Inspeccion de Cables

8/13/2019 Inspeccion de Cables

1/23

Wire Rope Inspection and ExaminationBy A. Noble & Son Ltd.

Courtesy of Casar

. W!y must "ire ropes be inspected and examined# $a%e

. W!at is Inspection' "!at is Examination# $a%e (

(. W!en must "ire ropes be inspected# $a%e )

). W!en must "ire ropes be examined# $a%e )

*. Sur+ey for remo+al criteria $a%e ,

,. W!ere must "ire ropes be inspected or examined# $a%e -

./iscard number of "ire brea0s

$a%e

1. Rope examination procedure $a%e (

1. E2uipment $a%e (

1. Locatin% of "ire brea0s $a%e (

1.( /etermination of t!e rope diameter $a%e *

1.) 3easurin% rope lay $a%e ,

1.* C!ec0in% t!e stability of t!e rope $a%e 1

1., C!an%es in rope structure $a%e 1

1. Inspectin% s!ea+es and drums $a%e 1

4. Electro5ma%netic "ire rope examination $a%e -

$a%e


2/23

Why must wire ropes be

inspected and examined?

Wire ropes are consumable items

"it! a limited life. /urin% ser+icet!e p!ysical properties of a "ire

rope "ill c!an%e.

At t!e commencement of ser+ice'

t!e indi+idual "ires and strands

settle into position and t!e rope

brea0in% stren%t! increases. After

reac!in% a maximum it decreases

rapidly 67i%. 8.

9!is decrease in brea0in% stren%t!

is caused by t!e pro%ressi+e loss

of t!e metallic cross5section due

to abrasion and corrosion' by "ire

brea0s and by c!an%es in t!e

structure of t!e rope.

A c!ain represents a series con5

nection of load bearin% elements.

If only one lin0 in t!e c!ain

brea0s' t!e "!ole liftin% de+ice

"ill fail completely. A "ire rope

represents a parallel connection of

load bearin% elements andconse2uently it can still be oper5

ated safely after one or more "ire

brea0s.

:enerally' t!ere is a steady rate of

increase in t!e number of "ire

brea0s durin% t!e life of t!e rope.

7i%. ( s!o"s t!e increasin% num5

ber of "ire brea0s as a function of

t!e number of cycles in a bendin%fati%ue test.

;ne of t!e ob


3/23

inspection and examination

procedures is to detect unexpected

dama%e or corrosion.

Inspections and examinations'

properly carried out' ensure t!ediscard of a rope before failure. In

addition' precautions can be ta0en

to a+oid a recurrence of dama%e

or excessi+e "ear to future ropes.

1. What is Inspection, what is

Examination?

An inspection is a careful andcritical assessment of t!e rope and

fittin%s carried out "it!out

dismantlin%.

An examination is a careful and

critical assessment of t!e rope and

fittin%s carried out by a competent

person. 9!is s!ould include'

"!ere necessary' a +isual assess5ment of t!e internal condition of

t!e rope' supplemented by ot!er

means suc! as measurement and

non5destructi+e testin%. In order

for end fittin%s to be examined

properly t!ey may need to be

dismantled.

$a%e (


4/23

2. When must wire ropes be

inspected?

Wire ropes s!ould be inspected at

t!e start of eac! s!ift' "or0 periodor more fre2uently' dependin%

upon past experience. >sually t!is

inspection "ill be carried out by

t!e operator of t!e indi+idual

piece of e2uipment or possibly by

a member of t!e "or0 force spe5

cially appointed.

9!e inspection s!ould be a +isualassessment of t!e condition of as

muc! of t!e rope len%t! as possi5

ble' includin% t!e points of at5

tac!ment to t!e e2uipment. W!en

a rope !as been remo+ed from

e2uipment and later fitted to t!e

same or different e2uipment' it

s!ould be inspected after fittin%

but before resumin% ser+ice.

