importancia de la alineación del eje en bombas

8/3/2019 Importancia de la alineacin del eje en bombas

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Premature shaft and coupling

failure.

Excessive seal lubricant

leakage.

Failure of coupling and

foundationbolts.

Increasedvibration and noise.

Shaft MisalignmentShaft misalignment is responsible

for as much as 50 percent of all

costs related to rotating machinery

breakdowns. Accurately aligning

shafts can prevent a large number

of machinery breakdowns and

reduce much of the unplanned

downtime that results in a loss of

production. In todays challengingenvironment of reducing costs and

optimizing assets, the necessity of

accurate shaft alignment has never

been greater.

Correct AlignmentMachines need to be aligned in

both the horizontal and vertical

planes. Misalignment can bedue to

parallel or angular misalignment, or

a combination of both.

Basically, there are two types of

misalignment: parallel (or offset)

misalignment and angular

misalignment.

With parallel misalignment, the

center lines of both shafts run

parallel to oneanother, but theyare

offset. With angular misalignment,

the shafts run at an angle to one

other.

Types of Shaft

MisalignmentParallel misalignment can be

further subcategorized as either

horizontal or vertical misalignment.

Correctly aligned shaft

A major part of keeping equipment

running smoothly involves regularmaintenance and upkeep and

ensuring that the machinery is kept

lubricated and properly aligned.

When shafts or belts on rotating

equipment are misaligned, the risk

of costly, unplanned machine

downtimerises dramatically.

Misalignment also damages sealsand couplings. Lubrication

problems often can be traced to

seals that have been compromised

by shaft or belt misalignment.

Simply replacing a seal will not stop

future seal failure and associated

loss of lubricant only correcting

the misalignment will solve the

problem.

Failure to align the shafts or beltsproperly will increase theamount of

stress on the units, resulting in a

range of potential problems that

ultimately can seriously impact a

companys bottomline:

Increased friction, resulting in

excessive wear, excessive

energy consumption, and the

possibility of premature

breakdown of equipment.

Excessive wear onbearings and

seals, leading to premature

failure.

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The straightedge is positioned ontwo bearings supporting one or

moreshafts, while themaintenance

inspector visually assesses

whether or not the components are

properly aligned. While such rough

alignment methods have the

advantage of being quick and

relatively easy, they are also highly

inaccurate and do not produce the

exacting degree of accuracy

required by today's precisionmachinery.

Dial indicators represent anothertraditional method of measuring

misalignment. But while dial

indicators do offer a higher degree

of accuracy, they also present

certain problems. Not only do they

require a high level of technical skill

to be used properly, but the effort is

also generally quite time-

consuming.

Furthermore, dial indicators do notprovide real-time values that

enable technicians to

simultaneously measure and attain

correct alignment.

Horizontal misalignment refers to

misalignment of the shafts in the

horizontal plane, while vertical

misalignment refers to

misalignment of the shafts in the

vertical plane. Parallel horizontalmisalignment results when the

motor shaft is moved horizontally

awayfromthe pump shaft, but both

shafts still operate in the same

horizontal plane and parallel.

Parallel vertical misalignment

occurs when the motor shaft is

moved vertically away from the

pump shaft, but both shafts still

operate in the same vertical plane

and parallel.

Similarly, angular misalignment can

be further subcategorized as either

horizontal or vertical misalignment.

Angular horizontal misalignment

occurs when the motor shaft is at

an angle with the pump shaft, but

both shafts still operate in the same

horizontal plane. Angular vertical

misalignment occurs when the

motor shaft is at an angle with the

pump shaft, but both shafts still

operate in the same vertical plane.

Serious instances of misalignment

can occur as a result of parallel

misalignment, angular

misalignment, or a combination of

thetwo.

Correcting Shaft

AlignmentTradit ional al ignment methods

still in common use today include

visual inspection combined with a

straightedge or ruler.

THE IMPORTANCE OF SHAFT ALIGNMENT

Overview of shaft alignment options -- (from left to right) straightedge, dial indicators, and

laser shaft.

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Shaft alignment laser-guided tools

typically consist of two units, each

capable of emitting a precise laser

beam and detecting a laser beam

from its mate, plus a handheld

control device.

The units securely mount to shafts

via magnetic brackets and/or amagnetic chain. To run them, the

operator activates the instrument

via thehandheld control device and

each unit emits a precise laser line

projected onto the other units

detector.

