New heat activated epoxy-based materials are now being used to repair leaking and corroded pipe work when operations are unable to shut down.
One key component in repairing leaking and corroded pipe work is the need to do in situ applications (which means in the original position or place). However, many systems have not been constructed with the ability to shut down portions of water lines without interrupting daily consumer activities. For this reason, the need for emergency repair materials has increased as underground systems have become older and more degraded each year.
As water districts across the U.S. struggle to maintain damaged water pipes and systems from decades of environmental attack, scientists have worked to develop repair materials that will efficiently accomplish these tasks. Besides providing rapid repair solutions, it is essential that these materials be easy to apply and tolerant to the surface contamination commonly found in these environments.
Over the last few years, chemists have successfully formulated two single component heat activated epoxy-based materials. One is in the form of a paste and the other is a less viscous coating. From plugging active steam leaks to protecting hot pipes from corrosion under insulation, these new heat activated materials have been used for a variety of fast and effective in situ applications. Several successful repairs have been performed on in-service pipes with temperatures up to 302-deg F (150-deg C).
These materials require no mixing or measuring and can be applied using a mastic gun, spatula, or paint brush (see Figure 1). Cure will not commence until the material is at temperatures above 158-deg F (70-deg C); therefore, the usable life is effectively unlimited at room temperature.
Figure 1. The paste grade polymer is being applied via metal spatula. Note the thick gloves the applicator has donned for protection against the heat.
These materials show exceptional adhesion to oily and unprepared metals, so long as rust or mill scale is removed. Tensile shear adhesion values at elevated temperatures (212-deg F/100-deg C) on clean, ground steel are 2800-psi for the coating material and 2200-psi for the paste grade. On a steel surface prepared according to ISO 8501-1 St 3 (manually abraded), tensile shear adhesion values are only slightly compromised to values of 2600-psi and 2100-psi for the coating and paste grades, respectively.
In extremely limiting conditions, where preparation can only be done via wire brush (ISO 8501-1 St 2), values of 1700-psi for the coating and 1200-psi for the paste material can still be accomplished. In addition to excellent adhesion, these materials also exhibit excellent resistance when immersed in various chemicals and also show no visible signs of corrosion after 1,000 hours of salt spray, according to ASTM B117.
The application described here was performed on active steam leaks by technical consultant LeRoy Johnson, as seen in Figure 2. The maintenance manager was unable to shut down the system and informed Johnson that welding was unsuccessful and the pipes were badly corroded and in a confined space.
Figure 2. The application area has been secured with yellow CAUTION tape. Steam can be seen emanating from the pipes.
Johnson was aware of the advantageous properties offered by these materials and was confident that he could provide a solution to the manager's problems. In Figure 3, an infrared thermometer shows that the steel surface temperature was about 200-deg F (93-deg C).
Figure 3. An infrared thermometer is used to determine the actual temperature of the pipes.
Once the pipes were prepared by hand wire-brushing, a generous layer of the paste grade polymer was applied. Then an aluminum sleeve was also covered with the heat activated material and tightened with a clamp (see Figures 4 and 5).
Figure 4. The paste grade polymer has been laid out prior to the application.
Figure 5. The aluminum sleeve has been placed over the repair area and the pipe clamp is being tightened in place. The coating grade polymer is being applied via brush over the entire repair area.
Once the material was cured, the entire area was coated with the coating grade polymer to further protect the pipe from corrosion and environmental attack. When the clamps were removed, no steam could be seen and the manager was amazed that the entire process was completed while the pipes were still in service. The leaks were repaired, and the pipes are now protected from further corrosion.
These new heat activated materials can be used to coat, repair, bond, and protect a variety of metallic substrates where typical maintenance materials would degrade at the high working temperatures found in these applications. Ease of use, fast cure, and excellent adhesion with minimal surface preparation make the newest heat activated materials a top choice for industrial repair situations, especially in the water and wastewater industry.
In fact, repairing active steam leaks is only one of the many possible problems the newest heat activated epoxy-based materials are capable of resolving. For example, one rapid-curing epoxy is simply mixed between the finger tips and then forced into a live water or chemical leak in order to allow drying time and preparation for the application of a permanent material.
For higher pressure live leaks, a doubler plate technique utilizing another metallic polymer substrate is employed. When done properly, this repair can permanently stop the pressurized fluid. New epoxies have been developed and used for applications to pumps, fluid handling systems, concrete, pipe work, expansion joints and conveyor systems in addition to leak repairs.
Pumps & Systems, November 2007
