| 摘要 |
<p>To tap a main pipe for connection of a branch pipe thereto, a tubular enclosure is applied to the main so that one end of the enclosure is formed by the main pipe side-wall to be holed. A drill is penetrated through the main pipe side-wall from the interior of the enclosure while being operated from outside the enclosure; the enclosure having its end remote from the main pipe filled by a removable plug which acts as a bearing for the drill-shaft. The enclosure is equipped with a closure member (such as that of a gate valve) which is used as a lock to prevent movement of the plug during drilling. After drilling, the means used to drive the drill are removed and replaced by an extension of the enclosure, the plug is then unlocked so that the plug and the drill retract into the extension under pressure of the main pipe's contents. The closure member is then operated to close the enclosure at a point between the retracted drill and the main pipe, and the tapping completed by removal of the plug, drill and extension from the enclosure.</p> |