If at any time a c!an%e in t!e rope

condition is suspected it s!ould be

reported immediately and t!e

e2uipment ta0en out of ser+ice

until t!e rope !as been examinedby a competent person. As a result

of t!is examination it may be

prudent to re+ie" and amend t!e

scope and fre2uency of t!e in5

spections.

3. When must wire ropes be

examined?

9!e 7actories Act 4, Section,' 9!e Construction 6Liftin%

;perations8 Re%ulations No.*1

and t!e ;ffs!ore Installations

6;perational Safety' ?ealt! and

Welfare8 Re%ulations 4,

No.-4 all re2uire a t!orou%!

rope examination at least once in

e+ery period of six mont!s.

$a%e )


5/23

9!e S!ipbuildin% and S!ip

repairin% Re%ulations 4,-

re2uires a t!orou%! examination

e+ery t!ree mont!s or mont!ly

after t!e first bro0en "ire !asbeen disco+ered.

;ne of t!e statutory re%ulations

listed abo+e "ill apply to t!e

location and type of rope usin%

e2uipment bein% examined.

It is t!e responsibility of t!e

indi+idual to institute and

maintain a pro%ram of periodic

examination "!ic! satisfies t!ere2uirements of t!e appropriate

re%ulations and t!e specific

operatin% conditions of t!e

e2uipment.

Examination s!ould be carried out

at re%ular inter+als. 9!e inter+als

s!ould be sc!eduled so t!at any

dama%e "ill be detected early.

Accordin% to BS ,*- examina5

tions s!ould be carried out @at

re%ular inter+als' t!e fre2uency of

"!ic! "ill be influenced by t!e

follo"in%

a8 Statutory re2uirements

b8 9ype of appliance andor

desi%n of t!e system

c8 ;perational en+ironmental

conditions

d8 3et!od and fre2uency of

operation

e8 3anufacturers recommend5

ations

f8 Results of pre+ious inspec5

tions and examinations

%8 Experience "it! pre+ious

ropes on t!e appliance or

systemD

/urin% t!e first fe" "ee0s after

t!e installation of a ne" rope t!edaily inspection can be used to

monitor performance as t!e rope

mi%!t !a+e been fitted incorrectly

or t!e type of rope mi%!t not be

suited to t!e e2uipment.

9!e inter+als bet"een t!e examin5

ations s!ould also be reduced after

t!e first bro0en "ire or ot!er

dama%e !as been detected.

If t!e rope !as been o+erloaded or

if non5+isible dama%e is suspect5

ed' t!e inter+als bet"een exami5

nations s!ould be reduced ac5

cordin%ly.

3oreo+er' t!e examinations

s!ould be carried out "!en a rope

is put bac0 into ser+ice after lon%periods of standin%.

If a liftin% de+ice !as been dis5

mantled and re5assembled' t!e

rope must be examined before it is

allo"ed to operate a%ain.

$a%e *


6/23

4. Survey o remova! criteria

A "ire rope must be remo+ed if

one or more of t!e follo"in% crite5

ria can be satisfied

8 Bro0en "ires.

A "ire rope must be discarded if

t!e permissible number of "ire

brea0s is reac!ed or exceeded. It

must also be replaced "!en local

concentrations of "ire brea0s

occur.

C!apter co+ers in detail t!e sub5


7/23

s!oc0 loadin%. Loop formations

are a


8/23

f8 9!innin% of t!e rope 67i%. ,a8.

9!innin% is a reduction in t!e

diameter of t!e rope o+er a s!ort

len%t!. It is often associated "it!

older fibre cored ropes usually inareas of sustained !ea+y loads

o+er s!ea+es. 9!e disinte%ration

and loss of t!e core can allo" one

of t!e co+erin% strands to ta0e t!e

place of t!e core. W!en t!is

condition occurs in ropes "it!

IWRC t!e distortion "ill most

often be in t!e +icinity of t!e

termination a"ay from drum. 9!e

most li0ely cause is rope rotation

"!ic! !as allo"ed t!e rope to

unlay' resultin% in t!e o+erload

and reduction in diameter orfailure of t!e IWRC.

