API RP*33SB 93        0732290 0532533 409 W      Recommended Practice      on Electric Submersible      Pump System Vibrat...
A P I RPt33SB 7 3             m      0 7 3 2 2 7 0 0 5 3 2 5 3 4 345        m                                             ...
A P I RP*33SB 93 D 0732290 0532535 281                                                         m           2              ...
A P I R P + L L S 8 93 W 0732270 0532536 3 3 8 W                         RP 1158:Recommended Practice on Electric Submersi...
A P I RPlrLLSB 93                 0732290 05L25L7 054            4                                             American Pe...
API RP*LLSB 93 m 0732270 05L25LB T90 m                             RP 11%: Recommended Practice on Electric Submersible Pu...
A P I RP*LLSB 9 3 M 0732290 0512519 927          6                                              American Petroleum inatitu...
A P I RP*lLSB 93             m 0732290 0512520                       b49    m                             RP llS8:Recommen...
8                                                    American Petroleum Institute           eliminate or reduce vibration ...
A P I RP*LLSB 93                    0 7 3 2 2 9 0 0 5 3 2 5 2 2 433         =                                    RP llS8:R...
10                                               American Petroleum Institute                                             ...
API RP*LLSB 93                 = 0732290 0512524                        294 D                               RP 1158:Recomm...
A P I RPlrLLSB 93       0732270 0532525 320             12                               American Petroleum Institute     ...
A P I RPwllSB 93             = 0732290 0532526 Ob7                              R llS8:Recommended Practice on Electric Su...
A P I RP*LLSB 73 H 0732270 0532527 T T 3 D           14                                           American Petroleum Insti...
API RP*lLSB             9 3 W 0732290 0532528 93T                                   RP llS8:Recommended Practice on Electr...
Order No. 811-05948                                            Additional copies available from                           ...
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  1. 1. API RP*33SB 93 0732290 0532533 409 W Recommended Practice on Electric Submersible Pump System Vibrations API RECOMMENDED PRACTICE 11S8 (RP 11S8) FIRST EDITION, MAY 1, 1993 American Petroleum Institute 1220 L Street, Northwest ry Washington, DC 20005COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  2. 2. A P I RPt33SB 7 3 m 0 7 3 2 2 7 0 0 5 3 2 5 3 4 345 m Issued by ARlERICAN PETRolwEuM INSTIITUTE Production Department FOR INFORMATIONCONCERNING TECHNICAL CONTENTS OF THIS PUBLICATION CONTACT THE API PRODUCTION DEPARTMENT, 1201 MAIN STREET, SUITE 2535, DALLAS, Tx 75202-3994 - (214) 748-3841. SEE BACK COVER FOR INFORMATIONCONCERNING HOW TO OBTAIN ADDITIONAL COPIES OF THIS PUBLICATION. Users of this publication should become familiar with its scope and content. This publication is intended to supplement rather than replace individual engineering judgment. OFFICIAL PUBLICATION REG. US. PATENT OFFICE Copyright Q 1993 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  3. 3. A P I RP*33SB 93 D 0732290 0532535 281 m 2 American Petroleum Institute TABLE OF CONTENTS Page POLICY ................................................................................................................................................... 3 FOREWORD ........................................................................................................................................... 4 SECTION 1 . GENERAL ................................................................................................................... 5 1.1 Introduction ................................................................................................................................. 5 1.2 Scope ............................................................................................................................................ 5 SECTION 2 . TERMINOLOGY ......................................................................................................... 6 SECTION 3 - VIBRATION ANALYSIS 3.1 Harmonic Motion ........................................................................................................................ 7 3.2 Concepts of Vibration ................................................................................................................. 7 3.3 Sources of Vibration ................................................................................................................... 