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SPM BC100 Скачать руководство пользователя страница 32

28

3 Patterns from poorly lubricated bearings

A high carpet value, very close to the maximum value, is
typical for dry running bearings. The dBm does not always
reach the red zone – typical for poor lubrication is that
the gap between dBm and dBc is very small. If the signal
is strongest on the bearing housing, it can have several
causes:
• insufficient lubricant supply to the bearing (poor oil

flow; old , caked, or cold grease)

• very low or very high bearing speed (preventing the

build-up of an oil film separation between the loaded
rolling elements and the raceway)

• installation fault (excessive preload) or out-of-round

bearing housing

• misalignment or bent shaft.

If possible, lubricate the bearing or increase the oil flow.
Measure immediately afterwards, and again a few hours
later. If the problem was insufficient lubricant supply, the
shock pulse level should drop and stay low.

In the case of very low or very high bearing speed, one
can try lubricants of a different viscosity or use additives
to prevent metal to metal contact between the bearing
surfaces.

In cases of installation faults, unround housings, and mis-
alignment) the shock pulse level may drop after lubrication
but will soon rise again. Misalignment normally affects the
bearings on both sides of the coupling or at both ends of
the shaft.

Cavitation and similar interference

The shock pulse pattern caused by a cavitating pump or by
persistent rubbing is identical with that from a dry running
bearing. You have an interference signal when the shock
pulse level is highest outside of the bearing housing and
is not affected by lubricating the bearing.

If you cannot remove the cause of interference, you have a
“blind spot”: up to a certain level, the interference signal
will mask the signal from one or more bearings. However,
you may still be able to detect bearing damage. When the
dBm rises above the interference level, it must be caused
by something else – probably bad bearing condition. In
that case, lubricating the bearing should cause the value
to drop, at least temporarily.

Cavita-
tion

Poor lubrica-
tion

dBm

dBc

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Содержание BC100

Страница 1: ...x 504 SE 645 25 Strängnäs Sweden Technical data are subject to change without notice Tel 46 152 225 00 Fax 46 152 15075 info spminstrument se www spminstrument comISO 9001 certified Copyright SPM 2008 06 71796 B User Guide ...

Страница 2: ......

Страница 3: ...g range 14 Creating acceptable measuring conditions 15 Measuring intervals 16 Shock pulse transducers 17 Bearing Measurement 19 Input data 19 Entering shaft diameter and rpm for dBi calculation 19 Entering dBi manually 19 Shock pulse measurement 20 Transducer Line Test 21 Storing measurement results 21 Listening to the shock pulse pattern 22 Evaluating the Bearing Condition 23 Identifying the shoc...

Страница 4: ......

Страница 5: ...lse measurement follows It is advisable that you read this as it is valuable in order to understand measurement results and to evaluate them correctly The shock pulse theories chapter is followed by chapters describing the hands on use of the instrument and how to confirm and evaluate measurement results References to icons displays and modes in the instrument are in bold text References to instru...

Страница 6: ...aphic display 4 gives the condition readings and the LED indicators 3 give an immediate evaluated bearing condition in green yellow red The shock pulse transducer 1 of probe type is built in All types of SPM shock pulse transducers for adapt ers and permanent installation can also be used connected to the transducer input 8 The dBi value is programmed into the instrument and the measurement is sta...

Страница 7: ...al settings Bearing measurement Input data Measurement Input dBi Memory TLT test Listening Back Return Main display Temperature measurement Stethoscope function Measure or press the probe tip Back Return Back Return Volume 1 8 Back to main menu Battery Unit About Temperature General settings ...

Страница 8: ... It can also be shut off by simultaneously pressing the LEFT and RIGHT arrow keys When switched back on the instrument will resume its last mode Start up 1 3 4 7 9 2 5 6 8 Serial number and software version To check which software version is in your instrument and find out the instrument serial number go to the Main display Press the DOWN arrow key to enter the General Settings mode Use LEFT RIGHT...

