Pipe liners provide an answer for both water infrastructure and efficiency concerns.
Pipelining technology in North America started out in the wastewater industry and has recently moved into the potable water industry. In some places, such as the United Kingdom, the wastewater pipeline infrastructure is older, so the need for rehabilitation came sooner than it did for drinking-water infrastructure. In North America many new municipal water systems went in after World War II, in the ’50s and ’60s. Now as these systems reach their half-century mark, they need more and more attention.
Corrosion’s Cost
The annual cost to the US economy from the water industry as a result of corrosion is approximately $36 billion per year, based on a 2002 government study. Cliff Johnson, director of public affairs for National Association of Corrosion Engineers (NACE) International in Houston, TX, points out that according to the study, about 25% of the water industry’s product is lost in moving water from point A to point B. NACE International has 17,000 members in 100 different countries worldwide. The nonprofit group organizes conferences, provides training, and develops standards for the industry.
“Unfortunately this issue is one of the things the water industry has not spent a lot of time with,” says Johnson. “For many municipalities, I think it comes down to ‘out of sight, out of mind.’ Since the pipe is in the ground, there may be less of an environmental or safety issue because it’s ‘just water,’ and when failure occurs it’s a transportation and water supply issue; therefore the point of criticality must oftentimes be reached before actual inspection of the pipe.
“But by then you have a pipe interruption in the middle of a street, flooding homes and causing other damage. The whole issue is commonly discounted because it’s not something that’s going to happen today and then tomorrow you’ll have the interruption. There is frequently a five- to 20-year lead time.”
With the average age of systems now being 40 to 50 years, but with a design life of 25 years, there is a major challenge looming with water systems. Corrosion is a main culprit.
History and Classifications
Trenchless means of rebuilding sewer systems in Canada have been steady since the late ’80s and early ’90s, but trenchless water rehab in Canada just started taking off in early 2000, according to Tim Henry, national practice leader in corrosion technology with UMA Engineering Ltd., a Vancouver, BC, engineering consulting group.
“What seems to be a significant driver when it comes to the push for trenchless technology is the ‘social impact’ or ‘soft costs,’” says Henry. “Combining these costs with the direct costs of excavating and developing in well-developed urban areas may be prohibitive, much more than if you were doing such work out in the middle of an undeveloped field. In addition, now there seems to be a focus on ‘carbon counting’ (comparing the total carbon contribution for treatments in a quest for carbon neutrality).”
For potable water systems, options for pipe liners must meet sanitation codes (i.e., NSF 61) so that there are no leachable materials that can move into the system and be a threat to human consumption. M28 is the standard the American Water Works Association (AWWA) has set up for structural classification. Under this category are four classes fitting into three different types. These liner types include non-structural, semi-structural, and fully structural. Depending on the condition of the water main the key is which of the different liners should be selected to suit that situation. For instance, if your main has good structural integrity, then a non-structural liner may be placed within the main.
An example of a non-structural liner would be when cement mortar is placed within the pipe or if epoxy or urethane coating is placed on the interior of the pipe. If, for instance, a steel main had some internal corrosion, the best option could be simply to put a non-structural liner inside to isolate the steel from the water.
The next category involves the semi-structural liner. Within that AWWA classification there are two different classes, I and II. Basically what they break down to is whether or not the liner has ring stiffness so it can support itself if there’s a pressure change or loss. Those types of liners are normally a thinner liner.
The last type of pipe liner is fully structural, the AWWA Class IV. With this type, sections of pipe are pulled in. The liner wall will be thicker. With a fully structural liner the host pipe can or will be fully deteriorated at the end of the liner’s life (i.e. the liner will be designed to take the full load, without assistance from the host pipe).
“It can have holes in it or multiple problems when the Class IV is used,” says Henry. “But when a semi-structural liner is utilized, existing holes must be limited to a certain size, in order for the liner to span such gaps. Basically, as your pipe gets more deteriorated, what you are actually doing is creating a new pipe that will withstand all the loading and pressures inside the host pipe (Class IV—fully structural), as compared to the other classes, which rely on the host pipe to assist with reducing the loading and pressure.
“One thing everyone in the industry accepts as a truism is that your most valuable asset is that hole in the ground,” says Henry. “If you’ve got that host pipe there—regardless of its condition—as long as it’s roundish, that’s a huge asset. Things can be pulled in and worked with. It’s when you lose that hole in the ground that you’re back to digging again.
“Each technology has its limitations, of course, and the technology in this area is changing rapidly, virtually on a monthly basis. It’s a booming technology. Typically the liners are split up into those for rehabilitation and those for replacement.”
Slip Lining and Pipe Bursting
What UMA Engineering Ltd. does for potable water systems is go through a comprehensive evaluation of the owner’s pipeline, starting with inventorying the normal seven steps of asset management, within the best practices technique developed in Canada. This program walks individuals through a program of managing assets. One of the first questions asked is simply: What do we have here? Information is collected on assets, what condition they are in, and finally what level of service needs to be provided.