8 3 4 Control of Vibration ................................................................................................................... 8 . 3.5 Vibration i ESP Systems ......................................................................................................... 9 n SECTION 4 - RECOMMENDATIONS 4.1 Vibration Limits ........................................................................................................................ 10 4.2 Measurement of Vibration ....................................................................................................... 10 APPENDIX A - UNITS CONVERSIONS ...................................................................................... 11 APPENDIX B - RELATIONSHIP BETWEEN DISPLACEMENT, VELOCITY, AND ACCELERATION ................................................................. 14 APPENDIX C - CLASSIFICATION OF SEVERITY OF MACHINERY VIBRATION ............15COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  4. 4. A P I R P + L L S 8 93 W 0732270 0532536 3 3 8 W RP 1158:Recommended Practice on Electric Submersible Pump System Vibrations 3 POLICY API PUBLICATIONS NECESSARILY ADDRESS PROB- TAINED IN THE PUBLICATION BE CONSTRUED AS LEMS OF A GENERAL NATURE. WITH RESPECT TO INSURING ANY ONE AGAINST LIABILITY FOR IN- PARTICULAR CIRCUMSTANCES, LOCAL, STATE FRINGEMENT OF LETTERS PATENT. AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED. GENERALLY, API STANDARDS ARE REVIEWED AND REVISED, REAFFIRMED, OR WITHDRAWN AT LEAST API IS NOT UNDERTAKING TO MEET DUTIES OF EVERY FIX% YEARS. SOMETIMES A ONE-TIME EX- EMPLOYERS, MANUFACTURERS, OR SUPPLIERS TO TENSION OF UP TO TWO YEARS WILL BE ADDED WARN AND PROPERLY TRAIN AND EQUIP THEIR TO THIS REVIEW CYCLE. THIS PUBLICATION WILL EMPLOYEES, AND OTHERS EXPOSED, CONCERN- NO LONGER BE IN EFFECT FIVE YEARS AFTER ITS ING HEALTH AND SAFETY RISKS AND PRECAU- PUBLICATION DATE AS AN OPERATIVE API STAN- TIONS, NOR UNDERTAKING THEIR OBLIGATIONS DARD OR, WHERE AN EXTENSION HAS BEEN UNDER LOCAL, STATE, OR FEDERAL LAWS. GRANTED, UPON REPUBLICATION. STATUS OF THE NOTHING CONTAINED IN ANY API PUBLICATION PUBLICATION CAN BE ASCERTAINED FOR THE API IS TO BE CONSTRUED AS GRANTING ANY RIGHT, AUTHORING DEPARTMENT (TEL. 214-748-3841). A BY IMPLICATION OR OTHERWISE, FOR THE MANU- CATmOG OF API PUBLICATIONS AND MATERIALS FACTURE, 6ALE, OR USE OF ANY METHOD, APPA- IS PUBLISHED ANNUALLY AND UPDATED QUAR- RATUS, OR PRODUCT COVERED BY LETTERS TERLY BY API, 1220 L ST., N.W., WASHINGTON DC PATENT. NEITHER SHOULD ANYTHING CON- 20005.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  5. 5. A P I RPlrLLSB 93 0732290 05L25L7 054 4 American Petroleum Institute FOREWORD (a) "his publication is under the jurisdiction of the API (d) Any Recommended Practice may be used by anyone Committee on Standardization of Production Equipment. desiring to do so, and a diligent effort has been made by (b) American Petroleum Institute (API) Recommended API to assure the accuracy and reliability of the data Practices are published to facilitate the broad availabil- contained herein. However the Institute makes no rep- ity of proven, sound engineering and operating practices. resentation, warranty or guarantee in connection with These Recommended Practices are not intended to obvi- the publication of any Recommended Practice and hereby ate the need for applying sound judgement to when and expressly disclaims any liability or responsibility for loss where these Recommended Practices should be utilized. or damage resulting from its use, for any violation of any federal, state or municipal regulation with which an API (c) The formulation and publication ofAFI Recommended recommendation may conflict, or for the infringement of Practices is not intended to, in any way, inhibit anyone any patent resulting from the use of this publication. from using any other practice.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  6. 6. API RP*LLSB 93 m 0732270 05L25LB T90 m RP 11%: Recommended Practice on Electric Submersible Pump System Vibrations 5 SECTION 1 GENERAL guidelines to establish consistency in control and analy- and analysis of electric submersible pump systems and sis of ESP system vibrations. These recommended prac- subsystems.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  7. 