeline joint repair construction should be carried out without affecting the line construction.

Before formal joint repair, the process parameters and procedures of joint repair should be determined through process test to ensure the quality of joint repair.

Repair of steel pipe joints shall be carried out in 15? Above c, the relative humidity of air is lower than 85%. If the above requirements cannot be met, corresponding measures should be taken for construction.

(3) Install the polyethylene sleeve

1. Before installation, clean the dirt and dirt inside and outside the casing and at both ends of the pipeline to ensure that the plastic bonding parts are clean.

2. Determine the lap size of the joint sleeve and the polyethylene outer sleeve, place the joint sleeve at the joint, ensure that the outer sleeve is centered, and then install the heat shrinkable tape.

(4) Installation of heat shrinkable tape

1, ready

(1) Remove the dirt and dirt at the joint between the heat-shrinkable sleeve and the outer sleeve, remove the greasy part with a width greater than that of the heat-shrinkable belt, and coarsen the bonded part with alcohol, with the coarsened width greater than that of the heat-shrinkable belt.

(2) Where there is water in the bonding part, it shall be dried or dried with a drying lamp.

2. Device

(1) Determine the lap length of the heat shrinkable tape and the heat shrinkable sleeve.

(2) Cut the length of the heat shrinkable tape.

(3) One end of the heat shrinkable tape is chamfered by 50×15 mm..

(4) Wrap the adhesive layer of heat shrinkable tape inward at the joint, and ensure that the heat shrinkable tape is centered at the lap joint.

(5) First, bake the overlapped two layers of heat shrinkable tapes with low fire until the adhesive layers are miniaturized and overlapped and fixed, then buckle the gland with baked adhesive layers on the overlapping seam in the middle, and then bake the gland evenly back and forth with medium fire until the gland and the heat shrinkable tapes are completely bonded without warping and bubbles. During the heating process, use gloves or rollers to grind the gland flat, so that it can be closely combined with the heat shrinkable tape.

(6) After the gland is pressed, the side overlapping with the sleeve should be baked from the middle of the heat shrinkable tape, starting from the bottom, following the baking rules from bottom to top and from inside to outside to avoid bubbles.

(7) Adjust the flame length of the spray gun. First, heat evenly along the central circumference of the heat shrinkable belt, and then heat both ends in turn after the center shrinks. During the heating process, the spray gun should move back and forth to ensure that the heat shrinkable tape will not overheat locally.

(8) When heating and shrinking, carefully observe whether there is hot melt adhesive overflowing at the edge of the heat shrinkable tape.

(9) After the contraction is completed, check the heat shrinkable tape and gland again for warping and bubbles. If there are bubbles, repair and eliminate them in time to ensure the smooth flow of heat shrinkable tape and gland.

(10) It is forbidden to soak the thermal insulation materials. If it is found that the insulation layer is soaked, the insulation material at the water inlet should be dug out and re-insulated.

(5) Air tightness test

1. Drill a hole at one end of the jacket, install the pressure gauge in the hole, and tighten the fixing bolt.

2, open the air compressor, use soapy water to raise the pressure to 0.02Mpa for inspection, and no leakage is allowed.

3. If there is leakage of polyethylene heat shrinkable tape, it should be repaired, and then the air tightness test should be carried out, and polyurethane foaming can be carried out only after it is qualified.

4. Enlarge the pressure hole on the outer sleeve into foaming discharge hole and air outlet hole.

(6) Polyurethane foaming

When the air tightness test is qualified and meets the corresponding regulations, polyurethane foaming can be carried out.

1, foaming: mechanical foaming is used for foaming.

2. The raw material is polyurethane.

3. Calculate the injection amount of polyurethane according to the length of the interface.

4. After the foam overflowed from the hole is completely solidified, knock test shall be conducted, and the foam shall be full and full.

5. Polyethylene plugging: Plastic plugging is used to seal foam holes.

Third, the construction site conditions

1. Although the water absorption rate of polyurethane in prefabricated directly buried insulation pipe is extremely low, it is not suitable for soaking in water. During the construction period, drainage ditches and collecting wells must be set up. The inner diameter of the collecting well is 0.8m, and the bottom of the well is 0.5m deeper than the bottom of the tank. Dig a 0.2m×0.2m drainage ditch along the trench, and the slope of the trench bottom is 1%. Drainage pump (with standby pump) is used to pump away accumulated water in time to ensure the dry tank operation during pipeline installation.

2. The size of the working pit of the joint should meet the requirements of the construction specifications, especially the distance between the bottom of the working pit and the bottom of the pipeline should be as large as possible, so as to ensure that the spray gun has enough room at the bottom of the pipeline when baking the heat shrinkable tape, and prevent the circumferential edge of the heat shrinkable tape from missing baking or insufficient baking.

3, the construction site drainage should be equipped with full-time management personnel, 24 hours on duty, to prevent the pipeline from being soaked in water.

4, in order to ensure the construction quality, should have a reasonable time limit for a project.

5. If conditions permit, a plurality of insulation pipes are assembled and welded on the groove, and the joints are hoisted into the groove after insulation is completed.

6, working pit should be based on the depth, soil and groundwater level and other specific circumstances to decide whether to set up support, to ensure the safety of construction personnel.

The above is a detailed description of the construction scheme of precast directly buried insulation pipe. I don't know if everyone knows. Let's talk about the relevant precautions here, such as resolutely not using insulation pipes with quality problems, and carefully investigating and studying relevant manufacturers before buying, otherwise it will cause incalculable consequences, so be very cautious. I hope the above contents are helpful to you.

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