Fractional shaft speed also . Produced by Predict Technologies 2. BPF = (2400 rpm) (10) / (60 s/min) = 400 Hz. radial . Vane pass frequency = (shaft speed) x (no. Fans will normally have a peak in the spectrum at "blade pass" or "vane pass" frequency. 1. 8th Jul, 2016. When the vane pass frequency, or the running speed of the fan multiplied by the number of blades on the fan, matches the acoustic natural frequency of the ducting it feeds, the ducting can fail, resulting in process losses[3]. Example - Blade Pass Frequency of Fan. No single peaks are of sufficient amplitude to be . (FFT) is used to understand the pressure fluctuations and hydraulic noise at the Blade Pass Frequency (BPF) and its harmonics. o Vibration due to imbalance shall not exceed 0.1 in./sec. BPFI Ball Pass Frequency Inner time domain. On rigidly mounted machines amplitudes will typically be highest in the horizontal direction versus the vertical direction, although raised amplitudes can also exist axially on overhung rotors. Moreover, two impeller vane pass frequency harmonics also have high amplitude. Resonance. Vane pass frequency = (shaft speed) x (no. The acceleration in the radial and axial directions is presented in Figure 7 for pump speed of 3590 rpm with a significant amount of air bubbles . Sidebands may be present around VPF and 2x VPF at 1x RPM. It is imperfections in the pump that generate additional discrete frequencies. The experimental work has been performed in the following sequence: 1 a centrifugal pump is run with 24 vanes brass impellers at various conditions (of impeller like non-defective, one vane removed, two vanes removed, three vanes removed) A TAP impulse modal test was performed on the pump and piping, and determined that a structural natural frequency dominated by vertical motion of the discharge pipe was nearly coincident with the first harmonic of the vane pass frequency, thereby causing a resonance. However, the values are still very low. Vibration signatures to consider would include elevated noise floors due to cavitation, pump vane pass frequency, the number of pump vanes multiplied by the run speed, and rotating looseness at run speed harmonics. Description: 4 There are four basic spectrum patterns: -Harmonics - Almost always caused by the TWF shape -Sidebands - Due to Amplitude or Frequency Modulation. However, large amplitude BPF . Blade or vane pass frequencies are inherent in pumps, fans and compressors and normally do not pose a problem. . wow and flutter (together, also known as harmonics or oscillation frequency) are minimized. Inlet guide vane performance. May be a bent rotor shaft as well. Small issues in the design and manufacture of VFD circuitry create variations, or harmonics, in the voltage . unevenly distributed mass in the fan rotor. The pulsations are traveling through water at around 4000 feet per second. Misalignment gears can also generate the first three harmonics of gear mesh frequency. RM. Fans will normally have a peak in the spectrum at "blade pass" or "vane pass" frequency. High amplitude VPF or BPF, often accompanied by harmonics of VPF or BPF. It is characterized by a prominent multiple of rotational speed equivalent to the number of impeller vanes times rotational frequency. Once TS is identified, determine TS harmonic relationships. ; ; When harmonics of TS are determined, other vibration peaks of interest and other harmonic relationships may be identified for analysis. More than one discharge volute (as in multiple rotor pumps) will create harmonics of tooth mesh frequency. 8 The pump spectrums (Fig 7) all show the mounding from 1x turning speed out to vane pass frequency that often indicate suction cavitation. These examples include harmonics of drive motor and pump running speed and vane/impeller pass frequency. 3. Round Leading Edge : Aerovane is modeled after an owl's wing. SX. 9/21/102:46 AM. However, large amplitude BPF (and harmonics) can be generated in the pump if the gap between the rotating vanes and the stationary diffusers is not kept equal all the way round. The noise floor can be raised. . Forces are generated by the pressure variations as a rotating blade, vane, or lobe passes a stationary housing or component. radial. 