An investigation into vibration criteria for rotating machinery

Abstract

Concern had been expressed by engineers of the Shell Chemical
Company regarding the validity of existing vibration criteria for
rotating machinery.
A survey showed that existing criteria were based solely on
the amplitude of vibration, normally of the bearing housings, with
no allowance being made for the dynamic properties of the support1ng
structure.
The feasibility of measuring the mechanical impedance of bearing
supports in order to assess the severity of vibration generated by a
machine has been investigated. It is suggested that in many cases the
oscillatory bearing force levels obtained for these measurements will
provide a quantitative indication of severity.
Theoretical and experimental work has been conducted on a
model rig, comprising a flexible shaft running in journal bearings
housed in flexible, asymmetric supports. The accuracy with which
the system behaviour could be predicted using measured support
impedances is discussed together with the extraction of uncoupled
support impedances from measurements on the complete rotating system.
Access was available to several industrial centrifugal
compressors. To enable the bearing support impedances of these
machines to be measured on site considerable attention has been
paid to the evolution of a technique involving the use of transient
excitation. To develop this technique the model rig and a large
rotary converter have been used as test structures. Methods have
also been devised and developed for the analysis of the transient
impedance data.

Date of Award	1968
Original language	English
Awarding Institution	Aston University
Supervisor	E. Downhan (Supervisor)