Buried polyurethane foamed insulating steel pipe has the advantage of thermal transmission pipeline. Heating system is an important part of public municipal system. According to the different requirements and uses of construction projects, there are many heating modes: low pressure steam heating, high pressure steam heating, low temperature water heating, high pressure water heating and waste heat heating.
At present, low-temperature water heating is widely used, because it can save 20-30% energy than steam. Heating system is composed of leading pipe, conduit, riser and radiator, valve, gas collecting tank, expansion water tank, decontaminator, pressure reducer and balance valve.
Outdoor heating pipeline is usually divided into primary heating pipeline and secondary heating pipeline. The pressure of primary heating pipeline is less than or equal to 1.6 MPa, the temperature of hot water is not more than 150 degrees, the pressure of secondary heating pipeline is less than or equal to 1.2 MPa, and the temperature of hot water is not more than 100 degrees. Installation of outdoor heating pipeline includes direct buried pipeline or overhead pipeline engineering.
II. Material and Tool Requirements
(1) Pipe material: Carbon steel pipe, seamless steel pipe. Pipe should not be bent; rust, no spur, heavy skin and uneven phenomenon.
(2) Pipe fittings: unbiased buckle, square buckle, random buckle, broken wire, no sand hole, crack and angle inaccuracy.
(3) Valves: specifications, models and applicable temperature, pressure in line with the design requirements. Foundry rules, no burrs, no cracks, flexible and tight switch, no damage to the thread, straightness and angle is correct, no damage to the handwheel. The strength and tightness test shall be carried out before installation with the factory certificate.
(4) Accessory devices: pressure reducers, traps, filters, compensators, flanges, etc. meet the design requirements, and should have product certificates and specifications.
(5) Other materials: section steel, round steel, pipe clips, bolts, nuts, oil, hemp, cushions, electric welding rods, etc. The selection should meet the design requirements.
(6) Machinery: grinding wheel saw, wire sleeve machine, drill, welding machine, bender, etc.
(7) Tools: pressure cases, bench vises, welding tools, pipe pliers, hammers, hand saws, flexible wrenches, etc.
(8) Others: steel tape, horizontal ruler, line drop, chalk, small line, etc.
3. Outdoor Pipeline Installation:
(1) To install directly buried pipelines, it is necessary to leveling and tamping the bottom of the trench, laying the position along the pipeline without any debris, and checking the width of the trench and the elevation of the trench bottom.
(2) Installation of trunk pipes in trenches shall be carried out after the trenches have been built and before the cover plate of the trenches has been covered, after the support crane frame has been installed.
(3) Installation of overhead trunk pipes should be carried out after scaffolding and stable installation of pipeline brackets.
4. Construction process and operation method
(1) Installation process of directly buried insulating pipe
Correction Welding of Lifting Pipeline for Placing Positioning Pipeline
Hydraulic Pressure Test of Weld Repair and Flaw Detection Test
Trial Operation of Installation and Heating of Weld Joint Corrosion and Insulation Compensator
5. Notices for Installation of Heating Pipeline
(1) Before the pipeline goes down the ditch, the elevation of the ditch bottom and the width of the ditch should be checked to meet the design requirements. The insulating pipe should check whether the insulating layer is damaged or not. If there is local damage, the damaged part should be put on it and marked well to facilitate unified repair.
(2) Pipeline should be welded sectionally outside the groove to reduce fixed weld joints. The length of each section is generally 25-35m. No one should stand in the ditch when the pipe is laid down. When the pipe is laid down by mechanical or manual means, the pipe should be slowly and straight underground into the ditch, and the pipe should not be bent.
(3) Pipeline welding in ditches must be cleaned and straightened before joining, and operation pits should be excavated at the welding site, which is easy for welding operation.
(4) Valves, fittings, compensator brackets, etc. shall be pre-positioned along the ditch edge in accordance with construction requirements before construction and installed before pressure test;
(5) Pipeline water pressure test shall comply with the design requirements and specifications, go through the procedure of hidden inspection and pressure test, and after passing the inspection, drain the water and flush the pipeline;
(6) pipeline anticorrosion should be centralized in advance. The distance between the ends of the pipeline should be set aside, and the anticorrosion of the welded door should be retreated after the test pressure. The polyurethane foam insulation pipe is tightly bonded to the outer skin of the steel pipe because of the rigid polyurethane foam insulation layer, which can prevent the infiltration of air and water, and can play a good anti-corrosion role. At the same time, its foaming holes are closed and its water absorption is very small. High density polyethylene shell and FRP shell have good anti-corrosion, insulation and mechanical properties. Therefore, the outer skin of the working steel pipe is very difficult to be eroded by the outside air and water. As long as the internal water quality of the pipeline is well treated, according to foreign information, the service life of the high temperature prefabricated directly buried insulation pipe can reach more than 50 years, which occupies less land and is faster than the traditional trench laying and overhead laying, and is conducive to environmental protection.
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