Key phaser Key phaser in turbomachines are necessary to find phase angle of unbalance mass at the time of dynamic balancing. Balancing of turbine rotor is essential. Manufacturers at there shop can balance the rotors with some other means even if key phaser is not present. But when rotor is to be balanced at user's site, key phaser is required. A signal used in rotating machinery measurements, generated by a transducer observing a onceper revolution event. !he keyphasor signal is used in phase measurements for analysis and balancing. "Keyphasor is a Bently #evada trade name.$ in our plant, for boiler feed pump % cooling water pump also having key phasor. what is the need of providing key phasor for these pumps& pumps& ump rotors are also dynamically balanced. (irst of all let's look at the real defination of the key phasor as below) *!he keyphasor is an electric pulse, or trigger or trigger , which is derived from a point on a rotating shaft. +t serves as a ero phase ero phase reference reference for determining where imbalance is on a rotor.* rotor.* Keyphasor is a trademark owned by the Bentley Bentle y #evada -ompany, but but has almost become a generic term te rm by popular usage. !he usage of key phasor is for online vibration analysis. et's take your e/ample wherein key phasor is used for turbine machine monitoring system. system. 0ou 0ou can monitor the machine health with vibration probes alone but if you want to analyse the cause of failuer of the machin you need three dimesional graph showing1analysing the vibrations at any point of time when machine is running. running . +f you dont install the key phasor you will come to know that there are vibrations in the machin but you will not point out at what direction, at what point, at what angle. 2hen you are providing MM3 for any rotating machin with key phasor means) you will have one notch on the shaft which will be referance point for analysis % with respect to that point vibrations will be measured "by knowing the displacment, velocity or acceleration$. !he key phasor will interact with the accelerometer type vibration probes % will plot 4 dimensional graph . 2hat is the purpose of keyphasor sensor in vibration monitoring sensor & 5very reply is mostly correct and +'ll add my two cents. !he Keyphaser is used as a reference point of the shaft, 6 to 476 degrees. 2hen analysis are performed via handheld, B# system or other, the viewing of the 89 and :9 signals are important, 9 is defined as the running speed of the machine. !he monitors read overall vibration signals at all frequencies, the Keyphaser is used to determine the speed. ets say your B( is running at ;,666 <M, with a Keyphasor, the instrument can filter the frequency to ;,666 rpm or =4.44 >. 2ith this signal, one can view the shaft behavior or orbit inside the bearing. !he phase is calculated as from the time the Keyphasor triggers to the first positive peak of the vibration signal. My recommendation, leave it installed in the event someone needs to analye data whether inhouse or outside vendor.
Setting Up The Bently Equipment NOTE: For more information look in the top left-hand drawer to find manuals for the Bently equipment the Os!illos!ope "nterfa!e and the os!illos!opes#
General Info •
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!he shaft should be flush with the right side of the first gap on the coupler "3ee figure to the right$ !he 3-3+ cable must be plugged into the computer before it before it is turned on !he masses and the tools needed for
the labs are in the top righthand drawer
Rotation Direction !he rotation direction, 9 a/is, and 0 a/is are defined as viewed by the driver "motor$ to the driven "shaft$. !he rotation direction can be confirmed by checking the -21--2 switch on the back of the 3peed -ontrol. !he system should be set up to rotate in the --2 direction.
!he 9 and 0 a/is are defined as follows...
Probes •
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The pro$es must $e staggered in the pro$e $lo!k %see figure to the right&
!he gap between the probe and the shaft can be determined by reading the voltage from the corresponding ro/ output on the back of the ro/imitor Assembly. !he voltage should be =?, give or take 6.;? !he Key hasor and 5ncoder probes "the two right ne/t to the motor$ should have a voltage of ;?, give or take 6.;? when the probe face is centered on the highest spot for each sprocket !he probe output to the oscilloscope must be eroed using the @scilloscope +nterface. +f the green 5 is lit then turn the knob -2 and if the red is lit then turn --2. !he vertical probe goes to robe 8 input of the
Oscilloscope Settings
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Both channels should be set on A-
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!he !ime1iv knob needs to be in 90 mode "!hese are the values marked in blue$
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3et 6.; ?olts1iv for both channels
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-enter the scope by switching both channels to D# and then using the position knobs at the top
NOTE: !he scopes will slowly wander so be sure to recenter occasionally
Aligning the Mass •
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!he system should be set up to rotate --2 when viewed from the motor looking towards the mass.
Shaft Balancing "'(O)T*NT:Before the
Slow Roll Balancing Technique 8. ower up the computer and Bently equipment :. -lick on *A<5 for 2indows* icon 4. (ile F @pen F AdrewinGdatabaseGsingle F @k C.
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Spee! "ontrol •
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Multiply the number on the *Ma/ 3peed 3etpoint* dial by 86 to get the <M "ie. knob reads :C4 I :C46 <M$ 3low
