| 摘要 |
<p>Before effecting a cut-out operation to remove a section 24 of a pipeline such as a gas main, the pipe 10 is pre-loaded by clamping clamp assemblies 12, 14 around the pipe 10 and locating yokes 16, 18 against the assemblies. Struts 20, 22 engage the yokes and include hydraulic cylinders 32 which can be pressurised by a pump 30. Nuts (38) can be tightened onto the cylinders 32 to maintain the pre-load when the hydraulic pressure is removed. The force applied equals the otherwise unbalanced gas load "A" or "B" provided by the gas pressure in the pipe 10 acting on the stop plugs. Each clamp assembly comprises thrust members 50 tightened against the pipe 10 by chains. The forces applied preloads the yokes equal to the forces provided by the gas pressure in the pipe 10 acting on the stop plugs. The thrust members are located on fabric straps which are adjusted to make the members equispaced and then tensioned to lock them in place before the chains are tensioned. <IMAGE></p> |
