As a professional engineer, in terms of PE pipe construction, you must be very clear about the construction process. Here we will share the PE pipe construction technology. This article mainly describes the rest part of the construction process: accessory installation, pipeline water pressure test and backfilling of pipe grooves.
Construction Plan and Technical Measures
Construction Plan and Technical Measures Previous article we introduce the PE Pipe Construction Technology - Part 1, here we will introduce the rest part 2.
7. Accessory Installation
Before installing gate valves and butterfly valves, check the packing. The glands and bolts should have sufficient adjustment margin. The operating machinery and rotating devices should be adjusted as necessary to make them moving flexibly, indicating accurate and checking the design requirements for correctness and clean up. It should be no debris. The gate valve should be installed horizontally. Large-diameter gaskets should be installed in a labyrinth form when splicing is required. Oblique lap joints or flat joints must not be used.
(a) The sealing surface of the flange and the gasket should be visually inspected. It must be no defects that affect the sealing performance;
(b) The end face of the flange should be kept flat. The gap error between the two flanges should not be greater than 2mm. And the method of tightening bolts should not be used to eliminate skew;
(c) The flange connection should be kept coaxial. The deviation of the bolt hole center should not exceed 5% of the hole diameter. And the free access of the bolts should be ensured;
(d) The bolts should use the same specifications. The installation direction should be the same. The bolts should be tightened symmetrically. And the fastened bolts should be exposed out of the nut by 2-3 buckles;
(e) It is strictly forbidden to use the method of tightening the flange bolts first, and then welding the flange plate welds.
8. Pipeline Water Pressure Test
After the pipeline installation is completed, strength and tightness tests should be carried out.
Water supply pipeline test
In order to ensure the safety of the water pressure test of the water supply pipeline, the following work should be done:
Preparations before the test
(1) Back Installation
According to the total jacking force, a section of trench is reserved without digging as the back (poor soil or low-lying areas can be used as artificial back). The supporting area of the back wall should be determined according to the soil quality and test pressure. Generally, the soil quality can be considered at a pressure of 15t/㎡. The back wall should be perpendicular to the centerline of the pipe, and a row of stilts should be placed horizontally against the back wall. It should be no gap between the back and the stilts. If there is a gap, it should be filled with sand. In front of the crossbar, place 3 to 4 larger beams or top irons upright, and then use jacks to support them firmly. The jack used for pressure test must be supported stably, upright and firm. To prevent accidents due to eccentric compression. The use of leaking jacks is strictly prohibited. During pressure test, if the back is found to move significantly, the pressure should be reduced immediately for maintenance. And the maintenance under pressure is strictly prohibited. Before the pressure test of the pipeline, in addition to the top support, soil should be used to backfill more than 1/2 pipe diameter on both sides of the middle of each pipe. The support piers should be set at the elbow and the tee of the branch line to prevent the pipe from shifting during the pressure test. To do this is in order to avoid an accident.
According to the longitudinal section of the pipe, an exhaust valve should be installed at any high point to meet the requirements of exhaust during water filling. The pipe plugs at both ends should have upper and lower holes. The upper hole is used for exhaust and pressure test to install a pressure gauge, and the lower hole is used for water intake and drainage. Exhaust work is very important. If the exhaust is poor, it is neither safe nor easy to ensure the pressure test effect. It must be noted that the high-pressure pump used must not be installed directly in front of the pipe block to prevent accidents.
Pressure Test Includes:
Relevant Regulations for Pressure Test: The length of the pipeline segment pressure test is generally not more than 1000m. The test pressure is 1.1Mpa according to the design requirements.
Pressure Test: The back and pipe plugs at both ends of the pressure test section must be particularly cautious when the interface is stressed for the first time. Full-time personnel should monitor the working conditions of the pipe plugs at both ends and the back. In addition, there must be a person to contact back and forth. In order to stop the pressurization and treatment in time when the problem is found, and ensure the safety of the pressure test. The pressure should be gradually increased during pressure test. The pressure should not be too high at one time to avoid accidents. After each pressure increase, observe and check immediately. After no problems are found, continue to increase the pressure and gradually increase to the specified test pressure. If the interface leaks during the pressurization process, immediately reduce the pressure and repair it and ensure safety.
9. Backfilling of Pipe Grooves
After the pipeline is installed, pipeline foundation is completed and the well chamber mortar strength reaches 70% of the design mark, the pipeline backfilling should be carried out. Backfilling is carried out in two steps. First fill in the 0.5m on both sides and the top of the pipe, leave the joints. Then do the hydraulic test. After the test and the pipeline installation meet the requirements, fill the rest. Backfilling should be symmetrical and layered, each layer is about 30cm, compact as required to prevent displacement, and measure the degree of compaction layer by layer.