Refurbishment of the Golden Pipeline
At 120 years old and 557 km in length, the Goldfields Pipeline between Perth and Kalgoorlie is one of the oldest and longest water pipelines in the world, an engineering landmark masterminded by the brilliant engineer CY O’Connor. To protect the inside of the pipe from corrosion, the pipeline was one of the first of its kind in the world to be lined with cement mortar, all 557 km of it by hand, back in the 1930’s.
In the 1990’s after almost 100 years, approximately 320 km of the original pipe remained in service. However, the 60 year old internal lining was breaking down resulting in internal corrosion that threatened catastrophic failure of long sections of the pipeline.
A world wide review of available technologies found no technically and financially viable solutions existed to refurbish this type of pipeline. What was found was that the steel in the pipeline was in relatively good condition, it was the breakdown of the cement lining which was causing the issues. To this end, in 1992 the Water Corporation developed an in house capability to remove the existing lining using high pressure water blasting and reinstating it with a modern cement mortar mix.
Over the next 20 years over 100 kms of the worst sections of the main was successfully refurbished, whether wholescale or selective (patching) depending on the condition of the main, at a cost of roughly a quarter of the cost of new pipe.
| THE SYMPTOM | THE CAUSE | THE SOLUTION |
|---|---|---|
| SELECTIVE REFURBISHMENT | ||
|
|
|
| Minor Burst | Localised defect - general lining good | Localised 'selective' refurbishment |
| WHOLESALE REFURBISHMENT | ||
 |
 |
 |
| Major Burst | General loss of lining | General 'wholesale' refurbishment |
EQUIPMENT SUITE
In order to provide the prolonged access necessary for inspection and refurbishment, a technique for stopping and bypassing the pipe flow was required which minimised interruptions to supply.
Stopping the Flow
A hot tapping and linestopping system was developed to enable the flow in the pipe to be stopped whilst under pressure and to provide a watertight seal without damaging the fragile pipe. This system allows the stopping of flows in pipes up to 1050mm regardless of physical protrusions such as locking bars or damaged lining or debris.
Bypassing the Flow
Once stopped, the flow was bypassed via a 300mm lay flat hose (max operating pressure = 1000kPa) with quick release couplings located on truck mounted reels for speedy deployment, retrieval and relocation. By using a leapfrogging system of bypasses a continuous supply of water was maintained to customers whilst allowing up to 2,500m of pipe to be taken off line.
Self Powered Vehicles
The Corporation developed a series of sophisticated special purpose vehicles to carry out the various operations inside the pipe. The vehicles were self powered and trailing hoses and umbilicals were eliminated. Wherever possible the equipment was made fully automated but when this was not an option remote control was used to minimize manual effort and reduce the amount of time required for operators inside the pipe.
Remote Controlled Condition Assessment
An advanced remotely operated vehicle (ROV) was developed for closed circuit television (CCTV) inspection and condition assessment of pipelines for a distance up to 5km from the point of entry. The vehicle could be launched into fully charged water mains, via existing manholes, thereby enabling quick and cost effective inspections without the time consuming process of draining and recharging the main. The ROV was also designed as a platform for further sophisticated diagnostic capabilities such as sonar, ultrasound, or laser profiling.
In addition to the vehicle itself, sophisticated condition assessment software provided the basis for assessing, monitoring and reporting on the condition of the asset before and after refurbishment.
Surface Preparation
The surface preparation process used water blasting at pressures up to 30,000psi from a remotely operated vehicle to remove failed or defective areas of lining and corrosion deposits from the internal surface of the pipe without damaging the underlying steel.
Debris Removal
After surface preparation, the debris and detritus is left on the invert of the pipe. The amount and concentration of this debris depends on the extent of the defects and can weight many tonnes. A two stage process was developed to remove this. Firstly, bulk removal by either a winched bucket or a self powered scraper/conveyor vehicle and then fine removal via a self powered vacuum/wash vehicle.
Application of the New Lining
Where wholesale or 360 degree lining was required, the traditional centri line process was utilised and the lining was trowel finished. Where selective lining was required, a shot creting method was used. The lining vehicle comprised of a mortar feed vehicle and an operator/application vehicle (refer earlier diagram). To avoid the need for the lining machine to exit the pipe after each batch of mortar is used up, a separate mortar transfer vehicle was used to refill the reservoir of the lining vehicle. Once again, all vehicles were self powered with no trailing hoses or umbilicals. A specially formulated mortar mix, combined with state of the art motor control technology, produced a high quality trowelled finish that met or exceeded all key performance criteria and standards for both factory applied and in situ linings.
OTHER APPLICATIONS
The inspection capability remains in daily use for water mains and drains across the Water Corporation and is continuously upgraded as new technology comes available.
While the Water Corporation no longer maintains a refurbishment capability, during its 20 year life it was also used to carry out in situ lining of the welded joints in the 105km 1400mm diameter Harvey Pipeline, and wholescale lining of the Murray River Crossing pipeline and sections of the South Dandalup and Mundaring Outlet mains.
CONCLUSION
Pipeline refurbishment is not a new concept, particularly for gravity or small diameter pipelines. However, in the 1990’s the techniques and equipment available for condition assessment and refurbishment of large diameter pressured pipelines was strictly limited. The Water Corporation developed and employed a unique suite of inspection, assessment and refurbishment equipment and processes that offered extensive savings to the traditional options, aspects of which are still in use today.
This summary is based on a paper titled 'Low Cost Solutions for Managing Large Diameter Pipelines High Tech Systems for Assessment, Maintenance and Refurbishment' prepared by Alan Hodgkinson, BSc, MICE, CEng and presented to the 18th International Conference & Exhibition on Trenchless Technology, October 2000. A copy of Alan Hodgkinson's paper is available by clicking here.
A video prepared by the Water Corporation titled 'Pipeline Refurbishment in Western Australia" showing the refurbishment process is available on YouTube by clicking here.
Author - Perry Beor
20 April 2020
