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21. Sidebands may be present around VPF and 2x VPF at 1x RPM. May excite rotor critical. 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 On a diffuser pump or compressor many of the harmonic components of vane pass will cancel due to the symmetry of the structure. o Vibration at the Ball Pass Outer Race frequency shall not exceed 0.03 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. (FFT) is used to understand the pressure fluctuations and hydraulic noise at the Blade Pass Frequency (BPF) and its harmonics. 2. The noise floor can be raised. radial. Fans will normally have a peak in the spectrum at "blade pass" or "vane pass" frequency. Small issues in the design and manufacture of VFD circuitry create variations, or harmonics, in the voltage . . 2021-10-25 Steel World Comments Off on Principle, structure, operation and maintenance of rotary vane vacuum pump. Forces are generated by the pressure variations as a rotating blade, vane, or lobe passes a stationary housing or component. unevenly distributed mass in the fan rotor. It is imperfections in the pump that generate additional discrete frequencies. The pressure fluctuation behavior along the impeller periphery is monitored at 30 . Except, if the new vane pass frequency is near a resonant condition, then vibration levels can be much higher. Some causes for these forced vibrations are misalignment of the pump and driver shaft, imbalance, bent shafts and damaged impeller vanes. 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 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. 3(d), where the . Screw Pumps . Note that the energy in the sound may be very high and annoying for the surroundings, especially for fans with few blades. 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. 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. 4. These sidebands will develop around the eccentricity frequency . number of vanes on the impeller - "vane pass" frequency) being generated by . 1. Once TS is identified, determine TS harmonic relationships. . OPERATION OF CUSPTRON OSCILLATOR FOR SIXTH HARMONIC FREQUENCY GENERATION WITH SIX-VANE CIRCUIT+ W. Namkung, J. Y. Choe, H. S. Uhm, and V. Ayres . Note limits for vane pass. However, the values are still very low. application with the pump vane frequency amplitude of 0.027 dB. 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. `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). If a fan with 10 blades rotates with 2400 rpm - the Blade Pass Frequency - BPF - can be calculated. Although inlet guide vanes don't increase turndown, they do enhance efficiency during turndown. ; ; However, these peaks will be unstable, increasing and decreasing as the flow pulsation occurs. First we'll make sure that certain terms are defined to avoid confusion. 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]. the cylindrical beam to pass through the magnetic cusp transition region, where the (v XB ) force converts . 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. But I have not seen stator slot pass frequ . Other . The magnitude of the pulse is inversely proportional to the distance between the moving vane and stationary volute lip. . In low-frequency range up to 800 Hz, vibration spectrum shows a decrease in amplitude at vane pass frequency . 3. frequency harmonics and 1X sidebands have been found in water-cooled canned motor pumps (CMP)where stator cans may have surface depressions due to setback of the stator slot wedges . However, wide - band noise around vane pass frequency indicates cavitation. . Centrifugal compressors generate spectra similar to centrifugal fans in that the vane pass frequency will be dominant. No single peaks are of sufficient amplitude to be . Anup Singh Yadav. radial . Check both ducts and possible clogged filtering systems. Example - Blade Pass Frequency of Fan. This frequency is inherent in pumps, fans and compressors and normally does not present a problem. Possible blockages in intake and more rare in air outlet. radial. . . These vibrations occur in the mid- to high-frequency range of 450 to 60,000 cpm (7.5 to 1,000 Hz). radial. of impeller vanes and harmonics. harmonics of pump. Resonance. When harmonics of TS are determined, other vibration peaks of interest and other harmonic relationships may be identified for analysis. . Some vibration will also be transmitted to the bearings via the shaft. If present, they typically indicate a rotor problem . The various harmonics, side bands and possibly other attributes of the frequency spectrum must be considered for both the rotating and stationary components. Blade Pass Frequency (BPF) = number of blades (or vanes) x RPM. Line Frequencies Line frequency related peaks commonly exist on every AC driven machine and are present to some extent at 2x of line frequency. Vane pass frequency = (shaft speed) x (no. - 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 3. May be a bent rotor shaft as well. IMAGE 1: Illustration of forced vibration due to imbalance and vane pass occur at 1 x rpm, and N x rpm. Several harmonics of rotor speed indicates looseness. Round Leading Edge : Aerovane is modeled after an owl's wing. Line Frequencies Line frequency related peaks commonly exist on every AC driven machine and are present to some extent at 2x of line frequency. The amplitude of the vibration response can be amplified 2.5 times or higher at or near a component natural (critical) resonant frequency. Once TS is identified, determine TS harmonic relationships. Since the number of revolutions is usually around 1.5 - 2 Hz and the number of blades n = 3 - 5, it is mainly the blade frequency (~ 4 . . radial . 