A display on the handheld device

provides real-time coupling and

feet values during the alignment

process, avoiding the need toremove and reinstall the measuring

units after each alignment

adjustment.

In addition, the laser system tool

documents the values, which can

be downloaded to a computer and

used as a benchmark for future

alignment inspections. More

advanced laser-alignment systems

come with a built-in step-by-step

alignment process, from

preparation, inspection andevaluation through correction,

reporting and analysis. Some

models also offer a unique

database to store data regarding

visual inspectionsonoil leakage, oil

level, foundation bolt status, and

wear indications.

Laser-alignment methods represent

a marked improvement over

traditional methods. A laser-drivenshaft alignment device allows one

to adjust alignment with far more

speed and accuracy than either the

straightedge or dial method.

Instead, the dial indicators must be

removed and then reinstalled after

each alignment adjustment is

completed. As a result, the process

for obtaining critical measurements,

such as feet values and coupling

values, can belengthy. Feet values

indicate whether the pedestal or

footing on which the machine restsis loose or compromised in some

other way. Coupling values attest to

the integrity of a coupling

connecting two shafts.

Laser -gu ided tools, generally

speaking, are quick, accurate,

easy-to-use, and require only a

single installation. In addition, they

deliver consistently better accuracy

than dial indicators and they do notrequire special skills to obtain

accurate results virtually every

time.

Overview of shaft alignment options -- (from left to right) straightedge, dial indicators, and laser shaft

by Dead Cat


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Belt or Pulley

AlignmentBelt alignment or pulley alignment

is also an important maintenance

task and, when carried out

correctly, can prevent unplannedshutdowns and achieve

considerable cost savings.

Because belt alignment depends

on the correct alignment of the

pulleys on which the belt operates,

belt and pulley alignment are

generally considered one process.

Belt alignment involves aligning the

belts in a manner that results in the

least wear on the belts and lowestenergy loss for the machine or

driver unit. In practice this means

the grooves of the pulleys are in

linewith one another.

Consequences of Belt

MisalignmentLike shaft misalignment, belt

misalignment can result in a wide

range of detrimental and

sometimes dangerousconsequences, including:

Reduced efficiency of the

machine.

Increased wear on pulleys and

belts.

Increasedfriction.

Excessive energy consumption.

Increased noise and vibration

and Premature bearing and belt

failure

Types of misalignment

Measuring prallel and angular misalignment using a straightedge or a piece of string.

by Dead Cat


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Vertical angle or twisted

misalignment occurs when one of

the pulleys has an angular error

from the vertical angle plane. This

is usually caused by incorrect

positioning of the machine and canbe corrected by lifting either the

front or rear feet of the motor to

which the pulley is attached,

depending on the direction of the

vertical angle error. This differs

from shaft alignment in that one

never moves both feet in a vertical

direction to reach the desired

result.

Horizontal angle misal ignmentoccurs when the driver and the

driven unit are not positioned

parallel to each other. Incorrect

positioning of applications, such as

the motor, typically can cause this

type of misalignment. Horizontal

angle misalignment generally can

be corrected by moving the front or

rear feet forward or backward on

their guides, depending on thedirection of the horizontal angle

error, in order to twist the motor

around its center.

Parallel misalignment is the least

complex form of misalignment. It is

often caused by the incorrect

positioning of the motor along its

shaft axis, positioned either too far

forward or backward compared to

the other shaft. Or it can be causedby incorrect positioning of the

pulleys on their respective shaft,

where one of the pulleys needs to

beadjusted on the shaft.

Belt Alignment Methods

Belt alignment can be performed

by either traditional visual methods

or the laser method. Traditional

methods usually employ strings

and/or straightedges. Lasermethods utilize a laser beam,

which provides for a much higher

degree of accuracy. The main

advantage of these traditional

methods is the limited length of

time needed for adjustment,

although the use of a straightedge

takes more time than visual

assessment alone. The major

disadvantage is the lack of

accuracy. For example, some beltmanufacturers recommend a

maximum misalignment of 0.5

degrees or even 0.25 degrees,

which is difficult to accomplish by

using visual assessment. These

traditional low-tech methods

involve a good deal of trial and

error, naked eye approximation,

and rough estimates. All told, that

means a large margin for error,which is unacceptable for precision

pulley alignment.

