Bending Flexibility of Bolted Flanges and Its Effect on Dynamical Behavior of Structures

Abstract

This paper presents a basis for determining the bending flexibility of flanged joints in complex piping systems for use in predicting natural frequencies, mode shapes, and response to excitation forces. Data was developed by a combination of laboratory testing and analysis. Highly instrumented testing initially identified and isolated the contributing deformations in a flanged joint and later provided overall flexibilities of flanged assemblies for verification of the analytical model. The analysis, its results, and model verification are presented in the paper. Further results are provided which compare predicted dynamic characteristics of reciprocating compressor manifold piping systems with measured data obtained in the field for vibration modes which are sensitive to flange flexibility. Consistent good agreement has been achieved of the techniques utilized in some 50 design and field analyses conducted at the Center for Applied Machinery and Piping Technology (CAMPT ) at Southwest Research Institute.