With the development of China's urban construction, the gradual improvement of urban beautification standards, underground pipelines (water supply, sewage, rainwater, heating, cooling, steam, natural gas, etc.) and lines (power lines, lighting lines, communications, broadband, etc.) With the increase in laying, the location of pipelines on both sides of urban roads is becoming less and less.
The original steam pipes were laid on the ground overhead or underground pipe trenches, and now they are all buried underground. The cost of overhead laying is low, construction and maintenance are convenient, but it affects the beauty of the town. The trench construction is not only slow in construction, but also requires a wider and deeper line. The actual construction site will not meet the construction requirements. Therefore, the application of steam pipe steel sleeve steel directly buried insulation pipe has been popularized in the past decade. In the 1990s, the plastic (glass fiber reinforced plastic) steel-covered direct-buried insulation pipe has many water intrusion accidents in practical applications. Even if there is no major accident, the actual operation has a large temperature drop and high heat consumption, especially in summer. During the rainy season, the groundwater level is high, and some pipes have a heat loss of 30%. This is because the outer sheath of the steel sleeve or the FRP sleeve is different from the material of the steel tube (plate) in the fixed bracket, compensator, and drain tube. The condensate pipes, steamed pipes, sterns, tees, and variable diameters are difficult to handle in terms of design, construction, technology, acceptance, etc. The steel-covered steel direct-buried insulation pipes overcome the above shortcomings of the above laying methods, so the steam pipelines are adopted. The direct laying method of steel sleeve steel is the best way.
It is divided into two types: the inner sliding type and the outer sliding type, which are divided into two types: the inner sliding type and the outer sliding type. The working steel pipe of the steel sleeve steel directly buried heat insulating pipe and the heat insulating material are sliding through the drag reducing layer, and the heat insulating material is used. It is required to have a certain pressure resistance and a low cost. The specific requirements are as follows: body seamless steel pipe (GB8163-99), nominal diameter DM200mm or more adopts welding according to GB/T3091-93 or welded pipe conforming to SY/T5037-92 and meets the requirements of water pressure test of GB8163-99.
The molybdenum oxalic acid acupuncture blanket with high temperature resistance, anti-corrosion candle, and rapid heat resistance is used as the drag reduction layer, and is firmly integrated with the steel pipe.
Project performance index test basis or description Bulk density kg/m3) 110GB/T5480.3-1985 slag ball) 9.3GB/T5480.5-1985 tensile strength MPa) 0.06GB/T17911.5-1999 heating line shrinkage 1999 Thermal conductivity project unit performance index test method density kg/m3180~200GB10699-89 thermal conductivity W/m-3, inorganic thermal insulation layer using microporous calcium silicate shell (or hydrophobic composite silicate shell) Wrapped outside the drag reducing layer, the core tube has a sliding space.
The device is cast with a rigid polyurethane foam filled between the inorganic insulation layer and the outer protective tube.
(The steel casing is welded according to GB/T3090-93 or welded according to SY/T5037-92, and 100% water pressure test is carried out at 0.6 MPa.
The outer casing of the steel casing is made of epoxy coal tar pitch cold-wrapped or glass-reinforced steel.
The working steel pipe and the heat insulating material of the steel sleeve steel directly buried heat insulating pipe are integrated, and are slid by a sliding bracket (supporting) between the working steel pipe and the outer steel pipe. The mechanical structure is simple, and an air layer (vacuum layer) can be left between the heat insulating material and the outer sleeve, and the gas permeability is good. The sliding structure is more demanding and the cost is higher. The specific requirements are as follows: body seamless steel pipe (GB8163-99), nominal diameter DM200mm or more adopts welding according to GB/T3091-93 or welded pipe conforming to SY/T5037-92 and meets the requirements of water pressure test of GB8163-99.
The molybdenum silicate thermal insulation tube (or centrifugal glass wool) is used, and the staggered layer is layered on the steel pipe, and is integrated with the steel pipe, and the thickness thereof is determined according to engineering design parameters.
The high-temperature and high-strength material PTFE is used to effectively avoid the -28-heat-free bridge and has reliable guiding properties.
Pipe or SY/T5037-92 welded pipe, and 100% hydraulic test of 0.6MPa.
The outer casing of the steel casing is made of epoxy coal tar pitch cold-wrapped or glass-reinforced steel.
At present, the general polyurethane foam has the thermal conductivity, compressive strength and water absorption rate basically meet the requirements, but the temperature resistance unit unit performance index test method density kg/m360~80GB6342-86 compressive strength MPa>0.2GB8813-88 water absorption rate normal temperature, 96h Test item name Unit of measurement Test result Fiber diameter (um) / 6 slag ball content / 0.001 Bulk density kg / m324-27 Thermal conductivity W / m - K0.035 Thermal load shrinkage temperature - 120-400 low, to make the temperature The gradient reaches its allowable temperature and requires a thicker inorganic insulation layer. The performance requirements are as follows: - the thermal conductivity of the i-th insulating material at the operating temperature; ti - the outer surface temperature of the i-th insulating material (C), determined according to the design requirements; § the thickness of the i-th insulating layer (m).
