Pruftechnik Ag - A Practical Guide Of Shaft Alignment

A Practical Guide to Shaft Alignment Care has been taken by the authors, PRUFTECHNIK LTD, in the preparation of this publication. It is not intended as a comprehensive guide to alignment of process machinery, nor is it a substitute for seeking professional advice or reference to the manufacturers of the machinery. No liability whatsoever can be accepted by PRUFTECHNIK LTD, PRUFTECHNIK AG or its subsidiaries for actions taken based on information contained in this publication. PRUFTECHNIK AG and/or its subsidiaries assume no responsibility directly or indirectly for any claims from third parties resulting from use or application of information contained in this handbook. Edition 4;4-03.007 © Copyright 2002 PRUFTECHNIK LTD All rights reserved Distributed in the U.S. by LUDECA Inc. • www.ludeca.com 1 © 2002 PRUFTECHNIK LTD. Introduction The purpose of producing this handbook is to provide basic information and guidelines for the implementation of good shaft alignment for standard rotating machine systems. Laser alignment is an essential component of a viable maintenance strategy for rotating machines. In isolation each strategy can help to reduce unexpected machine failure but taken together they form the hub of a proactive maintenance strategy that will not only identify incipient problems but allows extending machine operating life considerably. In each section of this handbook we have used one or two examples of the available methods for measuring the required parameters. We do not suggest that the methods illustrated are the only ones available. Prueftechnik are specialists in the alignment and monitoring of rotating machines, we have accumulated substantial practical knowledge of these subjects over the 30 years of our existence, in so doing we have produced many handbooks covering individual subjects and systems. This handbook is a distillation of this accumulated knowledge plus a brief overview in each section of the latest systems from Prueftechnik that address the specific applications concerned. We hope that this information is presented in a clear readable form and that it will provide for the reader new to the subject a platform to successfully apply profitable maintenance practice in their plant. We are indebted to our collegues in Prueftechnik AG (Germany) and our associates at LUDECA Inc. (USA) for permission to reproduce some of the graphics used in this handbook, additionally we have drawn on information previously published in Prueftechnik equipment handbooks for information on alignment standards, and graphical and mathematical methods of balance calculation. For this information we are grateful. 2 © 2002 PRUFTECHNIK LTD. Introduction Shaft Alignment 3 What is shaft alignment .. A definition .. Machine catenary .. Operation above critical speed Page Number 6 6 7 8 Expressing alignment .. Alignment parameters .. Angularity, gap and offset .. Short flexible couplings .. Spacer shafts 10 10 11 14 15 How precise should alignment be? .. Alignment tolerances 18 18 Troubleshooting .. Coupling strain and shaft deflection 21 21 Causes of machine breakdown .. Couplings and misalignment .. Bearings .. Seal wear .. Machine vibration .. Symptons of misalignment 23 23 24 24 25 25 Alignment methods a