%8 3isplaced ;uter Wires.

3isplaced outer "ires are "ires

forced out of position alon% t!e

line of t!e rope to form small flat5

tened loops. 9!is can be caused

by bad drum spoolin% or by t!e

rope bein% dra"n across a s!arp

$a%e 1


9/23

ed%e. Lan%s lay ropes are often

"orst affected. 3isplaced outer

"ires are a


10/23

*8 /ama%e caused by !eat.

?eatin% rope "ires to approxim5ately (--C and o+er' "ill lead toconsiderable reduction in tensile

stren%t! of t!e "ires 67i%. 8.

Wire ropes "!ic! !a+e been

sub


11/23

t"een rope and fittin% is often t!e

focal point for increased stress

caused by +ibration.

9!e dan%er of corrosion is also

increased by t!e retention ofmoisture in t!e area of contact

bet"een rope and fittin%.

d8 E2ualisin% S!ea+es. Ropes

"!ic! are often considered to be

stationary around E2ualisin%

S!ea+es can be sub


12/23

In eac! of t!e areas "!ere "ire

brea0s or ot!er defects are found'

t!e number and description alon%

"it! t!e location' must be

recorded.

#. $iscard number o wire

brea%s

9!e Construction 6Liftin% ;pe5

rations8 Re%ulations re2uires a

rope to be replaced "!en t!e

number of bro0en "ires reac!es

* of t!e total number of "ires

in t!e rope in - x d.

9!e 7actories Act' 9!e S!ipbuild5

in% and S!ip5repairin% Re%ula5

tions and t!e ;ffs!ore Installa5

tions Re%ulations do not specify a

particular number of bro0en "ires

for discard and lea+es t!is

decision to t!e discretion of t!e

examiner.9!e ?ealt! and Safety at Wor0

Act re2uires t!e pro+ision and

maintenance of plant and systems

of "or0 t!at are' so far as is

reasonably practical' safe and

"it!out ris0s to !ealt!.

9!e table on $a%e * s!o"s t!e

recommended number of discard

"ire brea0s for CASAR special"ire ropes. 7or t!e number of

discard "ire brea0s in ot!er types

of multi5strand ropes t!e user is

ad+ised to contact t!e rope manu5

facturer.

/ependin% on t!e 7actor of

Safety' t!e assessment of bro0en

"ires in , and 1 strand ropes

"or0in% o+er steel s!ea+es is di5

+ided into t"o %roups

7actor of Safety less t!an * *

of t!e number of outer strand

"ires excludin% 7iller "ires.

7actor of Safety %reater t!an

* - of t!e number of outer

strand "ires excludin% 7iller

"ires.

W!en bro0en "ires are detected'

t!e number and position' alon%

"it! t!e examinerJs opinion of t!e

%eneral rope condition' "illdecide "!et!er or not t!e rope

s!ould be discarded.

If local concentrations or %roups

of bro0en "ires are found' t!e

rope s!ould be discarded "!en

a8 9!ree or more bro0en "ires

are found in t!e close proximity of

t!e termination'

b8 9!ree or more bro0en "ires

are found in one strand or

c8 7i+e bro0en "ires are found

bet"een t"o ad


13/23

ma0e t!e termination. In suc!

cases it is recommend t!at t!e

soc0et is submitted for N./.9. and

!eat treatment. Care must be ta0en

to ensure sufficient turns of@deadD rope remain on t!e drum

after t!e termination !as been re5

made.

&. 'ope examination procedure

(.1 E)uipment

In order to carry out a proper

inspection' t!e follo"in% tools

s!ould be a+ailable

A list of t!e discard criteria 6t!is

manual8

Rope caliper or +ernier %au%e

Steel tape

$iece of "!ite c!al0

Wax pencil 6dar0 coloured8

Roll of addin% mac!ine paperS!eet of typin% carbon paper

Scre"dri+er

3a%nifyin% %lass

$encil

Roll of mar0in% tape

9"o sets of %roo+e %au%es

$iece of cleanin% clot!