10.Cavitation in a pump Due to cavitation in pump 22. `sf "Vane pass frequency"` ` = sf "8 vanes" xx sf "600 rpm"` ` = sf "4.800 rpm" = sf "80 Hz"` In this machine we have two axles (motor and pump). First we'll make sure that certain terms are defined to avoid confusion. If the device being driven is a pump or fan, there will be a blade or vane pass frequency, which again is a harmonic of the shaft rotational speed. This occurs when these high-energy (pump vane-pass) frequency excitations correspond with the frequency that will generate a standing acoustic wave inside a fluid filled channel. of blades or vanes) A problem with impellers vane appears as high vane-pass frequency harmonics with sidebands radial or axial. radically and 0.15 in./sec. 2. The calculations are as follows. Unbalance occurs at the shaft rotational speed, misalignment at both shaft rotational speed and two times this speed. Theoretical Consideration: Problems with blades and vanes are usually characterized by high vibration or near the harmonic frequency corresponding to the rotation speed X No. Inlet guide vanes should be mounted no more than one pipe diameter away from the inlet, but not so close that the vane swirl sets up harmonics with the impeller's vane pass frequency. However, these peaks will be unstable, increasing and decreasing as the flow pulsation occurs. Produced by Predict Technologies Use of rotary vane . In Figure 10, pump PF-8.6A pump vane . radial . 2x vane pass for the . 4. Possible blockages in intake and more rare in air outlet. speed peak Fig 6 . Enter the email address you signed up with and we'll email you a reset link. Note that the energy in the sound may be very high and annoying for the surroundings, especially for fans with few blades. Time waveform is clearly showing impacting at VPF. However, the values are still very low. at harmonic frequencies 5th and 10 th (vane passing frequency). These conditions cause approximately 75 per cent of all vibrations in industrial plant rotating equipment. harmonics of pump. Damaged or eroded vanes will cause increases in the level at the vane pass, and also will usually produce 1X sidebands around the vane pass. However, wide - band noise around vane pass frequency indicates cavitation. o Vibration at the Ball Pass Outer Race frequency shall not exceed 0.03 radial. The magnitude of the pulse is inversely proportional to the distance between the moving vane and stationary volute lip. Deterioration of the fan rotor caused. Check both ducts and possible clogged filtering systems. Broadband noise or noise skirts at the base of the spectral lines normally means looseness. It is normal to see this frequency in pump vibration data. Vane pass is not always a defect frequency but is an operational frequency. radial. can cause uneven growth of the fan rotor. Inlet guide vane performance. Figure 1 - Typical Spectrum Showing High Vane Pass Frequency ("VPF" = # of Vanes x RPM). radial . Rotor mass variation leading to an unbalanced condition is typically caused by three primary factors. This frequency is inherent in pumps, fans and compressors and normally does not present a problem. . 2) They are created by an impeller vane as it passes by a volute lip or diffuser vane. Figure 11 contains plots of spectrum (top) and time (bottom) of a vane-pass frequency from a four . . Changing the number of impeller vanes 2. On a diffuser pump or compressor many of the harmonic components of vane pass will cancel due to the symmetry of the structure. Many pump vibrations are directly related to the running speed of the pump (or multiples of the running speed) and the motor drive system. Centrifugal Compressors . narrow band. 3(d), where the . The Campbell diagram is an overall or bird's-eye view of regional vibration excitation that can occur on an operating system. Teeth . 12-6, 12-7 Thermal Rotor Bow in Electric Motors 18-9 Unbalance in Overhung Machines.. 12-11 V Vane Pass Frequency 20-2 Variable Capacitance . The key hydraulic design parameter appears to be a high number of vanes at the impeller outlet . Not sure of the configuration of your pump but maybe a check of suction pressures could lead to something. 9.Blade pass and vane pass vibrations Blade pass or vane pass frequencies are characteristics of pumps and fans. This occurs when these high-energy (pump vane-pass) frequency excitations correspond with the frequency that will generate a standing acoustic wave inside a fluid filled channel. peak velocity. 3. Irshad. The first bearing band alarm is 0.12 In/Sec Peak, 40 percent of the overall level. . J.J. Jenson, in Elsevier Ocean Engineering Series, 2001 6.6.2 Change of the Frequency of the Forces. Line Frequencies Line frequency related peaks commonly exist on every AC driven machine and are present to some extent at 2x of line frequency. 