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Construction Management of plastic pipe
Nov 26, 2018

The expansion of plastic tubes.

The pipe at both ends of the modified hard PVC drainage pipe is the plug, the pipe fittings are the inlet, most of them are connected by the socket bonding method, which is an immutable permanent connection, while the line expansion coefficient of the plastic products is large, and the pipeline is affected by the expansion length caused by the change of ambient temperature and sewage temperature.

UPVC Issues (1) The arrangement of drainage out of the household pipe has a great influence on the design flow of the system. Vertical pipe and discharge pipe connection to use different diameter elbow, out of the household tube is best than the riser large pipe diameter, out of the household tube should be as smooth as possible to discharge sewage outside, the middle does not have elbow or B-word tube.

Many projects have confirmed that the finer drainage out of the household tube and the increased pipe fittings on the discharge pipe will cause adverse changes in the pressure distribution in the tube, reduce the allowable flow value and in the future use of the process is prone to the phenomenon of poor drainage of the toilet. 

(2) uPVC spiral Tube drainage system in order to ensure that the spiral pipe flow spiral drop, thereby reducing drainage noise, the riser can not be connected with other riser, so it is necessary to adopt an independent single-riser drainage system, which is also one of the characteristics of the use of uPVC spiral tube.

Do not add to the snake, copy the cast iron pipe drainage system, in the high-rise building to increase the exhaust pipe, if the increase of the exhaust pipe, not only waste the material, but also destroy the drainage characteristics of the spiral pipe. 

(3) with the spiral pipe supporting the use of side water special three-way or four-way pipe fittings, belong to the NUT extrusion rubber ring sealed sliding joints, generally allow the telescopic sliding distance in the conventional construction and use phase of the temperature difference range, according to the uPVC pipeline expansion system, allowing the tube length of 4M, that is, whether it is riser or transverse branch

As long as the pipe segment is within 4M, do not set up another telescopic section. 

(4) connection of pipe. uPVC Spiral Tube using nut extrusion rubber ring sealing joint. This joint is a sliding joint that can act as a telescopic, so the appropriate reserved clearance after pipe insertion should be considered in accordance with the procedures. Avoid construction due to the individual operator diagram of the save, resulting in the reservation gap is too large or too small, in the future with the seasonal temperature changes, pipeline deformation caused by leakage. The prevention method is to determine the reserved gap value first according to the construction temperature at that time.

In each joint construction, first in the insertion tube to do a good job of insertion mark, operation to reach the insertion mark can be. 

(5) In some high-rise building designs, flexible drainage cast iron tubes are used for steering elbows and discharge tubes in order to strengthen the anti-water impact capability at the bottom of the riser of the spiral tube drainage system.

The construction shall Cheng the outer wall of the plastic pipe inserted into the cast iron, and increase the friction and fastening force of the filler with the seam. 

(6) Extending the roof of the ventilation pipe, due to indoor and outdoor temperature difference influence and storm attack, often appear ventilation pipe tube week and roof waterproof layer or insulation layer of the junction of the production of telescopic cracks, resulting in roof leakage.

The prevention method is to be around the roof vents to do higher than the top layer of 150mm-200mm resistance to the hydrosphere. 

(7) Two problems often occur in the construction of the discharge pipe of the buried land: one is that the laying of the pipeline below the indoor floor is not carried out after the backfill is compacted.

After the backfill is compacted, although the irrigation experiment is qualified before compaction, but after using the pipe interface cracking deformation leakage: the other is the hidden pipe when the left and right side and the upper part of the sand cover, resulting in sharp hard objects or stones, such as direct touch of the outer wall of the pipe, resulting in damage deformation or leakage of the pipe wall. 

