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Expansion Joints for Low-Temperature Above-Ground Water Piping Systems 低温地下水管道系统用膨胀节
在地下水分配系统中,由于管道埋在地下温度变化较小的深度,因此膨胀和收缩所需的补偿相对较少。然而,在永久冻土地区,水管系统通常安装在地面上。这些可能是永久性的配水系统,如公用事业系统,或仅限于夏季运行的水管。在这两种情况下,管道的设计必须允许膨胀和收缩与整个空气温度范围相称。 该范围可能高达160华氏度,对于钢管而言,这意味着每100英尺管道的长度变化为1 1/4英寸。对于温度约为40华氏度的水不断循环的配水系统,管道通常不会经历全范围的空气温度;然而,出于维护或改造的目的,这些系统有时必须关闭并排空。加拿大环境部汇编的运行经验- 地下水管道系统中的线型伸缩接头表明,如果在冬季必须关闭管道并进行排水,则经常会发生故障。已观察到一种内部支撑波纹管接头和使用dresser型联轴器的管道系统出现故障。从这些观察结果可以推断,伸缩缝出现故障的原因是,在低温下,伸缩缝变得更硬,或者是管道排水后留在伸缩缝中的残余水形成冰,妨碍了伸缩缝的正常运行。 提出了一项研究,以评估低温(亚冻结)条件下钢管系统中使用的多种类型膨胀节的性能。特别地。通过在实验室模拟这些条件,研究了它们在有水和没有水的情况下膨胀和收缩的能力。其主要目的是寻找在北方气候条件下性能良好的伸缩缝。引文:德克萨斯州达拉斯阿什雷交易录第82卷第一部分
In underground water distribution systems, relatively little compensation for expansion and contraction is needed since the pipes are buried at a depth at which ground temperature variations are small. In permafrost regions, however, water piping systems are often installed above ground. These may be permanent water distribution systems, as in a utilidor system, or merely water pipelines which are operational only during the summer months. In either case the piping must be designed to allow for expansion and contraction commensurate with the full range of air temperatures. This range may be as large as 160 deg F which for steel pipe translates into a length change of 1 1/4 in per 100 ft of pipe. In the case of a water distribution system in which water at approximately 40 deg F is constantly circulated, the pipe would not normally experience the full range of air temperatures; however, these systems must on occasion be shutdown and drained for the purposes of maintenance or modification.Operation experience compiled by the Canadian Department of the Environment with in-line-type expansion joints in above ground water piping systems has shown that failures frequently occur if the pipe must be shutdown and drained during the winter. Failures have been observed to occur with a type of internally supported bellows joint and with piping systems using dresser-type couplings. From these observations it was surmized that the reason the expansion joints were failing was that either the joints were becoming stiffer at the cold temperatures or that ice formed from the residual water left in the joint after the pipe was drained preventing the normal operation of the expansion joint.A study was proposed to evaluate the behavior of a number of types of expansion joints used in steel piping systems under low temperature (subfreezing) conditions. In particular. their ability to expand and contract both with and without water frozen inside them was to be investigated by simulating these conditions in the laboratory. The primary objective was to find expansion joints which will perform satisfactorily in northern climates.
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