In {HEAD ~ ventilation and air conditioning technology}, {TAIL ~ so called spiral pipes} have to be joined together in a tightly sealed manner at widely differing angles, which is generally carried out by segment bends and pipe sections 
In { HEAD ~ ventilation and air conditioning technology } , { TAIL ~ so called spiral pipes } have to be joined together in a tightly sealed manner at widely differing angles , which is generally carried out by segment bends and pipe sections
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