HDPE polyethylene pipe construction technology

1. Preparation for construction

1. The design drawings and other technical documents are complete and approved by the meeting.

2. The construction personnel are trained and familiar with the general performance of PE water pipes, and master the connection technology and operation points of the pipes.

3. Temporary facilities such as construction tools, construction site, construction water, electricity, and material storage can meet the construction requirements.

4. Before installing the PE piping system, carefully check the appearance and the tolerance of the fittings, and it is necessary to eliminate the dirt and sundries inside and outside the pipes and fittings.

5. When the temperature difference between the construction site and the material storage is large, the pipes and fittings should be placed on the site for a certain period of time before installation, so that the temperature is close to the ambient temperature of the construction.
Second, the construction process to prepare earthwork construction pipeline pressure test and flushing duct disposed acceptance
Third, the construction technology 1, earthwork

(1) Measurement 1) Measurement PE water supply line pipework comprising measuring alignment, leveling and direct measurement.

2) For alignment measurement, the center line and corner of the pipeline should be measured, and the positional relationship between the pipeline and the adjacent permanent building should be measured. If necessary, a mark should be set up on the ground, and the measurement accuracy should be +n(s). . n is the number of measuring stations. The distance between the pipeline and the building is shown in the following table: Distance between water supply pipeline and building structure and other pipelines (m) Structure pipeline railway building red line street tree center electric pole cable gas pipe heating pipe sewage pipe minimum horizontal distance 5 5 1.5 1.0 1.0 1.0~2.0 1.5 1.5
3) When performing pipeline leveling, temporary benchmarking points should be set along the line and connected with a fixed benchmarking point with a leveling wire. The accuracy of the fixed benchmarking point should not be lower than Grade 4, and the closure of the benchmarking point is poor. : +12k (mm), k is the horizontal distance between the benchmark points, the unit is km. Allowable deviation of direct measurement distance measurement serial number Fixed measurement distance (m) Allowable deviation 1<200 2=”” 3=”” 500=”” 5000=”” 10000=””>500 1/2000
(2), groove Excavation 1) When grooving in an area without groundwater, if the ditch depth does not exceed the regulations, the side slope may not be provided on the ditch wall. Filled sand and gravel soil 1m sub-sandy sub-contained soil 1.

2) When excavating trenches under the condition of no groundwater and uniform natural temperature structure in the soil, if the depth of the trench exceeds the specifications in the above table, but within 5m, the maximum allowable slope of the trench wall should meet the requirements in the following table. Soil category name Ditch side slope manually excavated and thrown the soil on the side of the ditch Mechanical digging at the bottom of the ditch digging at the bottom of the ditch Clay 1:10 1:0.75 1:10 Sub-sand 1:0.67 1:0.50 1 ：0.75 Sub-stained soil 1:0.50 1:0.33 1:0.75 Soiled 1:0.33 1:0.25 1:0.67 Gravel, pebble soil 1:0.07 1:0.50 1:0.75 Peatstone, chalk soil 1:0.33 1:0.25 1:0.67 Dry loess 1:0.25 1:0.10 1:0.33 Note: ①When the workers are digging the soil away at any time, the slope of the mechanical digging can be used. ②Sand soil in the table includes fine sand and silt sand, and dry loess does not include it. ③Soil and materials should not be piled up within 0.8m from the side of the ditch. 3) When excavating trenches in the backfill section or during rainy season construction, the side slope may be enlarged as appropriate or other corresponding measures may not be required to ensure that the trench does not collapse. When constructing in areas with high groundwater level, measures to lower the water level or drainage should be taken. The choice of method should be determined according to conditions such as hydrogeological conditions and trench depth: the accumulated water in the trench should be drained in time, and the length of the trench should not be allowed. Time is stagnant. 4) The vertical wall of the trench with a depth of less than 5m can also be reinforced with appropriate support types as specified in the following table. The condition of the soil The depth of the trench (m) Supporting type of clay soil with natural moisture, with very little groundwater 3 Disconnected clay soil with natural moisture support, with little groundwater 3.5 Continuous support for loose and high-humidity soil, with a lot of groundwater And there is a danger of taking away soil particles. If the groundwater reduction method is not adopted, it can be supported by slab pillars.
5) The width of the grooved bottom of the pipe should not be less than 0.5m outside the pipe, and the total width should not be less than 0.7m. 6) When excavating trenches, the undisturbed soil with a design elevation of +0.3-0.3 m at the bottom of the trench should be retained, disturbances are prohibited, and manual cleaning before laying pipes, but it is generally not advisable to dig below the design elevation of the trench bottom, such as local over-excavation , It needs to be filled with sand or qualified original soil and compacted in layers, and the bottom of the final trench is required to be flat, dense and free of hard substances.

