BACKGROUND OF THE INVENTION
The present invention relates to a device for anchoring a pipeline.
It is a requirement in the pipeline industry that pipelines be installed in a trench at depth below the natural ground surface. Almost all larger pipelines are positively buoyant and will tend to float to the surface if the local ground is saturated with water and the local ground material does not provide sufficient shear strength when returned to the trench. These conditions occur in areas such as swamps, muskeg, permafrost and bogs.
The pipeline industry has adapted several methods to overcome this positive buoyancy condition to ensure that the pipeline remains buried and stable in the ground. The most common method is to fix concrete to the pipeline. This method includes two different approaches. The first approach is to apply a continuous layer of concrete to the pipe in a coating plant and then transport the coated pipe to the ditch side. The pipe is then welded, the ditch dug and the weighted pipe installed in the trench. This method is expensive and requires the designer to know where the weighting in needed prior to ditching, which often leads to installing the weighted pipe in the wrong location.
A second approach is to install specially fabricated concrete weights to the pipeline prior to installing the pipe into the ditch. This approach is expensive and again requires that the locations and quantities be known prior to ditching operations. Not committing to weight location until after ditching will require that the ditch be left open an extended period of time to allow the work of hauling, stringing and mounting the concrete weights onto the pipe. This time delay is undesirable, particularly in winter construction in muskeg due to freezing of the backfil.
An alternate to concrete weights is screw anchors of the type described in U.S. Pat. No. 5,730,552. While this type of anchoring provides some benefits over concrete, it has not replaced concrete due to several problems in the application. Firstly, the screw anchor activity is done with the pipe in the trench. Two anchors are required which straddle the pipe. This method requires an extra wide trench and also requires that laborers work in the trench completing the strap installation raising safety concerns. The chance of accidently contacting the pipe with anchors or anchoring equipment is high. Any damage to the coating or pipe will initiate an expensive repair. This method is not feasible where the underlaying ground material contains cobbles or boulders or where the ditch is partially filled with water. Also, this method could not be used in permafrost areas because heat from the ground surface or pipeline would be transmitted down the screw anchor and melt the permafrost with potentially catastrophic consequence.
What is needed is a simple screw anchor design, which is inexpensive and can be installed quickly prior to the pipe being installed into the trench such that the screw installation does not have to be a precision operation. Also, what is needed is an anchoring system, which will not conduct heat from the ground surface downward into permafrost.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a device for anchoring a pipeline, which eliminates the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a device for anchoring a pipeline, which maintains the pipeline in buried conditions even in presence of saturated soil with inadequate shear strength to resist buoyant forces.
It is still a further feature of the present invention to provide a device for anchoring a pipeline which can be installed prior to the pipeline being set into a trench, which does not have metal in the vicinity of the completed pipeline, which will not thaw underlying thermofrost, and which will fit a large variety of pipeline diameters.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, a device for anchoring in a buried pipeline, which has a lower portion adapted to be screwed into soil so as to be anchored in the latter, a hollow extension having a lower end connected with said lower section and an upper end connectable to a rotary drive, and tether ropes which have lower ends fixed to said lower section and upper ends adapted to be strapped around a pipeline and to be fixedly held on the latter.
When the device is designed in accordance with the present invention, the lower section of the device is screwed into a soil, forms a hole, and is anchored in the soil, with tether ropes extending upwardly from the lower section through the thusly drilled hole, and when the extension is removed, the upper ends of the tether ropes are wrapped around the pipeline and firmly held on it, for example by a clamp, thus continuously maintaining the pipeline at the desired depth.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.