The Effects Of Vibration And Stress On Safety Characteristics Of Piping

Pressure piping is a kind of special installation with high risk in human life and production since it's easy to burst,leakage and fatigue damage;pressure piping is mainly used in numerous industries,like petroleum,chemical industry,metallurgy,electric power and municipal supply(e.g.water,heating and gas).The safety of pipeline is depend upon reasonable combination of piping stress and vibration,therefore,the key to pipeline safety assessment is to optimize the pipeline after the piping,which the stress and vibration factors can fit corresponding requirements.This paper is based on pipeline stress analysis;we studied the loads of industrial piping,the effects of load on pipe and the failure modes of the pipeline under load.Through the beam model,the mechanical condition of the pipeline is simulated and the calculated stress value is compared with the allowable stress value of the pipeline material.Ultimately,we provided prioritization schemes to the unreasonable structure and design factors on piping.In the analysis of the thermal stress of the pipeline,it is suggested that the shortest principle should not be the only target in the piping.Instead,the displacement and thrust caused by the thermal expansion of pipe should be taken into account.Then,the thrust to equipment and trestle caused by thermal expansion load can be eliminated by compensation capability of pipeline rout,for example,L shape or Z shape natural compensator.Secondly,whether the primary stress will be amongst the allowable value under sustained load is directly determined by the span of trestle.The maximum allowable span is determined by two factors: the strength and stiffness of the pipeline,and the smaller value is taken as the design basis.Finally,in the stress analysis with thermal stress of standpipe,if it adopted the bearing bracket,there would be different degrees of disengaging phenomenon and led to trestle failure when analyzed the pipeline displacement of trestle positions under running state.Consequently,spring trestle should be adopted in designing of trestle of standpipe.After the optimization of the pipeline stress analysis,we took the analog computation toward the vibration performance of pipeline.According to the calculated natural frequency of the pipeline,the piping system is optimized and the mechanical resonance of the pipeline is avoided.Therefore,this paper uses the finite element analysis method,and as a basis for the use of subspace iterative method to solve the inherent frequency of complex pipelines.By analyzing the relationship between the natural frequency and the stiffness of the pipeline,it is put forward to minimize the existence of the elbow in order to improve the natural frequency of the pipeline system when the pipe satisfies the flexible condition.It is concluded that this optimized pipeline design scheme can ensure the safe operation of pipeline system.