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Balancing training module for rotary equipment.ppt
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- 2. UNBALANCE • ANY ROTORWITH AN UNEVEN DISTRIBUTION OF MASS ABOUT ITS AXIS OF ROTATION HAS AN UNBALANCE. • A SIMILAR EFFECT IS CREATED BY OUT-OF-CENTRE MACHINING, NON-UNIFORM WINDINGS IN ARMATURES, BLADES OF DIFFERENT SIZES ON ROTORS, INTERNAL FLAWS IN CASTINGS, UNEVEN DENSITY OF MATERIAL. • WHEN THE ROTOR ROTATES,THE EXTRA MASS EXERTS A CENTRIFUGAL FORCE. • THIS CENTRIFUGAL FORCE MOVES AROUND WITH THE ROTATING MASS AND CAUSES DEFORMATION TO THE SHAFT AND VIBRATIONS TO THE SYSTEM
- 3. UNBALANCE AND CENTRIFUGALFORCE • U = m r • m = UNBALANCE MASS • r = RADIUS AT WHICH THIS MASS IS LOCATED • F = M V2/r = m r w2 = U w2 • V = LINEAR VELOCITY • w = ANGULAR VELOCITY • UNBALANCE IS INDEPENDENT OF SPEED
- 4. TYPES OF UNBALANCE •STATIC UNBALANCE THIS UNBALANCE EXISTS ONLY ON ONE SIDE OF THE ROTOR. THIS IS ALSO CALLED FORCE UNBALANCE. • COUPLE UNBALANCE HERE TWO EQUAL WEIGHTS ARE PRESENT IN TWO DIFFERENT PLANES. ONE WEIGHT IS ON TOP AND OTHER IS AT 180 DEG. WHEN THE ROTOR IS ROTATED, TWO EQUAL FORCES ARE PRODUCED WHICH CONSTITUTE A COUPLE AND GIVE RISE TO VIBRATIONS. EVEN THOUGH THESE FORCES ARE EQUAL AND ARE OPPOSITE IN DIRECTION THEY DO NOT CANCEL EACH OTHER AS THEY ARE AXIALLY DISPLACED • COMBINED UNBALANCE IN ACTUAL PRACTICE A LARGE NUMBER OF STATIC AND COUPLE UNBALANCE EXISTS SIMULTANEOUSLY IN A ROTOR.
- 5. DESCRIPTION OF UNBALANCE •UNBALANCE IN LEFT PLANE = 12 CM. G AT 135 DEG. • UNBALANCE IN RIGHT PLANE = 24 CM. G AT 30 DEG.
- 6. PRINCIPLE OF ABALANCING MACHINE • WHEN ROTOR IS ROTATED, EACH UNBALANCE ON ITS OWN GIVES RISE TO A CENTRIFUGAL FORCE. • F1 RESLOVED IN LEFT PLANE = 0.8 F1 • F1 RESOLVED IN RIGHT PLANE = 0.2 F1 • TOTAL UNBALANCE OF A RIGID ROTOR CAN ALWAYS BE REPRESENTED BY TWO WEIGHTS IN ANY TWO PLANES DESIRED • THE DYNAMIC BALANCING MACHINE OPERATES ON THE ABOVE PRINCIPLE
- 7. PRINCIPLE OF ABALANCING MACHINE • THE ROTOR TO BE BALANCED IS PLACED ON THE TWO SUPPORTING CARRIAGES OF THE BALANCING MACHINE AND ROTATED. • THE CENTRIFUGAL FORCES CREATED DUE TO THE UNBALANCE UNBALANCES ACT ON THE CARRIAGES AND ARE MEASURED. • THESE TWO FORCES GIVE US THE TOTAL UNBALANCE OF THE ROTOR IN THESE TWO PLANES. • PROPER AXIS OF ROTATION TO BE ENSURED
- 8. CORRECTION OF UNBALANCE •MEASUREMENT PLANE • CORRECTION PLANE • Urb = W2(b+c) - W1a • Ur = W2 (b+c)/b - W1 a/b • UL = UNBALANCE CORRECTION NEEDED IN LEFT CORRECTION PLANE • UR = UNBALANCE CORRECTION NEEDED IN RIGHT CORRECTION PLANE. • W1 = UNBALANCE IN LEFT MEASUREMENT PANE • W2 = UNBALANCE IN RIGHT MEASUREMENT PLANE • MR = UR/rR • rR = RADIUS AT WHICH CORRECTION IS TO BE MADE ON RIGHT SIDE • PLANE SEPARATION
- 9. BALANCING ACCURACY • SPECIFIEDAS PER ISO 1940 • NORMAL FOR PUMPS G 6.3 • NOW BEING ASKED G 2.5
- 10. DYNAMIC BALANCING MACHINES •A DYNAMIC BALANCING MACHINE IS A MACHINE ON WHICH A ROTOR CAN BE ROTATED AND THE UNBALANCE OF THE ROTOR CAN BE INDICATED ON SUITABLE MACHINES. • HARD BEARING MACHINE - MACHINES WHICH WORK WELL BELOW THEIR RESONANCE ARE CALLED HARD BEARING MACHINES. • SOFT BEARING MACHINE - MACHINES WHOSE PEDESTALS WORK WELL ABOVE THEIR RESONANCE ARE CALLED SOFT BEARING MACHINES. THE JOB SUPPORTS OF SUCH MACHINES ARE NORMALLY VERY FLEXIBLE AND CAN EASILY BE MOVED BY HAND. • RESONANCE TYPE MACHINES - MACHINES WHICH WORK AT OR CLOSE TO THEIR RESONANCE ARE CALLED “RESONANCE TYPE” MACHINES. THE DISPLACEMENT OF JOB SUPPORT AND THERFORE THE READINGS ON THESE MACHINES CHANGE DRASTICALLY WITH SMALL SPEED CHANGES.