The vibration analysis handbook (malestrom)

[...]... identifies the problems or problem areas Management, engineers, and technicians must determine the cause of the problems and direct the necessary repairs, or find the appropriate solutions to the problems Vibration analysis of rotating machinery involves calculating the frequencies the machine can generate and measuring the frequencies the machine is generating Then, relating the measured frequencies to the. .. Vibration A critical speed occurs when a machine speed equals a natural or resonant frequency of the machine or some machine part The mode shape explains the way the beam or machine is bending The first mode equals the first critical, the second mode equals the second critical, etc The second or higher criticals are seldom a harmonic of the first or higher critical The wavelength or lambda (A) is the. .. used to describe the vibration level from a velocity transducer or accelerometer The Root Mean Square (RMS) is the true measurement of the power under the curve In Fig 1-8, the RMS value is the cosine of 45 degrees times peak (0.707 x peak only applies to pure sine waves) The true RMS value is calculated by the square root of the sum of the squares of a given number of points under the curve For example:... Example 1-5: What is the fundamental frequency a machine will generate if the machine speed is 1180 RPM? Answer: CHAPTER 1 lntroductlon to Machinery Vibration AMPLITUDE MEASUREMENT The four different ways to express the vibration amplitude level are: peak-to-peak, zeroto-peak, RMS, and average Peak-to-peak is the distance from the top of the positive peak to the bottom of the negative peak The peak-to-peak... if the harmonic motion is within the halfpower points of the center frequency and contains enough energy The half-power points are down 3 dB on either side of the center frequency The CHAPTER 1 Introduction to Machinery Vibration F , - NATURAL FREQUENCY 18 Hz I I Fig 1-9 Relatively Damped Frequency frequency range between these half-power points is called the bandwidth of the natural frequency The. .. contains the menu contents The operator enters the frequency of interest and the vibration level in engineering units: either displacement, velocity, or acceleration The program then calculates the other two engineering units The program also calculates engineering units from dB and transducer sensitivity or calculates dB from transducer sensitivity and engineering units Fig 1-28 contains the frequency... and maximum vibration occurs at the peak of a loop In order to keep the mathematics to a minimum, the RADC software package is used This discussion explains the natural frequencies and mode shapes of a 6 by 6 by 0.25 inch H-beam The H-beam is six feet long and one end is fixed in concrete Fig 1-13 contains the mode shape for the first natural frequency The first natural frequency is 26.86 Hz The node... at the center frequency It is a general rule to stay at least 10% away from each side of the center frequency If some frequency is within the bandwidth of the natural frequency and this frequency contains enough energy to excite the natural frequency, the natural frequency will be present The term "critical speed" means the rotating speed of the unit equals the natural frequency When this occurs, the. .. peak-to-peak measurement of the vibration level is shown in Fig 1-6 This type of measurement is most often used when referring to displacement amplitude - o n e cycle peak to peak - - 1- 2 x zero to peak o n e cycle -1 zero to I I I Zero-to-peak or peak is the measurement from the zero line to the top of the positive peak or the bottom of the negative peak The zero-to-peak value of the vibration level is shown... 22-tooth pinion gear The bull b) gear is rotating at 6.4 Hz a) What is the gearmesh frequency (GF)? What is the speed of the pinion gear? Answer: GF no of teeth x gear speed - b) Since GF is the same fir both gears, the speed of the pinion is: 428.8 Hz 22 teeth - 19.5 Hz There are many other generated frequencies such as misalignment, bent shafts, bearing frequencies, looseness, etc These sources will . The four different ways to express the vibration amplitude level are: peak-to-peak, zero- to-peak, RMS, and average. Peak-to-peak is the distance from the top of the positive peak to the. -1 peak to peak - 2 x zero to peak - one cycle -1 I zero I to I Zero-to-peak or peak is the measurement from the zero line to the top of the positive peak or the bottom of the. peak. The zero-to-peak value of the vibration level is shown in Fig. 1-7 . This type of measurement is used to describe the vibration level from a velocity transducer or accelerometer. The