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APARIENCIA DE LAS DISCONTINUIDADES DE ACUERDO
CON LOS RESPECTIVOS PROCESOS DE FABRICACIN
Una discontinuidad es cualquier variacin enla homogeneidad de
una pieza o material,tanto en su estructura como en su forma.
A travs de la influencia que la discontinuidadtendr sobre la
utilizacin del material o delequipo es que se podrn definir
criterios deaceptabilidad.
Las discontinuidades pueden seratribuidas a diferentes
causas:
Pueden ocurrir durante el propio procesode fabricacin del
material (fundicin)
Durante el procesamiento (laminacin,forja,...)
Durante el uso del equipo en servicio(aplicacin de esfuerzos
mecnicos o decorrosin)
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Las discontinuidades ms comunes son:
Fisuras Grietas de filete Grietas de esmerilado Grietas de
tratamiento trmico Grietas en tubos Escamas de hidrogeno
Laminaciones Contracciones y micro contracciones Poros e
inclusiones
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SOLDADURA TIPO DE JUNTAS (AWS A3.0)
1. Junta a tope
2. Junta en esquina
SOLDADURA TIPO DE JUNTAS (AWS A3.0)
3. Junta en T
4. Junta de traslapo
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SOLDADURA TIPO DE JUNTAS (AWS A3.0)
3. Junta de borde
0 - 30
PREPARACION DE LA JUNTA
CHAFLAN CUADRADO CHAFLAN EN V
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PROCESOS DE SOLDADURA
SMAW (Shielded Metal Arc Welding):Soldadura de arco con
electrodo revestido
GMAW (Gas Metal Arc Welding):Soldadura de arco con gas de
proteccin
GTAW (Gas Tungsten Arc Welding):Soldadura de arco con electrodo
deTungsteno
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PROCESOS DE SOLDADURA
FCAW (Flux Core Arc Welding):Soldadura de arco con electrodo
tubular
SAW (Submerged Arc Welding):Soldadura de arco sumergido
OAW (Oxyacetylene Welding): Soldaduracon mezcla de oxigeno y
acetileno
DISCONTINUIDADES SUPERFICIALES EN JUNTAS SOLDADAS
(VISUALES)
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Grietas
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Inclusiones (poros escoria)
Falta de relleno
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Penetracin excesiva
Exceso de refuerzo
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Mordeduras
Desalineamiento (Hi-Lo)
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Traslape
Picaduras de arco y marcas de esmerilado
PICADURA DE ARCOMARCA DE ESMERILADO
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Distorsin Angular
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Los estndares ms comunes utilizados en este tipo de servicios
son: ASME Secc. V, AWS D1.5, AWS D1.1.
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CODE
AWS D1.1.
4.8.1 Visual Inspection. For acceptable qualification, welds
shall meet thefollowing requirements:
(1) The weld shall be free of cracks.(2) All craters shall be
filled to the full cross section of the weld.(3) The face of the
weld shall be flush with the surface of the base metal, and theweld
shall merge smoothly with the base metal. Undercut shall not exceed
1/32 in.[1 mm]. Weld reinforcement shall not exceed 1/8 in. [3
mm].(4) The root of the weld shall be inspected, and there shall be
no evidence ofcracks, incomplete fusion, or inadequate joint
penetration. A concave root surface isallowed within the limits
shown below, provided the total weld thickness is equal toor
greater than that of the base metal.(5) The maximum root surface
concavity shall be 1/16 in. [2 mm] and the maximummelt-through
shall be 1/8 in. [3 mm]. For tubular T-, Y-, and K-connections,
melt-through at the root is considered desirable and shall not be
cause for rejection.
CODE
API 1104.
6.4 VISUAL EXAMINATION
For a qualification test weld to meet the requirements for
visual examination, theweld shall be free from cracks, inadequate
penetration, and burn-through, and mustpresent a neat workman-like
appearance. The depth of undercutting adjacent tothe final bead on
the outside of the pipe shall not be more than 1/32 in. (0.8 mm)
or12.5% of the pipe wall thickness, whichever is smaller, and there
shall not be morethan 2 in. (50 mm) of undercutting in any
continuous 12 in. (300 mm) length ofweld.When semi-automatic or
mechanized welding is used, filler wire protruding into theinside
of the pipe shall be kept to a minimum.Failure to meet the
requirements of this subsection shall be adequate cause toeliminate
additional testing.
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CODE
API 1104.
9.7 VISUAL ACCEPTANCE STANDARDS FOR UNDERCUTTING
9.7.2 Acceptance Standards
When visual and mechanical means are used to determine depth,
undercuttingadjacent to the cover or root bead shall not exceed the
dimensions given in Table 4.When both mechanical and radiographic
measurements are available, themechanical measurements shall
govern
CODE
API 650
8.5 VISUAL EXAMINATION
8.5.1 A weld shall be acceptable by visual inspection if the
inspection shows thefollowing:
a. There are no crater cracks, other surface cracks or arc
strikes in or adjacent tothe welded joints.b. Maximum permissible
undercut is 0.4 mm (1/64 in.) in depth for vertical buttjoints,
vertically oriented permanent attachments, attachment welds for
nozzles,manholes, flush-type openings, and the inside
shell-to-bottom welds. For horizontalbutt joints, horizontally
oriented permanent attachments, and annular-ring buttjoints, the
maximum permissible undercut is 0.8 mm (1/32 in.) in depth.c. The
frequency of surface porosity in the weld does not exceed one
cluster (oneor more pores) in any 100 mm (4 in.) of length, and the
diameter of each clusterdoes not exceed 2.5 mm (3/32 in.).
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CODE
API 650
d. The reinforcement of the welds on all butt joints on each
side of the plate shall not exceed the following thicknesses:
The reinforcement need not be removed except to the extent that
it exceeds themaximum acceptable thickness or unless its removal is
required by 8.1.3.4 forradiographic examination.
CODE
ASME B 31.4
434.8.5 Required Inspection and Acceptance Criteria
(b) Inspection Methods and Acceptance Standards(1)
Nondestructive inspection shall consist of visual inspection and
radiographicexamination or other acceptable nondestructive methods,
and shall be inaccordance with API 1104. The methods used shall be
capable of producingindications of potential defects that can be
accurately interpreted and evaluated.Welds shall meet the
acceptance standards for discontinuities contained in API1104, or
the alternate acceptance standards for girth welds in Mandatory
Appendix Iof API 1104.
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CODE
ASME B 31.3
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