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Does the job.

For almost 50 years, PVC linings have been protecting structures in sewer systems from corrosion. There are two primary reasons for the long-term success. One reason is that PVC is impermeable to hydrogen sulfide gas; the other reason is that it can be manufactured free of pinholes and thin areas. However, until recently it could not be cost-effectively retrofitted to existing structures.

Several of the largest sewer authorities in the U.S. now use products and systems developed over the last 15 years by Linabond, Inc. (Los Angeles, California), which allow cost-effective retrofitting with impermeable, pinhole-free PVC sheets to rehabilitate pipelines and structures that have been damaged by corrosion. Linabond can also be used to protect new structures.

DEVELOPMENT OF THE SYSTEM

Jim Durden, senior civil structural engineer, Los Angeles County Sanitation District (LACSD), explained that his department was involved with the early development of the first Linabond Mastic System: "About 15 years ago, we were experiencing quite a bit of difficulty with sulfide. It happened rather quickly after we were required to place coverings over everything, mainly for odor control. This actually captured hydrogen sulfide and concentrated it in our system, particularly in areas with a lot of turbulence such as grit chambers, feeder channels, and the pump stations coming into the plant. When the corrosion began to affect us structurally, I became involved.

"The early epoxy and urethane coatings we put on were permeable by the sulfide gas and they would pinhole very badly. The sulfide molecules and Thiobacillus bacteria were so small, they would go right through the coatings and start their corrosive cycle on the substrate. In a very short period of time, the coatings would delaminate.

"We experimented with Linabond in the sedimentation tanks and in other structures in the primary end of our treatment plant where damage was very severe, and it held up. That was the first place that a co-liner was ever used.

"After that, we worked very closely with Linabond as their products evolved. They have always bent over backwards to accommodate us and try to make changes and do things that would solve our problems. But, we have done the same for them, so it has been a very good relationship."

A STRUCTURAL, EXPANDING POLYURETHANE

News of the system's success in L.A. soon spread to Seattle, Washington. The King County Wastewater Treatment Division (KCWTD) there called Rich Bertram, inventor of the system, and asked for help. Bertram explained it this way:

"They had a very badly corroded siphon in Seattle. At first they were going to apply a cementitious material to rebuild the surface, but they couldn't get it to stick. I told them I had been working on an expanded polyurethane, but they said they didn't have time to wait on that, and asked me to send a truck load of my polyurethane mastic. It worked, but the following year, they said they would like to try the expanded material.

"We sat around a conference table in the Exchange Building in Seattle and worked out the parameters for the material they needed. A foam that's about 2-1/2 pounds per cubic foot is considered high-density. What we developed was in the density range of 17 to 20 pounds per cubic foot. It's actually a structural material. We used it to rehabilitate the outlet of the siphon we had repaired the year before. I did the spraying myself. It worked well. In fact, it's still working well. That was in 1990."

Roger Browne, managing engineer, KCWTD, comments: "We have used the Linabond systems since 1990, and the results have all been good. Uniformly good. We have attempted to throw very bad conditions at this technology - freezing temperatures, no ventilation, live sewer, and short preparation times - yet it has managed to stick to the walls no matter what we do.

"This is one of the main reasons we like it so well. It's nearly contractor-proof. It does an excellent job of bonding. Much better than anything else we've tried. Over the years, we have conducted a series of coating tests similar to the ones that L.A. County has performed. So far, none of the coatings have ever succeeded, and none of the Linabond products have ever failed. On a purely economic basis, it has proved to be avery good choice for us.

"The co-lining system interlocks with the concrete and with its vinyl liner, so that when pull-off tests are performed, you essentially have to break the concrete in order to get the product off the pipe wall. That's about as strong as you can get. Anything stronger than that is wasted chemical.

"With Linabond, we get a superior bond, and we get the benefits of two lining systems at once. The polymer is a liner, and the vinyl is also a liner. We find that each, by itself, protects the concrete from hydrogen sulfide damage, but both, when fully bonded together, is as bulletproof as we can envision for a lining system.

"We have also used that system in about 2,000 ft of pipeline, and will do a lot more of it. Next year, we'll start a 10-year project in which we will line approximately 3,000 ft of 60-in. to 108-in. diameter a year. As far as we know, it will all be Linabond."

LARGE DIAMETER PIPELINE REHABILITATION

The Metropolitan Wastewater Department, San Diego, California, is using the product in a large diameter pipeline rehab project. Jim Mueller, senior civil engineer, Program Management Division related:

"We've used Linabond in repairs to concrete structures at our Plant Loma treatment plant. And, we've recently specified them for rehabilitation of 6,300 linear feet of our 108-in. diameter South Metro Interceptor sewer, which runs from the downtown area to the airport. This contract allowed Linabond and another technology to bid, and Linabond was the successful low bidder. One advantage of Linabond was that we could do the project at night without having a complete shutdown or bypass pumping. Another, of course, was the price.

"Linabond will cover the top 220 degrees to 270 degrees of the pipe. It would be very difficult to cover 360 degrees, and it is not necessary because you don't get corrosion below the flow line. We had some concerns about its ability to adhere to the concrete, so we made some tests which show that it really bonds firmly. Linabondhad other tests run which show their product also provides some structural enhancement.

"The real enemy is the bacteria which reside in the pipes and ingest hydrogen sulfide gas. Their waste is the sulfuric acid which corrodes the concrete. Linabond prevents the gas from reaching the pipe."

THE BOSTON PROJECT

In Boston,Jack Baylis, president of Linabond, started working with the Massachusetts Water Resources Authority (MWRA) and their design engineers on a major effort to protect the massive Deer Island and Nut Island treatment plants. MWRA had invested a lot of time and money into the new plants and wanted the best corrosion protection. Key MWRA staff, their design engineers (Metcalf & Eddy and Montgomery-Watson) and their construction manager (Kaiser Engineers), hired and relied on top corrosion experts to select and specify the right solution.

Randy Nixon, president, Corrosion Probe, Inc., Centerbrook, Connecticut, explained that his company was contracted to recommend a long-term solution for the high [H.sub.2]S concentrations and subsequent sulfide-related corrosion problems. He explains:

"Earlier linings were designed to be mechanically anchored into the concrete. What Linabond brings to the table is the ability to use PVC sheet linings for existing concrete applications using their co-lining technology. They are able to use the mastic to achieve good mechanical adhesion to the concrete, and to chemically adhere the PVC sheet to the mastic over the entire area of the lining. It takes a proven material performance and uses a very innovative co-lining technology to achieve application over existing concrete structures."

Baylis said, "We're in a technology and people business. The people who work directly for the company really care about doing a good job. Rich Bertram started a company culture and vision which we are now carrying into the future. We will continue to develop new technologies, meet or exceed our clients' requirements, and strive to provide a workplace where people are excited about being part of the solution."
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Title Annotation:Linabond Structural Polymer Pipeline System
Publication:Public Works
Date:Feb 1, 1998
Words:1387
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