As the FRP is superior in the corrosion resistance and is more inexpensive in material cost than corrosion resistant metallics, recently it is widely used for large diameter piping material.
To join the FRP piping of large diameter, a double lap joint is generally used, in which the secondary adhesion is applied on both inner and outer surface. Until now it is empirically said that the de sign water velocity is 3m/s and critical water velocity is 6-10m/s with regard to the peeling off of the second adhesion part laminated inner face produced by water flow. But the piping for sewer and water-conveyance that has been used until now is flat with low water velocity and low water head. The process piping of large diameter is provided with bends, branches, pipes with head, control valves and heaters in the piping system. The pressure, velocity and temperature vary greatly in the pipe. Therefore, it is necessary to consider whether the values on the basis of former experiment are suitable for the process piping. The purpose of this report is to make clear the basis of the peeling off limit in the former experiences. In this report of part 1, the experiment of the peeling off by the water jet is shown. This experiment is concerned with the forming factor and selection of material, disregarding the secular deterioration of resin. In the next report (Part 2), the same experiment on the secular deterioration of resin will be shown. The mechanism of peeling off by water flow will also be considered. Further a new method of the second adhesion joint which will prevent the occurence of the peeling off will be proposed.