Wire brus!

$air of %lo+esNoteboo0 or an inspection form

9!e pre+ious inspection records

(.2. *ocatin+ o wire brea%s

Identification of "ire brea0s can

be by +isual and p!ysical exam5

ination or by t!e use ofelectroma%netic e2uipment 6see

section 48.

9!e first step in "ire rope exam5

ination is to find t!e rope section

"it! t!e %reatest concentration of

"ire brea0s. 9!is is normally done

by first +isually inspectin% t!e full

len%t! of t!e rope.

In some cases it can be !elpful to

spool t!e rope slo"ly t!rou%! t!e

!and. Special attention !as to be

paid and stron% protecti+e %lo+es

must be "orn.

A piece of "ood !eld on t!e sur5

face of a mo+in% rope "ill be de5

flected by t!e protrudin% ends of

bro0en "ires. In t!e same "ay' asoft cotton or similar type clot!

!eld a%ainst a mo+in% rope "ill be

cau%!t by protrudin% ends and

t!us detect t!e bro0en "ires.

Smoot! synt!etic material is less

suitable for t!is purpose.

9!e detection of bro0en "ires in

t!e strand +alleys can be difficult.

9!e use of a scraper or piece ofs!aped "ood "ill !elp clean out

t!e +alleys. 9!e use of a "ire

brus! on a dirty' !ea+ily lubri5

cated rope can loosen' but not

al"ays remo+e' old lubricant and

t!e brus! may !a+e to be cleaned

fre2uently "it! a sol+ent.

W!ere sol+ents are used to clean

t!e rope surface' t!ey s!ould beused sparin%ly and t!e rope sec5

$a%e (


14/23

tion s!ould be t!orou%!ly lubri5

cated after"ards.

A li%!t lubricatin% oil used "it! a

"ire brus! is preferred for

softenin% old lubricant "!ic! cant!en be "iped off "it! a clot!.

W!en t!e "orst affected sections

of rope !a+e been found' t!eir

boundaries s!ould be mar0ed by

c!al0 or tape for furt!er

examination.

A %au%e s!ould be set to a len%t!

of - x d. 9!is can no" be mo+ed

"it!in t!e boundaries to locate t!esection "it! t!e maximum

number of "ire brea0s. 9!e

brea0s in - x d s!ould be count5

ed and entered in t!e records.

Wit! t!in ropes' +alley brea0s can

be detected by stron%ly flexin% t!e

unloaded rope 67i%. 18.

$a%e )


15/23

(.3. $etermination o the

rope diameter

9!e rope diameter s!ould be

measured on receipt for conformi5ty "it! t!e specification. Britis!

Standard 6BS (-41' Stranded

steel "ire ropes' $art . Clause

*.8 allo"s for a tolerance of K

to F) of t!e nominal rope dia5

meter.

9!e %enerally accepted met!od of

measurin% rope diameter for com5

pliance "it! t!e Standard is to usea caliper "it!


16/23

!as to be applied dia%onally to t!e

axis of t!e rope' so t!at at any

time a cro"n ad


17/23

measurement s!ould be made o+er

four lays and t!e len%t! di+ided

by four to find t!e a+era%e lay

len%t!.

;n ei%!t strand ropes t!e ei%!t'

sixteent!' t"enty5fourt! and

t!irty5second strands must be

mar0ed. >sin% a strai%!t len%t! of

t!e rope and "it! t!e rope under

no load' first mar0 any strand on

t!e cro"n "it! a piece of c!al0.

9!is strand no" becomes @cro"n

=eroD. Excludin% t!is strand' count

t!e next ei%!t strands and mar0

t!e ei%!t! strand "it! c!al0.

Exclude t!e ei%!t! strand and

repeat t!is procedure a furt!er t"otimes. 9!e measured len%t!

bet"een t!e outer c!al0 mar0s is

t!en di+ided by four to %i+e t!e

lay len%t!.

