Module 4: Repair Techniques Excavation, lining, patch, pipe-bursting, re-rounding

Trainer note:

Replacing the defective pipework by digging down removing and replacing with new clay or UPVC pipe, backfilling and reinstating.

Whilst this sounds simple enough factors such as the location, length, and in particular the depth of the excavation will all dictate as to whether the contractor carries out the excavation by hand or machine.

Whilst excavation as a method of

repair is highly labour intensive, in our

opinion it remains the best way to

repair a defective drain or sewer.

Trainer note:

In simple terms lining is where a pre-formed polyester tube is inserted into the drain or sewer and resins are introduced that cure leaving the liner in contact with the inner wall of the drain/sewer. There are several types of lining methods available today and these are explained in more detail below.

Average Blind Lining Distances:

100mm 15m

150mm 15m

Cold Cure Polyester Lining – This is the most common small bore i.e. 100mm – 225mm lining system. The major advantages are its low cost, speed to install and good chemical resistance. The disadvantages are that it has a lack of controllability in the sense that once the catalyst of resins has been mixed, there is no control over the curing time.

Warm/Hot Cure Polyester Lining – Warm/hot cure lining is designed specifically for the installation of longer continuous lengths of lining. The major benefit of this type of is its controllability. This controllability allows an infinite amount of pipe to be lined with the only real restriction being in terms of weight and the physical heating of the volume of water within the pipe.

Trainer note:

There are many types of lining vessels used to insert the liner. Here is a picture of 2 different types. We will go through how the lining is inserted over the next couple of slides

Trainer note:

Lateral cutters are used to re open a lateral that has been lined over.

Cold Cure Polyester Lining – This is the most common small bore i.e. 100mm – 225mm lining system. The major advantages are its low cost, speed to install and good chemical resistance. The disadvantages are that it has a lack of controllability in the sense that once the catalyst of resins has been mixed, there is no control over the curing time.

Warm/Hot Cure Polyester Lining – Warm/hot cure lining is designed specifically for the installation of longer continuous lengths of lining. The major benefit of this type of is its controllability. This controllability allows an infinite amount of pipe to be lined with the only real restriction being in terms of weight and the physical heating of the volume of water within the pipe.

Trainer note:

Flexi-Lining – Traditional needle felt lining products are not suitable for lining bends. Whereas a true flexi-line product is made of a material similar to a very heavy duty knitted sock. As a normal sock moulds to the shape of your foot, the flexi-liner moulds to the shape of the bends and curves within a host pipe.

Generally, an epoxy resin will be used which means that flexi-lining will become an integral part of the host pipe reinforcing it and avoiding the problems associated with polyester resins.

Epoxy Lining – Has significant and important differences to the commonly used polyester cold cure lining systems. The major advantages of epoxy lining are that it adheres to the host pipe and consequently not only forms a refurbished pipe within the existing pipe, but also reinforces the structural strength of the host pipe. This is in contrast a polyester cold cure liner that merely forms a mechanical fit to the existing pipe allowing it to continue to deteriorate and over time possibly result in the break down of the liner due to the structural support of the host pipe.

Trainer note:

Pipe Bursting

Pipe bursting is a minimum excavation technique that not only reduces the environmental impact (road closures, disruption to local business and residents) that traditional methods of drain/sewer instillation causes but it also reduces the need and therefore the cost of reinstatement.

In basic terms pushing steel towing rods through the drain that is to be burst carries out the first process of pipe bursting. Once these are in position an arrow blade is connected onto the end of the rods. Effectively the arrow blade and the rods are pulled through the pipe by the hydraulic winch that is located at the other end of the run. The arrow blade cuts the pipe as it progresses and is immediately followed by the bursting head that has the replacement pipe set inside it. The replacement pipe can be either the same size as the original or can be larger depending upon the size of the replacement pipe and soil conditions.

Pipe bursting requires a launch pit and a receive pit at either end of the run that is being burst. These pits allow the engineers to insert (launch) and remove (receive) the steel rods, arrow blade and towing head as well as the replacement pipe.

Trainer note:

Here is a bursting rig and launch pit. Receiving pit and bursting head.

We will go through how this all works over the next few slides

Trainer note:

Pitch Fibre pipes that have lost less than 20% in diameter and are uniformly-shaped but otherwise intact are suitable for re rounding and lining.

This system works through winching a specially developed ‘re-former’ designed to re shape the pitch fibre pipe and to remove any blistering (repeated if necessary). The pipe is flushed out with clean water to remove any debris and a cured-in-place pipe (CIPP) installed.

This can be carried out from 2 manholes avoiding costly excavations and reinstatements.