A laser belt alignment system

enables one to adjust alignment

with far more speed and accuracy

than with traditional methods.

Systems available on the market

can be categorized according to

the way the devices are attached to

the pulley and the way they align.Generally, there are two groups,

one that aligns the face of the

pulleys and one that aligns the

grooves of thepulleys.

Unless the misalignment is

corrected, a new replacement belt

will likely wear out quickly.

Continuous operation in a

misaligned state also will increase

wear on the pulleys themselves, aswell as their axles, shafts and

bearings.

Maintaining belts in proper

alignment is just as important as

aligning shafts. For that reason,

laser-guided belt aligning devices

are an essential part of an up-to-

date maintenance operators tool

kit.

Belt alignment laser-guided tools

consist of two components, a laser

emitting unit and a 3-D receiver.

The tool uses V-guides along with

powerful magnets that quickly

attach in the pulley groove to

facilitate alignment of pulleys even

if they have unequal widths or

dissimilar faces.

Nature of

MisalignmentAs with shaft misalignment, there

are various types of belt

misalignment. In practice, a

combination of different

misalignments is oftenencountered

simultaneously. For thisreason, it is

important that an alignment

instrument both diagnoses and

details the nature of the machine's

misalignment. The following

illustrations depict the three

different typesof belt misalignment.

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Bearings out of square with their

housings are another common

cause of misalignment. Often a

condition of wear, the out-of-square

bearing and/or its housing will need

to becorrected or replaced in orderto bring machines back into

alignment.

Maintaining Correct

AlignmentOnce misalignment is detected,

analyzed and corrected, an

ongoing alignment maintenance

program is important to keep

operations running smoothly. Aspart of this maintenance, alignment

checks should be performed to

document alignment conditions

before a machine is removed from

service. This gives users the ability

to install new or rebuilt machines

with the same proper alignment

values. In addition, a maintenance

program should include periodic

checks to verify conditions are still

within tolerance.

Taking these simple steps to

detect, correct and maintain proper

shaft and belt alignment can

prevent costly, unplanned

downtime. Fortunately, there is a

range of modern laser-alignment

options available to make this

processeasier than ever before.

Mark Ely is currently based inHolland as a product marketing

manager at SKF Maintenance

Products. He is a Marine Engineer

graduate and served in cruise ships

for a few years, where he quicklylearned the real world, hands-on

side of engineering. With nearly 25

years of service within SKF, Mr. Ely

has extensive experience in

maintenance applications and shaft

alignment, as well as product

development and product

marketing. Mr. Ely can be reached

at [email protected].

Karl Vietsch has worked for theSKF Condition Monitoring Centre,

Livingston, for almost three years.

During this time, Mr. Vietsch has

served as a Business Engineer

(BSc), and provided alignment

support service by telephone. In his

role as a project manager for

gearbox repair, he called SKF to do

the alignment job for a gearbox that

he and his team had repaired. Karlhas significant mechanical hands-

on experience and has strived to

make the lives of the alignment

engineer and management easier.

The result of his efforts is the

development of the SKF TKSA 60

and TKSA 80 shaft alignment

systems. Reach Mr. Vietsch at

[email protected].

Most products on the market use

the face or side of the pulley as a

reference for aligning the pulleys

and belts. The advantage of this

method is that it can be used for

belt types other than V-belts, suchas timing belts. V-belts, however,

comprise themajority of belts found

on the market, especially in

industrial applications. The main

disadvantage is that the face of the

pulley is the only reference point.

This means that only the faces of

the pulleys are aligned with each

other. This method results in

varying degrees of accuracy when

the pulleys are of differentthickness, brands or kinds(e.g. one

single-belt pulley and one multiple-

belt pulley) or when the faces are

not well finished.

Products that align using the

grooves of the pulleys in which the

belt runs tend to provide

substantially higher levels of

accuracy regardless of thethickness, brand or type of pulleys.

Soft FootSoft foot is a condition in which

one of the feet of a machine does

not sit flat on the baseplate. Soft

foot is among the most common

causes of misalignment.

Accordingly, one of the first steps to

take in an alignment check is to

assess the equipments foundationand employ a suitable shaft

alignment tool to identify and

correct potential soft foot

conditions.


by Dead Cat

importancia de la alineación del eje en bombas

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