① When the groove is rock, it should be removed to no less than 0.15m below the design elevation, and the excavated part should be backfilled with fine sand or fine soil, and the thickness should not be less than 0.15m; when the original soil is salt, it should be laid with fine sand or Fine soil.

②When the soil quality of the bottom of the trench is extremely poor, the trench can be dug deeper, and then fill the bottom of the deep pipe with sand and submerge it with water and then remove the water (water flooding method), so that the bottom of the pipe has sufficient support force.

③For areas that may cause uneven settlement of the pipeline, the foundation should be treated and other anti-settlement measures can be taken.

7) Drinking water pipelines are strictly prohibited to pass directly through pits, toilets and graves that can cause pollution. If such situations are discovered during trench excavation, they should be dealt with in coordination with relevant departments such as design and sanitation.

3) Backfilling

1) Backfilling after installation and laying of the pipeline. The time for backfilling should be at the lowest temperature in a day and night. The backfill soil on both sides of the pipeline and within 0.5m above the pipe top shall not contain gravel, bricks, or frozen soil. Blocks and other miscellaneous hard objects.

2) The backfill should be compacted in layers. The height of the backfill should be 0.1~0.15m. First, use fine sand or fine soil to backfill both sides of the pipe. After manual compaction, backfill the second layer until it reaches 0.5m above the top of the pipe. The support of the trough should be removed in the order of backfilling under the condition of ensuring construction safety. After the vertical slab is removed, the gap should be filled with sand.

3) Before the pipeline or pressure test, the height of the backfill soil above the top of the pipe should not be less than 0.5m, and the pipe joint cannot be backfilled within 0.2m, so as to observe the accident situation during the pressure test.

4) Large-area backfilling after the pipeline has passed the pressure test should be carried out when the pipeline is full of water. After the pipeline is laid, it is not advisable to stay in the empty pipe state for a long time. A small amount of stones with a diameter of not more than 0.1m are allowed in the backfill above 0.5m from the top of the pipe. When using mechanical backfilling, backfill from both sides of the pipe at the same time, and the machine must not drive over the pipe.

5) The depth of the backfill should be checked in layers, and the density of each part of the trench should meet the following requirements:

①The chest cavity should be filled with 90% soil. 95% of the trenches and 90% of the cultivated land

2. Pipeline connection (1) General regulations

① Polyethylene water supply pipe fittings and pipes may cause deformation and deterioration of pipes and pipe fittings due to transportation, loading, unloading, stacking or lax covering or long storage, and the appearance should be performed before connecting. Quality inspection is necessary.

②The connection application of polyethylene water supply pipeline adopts electric fusion connection (electric fusion socket connection) and hot fusion connection (hot fusion butt connection, hot fusion socket connection, hot fusion saddle connection). Threaded connection and bonding are not allowed. Polyethylene pipes must be connected with metal pipes and valves using steel-plastic transition joints.

③There should be corresponding special connection tools for different connection types of polyethylene water supply pipes. When connecting, do not use an open flame for heating.

④When the polyethylene water supply pipeline is connected by hot-melt welding, pipes and fittings of the same brand and material are used. The connection between pipes and pipes or pipe fittings of different grades and materials with similar performance shall be carried out after testing to determine that the connection quality can be guaranteed.

