vibration engineering for machine foundation

8/12/2019 Vibration Engineering for Machine Foundation

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KILN VIBRATION

Rotary kiln in normal use, the smooth uniform rotation, will not produce much noise, if the rotary kiln in

the production process that generates the noise, or the smooth operation of the frequency noise occurs,

how to judge which is the rotary kiln part of a problem, let's take a look at common problems.

ROTARY KILN VIBRATION ANALYSIS

Rotary kiln appeared abnormal vibration, where vibration may be a larger third gear, second gear where

the vibration is normal, this happens the possibility that depression occurs in second gear foundation, the

rotary kiln in central vacant, so that contact with roller pulley area is reduced, the occurrence of

movement, in which case, you need to use specialized tools to measure, find the center of axis

adjustment, if timely adjustments, over time, the rotary kiln cylinder will cause great harm , may result

in severe deformation of rotary kiln cylinder.

ROTARY KILN ADJUSTMENT METHOD

Through the rotary kiln to do both ends of the central axis of the cylinder plumb line, measuring the

stalls at the wheel with a vertical plane relative to the horizontal displacement, and then calculated

according to the diameter of each wheel with a gear wheel with a center at the horizontal position and its

changes case, round cylinder with a center and rotary kiln center in the same vertical plane, resulting in

rotary kiln cylinder axis horizontal straightness. By adjusting the data for analysis, adjusted for each file

tug to "trace several times, while adjusted while observing" to ensure consistency and installation, in the

future course of the feeding of the rotary kiln, the kiln temperature to be recorded, to detect production

problems, and make adjustments! Ensure therotary kiln work.
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FOUR MAIN CAUSES OF VIBRATION AND THEIR DETECTION TIPS

We normally have two types of dry kiln blower systems.

1. Line shaft blowers, which have long drive shafts with fans attached that have couplings, drive

sheaves, belts, and pillow block bearings throughout. These driveshaft systems reverse airflow by

reversing the rotation of the fan assemblies, and

typically rotate at 600 to 800 rpm.

2. Cross shaft or zone blowers have independent motor blowers driven by separate motors on each fan,

and speed is controlled by a variable frequency

drive (VFD).

The vibration analyst has to look for primary vibration problems at their source.

Most problems in kilns are broken down to the following categories.

1. Unbalance

2. Misalignment

3. Mechanical looseness

4. Bearing failure - both sleeve and anti-friction bearings.

The problems vibration can cause, fall into four categories I have indexed above. All four are heavy

contributors to the overall vibration in the kiln. Let's look at each problem.

Unbalance

Every rotating element has some unbalance, manufacturers set standards that are reasonable and

economical to attain. The primary source of unbalance vibration is the fan assembly. Most

manufacturers balance the hub assembly dynamically, that means balanced by spinning or running the


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assembly and correcting the imbalance by either taking weight off or adding weight to make the mass

center rotate around its shaft center. The fan blades are then static balanced, which means they are

typically weight matched, to a master blade. These blades are then assembled on the blower motor hub,

on site in the kiln. There is some chance of misassembly, and faulty blade pitching at this stage. Most

problems of this nature can be detected by a simple vibration meter or analyzer as to check for high

imbalance. We recommend checking each bearing point for high vibration on install and several times

throughout the year to insure dependability. If a unit is retrofitted to your existing kiln, be aware of

assembly faults, freight damage, and pay attention to manufacturer's instructions on blade angle, and

position of

the shaft to hub fits. These seem relatively unimportant in the assembly, but in reality are keys to your

continued smooth operating efficiency. Simple vibration meters can measure most vibration in kilns. A

typical meter would read displacement (in mils) which is 0.001 inches peak to peak movement.

Velocity, which is inches per second (IPS) and g's or bearing g's commonly known as spike energy. A

typical meter should cost less than $1,500.00 with some training included. Another way to keep

vibration levels monitored would be with hard-wired vibration sensors mounted on your motors with a

meter in the control room. You may then use set points to warn you, or shut down the system if high

vibrations are present. These usually run approximately $150.00 per point with a brain box costing

approximately $1,500.00. Remember there is more than one reason we have vibration. While the most

prevalent problems in a kiln are balance problems, the other problems can and will damage your

equipment. They are just as dangerous as high imbalance.


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Alignment

This is particularly important on line shaft kiln systems as they have many bearings on a common shaft

On the original start up the contractor aligns all bearing to shaft fits. It's only after crashes, heat

distortion, settling of the building, and normal wear and tear do we see alignment problems. We usually

find them by checking the bearing housings taking an axial reading on the bearing. Finding the

amplitude high or higher than the radial vibration is a cause for concern.

Mechanical Looseness

- The mechanical looseness in the system is caused by heat deterioration of the sub structure, poor

bearing fits, hub to shaft looseness, and the foundation deterioration of the primary base, the vibration

may be caused by cracked, warped pedestals, holddown bolts gone, welds broken etc. Your kiln was

originally designed to hold 100's of horsepower to mother earth. If you put any looseness into the

equation, you will not be happy with the results. We again find these problems by zoning your bearing

housings and comparing the horizontal, vertical, and axial amplitudes. Your vibration levels are always

higher perpendicular to its base, then second highest at the base direction, and at it's lowest level axial or

parallel to the shaft. If these amplitudes are high, you are in for premature failure.