02/17/2020 4:15 AM. IMAGE 1: Illustration of forced vibration due to imbalance and vane pass occur at 1 x rpm, and N x rpm. If present, they typically indicate a rotor problem . Severe flow turbulence will generate subsynchronous peaks and a raised noise floor. Variations in manufacturing can lead to. Initial fault frequencies should contain the operating speed, two-times operating speed, operating speed harmonics (multiples), and vane pass. peak velocity. Symptoms normally in the radial directions but may also be seen axially. Harmonics, also called a harmonic series, are components of a spectrum which are integral multiples of fundamental frequency. The most common pump suction hydraulic exiting forces come from turbulence or cavitation within a pump suction, which can become a problem when the suction energy at . If the device being driven is a pump or fan, there will be a blade or vane pass frequency, which again is a harmonic of the shaft rotational speed. Screw Pumps . Anup Singh Yadav. When harmonics of TS are determined, other vibration peaks of interest and other harmonic relationships may be identified for analysis. Increased amplitude of the peak indicates the possibility of clearance problems at the discharge of the scroll or flow restrictions causing high discharge pressure. The time harmonics contained in the variable frequency power supply interfere with the inherent spatial harmonics of the electromagnetic part of the motor to form various electromagnetic exciting forces. Figure 1.1 shows a Figure 1.1 shows a typical frequency spectrum of unacceptable vibration levels at the 5 th and 10 th VPF as Compressor surge is a fluid dynamic problem at the compressor output port that usually causes vibration at . Check Pages 701-750 of Plant_Engineering_Handbook in the flip PDF version. Increased amplitude of the peak indicates the possibility of clearance problems at the discharge of the scroll or flow restrictions causing high discharge pressure. It is the imperfections in thePump that generate additional discrete frequencies Vane pass frequency can be changed/ reduced by following ways 1. o Vibration at the vane pass frequency shall not exceed 0.15 in./sec. Resonance. Hindustan Aeronautics Limited. When the vane pass frequency, or the running speed of the fan multiplied by the number of blades on the fan, matches the acoustic natural frequency of the ducting it feeds, the ducting can fail, resulting in process losses[3]. This paper determines which radial and axial . of blades or vanes) Similar to GMF. harmonic frequency intercepts the dispersion curves as shown in Fig. In the case of the motor, the value 1X is 30 Hz, in addition we will . Carry out an impact test or a run up-run down to identify rersonances, first in the fan body and also in the suction and discharge ducts. efforts should focus on the higher harmonics of blade pass frequency where the Doppler shifted forced response frequency components are on the same order of magnitude as the . The "complex" signal shown below (still simplistic compared to data collected on most real machines) is made up of a 1x rpm component (e.g unbalance) and a 5x rpm component (e.g. Harmonic series are very common in spectra of machinery vibration. Diagnosis of submersible centrifugal pumps: A motor current and power signatures approach OPERATION OF CUSPTRON OSCILLATOR FOR SIXTH HARMONIC FREQUENCY GENERATION WITH SIX-VANE CIRCUIT+ W. Namkung, J. Y. Choe, H. S. Uhm, and V. Ayres . The pressure fluctuation behavior along the impeller periphery is monitored at 30 . Download Plant_Engineering_Handbook PDF for free. . In a centrifugal pump or a fan, the vane . Line Frequencies Line frequency related peaks commonly exist on every AC driven machine and are present to some extent at 2x of line frequency. fluctuating vane rate. The stationary component creates a non-uniform flow disturbance in the fluid or gas. tooth mesh = TX. Carry out an impact test or a run up-run down to identify rersonances, first in the fan body and also in the suction and discharge ducts. E.G. Exposure to high air stream temperatures. 0.5X, 1X. The Campbell diagram can be generated from machine design criteria or from machine operating data. BPFO = Ball Pass Frequency, Outer Race . Teeth . (from GM) If the frequency of any harmonic component of a periodic forcing phenomenon is equal to or approximates the frequency of any mode of a . - Induction Motor Frequency Calculator - Full detailed gears frequencies (main, harmonics, sidebands) up to 4X - Rolling element frequencies (BPFI, BPFO, BSF, FTF) given the bearing dimension or the bearing model number - Pump vane pass frequencies up to 4X - Fans blade pass frequencies up to 4X Blade pass frequency (BPF) = number of blades (or vanes) x rpm This frequency is generated mainly due to the gap problems between the rotor and the stator. Centrifugal