3. According to the model of the outer steel pipe sold in the market, determine the thickness and check the calculation.
Fourth, the application of anti-corrosion materials (A), FRP: performance requirements are as follows: 4, centrifugal glass wool external sliding material performance requirements are as follows: project unit index remarks (standard 78 tensile strength MPa> 78 maximum use temperature 100C serial number project unit Requires 1 baseband width mm125±5/250±10/400±152 baseband tensile strength N/cm>123 setting gel drying time 164 anti-corrosion layer appearance black light, surface smooth, tight bonding 5 anti-corrosion layer thickness mm>0.46 Spark leak detection kV2.5, no leakage point 7 adhesion 180° peeling) N/cm20, no peeling 8 impact resistance 1kg punch) cm50, through (2), the thickness of the multi-layer insulation material is usually calculated according to the interface temperature Control, the calculation formula is as follows: 1, the thickness of the first layer of insulation material should be calculated according to the following formula: into i - the thermal conductivity of the first layer of insulation material at operating temperature; ti - the outer surface temperature of the first layer of insulation material (C ), determined according to design requirements; § thickness of the first insulation layer (m).
2. The thickness of the i-th layer insulation material shall be calculated according to the following formula: (2) The performance requirements of the epoxy coal tar pitch cold-wrap belt are as follows: 5. The production process of the fixed bracket is as follows: 1. Put the asbestos rubber ring on the working steel pipe and the outside. Ring and compact; 4, the outer sleeve is sleeved on the other side of the outer ring and welded.
(1) Schematic diagram of the production of the inner fixed bracket: (2) The outer fixed bracket can not be used to eliminate the push or when there are special requirements, the outer fixed bracket can be used.
1. When the insulation pipe is used in the project, the design unit should also add the following technical measures to achieve the purpose of safety and economic operation. When the insulation pipe section is connected, the core pipe must be in accordance with the industrial metal pipe engineering construction and acceptance specifications, and the welding 100 light is adopted. Film or ultrasonic flaw detection, the outer protective tube is tested for strength and airtightness according to the regulations to achieve the overall strength of the pipe with high strength, good sealing, waterproof and anti-leakage. After the outer tube is welded -30-intensity airtight test, the exposed part must be treated with the same anti-corrosion treatment as the mother. The sacrificial anode protection measures commonly used at home and abroad make the service life of the anti-corrosion layer for 30 years. A drain should be provided near the fixed support of the pipeline to discharge the condensate even to the ground safety or condensate line. A venting pipe is arranged on the outer pipe of the appropriate pipe section of the pipeline (generally two sections of the fixed bearing) with a small displacement to eliminate the moisture in the pipe and the signal tube which also serves as a fault.
The thermal compensation of the pipeline should be based on high-quality balanced or axial bellows compensators and natural compensation, and they should be installed in the outer casing that can be freely moved by them, without the need for a pipeline well. Limiting the displacement of the compensator should design the fixed bearing and provide the thrust value and the setting position. The fixed support adopts the internal fixed support, and the external fixed support is used when there are special requirements.
2. The hoisting and transportation of the insulation pipe should be noted that the site of the insulation pipe should be leveled and free of debris such as gravel; the ground should have sufficient carrying capacity to ensure that no collapse and dumping accidents occur after stacking; Drainage and drainage are not allowed in the site; the stacking height should not be greater than 16m and 2m away from the heat source, and there should be fire-fighting measures; the two sides of the working tube of the steam-insulated pipe should be installed with protective plugging, and should be covered with tarpaulin when stored in open air; 3. When loading and unloading the insulation pipe, it should be noted that the hook is hooked on the earring or the sling with a width of more than 50mm is bundled on the outer casing for loading and unloading. It is strictly forbidden to directly attach and detach the steel wire rope to the outer anti-corrosion layer to damage the anti-corrosion layer. It should be lightly lifted to prevent bumping and it is strictly forbidden to drag on the ground.
Carefully read the design engineering drawings and construction instructions provided by the design institute; receive and inspect all the insulation pipes to be installed. According to the design drawings, the line is laid and excavated; the ground pipe drawing provided by the supplier is arranged to check the marking line of all the insulated pipe fittings (usually the earrings are marked upwards with the hanging earrings); the welding work steel pipe and its accessories are pressed and pressed It is stipulated that the 100% X-ray film shall pass the second-level inspection; the hydraulic pressure test shall be carried out according to the regulations (segmentable execution); the temporary support iron for pre-tensioning of the bellows compensator, the supporting iron for the straight pipe section, the sealing plate at the hoe head, etc. shall be removed. When cutting, cut 12cm away from the working steel pipe, and cut the cutting head outwards, so as not to accidentally cut to the working steel (turn down to page 41). The CPU load of the PLC is not heavy. When the budget is tight, 3-4 boilers can share a CPU. By expanding the rack to meet the number of modules. 3. The optimal oxygen content decreases with the increase of boiler output during boiler operation. The optimal oxygen content is a function of boiler load. In practical applications, the oxygen calibration procedure can be added for the design of the air supply control system. The effect is more ideal.
(Finish)
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