Bearings

Most systems use anti friction bearings. Years ago we used sleeve or brass bearings, but as the

technology has reverted to ball bearings, our problem solving is indexed to the antifriction ball bearing.

We definitely have to use an analyzer or spike energy type of vibration instrument for the following

reasons: The ball bearing has several components, the balls (usually 10), an inner race, an outer race

and a cage, to contain the balls. As a bearing faults, we see a velocity level over .15 inches per second,


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which in itself is not a high vibration, but we also have to see a high frequency associated with it

Typically 10 times the rpm as a starter frequency with up to 30 times the primary rpm is a typical

frequency. We would find the vibration over 6,000 to 10,000 cycles per minute as a problem. We can

see this with a vibration analyzer that displays amplitude and frequency or a spike energy meter as it

looks only at amplitudes above 10,000 cycles per minute. These instruments are readily available and

inexpensive. I have covered the most prevalent problems in the typical kiln. There are another nine

possible vibration anomalies, they do occur, but at a very low occurrence level. I have given hand outs

on vibration levels, and possible causes for excessive levels. All amplitudes are indexed by frequencies

they occur at. Most vibration analysts can index these causes. Again vibration usually starts with

imbalance, it then causes high wear of key components, which will cause catastrophic events to unfold.


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ROTARY KILN MONITORING

A typical case of embedded condition monitoring is illustrated by the diagnosis and correction of a

rotary kiln support roller misalignment problem. A faulty roller bearing had just been replaced along

with the complete kiln support roller assembly. After the kiln had warmed up to normal operating

conditions production personnel noticed that the same support roller area was showing an alarm

situation, as shown in Figure 5, and maintenance people were notified.

F igure 5. Alarmed point in r ed indicates a vibration problem in a kil n support rol ler. Clicking on that

point opens up a vibration analysis tool as shown in F igure 6.


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F igure 6. A signal sample from a troublesome support roller bear ing housing vibration

When the alarmed point was clicked a pop-window of the vibration pattern of that support roller showed

a cluster of pulses occurring in regular intervals in the vibration time trended signal, see Figure 6. The

impulse frequency was close to the characteristic impulses from a failed inner race roller bearing. But

the pattern was not exactly the same as a failed bearing and the impulses were not continuous. The

impulse series during a 19-second sample period appeared about once per support roller rotation period

of 11.1 seconds, corresponding to a rotation frequency of 0.09 Hz.


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Figure 7. The origins of wet end pulsations are determined by the integrated monitoring of the DCS system.

F igure 7. The origins of wet end pul sations are determined by the in tegrated monitor ing of the DCS

system.

After some thought and a site inspection it was noticed that the rotation of the kiln was not smooth and

there was a rumbling noise. This is a typical indication of an alignment error in the kiln. With a further

inspection it was noticed that the new support roller was slightly larger than the older one, so it was

carrying more load than the others. A realignment of the support rollers was completed and the kiln

mechanical operation returned to normal.


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BENEFITS OF EMBEDDED CONDITION ANALYSIS

By measuring, analyzing, trending and alarming vibration levels in mechanical systems immediate

mechanical faults can be detected and definitive corrective action can be taken at the right time for the

right reasons. In many cases this positive action, reinforced by precise and meaningful data, can avoid

unplanned failures and extensive and expensive machine downtime. Also, safety problems can be

foreseen and prevented. Machine runnability and product quality can be optimized by diagnosing

machine pulsation and vibrations and solving them at their source.

By archiving vibration data over extended periods, a maintenance history of a mechanical system can be

developed and maintenance can therefore be scheduled to ensure maximum machine uptime for the right

service actions and the lowest service costs. Only the most effective and targeted maintenance need be

done.

Condition monitoring embedded in a DCS also allows the analysis of pulsations and vibrations in

various paper machine sections from the wet end to paper finishing. The solution to these vibration or

pulsation problems often results in better paper quality or machine runnability. Figures 7 and 8

(previous page) illustrate how this analysis capability can be used to diagnose wet end pressure

pulsations and calendar barring problems. By STA analysis of vibrations in paper machine press and

calendar nips, the running condition of press fabrics and the condition of roll covers can be assessed

Fabrics and rolls can be removed at the optimum time so paper quality or runnability are not

compromised. In practice, roll grinding intervals can be extended as long as the covers are certified to be

in good condition. The use of condition monitoring in multi-nip soft calendering is particularly critical

as early warning of calendar hot spots can avoid premature, costly and dangerous roll cover failures.


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With a single system the linking of maintenance requirements to Computerized Maintenance

Management Systems (CMMS) is greatly simplified since there is only one link. Through the DCS

operator diary function, notes and comments by process operators can be transferred and made visible to

all. These communications include maintenance problems and their solutions during all shifts. Also

work orders may be activated if seen necessary. Once maintenance is completed a task-completed note

can be added to the diary entry and communicated back to the operators.

F igure 8. Synchronous time averaging (STA) analysis determines which roll in a supercalender is

causing a barr ing problem.

F igure 7. The origins of wet end pul sations are determined by the in tegrated moni toring of the DCS

system.


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DURING INSECTION


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ROTARY KILN

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