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 vane rings are split into two halves and installed in the split casing. Unbalance occurs at the shaft rotational speed, misalignment at both shaft rotational speed and two times this speed. Resonance. It is normal to see this frequency in pump vibration data. The diameter of impeller hub is 13 mm. Results show that vane pass frequency and its harmonics showed a considerable variation in amplitude . Changing the number of impeller vanes 2. Vane passing frequency vibration (VPF) involves a complex excitation-response system. Hindustan Aeronautics Limited. 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. 0.5X, 1X. The stationary component creates a non-uniform flow disturbance in the fluid or gas. 0.5X, 1X. The vibration at vane pass and 2x vane pass almost disappeared in the spectrum. Exposure to high air stream temperatures. Vane Pass Frequency. In a centrifugal pump or a fan, the vane . . These examples include harmonics of drive motor and pump running speed and vane/impeller pass frequency. tooth mesh = TX. However, the values are still very low. In perfect centrifugal pump, the vane frequency and most probably harmonics of it are the only discrete frequencies that would be generated. peak velocity axially over a frequency range of 2-1500 Hz. Teeth . . 02/17/2020 4:15 AM. one per rev. Produced by Predict Technologies steady. Check both ducts and possible clogged filtering systems. Vane pass = VX. Severe flow turbulence will generate subsynchronous peaks and a raised noise floor. ruben. 100 mm; width 10 mm; vane length 25 mm and number of vanes are 24. S = number of screw threads . . In Figure 10, pump PF-8.6A pump vane . fluctuating vane rate. Rotor Rub . Vane pass is not always a defect frequency but is an operational frequency. can cause uneven growth of the fan rotor. Fractional shaft speed also . Harmonics of vane pass are also common in such pumps. fluctuating vane rate. . This paper determines which radial and axial . The imbalance amplitude will increase by the square of speed (when the running speed is below the 1st rotor . BPFO = Ball Pass Frequency, Outer Race . Screw Pumps . 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. E.G. steady. IT Is Not A Sine Wave but A Pulse. Irshad. Gear mesh frequency is also at a harmonic of shaft rotational speed. Although inlet guide vanes don't increase turndown, they do enhance efficiency during turndown. 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 . Download Plant_Engineering_Handbook PDF for free. Find more similar flip PDFs like Plant_Engineering_Handbook. Speed of Impeller 3. When resonance results in undesirable vibration, the frequency of the forced vibration will need to . (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 . Vane pass = # vanes x rpm Often times many harmonics of rotational speed are also encountered, coupled with broad energy along the baseline. Compressor surge is a fluid dynamic problem at the compressor output port that usually causes vibration at . Read the Text Version. The Campbell diagram can be generated from machine design criteria or from machine operating data. The key hydraulic design parameter appears to be a high number of vanes at the impeller outlet . . tooth mesh = TX. . Vane pass = VX. This usually causes a mound to appear starting at Vane Pass Frequency (VPF), extending up to around 2x to 3x VPF 12 Flow Induced Mounds Suction . With its rounded edges, Aerovane allows air to flow over with minimum . Time waveform is clearly showing impacting at VPF. 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. Abstract and Figures. In my experience vibration at rotor bar pass frequency and 2*LF sidebands are relatively common for induction motors. Harmonics, also called a harmonic series, are components of a spectrum which are integral multiples of fundamental frequency. no. o Vibration due to imbalance shall not exceed 0.1 in./sec. 