Страница 9: ... instrument is used Full power is only consumed while a reading is in progress from pressing the meas uring key until a measured value is displayed Before long time storage of the instrument keep in mind to remove the batteries Batteries Battery check For exact battery voltage go to the battery setup menu From the Main display press the DOWN arrow key to enter the General Settings folder Use LEFT ...

Страница 10: ... to enter the General Settings mode Use the LEFT RIGHT arrow keys to highlight the Temperature icon then press the UP arrow key Use the UP DOWN arrow keys to set the measurement unit of your choice To save and return to the General Settings menu press the LEFT arrow key To return to the Main display use the LEFT arrow key to highlight the Return icon then press the UP arrow key Unit for bearing di...

Страница 11: ...permanently installed transducers 1 5 m 15286 Belt holder for external probe transducer 15287 Belt case for accessories 15288 Protective cover with wrist strap 15455 Protective cover with belt clip and wrist strap 93363 Cable adapter LEMO BNC 93062 Cable adapter BNC TNC plug jack Spare parts 13108 Rubber sleeve for probe tip chloroprene maximum 110 C 230 F 15288 15455 15287 15286 EAR12 TRA74 TRA73...

Страница 12: ... all rotating rolling bearings because of irregularities in the surfaces of the raceways and the rolling elements The magnitude of the shock pulses depends on the impact velocity Carpet value dBc Surface roughness small irregularities will cause a rapid sequence of minor shock pulses which together constitute the shock carpet of the bearing The magnitude of the shock carpet is expressed by the car...

Страница 13: ...er with the dBi before taking a reading the bearing condition will be indicated directly on the condition display in green yellow red for good reduced or bad operating condition for the measured bearing Bad operating condition can be synonymous with bearing damage but the term also includes a number of other bearing faults which can be detected by shock pulse measurement The initial value dBi of a...

Страница 14: ...ata rpm and shaft diameter have little effect on the evaluated measuring result Lubrication condition is indicated by the delta value i e the difference between dBm and dBc High read ings and a small delta value indicate poor lubrication or dry running This is sufficient for maintenance purposes dBm and dBc are measured in a fixed time window and automatically displayed The headphone is used to li...

Страница 15: ...ondition zones are valid 1 The signal path between bearing and measuring point shall be as short and straight as possible 2 The signal path must contain only one mechanical interface that between bearing and bearing housing 3 The measuring point shall be located in the load zone of the bearing Short means up to 75 mm 3 in but that depends also on how straight the path is bends cause re and deflect...

Страница 16: ...1 can be reached with a long adapter through a clearance hole in the bracket The hole must be large enough to allow bearing adjustment and still prevent metallic contact between bracket and adapter Measuring point 2 placed below and opposite to the pump outlet load direction can be reached with a long adapter through an opening in the pump shield Multiple bearings in one housing If there are sever...

Страница 17: ...frame Check installed equipment Incorrectly installed adapters or transducers can cause a significant damping of the shock pulse signal Check all installations Make sure that mounting holes are cor rectly countersunk and that the seat surfaces of adapters have good contact with the material of the bearing housings Any metallic machine part knocking or rubbing against the adapter will produce a dis...

Страница 18: ...direction and a low inter ference level make it easier to get readings from low speed bearings Successful SPM monitoring has been carried out on bearings with dBi 3 54 rpm shaft diameter 260 mm Note that the dynamic measuring range decreases when dBi values get below 0 For example a bearing with dBi 3 showed very heavy damages at dBn 40 Installed adapters required The installation of adapters is s...

Страница 19: ...maintained parts or badly adjusted operating parameters Therefore do not accept interfer ence try to remove the cause Coping with interference If the source of interference cannot be removed there are several possibilities If it is intermittent measure while there is no interference If interference is persistent measure its shock pulse level with the same dBi setting as the bearing and compare it ...

