Hyoungsan Kye, Kyunghoon Joo
A newly developed electro-foaming fusion (EFF) wrap for PE pipe is a fitting that wraps up the pipe and melts the PE sheet onto the pipe surface. The Electrofoaming fusion wrap adopts its foaming concept and welding technique for PE sewers and drainage pipes. The electro-foaming fusion wrap consists of a foaming sheet, a supporting sheet, and a clamping band. The foaming sheet is a melt blends of metallocene PE, LDPE, foaming agents, and additives. An electric thermal wire mesh was embedded in the foaming sheet; the electric thermal wire meshes transform electric energy into thermal energy, allowing the PE foaming sheet to fill the gaps between the pipe surfaces and the wraps. The standard processing temperature for PE sheet extrusion is above 200°C, but because the foaming agent starts to foam around 150°C, a low-temperature extrusion technique is applied on the melt blends of foaming agent and PE. The supporting sheet is made with metal mesh or HDPE embedded with tire cord in order to support the foaming sheet and to weld with the foaming sheet. The clamping band fastens the foaming sheet and the supporting sheet tightly during the welding to bind the foaming sheet and the pipe surface permanently. The clamping band is made with stainless steel plates or metal mesh bands and is removable and reusable. The mechanism for the fusion process is as follows. The electro-foaming fusion wrap starts to foam once electricity is injected into the electric wire embedded within the foaming sheet. Once the temperature reaches 150°C, the foamed PE fills up the voids between the pipe surfaces and the wraps. These voids are caused by sheet overlaps and shape (oval) differences. The benefit of foaming is that the foaming action starts only if the void exists. Otherwise, there is no foaming action and instead, the sheet bonds to the pipe surface tightly. This wrap fitting demonstrates excellent results on solid wall pipes and even on structured wall pipes. This wrap fitting is the only reliable solution for large diameter (400 mm up to 3000 mm) pipes with shape problems such as ellipsoidal deflection from transportation/storage, and pipes with diametric size differences caused by the pipe manufacturing process.