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Requirements for polyethylene pipe laying

一、General Instructions

7 西藏拉萨市供暖工程项目
(一)、The earthwork construction of polyethylene pipeline and steel frame polyethylene composite pipeline shall comply with the relevant provisions of the current national standard “Urban Gas Transmission and Distribution Engineering Construction and Acceptance Code” CJJ33.
(二)、When the polyethylene pipe is laid, the allowable bending radius of the pipe should not be less than 25 times the nominal diameter; When there is a socket fitting on the bent pipe section, the allowable bending radius of the pipe shall not be less than 125 times the nominal diameter.
(三)、When steel frame polyethylene composite pipe is laid, the allowable bending radius of steel mesh frame polyethylene composite pipe shall comply with the provisions in the following table, and the allowable bending radius of steel mesh belt polyethylene composite pipe shall comply with the provisions in the following table.
Wire mesh skeleton polyethylene composite pipe

二、

DN Allows bending radius
50≤DN≤150 80DN
150<DN≤300 100DN
300<DN≤500 110DN

mm Nominal diameter of pipe DN Allowable bending radius

nominal diameter of the pipeline is DN Allowable bend radius 
50≤DN≤110 150DN
140<DN≤250 250DN
DN≥315 350DN

(四)、When the pipeline is constructed in an area with high groundwater level or during the rainy season, the water level should be reduced or drainage measures should be taken to clear the water in the ditch in time. It is strictly prohibited to backfill the pipeline in floating state.
二、 The pipeline is buried and laid
(一)、 For trench laying pipelines (excluding the buried laying of feeding pipe method), the pipelines should be laid only after the trench bottom elevation and pipe base quality inspection is qualified.
(二)、 When piping down, do not use metal materials to directly bind and lift the pipe, and prevent the pipe from being scratched, twisted or subjected to excessive stretching and bending.
(三)、 Polyethylene pipe should be laid in meandering shape, and can be laid with the terrain bending; Steel frame polyethylene composite pipe should be laid in a natural straight line. The bending radius of the pipe shall comply with the provisions of this code. No mechanical or heating method shall be used to bend the pipe.
(四)、The horizontal and vertical clearances between pipelines and buildings, structures or adjacent pipelines shall conform to the provisions of this Code.
(五)、The minimum covering thickness of pipe buried shall comply with the provisions of Article 4.3.3 of this procedure.
(六)、When laying pipelines, metal tracer lines (belts), warning belts or other marks should be buried along the pipelines.

The tracer line (belt) shall be laid with pipe, and shall have good conductivity, effective electrical connection and signal source well.

The warning belt shall be laid in accordance with the following provisions:
1. The warning belt should be laid 300 ~ 500mm above the top of the pipe, but should not be laid in the roadbed or road;

2, for the diameter of the pipeline is not greater than 400mm, a warning belt can be laid above the pipeline; For the pipe with diameter greater than 400mm, two warning belts with horizontal net distance of 100 ~ 200mm should be laid parallel above the pipe;

3. The warning belt should be made of polyethylene or material that is not easy to decompose. The color should be yellow, and the warning belt should be printed with eye-catching and permanent warning words.

(seven), polyethylene coil or due to the construction conditions of polyethylene straight pipe or steel skeleton polyethylene composite pipe by the tow pipe method buried in the ground laying, in the pipeline dragging process, the bottom of the ditch should not damage the pipe surface stones and sharp objects, drag length should not exceed 300m.

(8) When the polyethylene coil is buried and laid by the feeding pipe method, the warning belt shall conform to the provisions of this code and be fed into the pipe groove together with the pipe. The bending radius of the pipe shall conform to the provisions of this code.

Three, pipe laying

(1) The section is suitable for the pipe laying method with the outer diameter of the pipe not greater than 90% of the inner diameter of the old pipe.

(II) A working pit shall be excavated at the start and end of the insertion, the length of which shall meet the construction requirements, and the allowable bending radius of the pipeline shall be ensured in accordance with the provisions of Article 6.1.3 of this procedure. The distance between the working pits shall not exceed 300m.

(3) Before the pipe is inserted, pigging equipment should be used to remove the sediment, sharp burrs, welding tumors and other debris on the inner wall of the old pipe, and compressed air should be used to blow the debris in the pipe. When necessary, the inner wall of the old pipe should be checked by pipe endoscope, or the polyethylene pipe section should be pulled over the old pipe, and the inner wall of the old pipe should be judged by checking the surface scratches of the polyethylene pipe section.

(4) The pipelines inserted and laid shall be connected by hot melt or electric melt according to the requirements of this code. If necessary, the flanging of hot melt butt connection or the binding post of electric melt connection shall be cut out.

(5) Before the pipeline is inserted, all welding joints of the connected pipeline shall be inspected one by one, and after the safety protection measures are effectively guaranteed, leakage detection shall be carried out, and the construction shall be qualified only. After insertion, the insertion pipe shall be tested for strength and tightness along with the piping system.

(6) When inserting and laying, a funnel-shaped guide slip with less hardness must be installed at the old pipe insertion port.

(7) When the insertion pipe is laid by dragging method, the dragging force shall comply with the provisions of Article 6.2.7 of this procedure.

(8) The length of the insert pipe extending out of the old pipe port should be able to meet the requirements of pipe reduction recovery, pipe shrinkage and pipe connection.

(9) Between the two insertion sections, it is necessary to set aside the allowance of cold shrinkage and uneven settlement of the pipeline, and riveted or fixed at the appropriate length of each section. At the end of each pipe section, the annular space between the inserted pipe and the old pipe shall be sealed with flexible materials. Old pipe openings between pipe segments should be protected by casing.

(10) When connecting the branch pipe on the inserted pipe, it can only be carried out after the main pipe recovers the diameter reduction and relaxes for 24 hours.

Four, pipeline crossing

(1) The time limit and procedure for laying pipelines across railways, roads, rivers and other pipelines and trenches as well as the construction organization plan shall be approved by the relevant administrative departments and conform to the relevant provisions of these procedures.

(2) During the construction of pipeline crossing, it is necessary to ensure that no subsidence, displacement or damage occurs to the buildings and structures around the crossing section.

(3) When the pipeline crosses, the drag force borne by the pipeline shall comply with the provisions of Article 6.2.7 of this procedure.

 


Post time: Dec-12-2022