Rudder and Rudder Stock Inspection in Dd

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  • 8/19/2019 Rudder and Rudder Stock Inspection in Dd

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    RUDDER AND RUDDER STOCK INSPECTION IN DD Guide Notes for Rudder, Rudder Stock and Pintle SurveRudder Stock and PintleThe following should be looked for on the rudder stock and pintle:

    • Excessive clearance between sleeve and bush of the rudder stock/pintle beyond the

    allowable limit specified by the Classification Society.

    • Condition of sleeve. f the sleeve is loose! ingress of water may have caused

    corrosion.

    • "eep pitting corrosion in the rudder stock and pintle ad#acent to the stainless steel

    sleeve.

    • Slipping of rudder stock cone coupling. $or a vertical cone coupling with hydraulic

    pressure connection! sliding of the rudder stock cone in the cast piece may causesevere surface damages.

    • %here a stainless steel liner/sleeve/cladding for the pintle/rudder stock is fitted into a

    stainless steel bush! an additional check should be made for crevice corrosion.

    http://indianmarineengineers.blogspot.com/2014/11/rudder-and-rudder-stock-inspection-in-dd.htmlhttp://indianmarineengineers.blogspot.com/2014/11/rudder-and-rudder-stock-inspection-in-dd.html

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    !"at to look for in Drdock

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    Defor#ationsThe rudder blade! rudder stock! rudder horn and propeller boss/brackets have to be checkedfor deformations.

    ndications of deformation of rudder stock/rudder horn could be found by excessiveclearance.

    &ossible twisting deformation or slipping of cone connection can be observed by thedifference in angle between rudder and tiller.f bending or twisting deformation is found! the rudder has to be dismounted for furtherinspection.

    $ractures$ractures in rudder plating should be looked for at slot welds! welds of removable part to therudder blade! and welds of the access plate in case of vertical cone coupling between rudderblade and rudder stock and/or pintle.

    Such welds may have latent defects due to the limited applicable welding procedure. Seriousfractures in rudder plating may cause loss of rudder.

    $ractures should be looked for at weld connection between rudder horn! propeller boss andpropeller shaft brackets! and stern frame.

    $ractures should be looked for at the upper and lower corners in way of the pintle recess incase of semi'spade rudders. Typical fractures are shown in Examples ( to ).

     $ractures should be looked for at the transition radius between rudder stock and hori*ontalcoupling +palm, plate! and the connection between hori*ontal coupling plate and rudder bladein case of hori*ontal coupling.

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    Typical fractures are shown in Examples - and . $atigue fractures should be looked for atthe palm plate itself in case of loosened or lost coupling bolts.

    $ractures should be looked for in the rudder plating in way of the internal stiffening structuressince +resonant, vibrations of the plating may have occurred.

    f the rudder stock is deformed! fractures should be looked for in rudder stock bynondestructive examinations before commencing repair measures! in particular in andaround the keyway! if any.

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    Rudder clearances

    udder and steering gear arrangements may have different wear criteria depending on themanufacturer. These calibration and running clearance limits should be checked +normallyindicated on drawings,.

    Some points to consider:

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    "imension +-, must be substantially greater than #ump clearance +0, to protect steering gearfrom damage in the event of grounding of skeg or rudder.

    "imension +, should be sufficient to cater for wear in carrier bearing and substantiallygreater than riding washer clearance +),.

    1sually +-, and +, are of the order 2 mm/) mm on a small/medium si*e vessel.f the riding washer clearance has reduced then the carrier bearing is wearing or the skeg isset up. Check for reduction in steering gear crosshead dimension +, to verify downwarddisplacement.

    Ensure no drydock keel blocks in way of skeg. 3lways apply the wear limits given by themanufacturer. The following table gives recommended maximum limits of clearances. 

    uder Type"iameter " +mm, rudder 

    stock/pintle in way of bearing

    4aximum clearance +mm,

    Type -! ! ( 5 )

    " 6 7 )2 (

    )2 6 " 6 7-22 2.2" 8

    -22 6 "

    2.22) 8 (.)

    +above value not to exceed 9.)

    mm maximum,

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    uder Type"iameter " +mm, rudder 

    stock/pintle in way of bearing4aximum clearance +mm,

    Types 0 5 to -2

    +spade and semi spade,

    " 6 7)2 .)

    )2 6 "

    2.229" 8 .

    +above value not to exceed .2

    mm maximum,

    These limits do not only take into consideration the functioning of the bearing but also theeffects of ;hammering< and damage to the rudder itself as clearances increase. Seemanufacturer=s recommendations for special rudder designs or the use of synthetic bearingmaterials. To avoid #amming and premature failure renewed bearings should have ade>uateclearance. Special care is re>uired with those synthetic materials which swell. udder shouldalways be swung in drydock when possible after repair to check free movement.?ere you have the 3@S criteria for rudder pintle clearence:

    n general initial clearances should be around 2.2)2< for a < pintle to around 2.92< for a -0<pintle. $ar in service acceptable clearance we feel about -/0A clearance per -A of diameterof pintle up to -B of diameter would be acceptable for another two years of service.

