Even under the best of circumstances, coating an existing pipeline out in the field can be difficult to say the least. If the pipeline is a 60-inch (152 cm) welded steel pipe coated with coal tar and asbestos paper that is located in an environmentally sensitive area, the rehabilitation job becomes even more challenging.
The San Francisco Public Utilities Commission was recently faced with such a situation when it was time for the Crystal Springs San Andreas Pipeline (CSSAPL) to be rehabilitated. “The CSSAPL runs adjacent to a heavily used public trail and the area is an environmentally sensitive area called Crystal Springs Reserve. It is a 750-foot [229 m] pipeline that crosses over many creeks and gullies,” said Darrell Wagoner, Western Regional Manager of Trenton Corporation.
Pipeline rehabilitation is a critical component of pipeline maintenance and is vital to ensuring the integrity of the metal pipe surface; therefore, a rehabilitation solution had to be found for CSSAPL that would protect the exterior of the pipeline and not comprise the environment. “It was ultimately decided that the application of Trenton’s cold-applied tape coating would be the least environmentally disruptive rehabilitation solution,” stated Wagoner.
And with that, a crew from Kiewit Corporation was chosen to apply the Temcoat 3000 primer and Trenton #2 Wax Tape, a non-stitched, synthetic fabric tape that is saturated with microcrystalline wax and corrosion inhibitors, to the CSSAPL.
Minimal Prep = Minimal Headaches
There are many reasons that Trenton’s Anti-Corrosion tape system was chosen for the CSSAPL project, but perhaps the most important is the fact that the system does not require the removal of the asbestos felt from the pipe’s exterior; the wax tape encapsulates the existing coating, protecting the environment, the general public, and the coatings crew from exposure to the asbestos.
“The removal, capture, and containment of the carcinogenic asbestos is extremely difficult and expensive, especially in areas such as this one that do not have a power source. Even if it had been decided to remove the asbestos, we would have had to helicopter gas- or diesel-powered generators in to the pipeline area, adding to the environmentally sensitive protocol,” said Wagoner.
According to Wagoner, the application of the primer and the wax tape requires minimal surface preparation — Society for Protective Coatings (SSPC) surface preparation (SP) 2: Hand Tool Cleaning, not NACE No. 2/SSPC-SP-10: Near-White Blast Cleaning. “SP-2 refers to hand tool cleaning and removes all loose mill scale, loose rust, loose paint, and other loose debris. It is not intended that adherent mill scale, rust, and paint be removed by this process,” explained Wagoner. For the CSSAPL job, this was a huge advantage, as once again, the removal of the asbestos and the lack of a power source would have increased the cost, timeframe, and environmental protection procedures.
Laying It On Thick
With the pipe ready to receive the Temcoat 3000 primer, the 4-man coatings crew from Kiewit got to work. “The primer is actually hand-applied. We wore latex gloves and dipped our hands into the can. It is a heavy paste that we basically smeared onto the pipe at a thickness of about 1/8 -inch [3 mm],” said J.O. Layton, the labor foreman on the job. As required by Kiewit, the crew also wore hard hats for the duration of the project as well as Tyvek suits. “Although the primer and the wax tape are non-hazardous, we wore Tyvek suits to protect our clothes. The materials can get you pretty messy,” laughed Layton.
According to Layton, the crew would apply about six feet (2 m) of the primer and then start to wrap the wax tape while the primer was still wet. “We would work toward each other while wrapping the pipe. We worked down the pipe, underneath it, and around,” explained Layton. The wax tape is 12 inches (31 cm) wide, and the crew applied the tape at a fifty percent overlap. It took the crew approximately one week to prime and wrap the pipeline completely.
As stated by Wagoner, the crew also applied two feet (61 cm) of MC Outerwrap at each soil-to-air transition. “Soil-to-air transitions require the use of a material that increases the mechanical strength of a coating. The material must aid in overcoming the stresses that the cycling of warm to cold air and soil temperatures place on the pipe,” said Wagoner.
It’s a Wrap
Although the CSSAPL job went smoothly, there were certainly some challenges for the crew. According to Layton, the terrain was uneven at points, and there were many areas where the pipe was high off the ground. In these instances, the crew cut a platform deck in the side of the hill so that they could work off of ladders and safely reach the pipeline.
Layton and his team also had to make sure they were organized before each day’s work. “We were able to drive on the paved fitness road for part of the way, so transporting the material wasn’t difficult, but we did have to make sure we packed the truck with all the necessary materials in order to avoid multiple trips back and forth,” explained Layton.
However, the uneven terrain and the somewhat remote location were not the team’s biggest hurdle on the job. “Our biggest challenge was rubbing out all the air bubbles that occurred while we were wrapping the pipe with the wax tape. We spent a great deal of time rubbing out air bubbles. We were meticulous about it; we wanted to make sure that we got all of them out before we moved on to the next section,” said Layton.
Thankfully, one challenge that the team did not have to contend with was Mother Nature. The weather cooperated for the duration of the project, and, although Layton stated that the mornings were cold and misty, work continued without interruption. In fact, even if it had rained, the job most likely would still have moved forward. “Rainy weather usually isn’t a problem when applying the primer or the wax tape. It is hydrophobic in nature and can be successfully applied underwater in both marine and freshwater corrosion protection applications,” said Wagoner.
All in all, the CSSAPL job was a resounding success thanks to skilled applicators and the right product for an environmentally sensitive job. As Wagoner said, “using the Trenton wax tape process eliminated the need to disrupt any of the asbestos coating and provided the pipe owner with a new coating that can last for decades.”