⑤When polyethylene pipes are connected by electrofusion, PE pipes and fittings produced with different materials and melt indexes can be welded.

⑥Before joining operators of polyethylene water supply pipelines, they should undergo special training and pass the examination and technical evaluation before they can take up their jobs.

⑦When the temperature difference between the storage of polyethylene water supply pipes and fittings and the construction site is large, the pipes and fittings should be placed on the construction site for a period of time. Make the temperature close to the temperature of the construction site.

⑧When connecting polyethylene water supply pipes, the pipe ends should be clean. The nozzle should be temporarily blocked every time work is closed.

⑨After the connection of the polyethylene water supply pipeline is completed, the appearance quality of the joint should be inspected. The unqualified person must rework and re-check the quality of the joint outside.

(2) Electrofusion connection

①Electrofusion connection equipment and electrofusion pipe fittings should meet the standards. When connecting, the voltage and heating time of the power supply should comply with the regulations of the electrofusion pipe fittings manufacturer, and they should be provided according to the voltage and current intensity used and the characteristics of the power supply. Corresponding electrical protection measures.

② During the cooling of the electrofusion connection, do not move the connector or apply any external force on the connection.

③The electrofusion socket connection should also meet the following requirements: i. The connection end of the electrofusion socket connection pipe should be cut vertically, and the dirt on the pipe and fittings should be wiped with a clean cotton cloth, and the insertion depth should be marked and removed. Its epidermis. ii. Before the electrofusion socket connection, the two corresponding parts to be connected should be straightened so that they are on the same axis.

④The electric fusion saddle connection should also meet the following requirements: i. The lower part of the main pipe connection should be supported by a special bracket, fixed and anastomosed. . ii. When connecting the electric fusion saddle, clean the dirt on the connecting surface with a clean cotton cloth, and use a scraper to scrape off the outer skin of the connecting part of the dry pipe.

(3) Hot-melt connection

① Before and after the hot-melt connection, the dirt on the heating surface of the connecting tool should be wiped off with a clean cotton cloth.

②The hot melt butt connection is generally divided into five stages: preheating stage, heat absorption stage, heating plate removal stage, docking stage, and cooling stage. The heating temperature and the pressure and time required for each stage should comply with the regulations of the pipe and fitting manufacturer of the hot-melt connection machine manufacturer. During butt welding by hot melt, the pipes or fittings are required to have the same melt index, and it is best to have the same SDR value. In addition, when pipe fittings from different manufacturers are used, a reasonable welding machine must be selected to achieve the best welding effect.

③The holding pressure and cooling time of hot-melt connection shall comply with the regulations of the hot-melt connection tool manufacturer and the pipe fitting and pipe manufacturer. During the guarantee and cooling period, the connection piece shall not be moved or external force shall be applied to the connection piece.

④The hot-melt butt connection shall meet the following requirements: i. Before butt connection, each of the two pipe sections shall extend a certain free length of the clamp, and the two corresponding connecting pieces shall be aligned so that they are on the same axis, and the wrong side should not be larger than the wall thickness. 10%. ii. The dirt on the connecting surface of pipes or pipe fittings should be wiped with clean cotton cloth, and the connecting surface should be milled to make it perpendicular to the axis and make it coincide with the special connecting section of the corresponding object. iii. The end face of the connection is heated with the butt connection tool, and the flat electric heating mold has a constant temperature of 2100C~2000C. iv. After heating, the connecting parts should be quickly separated from the butt-connected heating tool and apply uniform external force to make full contact and form uniformity. Keep the pressure and let the interface cool to about 400C to relieve the pressure. v. The automatic welding machine can automatically control the connection process.

⑤The hot-melt socket connection should meet the following requirements: i. The connecting end of the hot-melt socket connection pipe should be cut vertically, and clean cotton cloth should be used to clean the dirt on the connecting surface of the pipe and pipe fittings, mark the insertion depth, and scrape it off. epidermis. ii. Before the socket connection, the two corresponding parts to be connected should be straightened so that they are on the same axis.