1

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)

2

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

3

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

4

SOLDADURA TIPO DE JUNTAS (AWS A3.0)

3. Junta de borde

0 - 30

PREPARACION DE LA JUNTA

CHAFLAN CUADRADO CHAFLAN EN V

5

6

7

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

8

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)

9

Grietas

10

Inclusiones (poros escoria)

Falta de relleno

11

Penetracin excesiva

Exceso de refuerzo

12

Mordeduras

Desalineamiento (Hi-Lo)

13

Traslape

Picaduras de arco y marcas de esmerilado

PICADURA DE ARCOMARCA DE ESMERILADO

14

Distorsin Angular

15

16

Los estndares ms comunes utilizados en este tipo de servicios son: ASME Secc. V, AWS D1.5, AWS D1.1.

17

18

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.

19

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.).

20

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.

21

CODE

ASME B 31.3

22