Pipe Cleaning Technology Removes Bitumen and Coal Tar Lining
Pilot Projects in Canada Show How the Technology Works
By Andrew Bell Oct 11, 2012
Envirologics has developed a low-cost and energy-efficient technology for cleaning and rehabilitating deteriorated drinking-water distribution systems. The patent-pending Tomahawk Mark 1 system, which is now commercially available, can rapidly remove bitumen and coal tar lining, as well as tuberculation with no damage to the pipe.
Envirologics’ technology uses crushed stones with a high volume of low pressure air to clean and prepare the host pipe for subsequent lining using spray-in-place pipe (SIPP) or cured-in-place pipe (CIPP) technologies. The Tomahawk Mark 1 system can meet or exceed the draft ASTM standard for SIPP coatings, which will require a clean and prepared surface.
Recent Pilot Program Results
The technology’s first pilot project was completed in Napanee, Ontario, Canada, in July and involved preparing 6-in. and 8-in. tuberculated and bitumen-lined cast iron pipe for SIPP lining. The technology was initially requested as the SIPP lining crew could find no other method for cost-effectively removing the bitumen lining without damaging the host pipe or using chemicals. The Tomahawk Mark 1 system is waterless, uses no chemicals and does not damage the host pipe.
Initially, only sections of 6-in. tuberculated and bitumen lined pipe were cleaned and prepared for lining as the Envirologics crew was unsure the Tomahawk Mark 1 system could provide a high enough flow rate for cleaning 8-in. pipe. All of the 6-in. pipe on the jobsite was cleaned and prepared for lining without problems. After some trial and error, the crew discovered that the system was also capable of removing bitumen lining from 8-in. pipe.
With respect to both 6-in. and 8-in. pipe, there is a limit to the amount of tuberculation that can be removed. As the cleaning method involves a high velocity air stream, there has to be room in the pipe for air to flow. Completely blocked pipes cannot be cleaned without first poking a hole with another method. This hole can be easily made using a small diameter scraper for example.
Various lengths of 6-in. and 8-in. pipe up to 125 m in length were successfully cleaned and prepared for SIPP lining in Napanee. While the system is capable of cleaning distances longer than 125 m, it is not optimal. Lessons learned onsite in Napanee were summarized and applied to the second pilot project in August.
Peter Defoe, the director of utilities and public works construction for Greater Napanee Utilities says, “Not only is the ‘blown stone cleaning technology’ a fast and effective cleaning process but it also addresses the problem of pipe preparation thus enhancing liner bond. The significant time-savings alone will undoubtedly lead to a true one day return to service water rehabilitation operation.”
The second pilot project began on Tuesday, Aug. 21 in another small town in Ontario, Canada. Two sections of 6-in. diameter, coal tar-lined pipe were opened up to demonstrate a simulated same day return to service scenario. A 114-m section and an 82-m section were used for the demonstration.
At 7 a.m., the Envirologics field crew turned on the blower and dried the first section of pipe. After drying the pipe for a short period of time, the first hopper of stone was used. A softer rock was used initially in order to remove tuberculation. Next, the pipe was flooded with a harder rock at high velocity to scour the remaining coal tar from the surface. After CCTV inspection, it was determined that a single, 1-m long strip of coal tar remained on the pipe. A patent-pending deflector was used to target this area and successfully remove the strip.
After all of the coal tar was removed, the hydrants were back-flushed with water to remove any debris from up the Ts. This process guarantees that no stones remain in the waterline post-cleaning and can be accomplished using air as well, if desired. The section was then dried one final time and approved by the SIPP lining crew at 10:15 a.m.
Cleaning of the second section started at 11 a.m. There was only a single service connection in this section but it was much larger than regular service connections at 2 in. in diameter. It was inspected for stones and other debris after cleaning and prior to lining. No debris was found and the surface was ready for lining within one and a half hours. In fact, the cleaning process was so quick that a third section was cleaned with the trailers in the same position while waiting for the SIPP crew to finish lining the first section.
While the SIPP crew was setting up and spraying the second section, an Envirologics crew moved location and cleaned a fourth section of pipe. In total, Envirologics was able to clean and prepare 390 m of coal tar-lined pipe for SIPP lining in two and a half days. Cleaning four sections of pipe in a single day vs. the two required on this particular job, proves that the Tomahawk Mark 1 system is more than capable of delivering a cleaning solution for time sensitive jobs even when removing coatings as durable as coal tar.
In order to minimize, with the goal of ultimately eliminating, downtime on the jobsite the following measures were taken:
1. All service connections were disconnected and blown out with compressed air from the house to prevent water ingress to pipe during cleaning and drying.
2. Envirologics was consulted for the proper location of access pits in order to eliminate blind Ts and valves. Preferred lengths are 125 m or less.
3. The access pits were specified such that there was 18 in. of clearance under the pipe and the bottom was lined with a layer of gravel. This modification reduces setup time to less than 30 minutes.
4. Envirologics was given a test section that had been cut from the pipe in the ground in advance of the job to tailor a customized cleaning strategy.
Municipalities were pleased with the results of the Tomahawk Mark 1 system and contractors felt that the amount of additional preparation work was reasonable considering the benefits achieved in speed and cleanliness of pipe in preparation for lining. All of the above site preparation steps were carried out for the second pilot project. The first pilot project had already been started by the time the Envirologics crew was mobilized. The total cost of all site preparation steps for the second pilot project was less than a single day of downtime for the Envirologics crew.
Liner Testing Results
Independent, third-party testing of the bond strength of the SIPP liner to the host pipe was completed by the Centre for the Advancement of Trenchless Technology (CATT) at the University of Waterloo.
Professor Mark Knight says, “The patent-pending Tomahawk Mark 1 system creates a bondable surface for SIPP liners that prevents axial movement of the liner in our testing.” Axial movement of SIPP liners has been a documented problem for some companies in the past. This technology provides an added measure of security for the SIPP lining crew.
Both of these projects were a great success from a cleaning perspective. The ability to efficiently remove coal tar is relatively unique, as well. Envirologics Engineering president Randy Cooper says, “The patent pending Tomahawk Mark 1 system is a high performance, waterless cleaning innovation that produces a dry, bondable surface for all methods of pipe lining.”
Andrew Bell, MASc, is a research and development associate with Envirologics Engineering, based in Bracebridge, Ontario, Canada.