Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment Damsmust be properly joined (ASTM D 2657). Upon completion of the repair, theHDPE slipliner should be retested for leaks.Unlike bell and spigot pipe, such as PVC, heat fusion creates a continuous joint-freepipe of nearly constant outside diameter. Bell and spigot joints are susceptible toseparation as the embankment dam settles. Because the HDPE slipliner joint doesnot take up a large part of the original conduit, a larger inside diameter slipliner canbe used. This is an advantage when compared to flanged joints.During cold weather, additional time is required to warm up the fusion machine andto heat the ends of the HDPE pipe. A shelter (figure 166) may need to beconstructed for joining the sections of HDPE pipe in case of inclement weather.For additional cold weather procedures, see ASTM D 2657.Other joining methods for HDPE pipe include:• Joints made by extrusion welding.—Many prefabricated fittings (i.e., elbows, bends,and tees) can be joined to the HDPE slipliner with heat fusion (ASTM D 3261)in the field using an extrusion gun. The extrusion gun (figure 167) is a handheld extruder that preheats the surface of the HDPE pipe and feeds a moltenbead of polyethylene into the joint. Extrusion-welded joints are not as strongas butt fusion joints. Proper training is required for using the extrusion gun.Extrusion welding has been successfully used for connecting HDPE grout300Figure 166.—Cold weather shelter constructed for joining sections of HDPEpipe.