Inspeccion de Cables

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  • 8/13/2019 Inspeccion de Cables


    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


    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 -


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    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


    :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

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    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


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

    fittin%s carried out "it!out


    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


    $a%e (

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    2. When must wire ropes be


    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


    3. When must wire ropes be


    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 )

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    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


    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


    a8 Statutory re2uirements

    b8 9ype of appliance andor

    desi%n of t!e system

    c8 ;perational en+ironmental


    d8 3et!od and fre2uency of


    e8 3anufacturers recommend5


    f8 Results of pre+ious inspec5

    tions and examinations

    %8 Experience "it! pre+ious

    ropes on t!e appliance or


    /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


    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 *

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    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


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

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    s!oc0 loadin%. Loop formations

    are a

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    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

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    ed%e. Lan%s lay ropes are often

    "orst affected. 3isplaced outer

    "ires are a

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    *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


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    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

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    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


    #. $iscard number o wire


    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


    /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


    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

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    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 [email protected] rope remain on t!e drum

    after t!e termination !as been re5


    &. '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


    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


    3a%nifyin% %lass


    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 (

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    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


    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 )

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    (.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


    9!e %enerally accepted met!od of

    measurin% rope diameter for com5

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

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

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

    time a cro"n ad

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    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


    ;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


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    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


    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


    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


    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

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    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

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    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

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    "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


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    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.


  • 8/13/2019 Inspeccion de Cables


    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.