Piping
Vibration Analysis J. C. Wachel/S. J. Morton/K. E. Atkins,
19th Turbomachinery Symposium, Texas A&M University, September
1990.
Excessive piping vibrations are a major cause of machinery downtime,
leaks, fatigue failures, high noise, fires, and explosions in refineries
and petrochemical plants. Excessive vibration levels usually occur
when a mechanical natural frequency of the piping system is excited
by some pulsation or mechanical source. The vibration mode shapes
usually involve lateral vibrations and/or shell wall radial vibrations.
Simplified
methods are presented for analyzing lateral and shell wall piping
vibrations and judging their severity. The methods are thought
to be conservative and are intended to be used as screening criteria
to determine if more sophisticated analyses, such as computer
stress modeling or strain gage testing are necessary. Frequency
factors for calculating the mechanical natural frequencies for
the classical piping configurations (uniform straight beams) and
various piping bend configurations are presented. Factors are
presented to compensate the natural frequency calculations for
concentrated and distributed weight effects.
The relationship
between piping vibration displacement, velocity and stress are
presented and criteria for judging the severity of piping vibration
in terms of the endurance stress limit are shown. The mechanisms
that can excite piping vibrations will be discussed, as well as
methods for controlling their severity.
|