“In the case of the water supply infrastructure, there is often a push to keep pipes active despite their having deteriorated to some degree,” says Henry. “The ones that have deteriorated must be looked at in terms of maintaining that asset over a certain period through sustainable funding.”
This can be done a number of different ways. Perhaps the most economical is open-cut trenching, according to Henry. In this method the pipe is dug out and replaced. Other technologies, which can be economical, depending on where they are being used, include trench-less rehabilitation programs and keyhole technology.
Keyhole technology ensures less chance of collateral damage during excavation. This is especially effective in working in small or tight areas where damage from excavation equipment must be kept to a minimum. Also coming into play is the fact that utility lines may not have been accurately located or be in the best physical condition.
“If you have a piece of infrastructure underground that is not in very good shape, the last thing you want anyone doing is digging around it,” says Henry. “That is only going to aggravate the problem and possibly force a reactive rehabilitation or replacement.”
When utilizing a pipe liner is not feasible, pipe bursting or horizontal directional drilling are possible alternative technologies for keeping a water line in place. “Some of the things which would drive a system to go to pipe bursting might be a situation where the host pipe has collapsed or is in very bad shape,” says Henry.
“If it’s determined a larger water main is needed, in such a case, pipe bursting is virtually the only trenchless means to upsize (i.e., 30% larger), as all the others will only produce a smaller pipe. However, not all pipes need to be upsized to deliver more water. Typically, when liners are installed, their interiors are much smoother than the existing material.
“Pipe bursting can work for pipes in the 50- to 1,200-millimeter-diameter range. Slip-lining products can be composed of a number of materials, such as polyethylene, resin-impregnated membranes, PVC, steel, concrete, glass- or fiber-reinforced plastics, ductile iron, et cetera. Currently the polyethylene-based slip-lining products are perhaps the industry’s top runner for economics and versatility, doing pipe diameters from 50 millimeters all the way up to 4.0-meter diameter,” says Henry.
Water Systems: One Part of the Big Picture
Levelton Consultants Ltd.—a British Columbia and Alberta firm—supplies consulting services for municipal water systems. The firm also supplies these services for industrial underground infrastructures for the oil and gas industries. It also supplies offshore infrastructure protection. It does cathodic protection design along with corrosion engineering services, which include both corrosion failure analysis and corrosion in situ investigations. It also has different types of consulting engineering services in the geotechnical field, as well as the environmental, hazardous materials, metallurgy, and other disciplines.
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| Photo: City of Monroe Water Department |
| A water main in dire need of treatment |
In a situation where the interior lining may be degrading and there’s the goal of prolonging the life of the pipe, poor water quality may also dictate that something be done. Pipe liners may be the answer. There are two basic types of pipe liners. The first is a cosmetic type simply used when the integrity of the pipe itself is still intact. The liner can either be sprayed on or be pulled through as a long tube, and steam can be injected along the line, expanding the PVC tube out to the outside of the pipe.
The second type, structural liners, may actually be pulled in as a structurally integral liner that replaces the pipe itself and is sound enough to handle the pressure of the pipeline. “Pipe liners can be used to combat leaks, prolong the life of a pipe structure, [and perform] other related applications for various types of in situ rehabilitation techniques,” says Ian Thornton, Levelton Consultants Ltd. project manager and a corrosion technologist, certified through NACE International.
The Expanding Market for Pipe Lining on the Potable Water Side
Insituform Technologies Inc., a Missouri-based pipelining manufacturer, began in the early ’70s doing cured-in-place pipe as a trenchless method of rehabilitation. The company’s method can go manhole to manhole installing basically a pipe within a pipe. Until fairly recently, sewer gravity pipes were mainly what the company had done. Insituform started working with potable water pipelines less than 10 years ago.
“We didn’t do a lot in the drinking water segment, and what really held us back was we could renew the pipe, but when it came to reinstating the service connection, we would have to dig a hole at each service connection,” says Michele Lucas, marketing manager with Insituform. “Even though we had a trenchless product, we still ended up having to dig at each house or service connection.”
In the last year Insituform has introduced a new product called iTAP. This new technology features a robot sent into the water main. The robot can cut through the liner and then actually place a gasketed seal in place so there is now a sealed connection. This technique avoids all digging at each service connection.
“We think this method will really open up the trenchless market in the potable water segment,” says Lucas. “On the sewer side a lot more of the work is already being done trenchlessly—for some 30 years now. But on the drinking water side the percentage of trenchless work is very small. This type of work typically involves digging up pipes and doing parallel replacement so that customers can still have a functioning supply of drinking water.”
Insituform’s liners come in HDPE solutions, cured-in-place type solutions for pressure pipe, and a product called Thermopipe. The Thermopipe product and the HDPE, known as PolyFold or PolyFlex, are pulled through the pipe. The cured-in-place pipe product is actually inverted or turned inside out and propelled through the pipe with water. These products may be used for a number of different reasons such as poor water quality, water breaks, leakages, or pressure problems in the system. “We can renew the pipe so basically you are getting a new pipe without having to dig it up,” says Lucas. “With a 50-year lifespan on this product, we’re basically giving you a pipe within a pipe. Some of the solutions need the host pipe for structural reasons, while others are able to stand structurally on their own; it depends on each project which product we’ll use.
