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What is the meaning of 1x in vibration analysis?
Consider a pump is running at 3000 RPM i.e. 50 revolutions per second or 50 Hz. If the impeller of the pump is having static imbalance, the pump generates the vibration at 50Hz. Since the frequency of vibration is the same as the RPM of the pump, the frequency of vibration is expressed as 1 \times RRead more
Consider a pump is running at 3000 RPM i.e. 50 revolutions per second or 50 Hz. If the impeller of the pump is having static imbalance, the pump generates the vibration at 50Hz. Since the frequency of vibration is the same as the RPM of the pump, the frequency of vibration is expressed as 1 \times RPM. Similarly, if the pump is having radial misalignment with the motor, the pump will vibrate at 100 Hz frequency. Hence its frequency of vibration is 2 \timesRPM. It is very meaningful to represent the vibration of a fault in terms of RPM. 1\times represents the frequency of vibration of equipment (due to fault) in terms of its RPM.
See lessWhy measuring phase in vibration is important?
Phase angle represents the relative position of a vibrating object with respect to a fixed point or with respect to another vibrating object. Consider the following example where object-1 is moving up and simultaneously object-2 is moving down from their mean equilibrium position. The motion of objeRead more
Phase angle represents the relative position of a vibrating object with respect to a fixed point or with respect to another vibrating object. Consider the following example where object-1 is moving up and simultaneously object-2 is moving down from their mean equilibrium position. The motion of objects is plotted in the curve shown below. The horizontal gap between the peaks of the two curves is 180 degrees. Hence the phase angle between these two objects is 180 degrees which tells that the two objects are moving in opposite directions to each other.
Figure: Physical significance of phase angle.
See lessWhen to use displacement, velocity and acceleration?
Displacement is used to express vibration severity when the vibration frequency is less than 600 CPM (Cycles Per Minute) or 10Hz. Because the dominant mode of equipment failure at low range frequency is stress. The displacement or deflection of an object is directly proportional to stress. $ \sigmaRead more
- Displacement is used to express vibration severity when the vibration frequency is less than 600 CPM (Cycles Per Minute) or 10Hz. Because the dominant mode of equipment failure at low range frequency is stress. The displacement or deflection of an object is directly proportional to stress.
(From Hook’s Law)
(
represent the displacement of an object from its mean equilibrium position)
- Velocity is used to express vibration severity when the vibration frequency is in the range of 600 to 120,000 CPM or 10 to 2000 Hz. Because the dominant mode of equipment failure at medium-range frequencies is fatigue. Fatigue is a function of displacement-magnitude and its frequency. Velocity is also a function of displacement and time (Time=1/Frequency). Since velocity is the indicator of fatigue, velocity is used to express the vibration severity at medium-range frequencies.
- Acceleration is used to express the vibration severity when the vibration frequency is greater than 120,000 CPM or 2000 Hz. Because the dominant mode of failure at high frequencies is due to force. From Newton’s second law of motion, force is expressed as the product of mass and acceleration. Acceleration is proportional to the force. Indirectly, acceleration is representing the force. Generally, faults in the bearings occur at high frequencies.
See lessWhat are the benefits of measuring vibration velocity instead of vibration displacement?
Machinery vibration is measured in terms of displacement(microns), velocity(mm/s) and acceleration($ m/s^2) $). But velocity is the preferred parameter for measuring machinery vibration because most of the equipment failure during vibration is due to fatigue. (Fatigue failure occurs when an object iRead more
Machinery vibration is measured in terms of displacement(microns), velocity(mm/s) and acceleration(
). But velocity is the preferred parameter for measuring machinery vibration because most of the equipment failure during vibration is due to fatigue. (Fatigue failure occurs when an object is subjected to repetitive or cyclic loads). For example, consider a metal wire, when you try to break it by applying tension, it requires a good amount of load to fail it. But the same wire when subjected to and fro deflection or displacement, requires relatively less load to fail the wire. This is due to fatigue. Fatigue life depends on how much an object is deflected and its frequency of deflection. Metal wire fails early if the magnitude of deflection and its frequency is high. The vibration parameter that considers both displacement and frequency is velocity since velocity is the product of frequency and displacement.
See lessWhat are the characteristics of vibration?
