Fibreglass pipe fills an important niche and saves millions
The Big Horn Regional Joint Powers Board (BHRJPB) consists of multiple cities, towns, counties and other entities in the northern part of Wyoming. The district was formed to interconnect separate water systems scattered throughout the rural communities. One major element of the interconnection in Big Horn and Washakie counties is known as the Northern Supply Pipeline. The purpose of the pipeline was to effectively collect and treat water from wells that were spread throughout the area and distribute it via one pipeline. The job originally required 15 miles of 20 inch pipe that could handle the extreme conditions of the area. However, the original recommendation for the project changed after further investigation determined fibreglass reinforced pipe (FRP) was the best option for the job. Although FRP was not even considered as an option during the initial specification process, it ended up saving millions of dollars and provided the best solution.
The job’s original feasibility study, noted the pipe material selection would have the biggest impact to the initial project cost as well as the performance life of the proposed pipeline. The following pipe options were originally considered for the job.
Polyvinyl Chloride (PVC) pipe was initially recommended in this study because it is used extensively for water systems today. It was recommended as the material of choice on this project because PVC pipe does not have the high corrosion potential of metallic pipe when exposed to corrosive soils which were typical to the Big Horn Basin. It was also anticipated that the working pressure for this project would be below 150 pounds per square inch (psi). The original study did recognize that the pressure rating of PVC pipe is lowered when the water temperature exceeds 73.4 degrees F. HDPE Because High Density Polyethylene (HDPE) is chemically inert and resistant to corrosion, it was also recommend to be used on this project except the HDPE was only recommended at river crossings due to the higher cost of the material. If was also recognized that HDPE required a pressure derating at 73 degrees F.
Ductile Iron Pipe (DIP) was evaluated because it has higher pressure ratings when compared to PVC or HDPE pipe. However, it is susceptible to deterioration in corrosive soils which were expected in the project area. Polywrapping ductile iron pipe would provide some degree of protection from corrosion, although a cathodic protection system would still be required. Given the difficulties and expense of installing a cathodic protection system on ductile iron pipe, and the long-term maintenance issues associated with this type of system, it was recommended that the use of ductile iron pipe be avoided on this project.
Teflon Tape-wrapped or polyurethane coated steel pipe is similarly susceptible to corrosion as ductile iron pipe and therefore would also require the cost of installation and long-term maintenance issues associated with a cathodic protection system. However, it is easier and more reliable to electrically bond and cathodically protect steel pipe than ductile iron pipe. In addition, Steel pressure along with other pipe materials, such as ductile iron pipe and bar wrap concrete pipe, have internal liner systems which can be problematic. Mortar linings in these pipe materials can crack and de-bond from the interior pipe surface. This leaves the pipe exposed to corrosion and can affect the water quality. In addition, the recent phenomenon of water supplies being calcium deficient and pulling the calcium from the concrete and mortar lining leads to increased pitting of the pipe’s interior surface. The pipe’s rough interior causes an increase in energy cost for pumping material through these pipe materials as well as promotes bacteriological growth and the buildup of biofilms. Both of these have the potential to be a health risk if not addressed in our water supply systems.
According to the BHRJPB, further study of the geothermal activity in the region revealed the water coming out of the ground was under higher pressures and registered hotter temperatures than originally thought. The temperatures of the water ranged from 85 degrees F to 92 degrees F and the water pressures were greater than 200 psi. These circumstances along with the naturally corrosive nature of the soils required another evaluation of the most appropriate pipe for this application because these conditions were not advantages to any of the four pipe materials previously evaluated.
The BHRJPB researched and reviewed opportunities for FLOWTITE fibreglass pipe. FLOWTITE was chosen because of its corrosion resistant properties, its ability to handle fluids at elevated temperatures and pressures, and the cost savings it offered.
Benefits of FLOWTITE
FLOWTITE’s ability to handle the elevated water temperature and pressure allowed Big Horn to eliminate the need for a water pumping station that was included in the original project design. Additionally, engineers were also able to reduce the pipe size from 20 inches to 18 inches because of the larger inside diameter of FRP in comparison to the equivalent diameters of the other pipe materials. Also, fibreglass does not require cathodic protection and is less expensive to manufacture than steel and PVC. This saved Big Horn thousands of dollars in estimated construction costs. The elimination of a pumping station also reduced energy costs and long-term maintenance expenses. The total cost savings to BHRJPB was approximately $2 million. Big Horn Regional Joint Powers Board Director, John Joyce is a proponent of FLOWTITE and recommends the product. “FLOWTITE’s product fills an important niche. It is hard to come up with an alternative,” he said.