    -/0A 7 2.2-))A 7 2.(9 m/m

    &intle diameter 3cceptable for .) D ( years

    nches m/m nches m/m

    -).0 (/( 7 2.2(9 .0

    9 -99.0 9/0 7 2.-2 .

    2(. -/ 7 2.-) (.

    . /0 7 2.-02 (.

    -2 )0 ).( 7 2.-) 0.2

    -- 9.0 --/0 7 2.-9- 0.0

    - (20. (/- 7 2.-9 0.

    -( ((2. -(/0 7 2.2( ).

    -0 ()). 9/( 7 2.- ).

    The above applies to semi'balanced or balanced rudder with lignum'vitae or laminated'phenolic'resin gudgeon bushings

    Re%airs

    &ent rudder stocks

    @ent rudder stocks without any fractures may be repaired! depending on the si*e of thedeformation! either by heating or by cold straightening in an approved workshop according toan approved procedure. epair proposal should be submitted.

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    @ent rudder stocks with fractures may be repaired! depending on the nature and extent. f awelding repair is considered acceptable! the fractures are to be removed bymachining/grinding and the welding is to be based on an approved welding proceduretogether with post weld heat treatment as re>uired. epair proposal should be submitted.

    $ractures at rudder stock'"ori(ontal cou%lin) %late

    This can only be accepted on a case by case basis. Some types of fractures may re>uire adifferent solution to local grinding and welding. epair proposal should be submitted.

     Rudder stock and %intle re%airs * +eldin)

    epairs by welding may be accepted provided the weld material chemical composition issuitable for welding. epair proposal to be submitted.The welding procedures are to be identified as a function of the carbon e>uivalent +Ce>,.

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    $ollowing is guidance through the repair process:

    • emoval of the wasted area by machining and/or grinding! and F"E carried out

    • @uild'up welding by automatic spiral welding according to an approved welding

    procedure.

    • Extension of build'up welding over the area of large bending moments +shafts,

    according to the sketch below.

    • Sufficient number of weld layers to compensate removed material! at least one layer in

    excess +heat treatment of the remaining layer,.

    • Transition at the end of the build'up welding according to the following sketch.

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    • &ost weld heat treatment if re>uired in special cases +never for stainless steel cladding

    on ordinary steel,

    • $inal machining! at least two layers of welding material have to remain on the rudder

    stock +See the above sketch,

    • NDE to be carried out.

    T+isted rudder stocks

    f the rudder stock is twisted due to excessive forces such as contact or grounding and hasno additional damage +fractures! significant bending etc.,! the stock may be reused.

    Consideration will be given on a case by case basis.

    The Surveyor should seek advice before accepting any repair.Formally the keyway! if any! has to be milled in a new position.

    The following table! giving criteria in relation to the degree of twisting! is for guidance only.

    +-, $or 3 6 G/"Stock acceptable for further service without any heat treatment sub#ect to stock being free ofcracks or other defects.

    $or small angles of twist a ;stepped< or larger key may be considered as an alternative to anew keyway. &roposal is to be submitted.

    +, $or G/" 6 3 6 )G/":The stock is to be stress relieved. &roposal is to be submittedH-I.

    +(, $or 3 J )G/"Stock is to be fully annealed or normali*ed. &roposal is to be submitted.%here:

     3 7 3ngle of twist in degrees.

    http://www.blogger.com/blogger.g?blogID=4082296293004648676#_ftn1http://www.blogger.com/blogger.g?blogID=4082296293004648676#_ftn1

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    G 7 Gength of the stock over which the twist appears uniform.d 7 diameter of twisted portion of stock.

    Stainless claddin) of rudder stocks and %intleThis may be accepted depending on the weldability.&roposal is to be submitted.

    Rudder %lates

    $ractures in welding seams can be gouged out and re'welded with proper root penetration. fvibration may be the possible cause an alternative repair may have to be considered.$ractures in the lower and/or upper corners of the pintle recess of semi'spade rudders thatdo not propagate into vertical or hori*ontal stiffening structures may be repaired by gougingout and welding. $or longer fractures internal structure should be checked! and repairproposal should be submitted.

     3s a guide! the preheating temperature can be obtained from the diagram below using theplate thickness and carbon e>uivalent of the thicker structure.$or fractures at the connection between plating and cast pieces an ade>uate preheating is

    necessary. The preheating temperature is to be determined taking into account the followingparameters:

    • Chemical composition +carbon e>uivalent Ce>,

    • Thickness of the structure

    • ?ydrogen content in the welding consumables

    • ?eat input

     3s a guide! the preheating temperature can be obtained from the diagram below using theplate thickness and carbon e>uivalent of the thicker structure.

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      3ll welding repairs are to be carried out using >ualified/approved welding procedures.

    A*rasion of *us" and sleeve

    The abrasion +wear down, rate depends on the features of the ship such as fre>uency ofmaneuvering.

    ?owever! if excessive clearance is found within a short period! e.g. ) years! alignment of the

    rudder arrangement and the matching of the materials for sleeve and bush should beexamined together with the replacement of the bush.

    &earin) #aterials4anufacturers= recommendations should be followed for any work on the bearing material.eplacement synthetic bearing material should be type approved by the 3dministration orClass Society.