7. A P I RP*LLSB 9 3 M 0732290 0512519 927 6 American Petroleum inatitute SECTION 2 TERMINOLOGY Acceleration (a).Acceleration is a vector quantity that Natural Frequency (fn).Natural frequency is a fre- specifies the time rate of change of velocity; both linear quency of free vibration of a system. There are a large and angular. Common unita are inlsec2 (or cm/sec2) and number of natural frequencies in complicated systems, radiandsec2. though normally only a few have energy contents high Amplitude. Amplitude is the maximum value of a pe- enough to be of concern. riodic quantity. Oscillation. Oscillation is the time variation of the Angular Frequency ( i c l rFrequency). The an- Crua magnitude of a quantity (e.g., displacement). gular frequency of a periodic quantity, in radians per Peak-to-peakDisplacement (dpp). The peak-to-peak unit time, is the frequency multiplied by 2x. displacement of a vibrating quantity is the algebraic dif- Balancing. Balancing is a procedure for adjusting the ference between the extremes of the displacement. This mass distribution of a rotor so that rotating imbalance, is twice the amplitude of the sinusoidal displacement. as seen by vibration of the journals or the forces on the bearings at once-per-revolution, is reduced or controlled. Peak Velocity. Housing or case vibration is normally measured in u i s of peak velocity, the maximum velocity nt Critical Speed. Critical speed is a speed of a rotating occurring during the normal sinusoidal displacement. system that corresponds to a natural frequency of the system. Period. The time interval to complete one cycle of sinu- soidal oscillation, usually expressed in seconds. Damping. Damping is the dissipation of energy with time. Resonance. Resonance of a system in forced vibration Displacement (d). Displacement is a vector quantity exists when the forcing frequency is at or near a system that specifies the change of position of a body or particle natural frequency. Any change, however small, in the and is usually measured from ita position of rest. Dis- frequency of excitation results in a decrease in the re- placement is expressed in mils ( 1 mil = 0.001 inch) or sponse of the system. millimeters (imm = i o 3 meter). Rotating Speed 0. Rotating speed is the frequency at Excitation. Excitation is an external force (or other which the mechanical system rotates; generally expressed input) applied to a system that causes the system to in revolutions per minute (FPM). respond in some way. Simple Harmonic Motion. A simple harmonic motion is Filter. A filter is an analog or digital device for separat- a motion such that the displacement is a sinusoidal func- ing signals on the basis of their frequency. It introduces tion of time; sometimes it is designated merely by the relatively small loss to signals in one or more frequency term harmonic motion. bands and relatively large loss to signals at other frequencies. Steady-state Vibration. Steady-state vibration exists when period and amplitude are constant. Forced Vibration. The oscillation of a system is forced if the response is imposed by continuous excitation. Stiffness. Stiffness is the ratio of change of force (or torque) to the corresponding change in translational (or Foundation (Support). A foundation is a structure rotational) deflection of an elastic element. that supports the loads of a mechanical system. It may be fixed in space, or it may undergo a motion that pro- Subharmonic.A subharmonic is a sinusoidal quantity vides excitation for the supported system. having a frequency that is a fraction of the fundamental Frequency (f). The frequency of a function periodic in Bequency. time is the reciprocal of the period. The unit is cycle per Synchronous Vibration. The filtered component of vi- unit time. The unit cycle per second is called Hertz (Hz). bration at the frequency that corresponds to the machine Fundamental Frequency.The fundamental frequency rotating speed. of an oscillating system is the lowest natural frequency. Transducer (Pickup). A transducer is a device which g. The quantity g is the acceleration produced by the converts vibration or shock motion to an optical, a me- force of gravity, which varies with latitude and elevation chanical, or most commonly to an electrical signal that is of the point of observation. By international agreement, proportional to a parameter of the experienced motion. the value 32.1739 R/s& = 386.087 inJsec2 = 980.665 cm/ sec2 has been chosen as the standard acceleration due to Velocity ( ) Velocity is a vector quantity that specifies v. gravity. the time rate of change of displacement with respect to EL reference time frame. G. The ratio of local acceleration to the acceleration of gravity. For example, an acceleration of 38.6 in./sec2 or Vibration. Vibration is a term that describes oscillation 98.1 cm/sec2 is written 0.1G. in a mechanical system. Isolation. Isolation is a reduction in the response of a Vibration Meter. A vibration meter is an apparatus for system to an external excitation; attained by the use of the measurement of displacement, velocity, or accelera- a resilient support. tion of a vibrating body.