Whilst every effort is made to model the detail of a piping system, and every effort is made to position the first mode of vibration of the structure between the highest harmonic of the pumping frequency possible it is a fact that when any system is built in real life that the resonant frequencies of that system will not be exactly as predicted. It is also a fact that there are limitations to how much the first frequency of the first mode of vibration of the structure can be raised by additional support.
As with all engineered structures, when the real structure is built there will be differences and deviations from the design model. The impact of this in respect of API674 analysis is that the actual first mode, or natural frequency, of the system is unlikely to be where the design model says it will be, and so sufficient design margin must be allowed for this error.
Where piping runs are changed Flo-Dyne will check the mechanical integrity of the revised piping for static as well as thermal and dynamic stresses, such that any modification proposed back to the client has been fully evaluated prior to presentation.