Страница 20: ...ings in dubious or bad condition Check stand by equipment Vibration and corrosion can damage the bearings in stand by machines Check bearing condition each time such machines are being tested or used Synchronize with lubrication It may be necessary to synchronize regreasing and measuring intervals Grease lubricated bearings should not be measured until they have run for approximately one hour afte...

Страница 21: ...leeve is in contact with the surface Hold the probe steady to avoid rubbing between probe tip and surface The probe is directionally sensitive It has to be pointed straight at the bearing The centre of the probe tip should touch the surface Avoid pressing the probe tip against cavities and fillets which are smaller than the probe tip Shock pulse transducer with handheld probe The handheld probe ca...

Страница 22: ...cers and adapters are properly mounted see the instruction on SPM installations and in good condition You cannot expect a useful signal by attaching the quick connect trans ducer to a rusty lump of metal or from a transducer that is rolling on the floor on the other side of a partition Push and twist Installed transducer Measuring terminal Permanently installed transducers and measuring terminal A...

Страница 23: ...g key to return to Bearing mode Entering dBi manually Changing the dBi directly is faster when you know it from your records From the Main display press the UP arrow key to enter Bearing mode Use LEFT RIGHT arrow keys to highlight the dBi icon then press the UP arrow key First position the cursor using the LEFT RIGHT arrow keys then use the UP DOWN arrow keys to increase or decrease the dBi value ...

Страница 24: ...to the Evaluation Flow Chart on page 32 33 which must be used to further evaluate the bearing condition When you get high readings yellow and red zone you should immediately verify their nature and probable cause Do not give the verdict bearing damage before making a further investigation As a first measure use the headphones to identify the shock pulse pattern measure on and outside of the bearin...

Страница 25: ... transducer and instrument If the value is below 15 or if it is deteriorating from a previ ously higher value you need to check cables connectors and transducers for poor connections and moisture The TLT test can be temporarily turned off to force evaluated measurement results on transducers with TLT below 15 e g when measuring via coupling transformers In the TLT menu press the RIGHT arrow key to...

Страница 26: ...nal speeds the instrument can miss the strongest pulse simply because it does not occur during the measuring interval To listen to the shock pulse pattern after taking an SPM reading connect your headphones to the output connector 7 From the Main display press the UP arrow key to enter Bearing mode Use the LEFT RIGHT arrow keys to highlight the Listening icon then press the UP arrow key to enter l...

Страница 27: ... itself is correct If you find that bearing condition is good you do not have to evaluate the following readings on that measuring point as long as there is no significant change The other situation is when you notice a change in the readings or get high readings from the start Investigate any significant increase or decrease of the shock pulse level Again you want to be quite sure that you are me...

Страница 28: ...ibration in connection with loose parts and excessive bearing play vibration alone does not affect the reading Cavitation in pumps Gear tooth damage Load and pressure shocks arising during the normal operation of certain machines Identifying the shock pulse source Excessive play Gear tooth damage Cavitation Play scraping Shock pulses are strongest close to the source They spread through the materi...

Страница 29: ...The shock pulse pattern from a damaged bearing con tains strong pulses in the red zone a random sequence and a large difference between dBm and dBc When you lubri cate the bearing the values should drop but rise again 3 A dry running bearing has a high carpet value very close to the dBm When you lubricate the bearing the values should drop and stay low A similar pattern is caused by pump cavitatio...

Страница 30: ...when the measurement is completed This number corresponds to the pattern numbers below There may be times when the instrument displays a combination of the numbers 2 3 or 4 5 in which case the instrument can not distinguish between the two codes Use the headphones and listen to the pattern to determine condition code 1 Pattern from a good bearing A bearing in good condition should have a dBm value...

Страница 31: ...on Confirming bearing damage in this manual Cracked inner ring A clean crack in the inner ring of a bearing is difficult to detect especially at a low rpm You may get low readings through most of the bearing s rotation then one or two peaks while the crack is in the load zone Signal strength can differ considerably as the crack opens or closes de pending on bearing temperature In time the surface ...

