Comparison of Static to Dynamic Nozzle Loads on a Brick-Lined Oxygen Reactor

This paper on "Comparison of Static to Dynamic Nozzle Loads on a Brick-Lined Oxygen Reactor" was presented at the NAFEMS World Congress on The Evolution of Product Simulation From Established Methods to Virtual Testing & Prototyping - 24-28 April 2001, The Grand Hotel, Lake Como, Italy.

Overview

Dynamic loads have been known to contribute to local failure of nozzles in a large variety of vessels and process equipment. Dynamic nozzle loads generally resulted from piping loads, pumps, agitators, thermal loads, wind loads and so on. The main concern with any dynamic load is the excessive vibration that can result from resonance or close to resonance in a certain frequency range (when natural frequency of the equipment equals the frequency of the forcing load) that ultimately would lead to failure of the nozzle. In most instances and for practical purposes, vibrations due to dynamic loads cannot be eliminated completely, but their magnitude can be reduced by studying the nature of the dynamic loads and the way they behave. Once the pattern of the forcing load is understood, the dynamic loads can be applied to a finite element model of the nozzle and an analysis can be done successfully. One of the ways to reduce stresses locally (reduce dynamic loads on nozzles) is to reinforce the nozzles locally in such a way that the dynamic loads are distributed over a larger area (mass) thus dissipating the loads. Finite element analysis can be utilized for both preliminary and final solutions. By analyzing the dynamic loads, the process nozzles can be effectively reinforced locally to meet the required equipment fatigue life.
The through-put nozzle loads in oxygen reactors in pulp and paper industries are a good example of dynamic nozzle loads in process equipment. Oxygen reactors usually have 3 ft to 4 ft diameter nozzles located at the center of the top head.
The through-put is pumped into the reactor using two mechanical pumps 180^o apart. These pumps impose sinusoidal nozzle loads on the nozzle that can be out of phase with respect to each other.