美国史密斯公司研制了一种方钻杆泥浆阻流凡尔(见附图)。这种阻流凡尔,是一个内部装有一套籍弹簧关闭的凡尔总成的短节,安装在方钻杆和第一个钻杆接头之间。这个凡尔,在钻进或在循环泥浆时,在压差的作用下保持开启;而当停泵时即自动关闭,在方钻杆下方形成一个密封。 Smith of the United States has developed a square drill pipe flow blocker Versailles (see photo). The flow blocker, Versaille, is a short section containing a set of spring loaded closure Versailles mounted between the kelly and the first drill pipe joint. This valve, while drilling or circulating mud, is kept open by the pressure differential and automatically closes when the pump is stopped, forming a seal under the kelly.