[Company Logo Image] Leaders in Cutting Technology

No Dig Technology


No Dig Technology


        Have you or your company done any work in the underground industry?  If so, have you or your company done any lateral reinstatement?  Below is a general description of the underground industry as a whole, the relining process, and the uses and applications of our products in the industry and, more specifically, after the relining process.

What is the 'underground industry'?

    The underground industry uses a process of rehabilitating the infrastructure of utility services that does not or only minimally require(s) disrupting the services' surrounding location.  This process, also known as 'no dig', contrasts the previous process of 'open cut', which required complete removal of the services' surrounding location in order for the service to be repaired or replaced.  For numerous reasons, including being environmentally friendly, cost effective, less disruptive to traffic flow, etc., and more time efficient, the 'no dig' process is superior, which explains its exponential growth in recent years.

    This growth will likely expand the 'no dig' process into numerous types of projects, but currently there are generally five projects that utilize it: providing new or extended networks of pipelines or ducts, increasing existing network capacity, transferring services from above ground to below ground, replacing defective pipelines, and rehabilitating existing pipelines by enhancing and taking advantage of residual structural capacity.

    These projects generally require one of the three processes of 'no dig': new placement, replacement, or rehabilitation.  If new installations are required, pipe jacking, micro tunneling, or horizontal directional drilling (a/k/a guided boring) methods are used.  Pipe jacking installs pipes by using the thrust power of hydraulic jacks to push the pipes through the ground and into place to form a continuous string of them in the ground.  Micro tunneling cuts a tunnel through the ground using a machine with a cutting head.  The machine starts cutting at the 'launch pit' and finishes cutting at the 'reception pit', all the while the pipe is jacked into place behind the machine, and the spoil is removed via an auger to the surface.  Horizontal directional drilling (HDD) or guided boring is generally used to install pipelines below river beds.  A drill pipe is steered along the predetermined course, then the borehole is enlarged and conditioned, and finally the product pipe is pulled through the borehole.

    If replacement is required, the common method is pipebursting.  The defective pipeline is burst using either a pneumatic or hydraulic mole.  Then the fragments of pipe are forced into the surrounding ground or removed through the new pipeline that is pulled in behind the mole.  This method of replacement is generally only suitable in soft ground conditions and not for gravel or rock conditions.

    Sometimes only rehabilitation is required if the defective pipelines have some residual structural and physical life which can be used as a structure for the new line.  There are four general techniques for this process: Cured-in-Place Lining (CIPP), close fit lining, slip lining, and spray lining.  After using any one of these four techniques, the pipeline becomes a continuous unit and the service laterals become disconnected from the mainline pipe.  These laterals must be 'reinstated' or reconnected to the mainline.  The machines used for that purpose are called lateral reinstatement cutters, which is what our company provides to and developed for the underground industry and its contractors.   

How does the relining process work?

    Relining can be accomplished by any of the four techniques stated above.  For any one of the four, there are several common steps that are required before the actual relining process begins.  First, the pipelines need to be cleaned to remove any internal debris.  Second, the pipelines need to be inspected for breaks, obstacles, and service connections.  Third, obstructions must be removed or repaired.  Fourth, and finally, if the section of pipe designated for reconstruction requires that the flow be bypassed, the flow must be pumped from a point above the reconstruction section to a point below the reconstruction section.

    Here is a detailing of the relining techniques.  If you choose close fit linings, such as spirally wound liners, a PVC strip is fed through an access into the pipe, and the strip is wound into place against the pipe wall by a winding machine operated from within the pipe.  Slip lining requires putting pipe within a pipe and grouting the annulus between the new and old pipe.  Spray lining, generally used for repairing leaks but not structural defects, is a technique of spraying cement or resin into the pipeline.  One of the more involved techniques of relining is the CIPP technique, and therefore, it is detailed more explicitly here.

    CIPP is a technique of forming a hollow cylinder to an existing pipe via a process called inversion.  First, the tube is impregnated with a resin by vacuum pressure.  Then the tube is inserted in a vertical standpipe with the plastic membrane side out.  At this point, either a hydrostatic head or air pressure is used to invert the tube from the point of inversion to the point of termination, which causes the resined felt to be on the outside of the tube and against the original pipe.  During this inversion process, a pressure is maintained in the pipeline to hold the tube tight against the pipeline.  Once the tube has been completely inverted, it must be cured either by circulating heated water or steaming.  There are two cure periods: the initial cure and the post cure.  Both periods occur at specified temperatures.  The initial cure period ends when the new pipe appears to be hard, sound, and the specified temperature has been obtained and maintained.  Then the post cure is obtained by increasing the temperature to its specified temperature.  Lastly, the new pipe needs to be cooled down by introducing cool water into the new pipeline to replace the heated water or steam.

    As with any one of the four relining techniques, the next step is to reinstate/reconnect the laterals/service connections.  Our lateral reinstatement cutters were designed and built to make this an easy and efficient process for underground contractors.

    One Further Tip:  Once the mainline has been completely reinstated, inspection must occur.  There are three general tests that can be performed: gravity pipe leakage test, pressure pipe test, or delamination test.  Here is a quick, general description of each.  The leakage test requires that the new pipe be plugged at both end and filled with water.  Then the rate of exfiltration is tested to see if it is within established guidelines.  The pressure test is a similar test except that air pressure is used rather than water.  Established pressures must be able to be held within the new pipe.  The delamination test is tested on samples of the CIPP to see if it complies with established requirements.  Whichever of these tests will be used is predetermined in the contract documents by the owner of the pipeline to be rehabilitated.

What are the uses and applications of the Bowman Tool Company & Systems' products?

    For the rehabilitation of pipelines, BTCS's products are used after the relining process.  In a mainline construction there are numerous laterals/service connections.  After relining, those laterals are closed off from the mainline, and therefore they are non-usable.  Depending on the length and location of the relining contract, a contractor could have anywhere from 2 to 1,000s of laterals to reinstate/reconnect.  A contractor is going to need the equipment to open those laterals back up within a reasonable amount of time.  Our equipment provides that to the contractor.  With our equipment, the contractor does not need to worry about breaking down in the middle of the job - adding time and expense to the completion of their contract.  That is why BTCS is the leader in cutting technology.


                         Setup Type 1 (most common)                                                          Setup Type 2

Hook up of camera, reel, cutter/control to truck

More questions?  Please call 717-432-1403.



Last modified: 02/15/12