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  8. 8. A P I RP*lLSB 93 m 0732290 0512520 b49 m RP llS8:Recommended Practice on Electric Submersible Pump System Vibrations I SEC YON 3 VIBRATIO T ANALYSIS 3.1 Harmonic Motion. A system that experiences where, simple harmonic motion follows a displacement pattern dpp = peak-to-peak displacement, [mils] defined by: vp = peak velocity, [in./secl d = dosin(2&) = dosin(ot) [Eq. 3.11 where f is the frequency of the simple harmonic motion, ap = peak acceleration, [in/sec21 o = 2 d is the corresponding angular frequency, t is time, f = frequency, [Hzl and do is the amplitude of the displacement. In metric units: The velocity v and acceleration a of the system are found by differentiating the displacement d once and twice, dpp = 3.183(f) [Eq. 3.91 respectively: v = do(2dJc0~(2&) = doWos(wt) [Eq. 3.21 dPP = 0.5066 (%) [Eq. 3.101 a = -do(2dJ2sin(2&) = -&02sin(wt) [Eq. 3.31 where, The maximum absolute values of the displacement, ve- locity, and acceleration of the system undergoing har- dpp = peak-to-peak displacement, [mml monic motion occur when the trigonometric functions in vp = peak velocity, [cdsec] Eqs.[3.1] to [3.3] are numerically equal to unity. These values are known, respectively, as displacement, veloc- ap = peak acceleration, [cm/sec21 ity, and acceleration amplitudes; they are defined math- f = frequency, [Hzl ematically as follows: The relationship between displacement, velocity and do = do vo = (2dJdo = (2dPdo [Eq. 3.41 acceleration is shown graphically in Appendix B. It is common to express the displacement amplitude do 3.2 Concepts of Vibration. Vibration is a term that in mils when the English system of units is used and in describes oscillation in a mechanical system. It is defined millimeters when the metric system is used. The velocity by the frequency (or frequencies) and amplitude. An amplitude vo is expressed in inches per second in the excitation or oscillating force applied to the system is English system (centimeters per second in the metric vibration in a generic sense. Conceptually, the ensemble system). The acceleration amplitude a. usually is ex- or time-history of vibration may be considered sinusoidal pressed in Gs. or simple harmonic in form. Although vibration encoun- Factors for converting values of rectilinear velocity and tered in practice oRen does not have this regular pattern, accelemtion to different units are given in Table A.l. it may be a combination of several sinusoidal quantities, Similar factors for angular velocity and acceleration are each having a M e r e n t frequency and amplitude. If the given in Table A.2. vibration ensemble repeats itself aRer a determined in- terval of time, the vibration is termed periodic. Mechani- For certain purposes in analysis, it is convenient to ex- cal systems experiencing forced vibrations continue un- press the amplitude in terms of peak value, the peak-to- der steady-state conditions because energy is supplied to peak value, the average or the root-mean-square (rms) the system continuously to compensate for that dissi- value. These conversion factors are set forth in Table A.3 pated by damping in the system. In a free vibrating for ready reference. Peak-to-peak displacement and peak system, there is no energy added to the system but rather velocity amplitude as a function of frequency are shown the vibration is the continuing result of an initial dis- graphically, in English units, in Fig. A.l and, in metric turbance. In the absence of damping, free vibration is units, in Fig. A.2. assumed to continue indefinitely. The peak-to-peak displacements in terms of simple har- In general, the frequency at which energy is supplied monic motion are given below: (i.e., the forcing frequency) appears in the vibration of the system. The vibration of the system depends upon the relation of the excitation or forcing function to the dpp = (2) [Eq. 3.51 $p = (a2) [Eq. 3.61 properties of the system. This relationship is a prominent feature of the analytical aspects of vibration. The tech- nology of vibrations embodies both theoretical and ex- In English units: perimental facets. Thus, methods of analysis and instru- dpp = 318.3 (7) [Eq. 3.71 ments for the measurement of vibration are of primary significance. The results of analysis and measurement are used to evaluate vibration environments, to devise dpp = 50.66 (3) [Eq. 3.81 testing procedures and instruments, and to design and operate equipment and machinery. The objective is toCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  9. 