As a rou%! c!ec0 on t!e o+erall

accuracy of t!e c!al0 mar0in%' t!e

len%t! of lay for ei%!t strand ropes

is approximately ,.* 5 ,.* x t!ediameter of t!e rope. e.%. usin% a

lay len%t! of ,.* x rope diameter'

four lay len%t!s of a ( mm

diameter rope "ill be ( mm x ,.*

x ) 1( mm.

An alternati+e met!od of meas5

urin% t!e rope lay is to secure t!e

free end of t!e roll of addin%

mac!ine paper to t!e rope "it!ad!esi+e tape. 9!e paper is rolled

$a%e


18/23

out o+er t!e rope and simultane5

ously t!e "ax pencil is dra"n

o+er t!e paper' pro+idin% a clear

print of t!e outer "ires of t!e

rope. 9!e finis!ed print can befiled for comparison "it! later

measurements.

A t!ird met!od is to "rap typin%

carbon papers round t!e rope

under t!e roll of paper. By rub5

bin% alon% t!e paper "it! a piece

of cardboard' t!e carbon mar0in%

on t!e underside of t!e paper can

be confined to t!e tops of t!estrand cro"ns.

(." -hec%in+ the stabi!ity

o the rope

A rope in %ood condition "ill

!a+e all strands ti%!tly laid. A

scre"dri+er inserted bet"een

strands "!en t"isted s!ould meet"it! stiff resistance. If t!e

scre"dri+er can be t"isted

bet"een different pairs of strands

"it!out muc! resistance' a full

examination s!ould be carried out.

9!e uns0illed use of a scre"dri+er

or 3arlin Spi0e to examine t!e

rope core can cause serious dam5

a%e to t!e rope.

(.# -han+es in rope

structure

In addition to t!e examination

areas detailed in section )' defor5

mation caused at any point in t!e

main "or0in% area can mo+e

alon% t!e rope. Wa+iness' and in

particular' birdca%e can be mo+ed

alon% t!e rope by t!e action of t!e

s!ea+es. A de%ree of slac0ness in

t!e outer co+er of a multi5 strand

rope may not be sufficient to form

an immediate birdca%e. ?o"e+er'slac0ness can be @s2uee=edD alon%

t!e rope. Wit! t!e normal len%t!

of rope out any slac0ness in t!e

outer co+er "ill usually be found

at t!e end termination or "!ere

t!e rope meets t!e drum.

(.& Inspectin+ sheaves and

drums

Remar0s in t!is section are in5

tended to apply e2ually to s!ea+es

and drums.

A ti%!t %roo+e in a S!ea+e or

drum "ill sub


19/23

S!ea+e %roo+e' templates for t!e

si=es abo+e and belo" t!e recom5

mended si=e "ill be re2uired.

9!e sides and tread of s!ea+es

"!ic! !a+e been in use for sometime' are often !ea+ily coated "it!

old lubricant' some of "!ic! may

first !a+e to be remo+ed "it! a

scraper. By insertin% t!e template

as far as possible and dra"in% it

t!rou%! t!e remainin% lubricant'

t!e fit of t!e template relati+e to

t!e S!ea+e tread can be assessed.

9!e correct template s!ould be in

contact "it! t!e S!ea+e tread for

about (-. If t!e template only

touc!es t!e side flan%es' t!e %roo5

+e is too ti%!t. If t!e template

touc!es only t!e bottom part oft!e tread' t!e %roo+e is too "ide.

Attention s!ould also be %i+en to

t!e flan%es of t!e s!ea+es. Ab5

sence of lubricant' scratc!in% or

unexpected "ear on one side "ill

indicate 6a8 misali%nment of t!eS!ea+e and 6b8 t!e dan%er of

tor2ue bein% induced into t!e rope

due to t!e rope rollin% do"n t!e

flan%e into t!e tread.

9!e tread s!ould be cleaned and

carefully examined for any si%n of

rid%in% or imprintin%. In t!e case

of imprintin% "it! t!e rope profile

t!e rope in ser+ice may !a+e

caused t!e dama%e and is unli0ely

to be seriously affected. A re5

placement rope "ill not fit exactly

into t!e imprint and "ill suffer

serious dama%e durin% t!e early

part of its ser+ice.

