Vibration Analysis And Retrofit Research For A Boiler Flue System

Thermal power generating units is a large and complex system, any part of the problemmay affect the safe and economic operation of the unit. The vibration problem is that the unitis running more often and difficult to solve a class of problems. Thermal power plants have alot of vibration equipment, such as smoke, air duct system, steam turbine, delivery- induceddraft fan, generators, all kinds of valve and so on. Currently, the induced draft fan system ofgenerator sets which have run for many years all have different export flue levels of vibrationin the domestic. Especially in the design and construction process, due to the limitations ofspace and costs, and will often select a few boiler exit flue parallel use by the same chimneyflue to exclude, which will inevitably lead to many flue dead ends and bend, and then the fluegas in the flow of the process due to the uneven flow, leading to severe vibration of the fluewall. It will result in frequent tearing of the flue and the generating units will be forced toshutdown when the situation is serious. The vibration of the boiler flue system is a complexengineering problem, which involves a large number of subject knowledge. Therefore, it isnecessary to carry out research on the vibration of the power plant boiler flue system, graspthe main reason caused by the vibration and the vibration mechanism and take correspondingmeasures to ensure the safe and economic operation of the unit, to avoid personal injury andequipment damage accidents.This paper expatiates on the boiler flue caused the vibration of the vibration systemmechanism and vibration causes. Combined with the unit system structure of the special flueactual situation and vibration test results, the results show that the vibration of the flue duct iscaused by the non-uniform flow which is resulted from the system organization, the whirlingflow-away in the fan, the eddy current generated while flow through the pillar and the flue gassystem’s bending rigidity is not enough.According to the strong vibration of the induced draft for one steel company limited utilityplants 2#、4#and 5#boiler flue, mainly through numerical simulation to analyze the cause ofthe root causes of the flue vibration, and then combining with vibration test results andtransform experience, then propose the appropriate measures for improvement. Theimprovements start from the following three aspects: first, through numerical simulation ofthe appropriate location within the main flue installation of deflector, internal flow field in themain flue uniform and stable; second, by installing an air flow arc panel in the induced draftfan, a rectifier in the induced draft fan and a guide vanes in the induced draft fan at the exit , the gas flow of induced draft fan to enter the flue more uniform and stable; third , reinforcethe lateral wall of the flue and the induced draft fan and install the inner pole inside the flueproperly to reduce the number of reinforcement rib. After the completion of the modificationconstruction, according to the transformation of the former six conditions of the same point ofthe spectrum testing, through comparing found: the point the point the amplitude of vibrationis greatly reduced and generally not more than 450μm, to reform the purpose.