9. 8 American Petroleum Institute eliminate or reduce vibration severity or) alternately, to cially prominent in slender, long shafts. Misalignment design equipment to withstand its influences. may result in large axial vibration. 3.3 Sources of Vibration. Several potential sources of A characteristic of misalignment and bent shafts is that vibration are discussed in the following paragraphs. The vibration will occur in both radial and axial directions. correspondencebetween observed vibratory response fre- In general, whenever the amplitude of axial vibration is quencies and the likely cause of that response is shown greater than 50% of the highest radial vibration, then in Table 3.3. misalignment or a bent shaft should be suspected. 3.3.1 Mass Unbalance 3.3.3 Flow induced. Pump vibration can occasionally be caused by flow through the system. The amplitude a Dissymmetry due to core shifts in casting, rough usually depends upon where the pump is operated on surfaces on forging, or unsymmetrical configura- the head-capacity curve, and the cause of the vibration tion. is usually turbulence. In diffuser type pumps certain b Nonhomogeneous Material. General observations . combination of impeller blades and diffuser vanes are include blowholes in castings, inclusions in rolled or more likely to produce vibration than others. Aithough forged materials, slag inclusions or variations in this phenomenon can produce vibration amplitudes that material density. are unacceptable, especially a t rates conducive to cavi- tation problems, testing indicates that when the pump c. Eccentricity. Sources of vibration due to eccentric- is operated within its recommended operating range, ity include: the impact of turbulence is minimal. Non-symetrical 1. Journa!s not circular or concentric to shaft. fluid passages in a pump can induce hydraulic imbal- ance which may be seen as a gnce per revolution vibra- 2. Bent or bowed shafts. tion. Multi-phase flow can also induce vibration. 3. Tolerances or clearances of rotating parts may 3.3.4 Journal Bearing Oil Whirl. A condition caused allow eccentricities that result in unbalance. by hydrodynamic forces in lightly loaded journal bear- 4. Non-concentric shaft and coupling interfaces. ings that results in a vibration at slightly less than one- half (42-4896) the rotating frequency. 5. Non-uniform thermal expansion. 3.3.6 Bearing Rotation. Journal bearings that are not 3.3.2 Misalignment properly secured can rotate with the shaft and produce There are two basic types of misalignment: angular vibration at one-half rotating frequency. misalignment, where the center lines of the two shafts 3.3.6 Mechanical Rub. Contact between the rotating meet a t an angle, and offset misalignment, where the and stationary surfaces results in a vibration at a fre- shaft centerlines are parallel but displaced from one quency normally U or i / 2 the operating speed. Natural 3 another. frequencies may be excited. Misaligned couplings or shaft bearings can result in 3.4 Control of Vibration. Methods of vibration control transverse vibration (vibration perpendicular to the may be grouped into three broad categories: reduction at shaft). Flexible couplings with angular misalignment the source, isolation of external sources, and reduction of may produce an axial mode of vibration. This is espe- the response. Table 3.3 Vibration Analysis o ESP Phenomena f ESP (Machine) parts Response Frequency Probable causes relative to ESP rotating of problem speed (mm) ~ Rotor and shafts 1 or 2 x rpm Bent shaft All rotating parts lxrpm Mass or hydraulicunbalance or off ~ Couplings, shafts, I O h n i to 2 x rpm, center rotor Misaligned coupling andor shaft bearintzs Sleeve bearing 1 sometimes 3 x mm LessthaniDxrpm bearing. Ol whirl, lightly loaded bearing. i More prominent in seal chamber section Anti-friction bearing Relatively high, Excessive friction, poor lubrication, too tight fit Contact between stationary and rotating surfaces Journal bearing rotation 112 x rpm Journal rotating with shaft Armature and electric 1 x rpm Eccentric armature (either OD or motors journals)COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  10. 