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 . A problem with impellers vane appears as high vane-pass frequency harmonics with sidebands radial or axial. Figure 1 - Typical Spectrum Showing High Vane Pass Frequency ("VPF" = # of Vanes x RPM). As with vibration and lubrication, infrared thermography plays a role as well through anomalies noted with liner wear in the pump . When harmonics of TS are determined, other vibration peaks of interest and other harmonic relationships may be identified for analysis. The system frequency is along the Y axis. radically and 0.15 in./sec. Misalignment gears can also generate the first three harmonics of gear mesh frequency. Detection of incipient cavitation and its development in a centrifugal pump is studied by Ni Yongyan using vibration analysis. 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. The shrouded stator rows have similar vane counts of 44 except for S3, which has 50 vanes. More than one discharge volute (as in multiple rotor pumps) will create harmonics of tooth mesh frequency. Prominent vane pass harmonics should be trended to determine if they indicate a developing fault condition. . harmonic frequency intercepts the dispersion curves as shown in Fig. BPFI Ball Pass Frequency Inner time domain. The 7 bladed rotor will have a spectrum of frequencies, the fundamental being its rotational speed, i.e. High amplitude VPF or BPF, often accompanied by harmonics of VPF or BPF. In addition, the spectra will still be dominated by 1X RPM and blade pass frequency. The pulsations are traveling through water at around 4000 feet per second. Any of these conditions can cause a 1X shaft speed vibration or harmonics of that frequency. Trimming operation on vane outlet and volute tongue are performed and noise behaviour is studied using Detached Eddy Simulation. The first bearing band alarm is 0.12 In/Sec Peak, 40 percent of the overall level. 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. Teeth . Harmonics of concern usually are limited to 2,3, or 4 times the vane passing frequencies, since above the 4th harmonic sufficient energy to damage the pump or the feed water system components usually does not exist. Typical acceptable margins are 15-25%. harmonics of pump. effect of this condition is seen as multiple sidebands of odd harmonics of the line frequency powering the motor. 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. . It is characterized by a prominent multiple of rotational speed equivalent to the number of impeller vanes times rotational frequency. Propeller-induced forces contain components, which vary in time with multiples of the blade frequency (= number of revolutions x number of propeller blades). Diagnosis of submersible centrifugal pumps: A motor current and power signatures approach 9.Blade pass and vane pass vibrations Blade pass or vane pass frequencies are characteristics of pumps and fans. In the case of the motor, the value 1X is 30 Hz, in addition we will . 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. 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. Blade or vane pass frequencies are inherent in pumps, fans and compressors and normally do not pose a problem. Rotor mass variation leading to an unbalanced condition is typically caused by three primary factors. Moreover, two impeller vane pass frequency harmonics also have high amplitude. peak velocity. Enter the email address you signed up with and we'll email you a reset link. Fault frequencies should be listed for the belt-passing frequency. Many times, multiples of the vane pass frequency appear with larger amplitudes than at vane passing. 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. Harmonic series are very common in spectra of machinery vibration. narrow band. The second bearing band alarm is 0.09 In/Sec Peak, 30 percent of the overall level. 10.Cavitation in a pump Due to cavitation in pump 22. of blades. S = number of screw threads . narrow band. Symptoms normally in the radial directions but may also be seen axially. ruben. 2. Blade passing frequency = N vane no./60: f 1: Acoustic frequency = velocity of pulsation (ft/sec)/wave length 1 (ft) GHP: Gas horsepower: H: . J.J. Jenson, in Elsevier Ocean Engineering Series, 2001 6.6.2 Change of the Frequency of the Forces. Centrifugal Compressors . The vibration in the time waveform will be sinusoidal. . wow and flutter (together, also known as harmonics or oscillation frequency) are minimized. RM. . Produced by Predict Technologies SX. of blades or vanes) A problem with impellers vane appears as high vane-pass frequency harmonics with sidebands radial or axial. However, large amplitude BPF . Many pump vibrations are directly related to the running speed of the pump (or multiples of the running speed) and the motor drive system. Deterioration of the fan rotor caused. Not sure of the configuration of your pump but maybe a check of suction pressures could lead to something. Copy Link to Reply; . Increased amplitude of the peak indicates the possibility of clearance problems at the discharge of the scroll or flow restrictions causing high discharge pressure. Inlet guide vane performance. 