——— Ideal Riser Design ———
From a piping standpoint, minimum stresses can be obtained through the use of an anchored system. Generally Isolators should be designed to support the weight load of the pipe. In cases where there is a section change in the pipe, Isolators should also be designed to absorb the hydraulic thrust that is generated. If anchored at the bottom, the anchor should absorb the load generated by the water column without transferring the load "up the pipe". If anchored at the top, the bottom isolator should be a preloaded coil with sufficient capacity to absorb the water column load.
With this arrangement, the pipe in service, will be exposed to the lowest stresses possible and the large hydraulic load can be dissipated at the bottom of the structure rather than spreading it out over several floors and then bringing it back down through the structure.
The use of restrained isolators in this arrangement will further reduce stresses in the pipe and structure during the installation process.
While this is ideal from a riser standpoint, it requires that the structure be capable of taking a large point load at the bottom of the riser that often times they cannot.