(8) Indoor Ming set UPVC spiral pipe installation should be in the civil wall whitewashing after the completion of continuous. In fact, due to the duration of the construction period, most of them are synchronized with the decoration after the completion of the main structure. This will cause smooth and beautiful surface contamination, the best solution is with the installation of uPVC spiral pipe timely with plastic cloth winding protection, to be completed after the removal can be removed. In any other, it is necessary to strengthen the finished product protection of the uPVC spiral pipe during the construction process, and it is strictly forbidden to climb the pipe, fasten the safety rope, build the foot plate, use it as a support or borrow it. The top elevation of the water leakage of the floor shall be lower than that of the ground 5~10mm, and the depth of the leakage seal shall not be less than 50mm. The aim is to prevent the harmful gas in the sewage pipeline from entering the indoor polluted indoor environmental hygiene after the water seal is destroyed. However, few people in the design instructions of water supply and drainage mentioned that construction and construction units in order to reduce the cost of using the market low price floor drain, this kind of leakage seal is generally not more than 3 cm, can not meet the depth of water seal requirements. In addition, residents decorate the house when choosing to decorate the market stainless steel floor drain instead of the original plastic floor drain, although the appearance of bright and beautiful, the internal water seal is also very shallow. When draining, the water seal of the floor drain is damaged due to positive pressure (lower floor) or negative pressure (higher floor), and the stench enters the room. Many residents reflect the stench in the home, and the kitchen hood is more serious when it is opened, which is why the water seal is damaged due to pressure fluctuations. Some residential kitchens set up a floor drain, due to long time did not replenish water, especially in winter heating water seal easy to dry up, should often give water leakage recharge. It is suggested that high water seal or new type of anti-reflux overflow leakage should be used in the design and construction. There is less splash on the ground in the kitchen and no floor drain can be set.

Pipeline Foundation laying. 

(1) In order to ensure close contact between the bottom of the pipe and the foundation and control the axis elevation and slope of the pipeline, the Pvc-u pipeline should still do the cushion foundation. For the general soil usually only make a layer of 0.1m thick sand cushion can be. For soft soil foundation, and when the bottom of the trough is below the underground water level, it is advisable to spread a layer of gravel or gravel, thickness is not less than 0.15m, gravel particle size 5~40mm, above and then spread a layer of thickness not less than 0.05m sand cushion, in order to facilitate the stability of the foundation. The foundation should be left out of the groove at the connection of the socket to facilitate the placement of the bearing port, and then backfill with sand after installation.

The axillary angle connected with the foundation must be filled with coarse sand or sand, and the part of the bottom of the pipe should be tightly encased to form an effective support. 

(2) Pipeline installation is generally manual installation, groove depth greater than 3m or pipe diameter greater than dn400mm pipe can be used non-metallic rope to hoist pipe in the groove. When the socket tube is installed, the socket should be in the direction of flow, and the direction of the bearing will be installed upstream and downstream. The length of the pipe can be cut by hand saw, but the section should be kept vertically flat and must not be damaged. The installation of small-caliber pipe can be used manpower, in the pipe end of the wooden bezel with a crowbar so that the installed pipe alignment axis into the bearing mouth. Pipes larger than dn400mm in diameter can make hand-propelled gourd and other tools, but not with construction machinery forced to push the top pipe in place. Pipeline interface to rubber ring interface is mostly, construction operation is simple, but should pay attention to the rubber ring cross-sectional type and sealing effect. Round rubber ring Sealing effect is not good, and deformation resistance is small and can prevent rolling of the special-shaped rubber ring sealing effect is better. The normal bonding interface is only suitable for tubing under dn110mm.

Rib winding Tubes must use special fittings and adhesives in the production plant to ensure the quality of the interface. 

(3) The connection between the pipeline and the inspection well should be flexible interface, which can be connected by a bearing intubation piece. Prefabricated concrete ring connection can also be used, the concrete ring in the inspection well wall, the ring between the inner wall and the pipe with rubber ring seal, forming a flexible connection. Cement mortar and pvc-u combination performance is not good, it is not appropriate to pipe or pipe fittings directly masonry in the inspection of the well wall. Intermediary layer approach can be used, that is, in the outer surface of the pvc-u tube evenly coated with a layer of plastic adhesives, followed by a layer of dry coarse sand on top, curing 20min after the formation of a rough surface of the intermediary layer, built into the inspection well can ensure a good combination with cement mortar.

For in pit ponds and soft soil areas, in order to reduce the uneven settlement of pipes and inspection wells, an effective way is to first use a short tube not less than 2m and the inspection well, and then connect with the whole long pipe, so that the inspection well and pipeline settlement difference to form a smooth transition. 