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. Description: 4 There are four basic spectrum patterns: -Harmonics - Almost always caused by the TWF shape -Sidebands - Due to Amplitude or Frequency Modulation. More than one discharge volute (as in multiple rotor pumps) will create harmonics of tooth mesh frequency. The calculations are as follows. Unbalance occurs at the shaft rotational speed, misalignment at both shaft rotational speed and two times this speed. 4. The Campbell diagram is an overall or bird's-eye view of regional vibration excitation that can occur on an operating system. 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) Although sometimes a relatively simple sine wave, it will far more often be a complex signal with a number of different frequency components. Severe flow turbulence will generate subsynchronous peaks and a raised noise floor. Vane passing induced vibration is caused by pressure pulsations in the diffuser (or volute) being transmitted to the pump housing and the bearings. FUNDAMENTAL: This is running speed or 1X; referred to as the machine's fundamental or fundamental component. 9/21/102:46 AM. 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. Rotor Rub . 8 The pump spectrums (Fig 7) all show the mounding from 1x turning speed out to vane pass frequency that often indicate suction cavitation. Pump flow pulsation is a condition that develops when a pump is operating near its shut-off head. radial . . Possible blockages in intake and more rare in air outlet. Initial fault frequencies should contain the operating speed, two-times operating speed, operating speed harmonics (multiples), and vane pass. A comparison of the amplitude of Figures 6(a) and (b) indicates that the pump has higher vibration in the axial direction. BPF = (2400 rpm) (10) / (60 s/min) = 400 Hz. peak velocity. There are harmonics of special interest, for example, in a six-vane pump, there will usually be a strong spectral peak at 6X. of blades or vanes) Similar to GMF. A margin of safety should be provided between the pump/vane pass speed/frequencies, and major structural (and/or pipe hydraulic) natural frequencies. Centrifugal pumps at Vane Pass Frequency = RPM . 4. . speed peak Fig 6 . Gear mesh frequency is also at a harmonic of shaft rotational speed. Plant_Engineering_Handbook was published by sureshkumars on 2018-07-19. Blade pass frequency usually exists in normal operating machines, but . It is normal to see this frequency in pump vibration data. Vibration over narrow ranges of flow and speed occur with resonant response of the bearing housing, shaft and . 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 . radial. SX. Small issues in the design and manufacture of VFD circuitry create variations, or harmonics, in the voltage . Some peaks will be higher than others when they coincide with structural resonances or other sources of vibration, for example vane pass frequency. Be aware that the Blade Pass Frequency . Aerovane II is the first vane ever to employ airfoils for archery arrows, flying flatter, straighter and more quietly. It is high time to find root cause. 3. Vane pass is not always a defect frequency but is an operational frequency. May excite rotor critical. 2x vane pass for the . As evident in equations (1) and (2), the vane frequency can be Re: Vane Pass Frequency. Check Pages 701-750 of Plant_Engineering_Handbook in the flip PDF version. Use of rotary vane . . at harmonic frequencies 5th and 10 th (vane passing frequency). Broadband noise or noise skirts at the base of the spectral lines normally means looseness. This writing is to serve as a help and guide to assist in diagnostics of vibration problems. Vane pass frequency = (shaft speed) x (no. Higher vane pass frequency with harmonics may imply improper rotor centering, damaged diffuser vanes/ impeller vanes. radial . 3. and at vane pass frequency. 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 . 2. 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. Inlet guide vane performance. Figure 11 contains plots of spectrum (top) and time (bottom) of a vane-pass frequency from a four . A harmonic series in a spectrum is the result of a periodic signal in the wave form. o Vibration at the vane pass frequency shall not exceed 0.15 in./sec. Figure 16-1 - Bearing loose in a housing Harmonics can extend beyond 10x. 8th Jul, 2016. 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. Based on this analysis, the recommendation was to change out the pump bearings, check the alignment tolerances and balance the pump impeller. These conditions cause approximately 75 per cent of all vibrations in industrial plant rotating equipment. A long process, but one that proved its worth. Variations in manufacturing can lead to. Expert vibration analysis coupled with rotordynamic and structural . 2) They are created by an impeller vane as it passes by a volute lip or diffuser vane. 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]. 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 . 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.