10. A P I RP*LLSB 93 0 7 3 2 2 9 0 0 5 3 2 5 2 2 433 = RP llS8:Recommended Practice on Electric Submersible b p System Vibrations 9 0 3.4.1 Reduction at the Source a Balancing of Rotating Masses. Where vibration . b. Operating at non-ResonantFrequencies.Some- times ESPs are operated with variable speed drives. Operation at a frequency corresponding to a critical results fro& the unbalance of rotating components, the magnitude of the vibratory forces, and hence speed should be avoided to minimize damage to the the vibration amplitude, can often be reduced by system. balancing. c. Additional Damping. The vibration response of a b. Balancing of Magnetic Forces. Vibratory forces system operating at resonance is strongly related to arising in magnetic effects of electrical machinery the amount of damping present. Techniques are are minimized by proper design and fabrication of available to increase the amount of damping. The the stator and rotor; details of which are beyond the addition of damping decreases unit efficiency. scope of this RP. 3.5 Vibration in ESP Systems. The potential for vi- c. Control of Clearances.Vibration can result when brational problems is inherent with any rotating equip- ESP system components and parts, operating within ment having an extreme shaft length-to-diameter ratio the clearances that exist between them, strike each such as an ESP system; consisting of a motor, seal cham- other or otherwise come into impact-type contact ber section, gas separator, and pump(s) all connected by during operation. Vibrations from this source can be a small diameter, high strength, coupled shaft. Recogniz- minimized by avoiding excessive bearing clearances ing that all ESP machinery operates in some state of and by ensuring that dimensions of manufactured unbalance, a reasonable displacement amplitude for new parts are within acceptable tolerances. equipment should be established to allow a margin for deterioration in service. Guidelines are set forth in the d. Straightness of Rotating Shaft. Rotating shafts section following. should be as straight as practical since lack of shaft straightness will have a large effect on system 3.5.1 Vibration Modes. Vibration modes can be axial, vibrations. lateral (transverse), torsional, or combinations of all three. Torsional vibration is known to be a potential 3.4.2 Isolation of External Sources. problem particularly when starting and when changing Other machines or equipment, unless properly isolated, speeds Axial and transverse vibrations on shaft seals may transmit vibration to an ESP under test or in and thrust bearings may be important under certain operation. For example, a horizontal pump delivering circumstances. high pressure water may experience vibration inter- 3.5.2 Critical Speeds. Torsional and lateral critical ference from neighboring pumps and drivers through speeds exist in ESP systems. If possible, operation of 0 the foundation). Accepted practice is to avoid the structure’s natural frequency by approximately 25% above or below. the ESP near a critical speed for an extended period of time shopld be avoided. When this problem is identified over specific, planned rotating frequencies, alteration Isolation of equipment being tested is the responsibil- of the response may be in order and should be ad- ity of the tester. Isolation of equipment in service is the dressed. This problem may be particularly acute when responsibility of the user. the ESP is operated over a wide speed range or during start-up. 3.4.3 Reduction of the Response Torsional critical speeds for the ESP system are gener- a Alteration of Natural F’requency. If a natural frequency of the system coincideswith the frequency ally calculated for the system as an entity by the Holtzer method (Shock and Vibration Handbook 3rd Edition of the excitation, the vibration condition may be made much worse as a result of resonance. Under McGraw-Hili, page 38-91, and can be furnished by the such circumstances, if the frequency of the excita- manufacturer for a specific system configuration. tion is substantially constant, it often is possible to Lateral critical speeds for the ESP system “can be cal- alleviate the vibration by changing the natural fre- culated using either eigenvalue or Myklestadt-Prohl quency of such system. This generally involves Methods (‘Theory of Vibration”, William T. Thompson, m o d i m g mass andor stiffness of the system. Prentice-Hall Inc., Englewood, N. N., 1965, pg. 243.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  11. 11. 