(4) Groove Backfill Flexible pipe is based on the joint work of the pipe soil to bear the load, Groove backfill material and backfill degree of compaction on the pipeline deformation and bearing capacity has a great impact. The larger the deformation modulus of backfill, the higher the compaction degree, the smaller the deformation of the pipe, the greater the bearing capacity, the design and construction should be carefully considered according to the specific conditions. Groove Backfill In addition to the general provisions of the pipeline works, but also in accordance with the characteristics of the pvc-u tube to take the corresponding necessary measures, the pipeline installation should be immediately backfill, should not be long stop and backfill. Backfill materials from the bottom of the tube to the 0.4m range above the top of the tube must be strictly controlled. Gravel chips, gravel, sand coarse sand or excavated good soil can be used. Pipeline is located under the roadway, and when laying the pavement, we should consider the impact of Groove backfill settlement on the pavement structure, the bottom of the pipe to the top 0.4m range of the pipe should be used medium, coarse sand or stone chip layered backfill compaction. In order to ensure the safety of the pipeline, the top of the pipe above the 0.4m range should not be compacted with tamping tools.

The compaction coefficient of backfill shall be greater than or equal to 95% from the bottom of the pipe to the top of the pipe; the range of 0.4m above the top of the pipe shall be greater than 80%; and the other parts should be greater than or equal to 90%. The rainy season construction should also pay attention to prevent grooves from standing 

(5) The tightness test after the installation of the pipeline may use closed water test or close test. The closed-closed test is simple and rapid, and can best fit the characteristics of the fast construction speed of pvc-u pipeline, but there is no test standard and special inspection equipment, which should be further studied. The tightness of the Pvc-u pipeline is better than that of the concrete pipe, and the good rubber ring interface can be completely non-leaking. Because of the Pvc-u pipeline closed water test of the allowable leakage is more stringent than the concrete pipeline, China has no specific provisions, the United States stipulates that per mm pipe diameter per km of pipe length of 24h leakage should not exceed 4.6 liters, can be used for reference.

A method of laying a dark setting. 

(1) In the case of a brick wall, for the branch pipe, it is advisable to open the tube groove on the brick wall, the pipe is directly embedded and the pipe card to secure the pipe in the tube groove. Pipe Groove width should be pipe outer diameter de+20mm, Groove deep tube outer diameter de, as long as the pipe does not reveal brick wall surface can be.

The groove pipe is as far as possible without pipe fittings, and the groove bending radius should satisfy the minimum bending radius of the pipe. 

(2) If it is a reinforced concrete shear wall, the branch should be laid on the wall surface, and the tube clamp fixed on the wall, to be constructed on the construction of the civil wall, with high-grade cement mortar, or with steel plate mesh wrapped in the outside of the pipeline (laying the local wall of the pipe or laying the entire wall of the pipe) with cement

Then attach decorative materials such as tiles to the outside.

(3) When laying in the ceiling, should deliberately bend the direction, and make a support frame. 

(4) In the case of a family of Yi Wei, three guards and crossing the living room, one way is to bury the pipe directly in the floor leveling layer (applicable only to DE20). The pipe buried in the leveling layer shall not have any connectors.

Or laid in a reinforced concrete floor, but must have a casing, and there are measures to prevent the flow into the casing when the coagulation is smashed.

(5) The riser shall be laid in a pipeline well. 

(6) The pipes in the kitchen should be laid behind the cabinets without having to be embedded in the wall. The dark riser should be made into a fixed support point at the crossing floor to prevent the cumulative expansion of the riser from generating displacement stress at the top of the upper branch pipe. The pipe of the riser de≤40mm, in addition to crossing the floor for the fixed support point, it is advisable to set up two support points in the middle of each layer, de≥50mm the riser, and set only one support point between the layers. The support point does not have to be set at equal distance, and it is hoped that a support point will be set at the three-pronged fittings of the riser. When the riser is arranged in a pipeline well, a fixed support point shall be set at the three-part fittings where the pipe is raised on the riser, and the intermediate support is still set according to the above principles.

All of the above dark pipes need to be after the test pressure without leakage in the case of civil construction.