對開(kai)三通(tong)主要用于(yu)帶(dai)壓不(bu)停(ting)(ting)輸開(kai)孔(kong)(kong)（hot tap）。帶(dai)壓不(bu)停(ting)(ting)輸開(kai)孔(kong)(kong)是在不(bu)停(ting)(ting)產(chan)情況(kuang)下進(jin)行(xing)開(kai)孔(kong)(kong)接點(dian)，適用于(yu)除氧(yang)氣(qi)(qi)以(yi)外的任何介質以(yi)及不(bu)同直徑的各類管(guan)(guan)(guan)道。開(kai)孔(kong)(kong)機(ji)在開(kai)孔(kong)(kong)過程(cheng)中是在完全封(feng)閉的空腔內進(jin)行(xing)的，刀(dao)具(ju)切削過程(cheng)與空氣(qi)(qi)隔絕(jue)，無(wu)著火、爆(bao)炸的可(ke)(ke)能性(xing)。由(you)于(yu)封(feng)閉開(kai)孔(kong)(kong)、無(wu)泄漏，有毒有害介質不(bu)能排放到大氣(qi)(qi)中，因此(ci)對環境無(wu)污(wu)染。管(guan)(guan)(guan)道不(bu)停(ting)(ting)輸帶(dai)壓開(kai)孔(kong)(kong)、封(feng)堵技(ji)術可(ke)(ke)避免作(zuo)業風險(xian)，提高安全性(xing)，使維(wei)修既(ji)迅(xun)速又(you)經濟(ji)可(ke)(ke)靠(kao)。此(ci)技(ji)術先進(jin)，設備操作(zuo)簡單，與停(ting)(ting)產(chan)開(kai)孔(kong)(kong)作(zuo)業相比，其經濟(ji)效益和社會效益顯著。在石油、天然氣(qi)(qi)管(guan)(guan)(guan)道及熱力管(guan)(guan)(guan)線(xian)上均可(ke)(ke)帶(dai)壓開(kai)孔(kong)(kong)。典型對開(kai)三通(tong)見圖4.6.23。

  對(dui)開三通有(you)關標(biao)準規范：API 2201《Safe Hot Tapping Practices in the Petroleum ＆Petro-chemical Industries》；SY／T 6554《石油工業帶壓開孔作業安全規程(cheng)》。