Unisert evaluates each piping project individually and employs one of three Design Levels based on the project parameters.
The liner is designed to handle the system operating pressure and criteria without relying on the existing outer case pipe for pressure containment. The outer case pipe is used primarily as a conduit for the liner and to provide structural support and impact protection.
Operating the liner up to its short term burst pressure capabilities. The primary reasoning behind this design level is that in FRP pipe, there is a 5-1 to 7-1 safety factor designed into the piping system to compensate for cyclic loading. The failure mode, in this case, is the shear between the glass and the resin due to the yield of the pipe, which creates the shear. Therefore, the liner being in a compressed mode in the multiwall structure does not see that strain, therefore negating that particular failure mode.
Operating the liner above its short term burst pressure capabilities. This also refers to the level of quality control measures taken during installation. The outer case pipe (steel in this case) is used to handle the pressure containment for the system.