$a%e 4


20/23

W!en a rope c!an%e is made' t!e

s!ea+es s!ould be c!ec0ed for

eccentricity and t!e bearin% for

"ear and free runnin%.

. E!ectro/ ma+netic wire

rope examination

After a period in ser+ice surface

"ear andor a number of "ire

brea0s "ill indicate t!e rope con5

dition !as deteriorated and discard

may be imminent. Specific

"or0in% conditions !o"e+er' may

lead to internal "ire brea0s and to

internal loss of metallic area. It

may be surprisin% to learn t!at t!isapplies in particular to ropes

"!ic!' for safety reasons' are

operated "it! lar%e diameter

s!ea+es and !i%! factors of safety.

/ynamically loaded ropes or

ropes "!ic! are sub


21/23

"it! plastic or all plastic s!ea+es'

t!ese s!ea+es offer more elastic

support t!an steel s!ea+es. 9!e

pressure bet"een outer "ires and

t!e S!ea+e %roo+es can bereduced to suc! an extent t!at

"it! some rope constructions t!e

first "ire brea0s "ill occur' not on

t!e surface' but "it!in t!e rope. In

all t!ese cases Electro5ma%netic

testin% "ill allo" nondestructi+e

examination and appraisal of t!e

ropes internal condition.

Electro5ma%netic testin% e2uip5ment a+ailable on t!e mar0et al5

lo"s' dependin% on indi+idual

desi%n' indication or continuous

recordin% of localised dama%e

suc! as sin%le bro0en "ires'

brea0s of strands' soldered and

"elded


22/23

of suspended ropes of Rope5"ays'

t!e test !ead is dra"n alon% t!e

"ire rope. /urin% t!is procedure

all test data are transmitted +ia

cable or radio to an amplifier. 9!etest data are indicated eit!er opti5

cally or acoustically' recorded on

ma%netic tape or represented

%rap!ically durin% t!e test. An

Electro5ma%netic test instrument

is s!o"n in 7i%. ).

Calibration of t!e testin% e2uip5

ment re2uires %reat care. A re5

commended met!od of c!ec0in%

t!e function and accuracy of t!e

e2uipment is to attac! len%t!s of

"ire' !a+in% diameters e2ual to

t!e lar%est and smallest si=es in

t!e rope' alon% t!e first metres ofrope len%t!. By means of

cellotape t!ese "ires can be

secured in t!e strand +alleys. At

t!e be%innin% of t!e recordin%

strip c!art t!e examiner "ill

obtain reference data indicatin%t!e si=e of t!e amplitudes of t!e

test "ires.

$a%e


23/23

7i%. *a illustrates a typical dia5

%ram of a rope section "it! "ire

brea0s. 7i%. *b s!o"s t!e re5

cordin% of a rope section affected

by corrosion.Selectin% t!e suitable test instru5

ment' competent !andlin% and t!e

correct interpretation of t!e data

re2uire a lot of experience and

expert 0no"led%e. arious

uni+ersities' test institutes as "ell

as commercial firms' render Elec5

tro5ma%netic inspection of "ire

ropes as a ser+ice.9!e discard numbers of "ire

brea0s specified in t!e Standards

refer solely to external "ire

brea0s. Appraisin% t!e condition

of t!e "ire rope "it! re%ard to

internal "ire brea0s is t!erefore

left to t!e inspector. It "ould be

ad+isable to discard a "ire rope

"!en t!e total number of external

and internal "ire brea0s' added

to%et!er' reac!es t!e discard

number of "ire brea0s specified

in t!e Standards.Electro5ma%netic tests cannot' and

must not' totally replace +isual

inspections. Met' t!ey pro+ide

+aluable additional information on

t!e conditions of "ire ropes and

must be re%arded as a useful

addition to t!e +isual inspection.

Inspeccion de Cables

Documents

Transcript of Inspeccion de Cables