“There are a lot of water pipes out there which have been in the ground 100 years. They are past their useful life, and municipalities are experiencing water main breaks at an accelerating rate. This is a good way to rehabilitate the pipe without disruptive construction.”
Pipe Lining for Various Efficiencies—and Water Quality
The City of Monroe, MI, had an ongoing problem with potable water coming out of the tap with a rust color, indicating a corrosion problem. According to Barry LaRoy, Monroe director of water and utilities, the city also had some reliability issues with water main failures and fire flows because of the aged lines and reduced pipe diameter. For fire fighting there’s a certain requirement of gallons per minute, an important issue for the fire department.
After November 2006 the city cleaned a particular section. The line was cleaned with sewer cleaning–type equipment as well as disinfected before being placed back in service. This increased the fire flows, but there were still issues with rusty water. “When the pipe is cleaned, you basically have unlined pipe once more, and it continues to rust. Another concern is the pipes are becoming less efficient in water transport that reduces overall energy efficiency as well. It takes more power to pump water through such pipes,” says LaRoy.
As a result of the test and a review of the products offered by Insituform, a proposal was awarded by the City of Monroe to Insituform in January 2007. LaRoy likes the important side benefit of the fact that through this lining process, the city’s flushing program for pipe dead ends was reduced.
Pipe flushing by the city had traditionally been done at night when customer water use is low, and it involved a lot of overtime hours for employees. Also, many of the cast-iron pipes, when they were first installed, contained a substantial number of lead joints as well as frequent main breaks. The city ended up using Insituform’s Thermopipe, a polyester-reinforced polyethylene lining system, NSF-61 approved for contact with water.
“This is Insituform’s first Thermopipe project in Michigan, and we were required to obtain a Michigan Department of Environmental Quality drinking-water construction permit as they had to investigate the product,” says LaRoy. “We successfully obtained a permit, receiving that in early spring 2007. As the installation proceeds, customers are placed on ‘bypass,’ a 2-inch service line tied into adjacent street fire hydrants. Through the entire project all customers continue to have water service.”
When the fire flows were tested in November, they varied at two test sections, between 900 and 1,100 gallons per minute (gpm) at 20 psi. When they were tested after the cleaning of the pipe, the fire flow was 1,800 gpm, effectively doubling the capacity. But after the liner was installed, the fire flow increased up to 2,200 gpm. The liner is less rough than the unlined cast-iron pipe. “The liner is close to PVC pipe in its c-factor, rated at close to 140. The previous c-factor for the iron pipe was approximately 80—about a 75% increase—before we did anything. Now after having the pipe lined, there’s a huge increase in water efficiency all around,” says LaRoy.
For the current process, whenever there is a tee or valve in a line, digging must occur at that location, and a mechanical fitting is provided for connecting at those points. At present, the technology is unavailable to line through such locations without excavation, according to LaRoy.
When the liner is pulled through the pipe with a winch, the product is shaped like the letter C, and unreels off a roll. It is then inflated with steam. Once steam starts to escape from the other end of the pipe—the section then only needs to cure roughly 15 to 30 additional minutes—the product cures up against the inside of the existing pipe, taking the shape of the inner pipe diameter. It is flexible and formless at first, and then when it’s cured, it is semi-rigid.
“This lining is pressure-rated at well over 200 psi,” says LaRoy. “It doesn’t stick to the inside of the pipe wall for the important reason that even if the pipe itself were to move, this liner isn’t stuck to the pipe walls and therefore reduces the chance of shearing the liner. The host pipe is not relied upon to supply pipe rigidity.
“We had a total of eight locations which we had to dig up, because at each fire hydrant there is a tee,” says LaRoy. “Nine feet had to be cut out in order for there to be enough room to go both directions with their cameras and our cleaning equipment. There was enough room to work and for us to make our connections mechanically. We ended up replacing all the hydrants and valves in that section as well. We now have all new infrastructure, and it’s much more reliable.”
As with others, LaRoy echoes the idea that minimum disruption of the existing roadways, driveways, lawns, and landscaping also represents a major cost savings in all this. “Once things were coordinated with Insituform, everything went quickly,” adds LaRoy. “The whole section was lined within about a week. Then the testing had to be completed. The system has some 65 miles of cast-iron piping, and we hope to eventually line the larger pipe diameters completely and replace the smaller diameters in the not-too-distant future.”
“Rust and corrosion of pipe are basically different names for the same thing,” says NACE International’s Johnson. “Cast-iron pipe and its corrosive properties have been well understood ever since it was first placed in the ground—but it just hasn’t really been addressed as an issue. With so many systems out there reaching the end of their lifespan, the greatest challenge is getting the potable water industry to have a greater awareness of how widespread and potentially devastating corrosion in water piping systems is.
“The first step is to acknowledge what your system’s constructed of, address what your problems are, and then take the appropriate action. We’re here for those wondering where to start with this important issue.”