Classification of cold insulation materials: the installation and use temperature of cold insulation materials can be divided into normal temperature anti-condensation insulation materials and ultra-low temperature insulation materials. Generally, the central air-conditioning pipes are made of cold insulation materials at room temperature, and the insulation materials of air-conditioning ducts mainly include glass wool board, plastic board and polyethylene foam insulation board. The ventilation pipe of central air conditioning adopts rubber-plastic insulation pipe, polyurethane insulation pipe and polyethylene foam insulation pipe, and the pipe bracket adopts polyethylene pipe bracket, wood bracket, polyurethane pipe bracket and low-temperature adhesive. Ultra-low temperature pipeline is used in liquid nitrogen medium insulation engineering and gas storage system cold insulation engineering. The main cold insulation materials used are polyethylene foam cold insulation shell, polyurethane foam cold insulation shell, polyurethane pipe support and other series of cold insulation materials.
Usage standard of cold insulation materials: thermal conductivity is the main criterion to determine the performance of materials, followed by oxidation index is one of the criteria to ensure flame retardancy, and density is the criterion to determine the life and cold insulation effect of cold insulation materials. The thermal conductivity of glass wool is w/m.k 0.049-0.042 0.045-0.032 GB/t13350-2000, that of rubber-plastic thermal insulation material is 0.034w/mk, that of polyethylene foamed thermal insulation pipe is 0.028-0.032w/mk, and polyurethane foamed thermal insulation pipe is adopted. The best flame retardant is B 1 grade.
Installation requirements of cold insulation materials: The sealing effect and bonding performance should be considered when installing cold insulation materials in pipelines. The external protection material of the pipeline is aluminum skin, and the sealing material of the pipeline is daub or sealant and moisture-proof layer. Polyurethane pipe bracket and polyethylene foam pipe have good waterproof and dewproof properties in ultra-low temperature environment. LNG is mainly used to build storage tanks, and large-scale low-temperature storage tanks are rarely built. The cryogenic storage tank we usually refer to is a vertical cylindrical cryogenic storage tank with a nominal volume greater than or equal to l0000m and a design temperature not higher than -45℃ and not lower than-168℃. Low temperature steel has very strict requirements on the main installation process, especially on the construction process and installation sequence. Crude oil storage tanks are mainly used for the construction of storage tanks, and large-scale low-temperature storage tanks are rarely built. The cryogenic storage tank is a vertical cylindrical cryogenic storage tank with a nominal volume greater than or equal to10000m and a design temperature not higher than -45℃ and not lower than-168℃. Low temperature steel has very strict requirements on the main installation process, especially on the construction process and installation sequence.
Acceptance monitoring of cold insulation materials: 1, with weld distribution map attached. 2. Weld appearance inspection shall be spot-checked by 10%, and NDT shall be inspected by 100% (NDT records and reports shall be inspected). The third-party testing platform for cold insulation materials is used for reliability testing, performance evaluation, aging testing, composition analysis and formula reduction of composite materials. Can test and analyze all kinds of composite materials and issue third-party test reports.
Life and anticorrosion of cold insulation materials: The design life of cold insulation materials is 60 years. First, the requirements for pipeline cold preservation material anticorrosion, pipeline external anticorrosion, pipeline cathodic protection and above-ground pipeline anticorrosion. Requirements for external anticorrosion coating of buried pipeline: good corrosion resistance to soil, water and mold, good construction performance and good electrical insulation performance. When used in combination with cathodic protection, the anticorrosive coating should have certain resistance to cathodic peeling strength and sufficient mechanical strength to ensure that the coating will not be damaged under the action of handling and earth pressure. The external anticorrosion coating technology of buried steel pipe includes petroleum asphalt coating, epoxy coal asphalt coating, coal tar enamel coating, polyethylene tape, molten epoxy powder coating, two-layer pe coating, three-layer pe coating and polyurethane rigid foam composite structure. The latter three methods are commonly used. .
Design and temperature of cold insulation material: The design standard for calculating the thickness of cold insulation layer of LNG pipeline is expounded in detail, and the calculation method and parameter selection are expounded. At the same time, three constraints are considered, such as preventing dew condensation on the outer surface of cold insulation layer, allowing maximum cooling loss and limiting the temperature of LNG entering the cold station. Compared with foreign standards such as JIAS A9501and ISO 1, the calculation methods of domestic standards such as GB 50264, SH/T 30 10 are different, and the values of external surface heat transfer coefficient and other parameters are also different. From the calculation results of an example, it can be seen that the calculation results of the thickness of the cold insulation layer between domestic standards and foreign standards are slightly larger, which keeps the cold.
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