| 摘要 |
For "live insertion" of a new gas pipe 18 into an existing main 10 through a gland seal 114 , the front end of the pipe 18 is provided with an insertion head unit (130, fig.3) having front and rear cylindrical portions (150, 126, fig.3) with respective pluralities of radial bores (154, 128, fig.3) opening into a central bore (152, fig.3). The head unit can be pushed part way through the gland seal 114 so that the bores (154, fig.3) of the front portion are within the main, so gas can pass via them and the central bore (152, fig.3) into the new pipe 18 , while the rear portion's bores (128, fig.3) are sealed from the main 10 by the annular seals (170-176, fig.4) of the gland seal 114 (preferably including an inner seal (170, fig.4) of greater radial extent, initially closed by a rupturable membrane (178, fig.4)). Subsequently the head unit is pushed fully into the main. Also claimed is a gland seal for use in the above method. |