compressors generate spectra similar to centrifugal fans in that the vane pass frequency will be dominant. Note limits for vane pass. The most common pump suction hydraulic exiting forces come from turbulence or cavitation within a pump suction, which can become a problem when the suction energy at . Blade passing frequency = N vane no./60: f 1: Acoustic frequency = velocity of pulsation (ft/sec)/wave length 1 (ft) GHP: Gas horsepower: H: . The vane rings are split into two halves and installed in the split casing. If a fan with 10 blades rotates with 2400 rpm - the Blade Pass Frequency - BPF - can be calculated. Vibration over narrow ranges of flow and speed occur with resonant response of the bearing housing, shaft and . . It is high time to find root cause. speed. Although inlet guide vanes don't increase turndown, they do enhance efficiency during turndown. . A harmonic series in a spectrum is the result of a periodic signal in the wave form. 2. 3. In addition, the spectra will still be dominated by 1X RPM and blade pass frequency. INTRODUCTION FieldVibrationProblem During 2004 a common vibration problem was experienced in four different plants (refineries) in the USA with the same pump type/size operating apparently with different conditions of A margin of safety should be provided between the pump/vane pass speed/frequencies, and major structural (and/or pipe hydraulic) natural frequencies. More than one discharge volute (as in multiple rotor pumps) will create harmonics of tooth mesh frequency. When resonance results in undesirable vibration, the frequency of the forced vibration will need to . May excite rotor critical. These sidebands will develop around the eccentricity frequency . . . The shrouded stator rows have similar vane counts of 44 except for S3, which has 50 vanes. Typical acceptable margins are 15-25%. The system frequency is along the Y axis. Prominent vane pass harmonics should be trended to determine if they indicate a developing fault condition. As evident in equations (1) and (2), the vane frequency can be Vane passing induced vibration is caused by pressure pulsations in the diffuser (or volute) being transmitted to the pump housing and the bearings. Expert vibration analysis coupled with rotordynamic and structural . Also have had 60Hz single suction vacuum pumps running choked up and created so much heat that it took the bearings out in less than 20 days. There are harmonics of special interest, for example, in a six-vane pump, there will usually be a strong spectral peak at 6X. peak velocity axially over a frequency range of 2-1500 Hz. . Propeller-induced forces contain components, which vary in time with multiples of the blade frequency (= number of revolutions x number of propeller blades). Higher vane pass frequency with harmonics may imply improper rotor centering, damaged diffuser vanes/ impeller vanes. effect of this condition is seen as multiple sidebands of odd harmonics of the line frequency powering the motor. . . Pump flow pulsation is a condition that develops when a pump is operating near its shut-off head. Although inlet guide vanes don't increase turndown, they do enhance efficiency during turndown. Any of these conditions can cause a 1X shaft speed vibration or harmonics of that frequency. Vane Pass Frequency. May excite rotor critical. . Figure 16-1 - Bearing loose in a housing Harmonics can extend beyond 10x. Find more similar flip PDFs like Plant_Engineering_Handbook. SX. Tracing the forces at and near the blade passing frequency and its harmonics during the pump operation can be used to detect flow separation in the diffuser and to adapt the operating conditions to . Blade Pass Frequency (BPF) = number of blades (or vanes) x RPM. Harmonics of vane pass are also common in such pumps. The diameter of impeller hub is 13 mm. The vibration in the time waveform will be sinusoidal. Other . Abstract and Figures. 100 mm; width 10 mm; vane length 25 mm and number of vanes are 24. 21. Vane pass = VX. A typical Campbell diagram plot is shown in Figure 5-25.Engine rotational speed is along the X axis. Inlet guide vanes should be mounted no more than one pipe diameter away from the inlet, but not so close that the vane swirl sets up harmonics with the impeller's vane pass frequency. With its rounded edges, Aerovane allows air to flow over with minimum . Small issues in the design and manufacture of VFD circuitry create variations, or harmonics, in the voltage . In a perfect centrifugal pump, the vane frequency (vane passing or vane rate) and most probably harmonics (multiples) of it are the only discrete frequencies that would be generated.