10 American Petroleum Institute SECTION 4 RECOMMENDATIONS 4.1 Vibration Limits. It is generally acknowledged that generally have a wide frequency response range (10- severe vibration can decrease ESP system run life. Ap- 10,000 H ) It is common to obtain the velocity and z. pendix C contains general industrial guidelines for as- displacement amplitudes by mathematically integrat- sessing vibration severity. Vibration limits for ESPs are ing the acceleration signal. Below 15 H ,integrated z given below. displacement values may be suspect. For ESP systems or components, a maximum velocity 4.2.1.2 Velocity probes measure velocity directly. These amplitude of 0.156 idsec (0.396cdsec) - peak at the transducers have a useful frequency range of approxi- intended synchronous operating frequency or over the mately 10-3000 Hz. range of intended operating frequencies, with no other 4.2.1.3 Proximity probes. Proximity probes, which individual frequency component greater than 0.100 id could be mounted within the machinery housing to sec (0.254 cdsec) - peak as measured on the housing measure the relative displacement between the shaft or case, is recommended. For pumps the vibration limit and the housing, are not usually used to measure ESP should be applied over the manufacturer’s recommended vibration because of the difficulties associated with operating flow range (Ref. API RP11S2,sec. 2.1.10) mounting them. Velocity measurements should be made in accordance 4.2.2 Selection of Measurement Location. Vibration with Section 4.2, following. The relationship between measurements should be taken at several bearing loca- displacement, velocity, and acceleration amplitudes is tions along the ESP system component. given by equation 3.4. 4.2.2.1 Pump Accuracy and calibration of the measuring system should be considered when establishing vibration test accept- It may be advantageous to conduct the vibration test ance limits. along with the pump acceptance test recommended in API RP-11S2on ESP pumps. At a minimum measure- During testing, the frequencies of critical speeds should ments should be taken at the mid-point on the housing, be recorded for future reference. Operation at critical top radial bearing location, and bottom radial bearing speeds is not recommended. location. Pump rate should be held constant while 4.2 Measurement of Vibration. The first step in es- measurements are being taken. tablishing a condition-monitoring program for rotating 4.2.2.2 G s Separatorbtake a machinery is to determine what shall be measured shaft vibration or bearing vibration. When the shaft is acces- At a minimum, measurements should be taken at the sible, then the displacement amplitude a t the shaft is mid-point on the housing, top radial bearing location, measured with a displacement transducer such as a and bottom radial bearing location. proximity probe. For ESP system components, accessi- 4.2.2.3 Seal Section bility to the shaft is difficult and therefore one must rely on measurement of acceleration or velocity amplitudes At a minimum, measurements should be taken at the a t a suitable location on the component housing (bear- mid-point on the housing, top radial bearing location, ing). Transducers have moving parts and thus may be and bottom radial bearing location orientation sensitive. They should be mounted in a man- 4.2.2.4 Motor ner that will provide accurate, repeatable measurements. At a minimum, measurements should be taken at the 4.2.1. Transducers mid-point on the housing, top radial bearing location, 4.2.1.1 Accelerometers generally exhibit excellent lin- and bottom radial bearing location. earity of electrical output vs. input acceleration under 4.2.3 Drive Motor. Caution must be exercised in com- normal usage; a dynamic range of 10,000 to 1 or more ponent testing. The drive motor will contribute to the is not uncommon. Accelerometers are relatively insen- measured vibration amplitude. To minimize this effect, sitive to temperature and magnetic influences, and a well balanced test driver should be used.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  12. 12. API RP*LLSB 93 = 0732290 0512524 294 D RP 1158:Recommended Practice on Electric Submersible Pump System Vibrations 11 APPENDIX A UNITS CONVERSIONS Table Al Conversion Factors For Translational Velocity and Acceleration Multiply g-sec Wsec in/sec cdsec Value in => g Wsec2 in/sec2 cdsec2 or => BY To Obtain value in g-sec 1 0.0311 0.00259 0.00102 g Wsec 32.16 1 0.0833 0.0328 Wsec2 idsec 386 12 1 0.3927 in/sec2 cdsec 980 30.48 2.54 1 cdsec2 Table A2 Conversion Factors For Rotational Velocity and Acceleration Multiply radlsec degredsec revlsec revlmin Value in => radsec2 degredsec2 revIsec2 rev/midsec or => BY To Obtain value in radsec 1 0.01745 6.283 0.1047 radsec2 degredsec 57.30 1 360 6 degredsec2 revlsec 0.1592 0.00278 1 0.0167 revIsec2 revlmin 9.549 0.1667 60 1 rev/in/sec Table A3 Conversion Factors For Simple Harmonic Motion Multiply numerical Amplitude Root-mean- Peak-to-peak Value in terms of => Square value value BY (ms) to obtain value in terms of Amplitude 1 1.414 0.5 Root-mean-square value 0.707 1 0.354 (rms) Peak-to-peak 2 2.828 1 valueCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  13. 