Since the vibratory motion of an object is characterized by a waveform, the vibration has similar characteristics to a wave. Vibration has 5 characteristics as follows. Frequency Displacement Velocity Acceleration Phase
- Since the vibratory motion of an object is characterized by a waveform, the vibration has similar characteristics to a wave. Vibration has 5 characteristics as follows.
- Frequency
- Displacement
- Velocity
- Acceleration
- Phase
See lessWhat is predictive maintenance?
Predicting the future of equipment and preventing it from catastrophic failure based on the present condition of the equipment is called predictive maintenance. The present condition of the equipment is monitored using condition-monitoring techniques like vibration, noise, temperature…etc. DevelopinRead more
Predicting the future of equipment and preventing it from catastrophic failure based on the present condition of the equipment is called predictive maintenance. The present condition of the equipment is monitored using condition-monitoring techniques like vibration, noise, temperature…etc. Developing faults can be identified by measuring and trending the vibration. The root cause of the fault can be detected by performing a frequency analysis of the vibration.
See lessWhat is bearing life?
The bearing life of an anti-friction bearing is defined as the number of revolutions (in millions) or the number of hours at a given speed that 90% of bearings in a lot will withstand before the signs of the first failure.
The bearing life of an anti-friction bearing is defined as the number of revolutions (in millions) or the number of hours at a given speed that 90% of bearings in a lot will withstand before the signs of the first failure.
See lessWhy measuring the vibration of a machine is important?
In general, the vibration of rotating or reciprocating equipment under operation (pumps, compressors…etc.) obeys the following governing differential equation of motion M\ddot{x}+C\dot{x}+Kx=F_{Exciting \, Force}. The LHS of the equation represents the sum of the inertia force, damping force and sprRead more
In general, the vibration of rotating or reciprocating equipment under operation (pumps, compressors…etc.) obeys the following governing differential equation of motion M\ddot{x}+C\dot{x}+Kx=F_{Exciting \, Force}. The LHS of the equation represents the sum of the inertia force, damping force and spring force of the equipment. The RHS of the equation represents the excitation force due to faults in the running equipment. Faults like unbalance in the impeller, misalignment between motor and the pump, structural looseness, bearing failure, cavitation & flow turbulence in case of centrifugal pumps..etc induce F_{Excitation \, Force}. If RHS is greater than LHS, i.e. the magnitude of the exciting force is greater than the restoring force of the equipment, then the equipment is subjected to significant vibration. By analysing the frequency and the magnitude of the F_{Exciting \, Force}, the source of fault can be identified. Hence measuring the vibration of equipment indicates its health condition. By analysing the vibration, the incipient faults can be identified and equipment can be saved from a catastrophic failure.
See lessHow do you measure vibration?
Vibration is measured in terms of displacement, velocity and acceleration. Vibration is defined as to and fro motion of an object from its equilibrium or means position as shown in the following figure. The distance travelled by an object between the mean position and the extreme position is calledRead more
Vibration is measured in terms of displacement, velocity and acceleration. Vibration is defined as to and fro motion of an object from its equilibrium or means position as shown in the following figure. The distance travelled by an object between the mean position and the extreme position is called displacement and similarly, the distance travelled between the extreme left and extreme right position (with respect to the following figure) is called peak displacement. The velocity of an object is zero at its extreme positions and maximum at the mean position. Since velocity is changing with respect to the position, average velocity or Root Mean Squared (RMS) velocity is preferred. Sometimes peak velocity is also used. Since an object changes the direction of motion at its extreme positions, the acceleration is maximum at the extreme positions and zero at the mean position. Since acceleration also changes with respect to the position of an object, average acceleration or Root Mean Squared (RMS) acceleration is preferred.
Figure: Spring mass sytem
See lessWhat is vibration?
Vibration is defined as to and fro motion of an object from its mean equilibrium position. The oscillation of an object is also similar to vibration but with a relatively low frequency and relatively high amplitude (displacement). Whereas the vibration of an object has low amplitude (displacement) aRead more
Vibration is defined as to and fro motion of an object from its mean equilibrium position. The oscillation of an object is also similar to vibration but with a relatively low frequency and relatively high amplitude (displacement). Whereas the vibration of an object has low amplitude (displacement) and high frequency. Ex. The motion of a simple pendulum is defined as oscillation but not as vibration.
See less