Страница 32: ... lubricants of a different viscosity or use additives to prevent metal to metal contact between the bearing surfaces In cases of installation faults unround housings and mis alignment the shock pulse level may drop after lubrication but will soon rise again Misalignment normally affects the bearings on both sides of the coupling or at both ends of the shaft Cavitation and similar interference The ...

Страница 33: ...e shaft or in the housing In case of a heavily loaded bearing with previous readings in the red zone suspect cage failure dBm dBc dBm dBc 5 Rhythmical peaks Single rhythmical peaks can be caused by load and pressure shocks which occur during the machine s normal operation Other possible causes are clicking valves or loose parts knocking regularly against the machine frame If the signal is stronges...

Страница 34: ... the bearing and repeat the measurement Meas ure immediately after lubricating and again a few hours later Make sure that the lubricant reaches the bearing Typically you will get the following results A The shock pulse level remains constant The signal is caused by interference or cross talk from another bearing B The shock pulse level drops immediately after lubricating and remains low Foreign pa...

Страница 35: ...red does not apply See also chapters Normalized shock pulse values with dBi and Input data 2 Work out the direction of possible cross talk You know that the stronger source can mask the signal of the weaker source In this case cross talk must go from bearing A to bearing B 3 Subtract the dBi values from the dBsv values In the example you get 26 dBN for bearing A 40 dBN for bearing B You can now dr...

Страница 36: ... The reading can be caused by interference from other defective bearings cavitation in pumps or mechanical rubbing If possible isolate the source of disturbance and test again Locate the signal source If possible isolate the source of disturbance and test again Adjacent to the bearing housing Check the value of adjacent bearings Are the signals from these bearings similar to the tested bearing Loc...

Страница 37: ...ading drops but the max value increases again within a few hours Probable causes insufficient lubrication which probably has caused minor bearing damage The reading does not drop Probably causes Incorrect bearing installation Cavitation in pumps Mechanical rubbing Gear tooth damage The reading drops but the dBm increases again within a few hours Probable causes insufficient lubrication which proba...

Страница 38: ... at the distance of the probe tip and 115 mm at a 10 cm distance To measure temperature From the Main display press the LEFT arrow key to enter Temperature mode Hold the probe tip against the surface you wish to measure and press the measuring key to get a temperature reading For most accurate results take two consecutive readings a few seconds apart Measurement will continue as long as the measur...

Страница 39: ... From the Main display use the RIGHT arrow button to enter the Stethoscope mode Hold the probe tip against the object Use UP DOWN arrow keys to adjust the volume 1 8 NOTE Setting the volume to the maximum level may harm your hearing To return to the Main display press the LEFT arrow key Using the Stethoscope Function Stethoscope function Volume 1 8 7 Back Return ...

Страница 40: ...nguage independent menus with symbols storage of up to 10 measurement values Shock pulse measurement Measurement technique dBm dBc measuring range 9 to 90 dBsv 3 dBsv Transducer type Built in probe transducer Temperature measurement Temperature range 10 to 185 C 14 to 365 F Resolution 1 C 1 F Transducer type Thermopile Sensor TPS 334 3161 built in contact free IR sensor Stethoscope Headphone mode ...

Страница 41: ...l and electronic equipment The purpose of this directive is as a first priority the prevention of waste electrical and electronic equipment WEEE and in addition the reuse recycling and other forms of recovery of such wastes so as to reduce the disposal of waste This product must be disposed of as electronic waste and is marked with a crossed out wheeled bin symbol in order to prevent it being disc...

Страница 42: ...40 50 30 20 10 dBN 40 50 30 20 10 dBN 40 50 30 20 10 dBN M 40 50 30 20 10 dBN dB dBC dBi d n M dB dBC dBi d n d dBi n M dB dBC dBi dB M dB C d n SPM Follow up form ...

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