13. A P I RPlrLLSB 93 0732270 0532525 320 12 American Petroleum Institute 0 1000 P E V A E K L T 0 0 C I P 7 E Y 0.mo A K A 0 M I P L P I L T U 0.010 A C 0 0 M E E N T i n / m 8 I e 0.001 I S C 1ooo 3600 moo ROTATNG SPEED, rpm FIGURE Al RELATION OF FREQUENCY TO THE AMPLITUDES OF DISPLACEMENT AND VELOCITY ENGLISH SYSTEM OF UNITS 0COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  14. 14. A P I RPwllSB 93 = 0732290 0532526 Ob7 R llS8:Recommended Practice on Electric Submersible h m p System Vibrations F 13 1000 P E V 09 A E K L T 0 0 C I P ;0 . m E A 0 9 A M D I P S L P I L T " 0.010 A C O E 0 @E E N T C m / m 3 m g 0.001 C m 1ooo 3600 10000 ROTATNG SPEED, rpm FIGURE A2 RELATION OF FREQUENCY TO THE AMPLITUDES OF DISPLACEMENT AND VELOCITY METRIC SYSTEM OF UNITSCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  15. 15. A P I RP*LLSB 73 H 0732270 0532527 T T 3 D 14 American Petroleum Institute APPENDIX B RJILATIONSHIP BETWEEN DISPLACEMENT, VELOCITY, AND ACCELERATION 0 a = ACCELERATION v = VELOCITY d DISPLACEMENT t = TIME x = AMPLITUDE -D -F At position D the velocity (VI is at its maximum; it approaches position B where the velocity is zero and continues in a negative direction to position -D, another maximum, then toward position C, where its velocity is zero. Then it continues on toward D at maximum velocity. The time interval for this total motion from D to B to -D to C to D is one period. Notice the displacement (d) curve. At Al, the displacement amplitude (do)is zero; it approaches maximum amplitude at F and reverses direction toward A2 again where it approaches zero. The displacement continues toward position -For maximum amplitude again, and finally reaches one complete period at A,. Notice that the acceleration (a) curve follows the same pattern as displacement, except that the curve is generated in the negative direction, because of the change in velocity direction at B and C. The peak velocity (v,) is denoted each time it passes through position D. Displacement has two peak amplitudes (XI, namely at positions F and -F, and therefore, is measured in terms of peak-to-peak displacement (d,, = 2x1.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  16. 16. API RP*lLSB 9 3 W 0732290 0532528 93T RP llS8:Recommended Practice on Electric Submersible Pump System Vibrations 15 APPENDIX C CLASSIFICATION OF SEVERITY OF MACHINERY VIBRATION In the classification of severity of machinery vibration, having flexible rotors in which bearing cap vibration is the amplitude variable that is used (displacement, veloc- a measure of the shaft motion. Table C.l lists the allow- ity, or acceleration) depends on the type of standard, the able vibration severity along with a corresponding peak- frequency range, and other factors. The International to-peak displacement amplitude calculated at 3,600 rpm. Standards Organization (ISO) has a special measure, vibration severity, which is defined as the highest value of the broad-band, velocity amplitude in the fre- quency range from 10 to 1,000 Hz as evaluated on the IRD Mechanalysis Severity Criteria. An accepted structure at prescribed points (bearing caps or pedestals). guide for vibrational evaluation is shown in Table C.2 IS0 IS 2372. IS0 standard 2372, applies to rotating and is based on filtered reading taken on the machine machinery having rigid rotors and to those machines structure or bearing cap. Table C.l Vibration Severity Criteria (After IS0 IS 2372,1974) Peak velocity ranges of Vibration Severity Peak-to-peak displacement vibration severity amplitude @ 3,600 rpm (idsec) (cdsec) (mils) (mm) <0.014 <0.036 Extremely smooth <0.074 <0.0019 0.028 0.071 Very smooth 0.148 0.0038 0.042 0.107 Smooth 0.233 0.0057 0.057 0.145 Very good 0.302 0.0077 0.099 0.251 Good 0.525 0.0133 0.156 0.396 Fair 0.828 0.0210 0.255 I 0.648 Sightly rough 1.353 0.0344 0.396 1.006 Rough 2.101 0.0534 0.622 1.580 Very rough 3.300 0.0838 >0.622 21.580 I Extremely rough I >3.300 >0.0838 Peak velocity ranges of Vibration Severity Generalization Peak-tupeak displacement vibration amplitude amplitude @ 3,600 rpm *Non-harmonic,(non-interger multiples)COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  17. 17. Order No. 811-05948 Additional copies available from AMERICAN PETROLEUM INSTITUTE Publications and Distribution Section 1220 L Street, NW Washington, DC 20005 (202) 682-8375COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services

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