Polyurethane insulated steel pipe has a wide range of applications in indoor and outdoor pipelines, including central heating, central air conditioning, chemical industry, medicine and so on. There are many preparations to be done before the construction of polyurethane direct buried insulation pipe. We should follow the correct steps. If there are some problems in the process of using polyurethane directly buried insulation pipe, it is likely that our use method is wrong, so we should strictly abide by the operation procedures before construction, without any mistakes.

　　使用了聚氨酯直埋保溫管導(dǎo)熱系數(shù)低、隔熱性能好的硬質(zhì)聚氨酯作為隔熱材料，具有優(yōu)異的隔熱性。預(yù)制直埋保溫管現(xiàn)場(chǎng)接頭保溫須在試壓合格后方可進(jìn)行，現(xiàn)場(chǎng)接頭保溫施工。這一項(xiàng)內(nèi)容是預(yù)制直埋保溫管道施工特有的施工質(zhì)量好壞直接影響使用壽命。保溫層有現(xiàn)場(chǎng)發(fā)泡施工和保溫瓦施工兩種方法，不論采用哪種方法施工，都不能出現(xiàn)環(huán)形空間，開裂、脫層等缺陷，維護(hù)層的做法有多種（如高密度聚乙烯和玻璃鋼保護(hù)層）但都能保證接頭的整體性，嚴(yán)密性，防水性。

　　The rigid polyurethane with low thermal conductivity and good thermal insulation performance is used as thermal insulation material, which has excellent thermal insulation. The on-site joint insulation of prefabricated directly buried insulation pipe can only be carried out after the pressure test is qualified. This content is that the special construction quality of prefabricated directly buried insulation pipeline directly affects the service life. There are two methods for the construction of thermal insulation layer: field foaming construction and thermal insulation tile construction. No matter which method is adopted, there shall be no defects such as annular space, cracking and delamination. There are many methods for the maintenance layer （such as high-density polyethylene and glass fiber reinforced plastic protective layer）， but they can ensure the integrity, tightness and water resistance of the joint.

　　聚氨酯直埋保溫管由于聚氨酯硬質(zhì)泡沫保溫層緊密地粘結(jié)在鋼管外皮，隔絕了空氣和水的滲入，能起到良好的防腐作用。同時(shí)它的發(fā)泡孔都是閉合的，吸水性很小。高密度聚乙烯外殼、玻璃鋼外殼均具有良好的防腐、絕緣和機(jī)械性能。因此，工作鋼管外皮很難受到外界空氣和水的侵蝕。吸水率低的原因是由于聚氨酯泡沫的閉孔率高達(dá)92%左右。

　　The polyurethane directly buried thermal insulation pipe is tightly adhered to the outer skin of the steel pipe because of the rigid polyurethane foam insulation layer, which can isolate the infiltration of air and water, and can play a good anti-corrosive effect. At the same time, its foam pores are closed and its water absorption is very small. HDPE shell and FRP shell have good anticorrosion, insulation and mechanical properties. Therefore, the outer skin of the working steel pipe is hard to be eroded by the outside air and water. The reason for low water absorption is that the polyurethane foam has a closed porosity of about 92%.

　　低導(dǎo)熱系數(shù)和低吸水率，加上保溫層和外面防水性能好的高密度聚乙烯或玻璃鋼保護(hù)殼，改變了傳統(tǒng)地溝敷設(shè)供熱管道“穿濕棉襖”的狀況，大大減少了供熱管道的整體熱損耗。

　　Low thermal conductivity and low water absorption, combined with thermal insulation layer and high-density polyethylene or glass fiber reinforced plastic protective shell with good waterproof performance, change the situation of "wet cotton padded jacket" of traditional trench laying heating pipeline, greatly reduce the overall heat loss of heating pipeline.