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1前言防倒流污染技术的每一步进展都是技术发展的必然趋势。从行业规范里相关条文规定的出现,到规范有了区分倒流污染危险等级相关条文的规定,从只有一项技术标准到有多项技术标准出台(见附录),这标志着我们从对倒流污染问题的重视程度与日俱增;从防倒流污染专用阀具——倒流防止器的问世,到减压型和非减压型倒流防止器的突破以及对产品水头损失方
1 Preface Every step of anti-reflux pollution technology is the inevitable trend of technological development. From the provisions of the relevant provisions of the industry norms to appear to have a distinction between the provisions of the relevant provisions of the dangerous level of reverse pollution from a single technical standards to the introduction of a number of technical standards (see appendix), which marks our from the backflow of pollution The issue of increasing emphasis degree; from the anti-reflux pollution-specific valve - the advent of counter-flow prevention device to decompression-type and non-decompression-type backflow preventer breakthrough and the loss of product head square